Less Invasive Unilateral Arytenoid Lateralization: A Modified Technique for Treatment of Idiopathic Laryngeal Paralysis in Dogs: Technique Description and Outcome Dirsko J. F. von Pfeil1,2, Dr Med Vet, DVM, Diplomate ACVS, Diplomate ECVS, Michael R. Edwards1, DVM, MS, Diplomate ACVS, and Loïc M. Déjardin2, DVM, MS, Diplomate ACVS, Diplomate ECVS 1
Veterinary Specialists of Alaska P.C., Anchorage, AK and East Lansing, Michigan
Corresponding Author Dirsko J.F. von Pfeil, Dr Med Vet, DVM, Diplomate ACVS, Diplomate ECVS, Veterinary Surgical Centers, 140 Park St SE, Vienna, VA 22180. E‐mail: [email protected] Submitted December 2012 Accepted December 2013 DOI:10.1111/j.1532-950X.2014.12151.x
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Department of Small Animal Clinical Sciences, Michigan State University,
Objective: To (1) describe a modification of conventional unilateral cricoarytenoid lateralization (UCAL), called less‐invasive unilateral cricoarytenoid lateralization (LI‐UCAL) for treatment of idiopathic laryngeal paralysis (LP); (2) report clinical outcome of LI‐UCAL; and (3) describe the effect of early discharge after surgery. Study Design: Retrospective clinical study. Animals: Dogs (n ¼ 22). Methods: Medical records (January 2009 to October 2011) of dogs diagnosed with idiopathic LP that had LI‐UCAL were reviewed. Signalment, clinical signs, laboratory tests, imaging, concurrent medical conditions, information from the anesthesia record, and hospitalization time were documented. Follow‐up was obtained by direct examination, questionnaire, and review of medical records from referring veterinarians. Results: Dogs included in the study had variable degrees and duration of respiratory distress before surgery. Median surgery time was 32 minutes. Median hospitalization was 6 hours, and median follow‐up was 427 days. Long‐term respiratory function, as reported by owners at last follow‐up, improved in 95.5% of dogs after surgery; exercise tolerance improved by 90%. Major complications included death secondary to aspiration pneumonia (9%), aspiration pneumonia from which dogs recovered within 3 days after administration of antimicrobials (9%), and development of right‐sided laryngeal collapse that required right sided LI‐UCAL (4.5%). At long‐term follow‐up, 95.5% of owners were satisfied with the surgical outcome. Conclusion: LI‐UCAL is a feasible surgical technique and resulted in improvement of clinical signs related to LP. Calm recoveries without adverse effects such as respiratory distress were associated with early discharge. LI‐UCAL could be considered an alternative to conventional UCAL.
Idiopathic laryngeal paralysis (LP) has been thoroughly described and surgical unilateral cricoarytenoid lateralization (UCAL) is considered the standard of care for alleviating secondary airway obstruction.1–8 The original UCAL surgical approach involves a 7.5–10 cm long skin incision over the left side of the larynx.3 After soft tissue dissection, the entire thyropharyngeus muscle is transected, the cricoarytenoideus dorsalis muscle is dissected from its attachment on the muscular process of the arytenoid cartilage and the cricopharyngeus muscle is retracted or transected to allow separation of the cricoarytenoid and cricothyroid articulations and transection of the sesamoid band.3 Next, 2 strands of suture are placed around the caudal end of the thyroid cartilage and then through the muscular process of the arytenoid cartilage.3 This allows Presented in part at the Annual Symposium of the American College of Veterinary Surgeons in San Antonio, TX, 2013.
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abduction of the arytenoid cartilage and subsequent opening of the rima glottidis.3,4,6–9 Careful attention to detail should allow every surgeon to identify the nerves around the larynx and inadvertent severance of these nerves must be avoided. However, according to previous anatomic studies, complete transection of the thyropharyngeus and the cricopharyngeus muscles may jeopardize the cranial laryngeal nerve and its branches, the ramus anastomoticus, the caudal laryngeal, and the para‐recurrent nerves.10–16 Indeed, compromised laryngeal muscle function and a potentially increased risk of aspiration pneumonia has been suggested to occur as a result of thyropharyngeus muscle transection.17 A less invasive approach could better preserve the local neurovascular anatomy and reduce the risk for aspiration pneumonia while maintaining a favorable surgical outcome of UCAL. Sparing soft‐tissue‐structures such as the cricothyroid muscle18,19 or splitting the thyropharyngeus muscle along the
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direction of its muscle fibers have been suggested as means to minimize laryngeal muscle damage, thus preserving laryngeal function and sensation.17,20–22 Whereas disarticulation of the cricoarytenoid articulation, caudal retraction of the cricopharyngeus muscle, and placement of a single arytenoid abduction suture (AAS) have been advocated and described in vitro,16,21,23–26 studies evaluating the clinical outcome of these combined soft‐tissue‐sparing techniques17 have not been conducted. An additional challenge is achieving sufficient opening of the rima glottidis to improve airflow, while minimizing the risk of aspiration pneumonia associated with excessive opening of the rima glottidis.23–25,27–29 Furthering this idea, White and Monnet suggested that optimal opening of the rima glottidis could be achieved by placement of an endotracheal tube of the largest possible diameter, followed by minimal tension applied to the AAS.21,26 To our knowledge, clinical evaluation of these techniques has not been reported. Finally, there is controversy on the most appropriate time of discharge from the hospital after UCAL. Whereas some surgeons prefer to monitor patients for 1–3 days after surgery,3,4,8,9 others suggest earlier discharge.21 Results of a study investigating the effect of early discharge after UCAL are lacking. Thus our purposes were: (1) to describe a less invasive alternative technique to UCAL; (2) report the clinical outcome of this technique in 22 dogs; and (3) evaluate the effect of early discharge from the hospital. We hypothesized that this less invasive UCAL (LI‐UCAL) would provide adequate lateralization of the arytenoid cartilage, minimize postoperative morbidity, result in clinical outcome similar to that reported with conventional UCAL, and that dogs recover well when discharged soon after surgery.
MATERIAL AND METHODS Inclusion Criteria Medical records (January 2009 to October 2011) of dogs that had LI‐UCAL for treatment of LP were reviewed. All dogs were operated by 1 surgeon (D.V.P.). To be included in the study, the following information had to be available: signalment; body weight; clinical signs; duration of clinical signs; surgery‐, anesthesia‐, and hospitalization time; short‐ term follow‐up information obtained at our hospital or by the referring veterinarian; complications; and completed final questionnaire, including long‐term follow‐up information. Anesthesia Anesthesia was induced using propofol (4–6 mg/kg intravenously [IV]) to effect. Direct laryngoscopy was performed to confirm the diagnosis of LP. Dogs were intubated using the largest endotracheal tube that could be placed without damaging the larynx. After intubation, anesthesia was maintained using isoflurane in oxygen. Then acepromazine (0.5 mg/kg IV), butorphanol (0.2 mg/kg IV), atropine
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(0.02 mg/kg IV), metoclopramide (0.2 mg/kg subcutaneously), dexamethasone‐SP (0.5 mg/kg IV), cefazolin (10 mg/kg IV), and Normosol‐R (22 mL/kg/hr IV) were administered. Surgical Procedure Dogs were positioned in right lateral recumbency with the neck extended and supported with a vacuum bag so that the left side of the larynx was facing upward and laterally. The thoracic limbs were retracted caudodorsally. After aseptic preparation, a 2–3 cm long skin incision, made immediately ventral and parallel to the jugular vein, was centered over the caudal edge of the cricoid cartilage. After connective tissue dissection including the platysma muscle, the thyropharyngeus muscle was exposed and then incised transversely to the direction of its muscle fibers over the area medial to the muscular process of the arytenoid cartilage along the dorsocaudal edge of the thyroid cartilage. The extent of the dissection line was limited to 25% of thyropharyngeus muscle length. A single stay suture of 2‐0 polyamide was inserted through the freed thyroid cartilage to facilitate ventrolateral retraction. The fascial membrane of the larynx was incised. Using bipolar electrosurgery, bundles of the frequently atrophied cricoarytenoideus dorsalis muscle were dissected as needed from the muscular process of the arytenoid cartilage to improve its exposure. Care was taken to remain as close to the muscular process as possible to minimize the risk of inadvertent damage to the surrounding soft tissue structures. A curved Halsted mosquito forceps was used to dissect the cricoarytenoid articulation, preserving the cricopharyngeus muscle. The caudodorsal aspect of the cricoid cartilage was palpated and a Kelly hemostatic forceps was used to create a small opening through the connective tissues at the dorsolateral cricotracheal junction. Although not visible during dissection, the anatomic structures bordering this area may aid the reader to understand the precise location of this opening. These borders include dorsally the esophagus, rostrally the cricopharyngeus muscle, and ventrally the sternothyroideus muscle. Caudally the opening was bordered by the ventral aspect of the esophagus and dorsal aspect of the sternothyroideus muscle. A Kelly hemostatic forceps was placed caudal to the edge of the cricoid cartilage with its tip pointing rostrally. The hemostat was then “hooked” behind the caudal edge of the cricoid cartilage. The swaged‐on taper needle of a 1 polypropylene suture was bent slightly to reduce its curvature. The needle was passed between the opened jaws of the preplaced Kelly hemostatic forceps and pushed craniolaterally to exit 2 mm caudal to the muscular process of the arytenoid cartilage. While passing the needle, care was taken to maintain the tip of the needle against the medial wall of the cricoid cartilage. This was done in an effort to minimize the risk for penetration of the laryngeal respiratory epithelium. The Kelly hemostatic forceps was removed and the area immediately caudal to the muscular process exposed. The suture was then driven through the center of the articular surface of the muscular process. This was facilitated by lifting the muscular process with a Brown‐Adson tissue forceps. A Senn retractor, placed cranial to the muscular
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Postoperative Follow‐Up
Figure 1 Tunneling of hemostat to grasp AAS. 1 ¼ intact cricopharyngeus muscle, 2 ¼ caudal end of the AAS. Note formation of loop before being grasped in an effort to reduce soft tissue damage when pulling rostrally. 3 ¼ stay suture, 4 ¼ thyropharyngeus muscle, 5 ¼ muscular process, 6 ¼ cranial end of AAS, 7 ¼ cricoarytenoideus dorsalis muscle.
process, was used to direct the tip of the needle laterally without incorporating surrounding soft tissue structures. A Kelly hemostatic forceps was used to create a tunnel underneath the cricopharyngeus muscle and its associated neurovascular bundle starting caudal to the muscular process and exiting at the caudodorsal edge of the cricoid cartilage. The free end of the AAS was then pulled rostrally through the tunnel (Fig 1). The suture ends were then pulled alternately to check for drag, which could be indicative of endotracheal tube entrapment. If entrapment was suspected, the endotracheal tube was moved by the anesthesiologist. If the surgeon felt movement of the AAS, it was removed and repositioned. A surgeon’s knot was used to tie the suture with minimal tension and 4 additional single interrupted knots were added. After lavage, routine closure with 3‐0 polyglactin 910, simple continuous pattern interrupted by Aberdeen knots, was used to conclude the procedure. The degree of left arytenoid cartilage abduction and patency of the rima glottidis were evaluated after surgery by direct laryngoscopy. Dogs were re‐intubated before anesthetic recovery. Postoperative Care After extubation, dogs were closely monitored for signs of respiratory distress. Dogs were released from the hospital as soon as possible—once ambulatory and showing normal breathing pattern. Postoperative medications included cefpodoxime (5–10 mg/kg orally once daily for 14 days) as preventative measure to decrease the risk of infection in these geriatric dogs and tramadol (1–4 mg/kg orally twice daily as needed for 5 days) for analgesia.
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Owners were contacted the day after discharge to check the status of the dog. Clinical re‐examination was performed 2 weeks postoperatively or earlier if necessary. During these conversations, owners were also asked whether they felt that their dogs had been anxious or calm the first days after surgery. At the time of final data collection, owners were contacted again and asked to complete a questionnaire and report on the improvement of clinical signs of their dogs (Appendix A). If the dog had died, owners were asked whether the cause of death was related to respiratory disease, whether clinical signs or a diagnosis of recurrence had been made before death, and whether they could still provide information listed in the questionnaire. Complications were recorded as major or minor. Major complications were defined as: (1) those requiring a 2nd laryngeal surgery; (2) infection; (3) aspiration pneumonia; and (4) death related to complications of the procedure. Aspiration pneumonia was defined as a radiographic alveolar pattern in the presence of clinical signs and supportive laboratory findings. Other complications were considered minor. Occasional coughing, gagging, throat‐clearing, and panting were not identified as complications because such behaviors are frequently encountered after UCAL and can be expected.3,5,9 Data Analysis Descriptive statistics (median, range, and percentage) were used to report data.
RESULTS Twenty‐two dogs (10 castrated and 2 intact males, 9 spayed and 1 intact female; median age, 12 years [range, 9–14 years], median weight, 35.2 kg [range, 14.1–53.6 kg]) fulfilled the inclusion criteria. There were 14 Labrador Retrievers (64%), 3 dogs of mixed breeding (13.5%), 2 Golden Retrievers (9%), 2 Brittany Spaniels (9%), and 1 Chesapeake Bay Retriever (4.5%). History and Clinical Findings Duration of respiratory distress varied between acute onset and progressive worsening over a period up to 17 months (mean, 6.1 months). Clinical signs included (1) exercise intolerance in 18 dogs (82%); (2) coughing, gagging, or throat clearing while eating in 6 dogs (27%); (3) slower than normal eating in 4 dogs (18%); and (4) mild occasional regurgitation of small amounts of food after eating in 2 dogs (9%). As reported by the owners, these 2 dogs had shown mild regurgitation for most of their lives, usually associated with exciting events, such as greeting the owner when he/she returned home after a longer time of absence, preparing for longer hikes, playing hard and rough, or when receiving rare treats. Thoracic radiographs of these dogs were normal. Before surgery, these 2 owners were informed about the increased risk for development of aspiration
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pneumonia and permanent tracheostomy was offered as a treatment. Both owners declined permanent tracheostomy but opted for LI‐UCAL. Acute episodes of collapse and cyanosis were reported in 9 dogs (41%). Six of these had been admitted to an emergency hospital before referral. The other 3 dogs were referred after they had recovered at home and been examined by a veterinarian. Before surgery, using a 1 (worse) to 10 (best) scale, clients subjectively rated the quality of breathing to be a median of 2 (range, 1–5). The main respiratory signs during pre‐surgical physical examination were stridor of variable severity in 22 dogs (100%), panting in 7 dogs (32%), and labored breathing in 7 dogs (32%).
Laboratory Tests and Diagnostic Imaging Preoperative hematologic and serum biochemical profiles (16 dogs; 73%) had no abnormalities. Preoperative thoracic radiographs (11 dogs; 50%) demonstrated a typical geriatric bronchointerstitial lung pattern, without evidence of aspiration pneumonia or megaesophagus. Perioperative Data All dogs had a laryngeal examination performed immediately after induction of anesthesia and before left‐sided LI‐UCAL. Findings were consistent with bilateral LP in all dogs. Additional surgical procedures were performed in 9 dogs (41%) and included excision of benign skin masses in 8 dogs. One dog was castrated after LI‐UCAL. Median surgery time for LI‐UCAL was 32 minutes (range, 24–64 minutes). Median total anesthesia time, including additional procedures was 95 minutes (range, 72–168 minutes). As expected, duration of anesthesia increased with the number of additional procedures. Endotracheal entrapment was not noted in any dog. Left arytenoid cartilage abduction and patency of the rima glottidis were judged appropriate in all dogs. Median hospitalization time was 6 hours (range, 4– 8 hours). Postoperative Clinical Evaluation Owners of all dogs (100%) were called the day after the surgery. Eighteen dogs (82%) were examined 2 weeks postoperatively at our clinic and the other 4 dogs (18%) were examined by the referring veterinarian. All owners reported calm recoveries without adverse effects such as respiratory distress. Compared to preoperative respiratory clinical signs, 19 dogs (86%) had marked improvement by 2 weeks, whereas increased frequency of coughing remained in 3 dogs (14%). By 4 weeks, coughing in these dogs had noticeably improved.
Outcome Median follow‐up was 427 days (range, 214–866 days). Six dogs (27%) died or were euthanatized for reasons unrelated to
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surgery at a median of 320 days after surgery (range, 183–762 days). Causes of death in these dogs included severe weakness and ataxia (2), sudden death without any prior signs of respiratory dysfunction (2), pancreatic neoplasia (1), nasal neoplasia, and simultaneous kidney failure (1). Fourteen dogs (64%) were alive at final follow‐up. Clinical signs as reported by the owner at last follow‐up or before death revealed that stridor, labored breathing, and panting had improved in 21 dogs (95.5%). One dog (4.5%; dog 13) had recurrence of stridor at 8 months and had associated relapse of decreased exercise tolerance; the owner declined further evaluation and treatment. Based on the same 1–10 scale used preoperatively, owners subjectively rated the quality of breathing at final follow‐up or before death to be a median of 8 (range, 2–10). None of the dogs collapsed or needed to be admitted to an emergency hospital for respiratory distress or cyanosis at any time after surgery. All 18 dogs that had exercise intolerance before surgery had improved exercise tolerance by 20–100% (median, 90%); 14 dogs (78%) had returned to 80–100% activity level. The owner of dog 13 reported that exercise improvement was 70–80% for the first 8 months after surgery, then declined to 20% (laryngeal examination and additional treatment were declined). The owners of the other 3 dogs (4, 11, 16) reported improvement of 50%, 60%, and 60%, respectively, but felt that osteoarthritis, not airway disease, was the major factor limiting exercise. The 6 dogs that had coughing, gagging, and throat clearing while eating before surgery showed improvement of these clinical signs (median, 80%; range, 20–90%) after surgery. Slow eating in the 4 dogs with this as an initial complaint improved (median, 85%; range, 60–95%). Improvement by 70% and 80%, respectively, was reported for the 2 dogs that had presurgical regurgitation. Major complications occurred in 5 dogs (22%). Four dogs (18%) developed aspiration pneumonia; 2 dogs (9%) died as a consequence at 346 and 858 days, respectively. One of these dogs was concurrently diagnosed with megaesophagus, which was not evident on preoperative radiographs. The other 2 dogs (9%) developed a cough secondary to aspiration pneumonia, confirmed on clinical examination and thoracic radiography by the referring veterinarian at 2 and 671 days postoperatively, respectively. Both dogs were administered clavamox (13.75 mg/kg orally twice daily) and clinical signs resolved within 3 days. One dog (4.5%) that developed right‐sided laryngeal collapse, associated with recurrent cough and marked stridor at 9 months, was treated with right‐sided LI‐UCAL, and clinical signs resolved. Minor complications consisting of recurrent, chronic cough were reported in 2 dogs (9%). One dog developed coughing episodes 2 months postoperatively; thoracic radiographs at 2 and 5 months did not reveal signs of pneumonia. Supportive treatment (hydrocodone, 0.2 mg/kg orally every 8 hours) was initiated and resolution of the cough occurred within 4 weeks. The other dog developed chronic cough 1 year postoperatively unassociated with pneumonia as confirmed by thoracic radiography. The owner declined further investigation
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or treatment because of the absence of signs other than cough. Dog 13 developed recurrence of stridor 8 months after surgery but the owners opted not to pursue further diagnostics so the cause was not identified. Overall, 21 owners (95.5%) reported they were satisfied with the surgical outcome at last follow‐up, and 1 owner (4.5%) of the 1 dog that developed recurrent stridor at 8 months was not satisfied.
DISCUSSION LI‐UCAL was developed in an effort to minimize regional soft tissue injury, to achieve appropriate rima glottidis opening, and to accomplish outcomes similar to previous reports on UCAL. Our findings demonstrate that those goals were achieved. Quality of breathing increased from a median of 2 (range, 1–5) before surgery to a median of 8 (range, 2–10) after surgery. Owners were satisfied with the surgical outcome in 95.5% of dogs. We attempted to implement previous recommendations to protect regional muscles and nerves during UCAL7,17,20 as follows. First, the transverse incision of the thyropharyngeus muscle was limited to 25% of its entire length. This muscle was neither retracted nor transected. Dysfunction of this muscle, possibly secondary to regional nerve damage, can result in dysphagia, regurgitation, aspiration, coughing, or cricopharyngeal achalasia.30,31 To prevent these possible complications, the innervation to the cricopharyngeus muscle, arising from the glossopharyngeal and branches of the vagus nerves32,33 should be preserved during laryngeal surgery. Splitting the thyropharyngeus muscle along its fibers17 may have been even less invasive but because of poor visualization when having attempted this technique in other cases, this was not performed. Second, based on previous anatomic descriptions,10–16 it can be hypothesized that additional regional nerve damage is minimized with LI‐UCAL. Protection of the intrinsic branches as well as the ramus anastomoticus of the cranial laryngeal nerve preserves the sensory supply to the laryngeal mucosa.12 Similarly, protection of the recurrent laryngeal nerve is essential as it not only innervates the laryngeal muscles but also receives sensory fibers from trachea, esophagus, and laryngeal mucosa.11–12 Finally, damage to the 1st cervical nerve16 may also be decreased during LI‐UCAL. Nerve velocity conduction and anatomic evaluation of nerve damage, performed in purpose bred dogs as part of a comparative laboratory study would be necessary to evaluate the potential benefits of LI‐UCAL compared to UCAL. Such investigations were beyond the scope of our clinical study. Third, the cricothyroid joint was preserved. Its disarticulation might increase the risk for laryngeal collapse27; however, it may facilitate more precise suture position.7,16 In our study, accurate suture placement was achieved while maintaining this joint’s integrity. We suggest cricothyroid joint disarticulation is not necessary during LI‐UCAL. Fourth, the sesamoid band was preserved to reduce the risk for esophageal injury and aspiration pneumonia3,7,25,27,28
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and because its transection neither significantly changes rima glottidis opening nor reduces airway pressure.25,28 Other less invasive surgical steps included an attempt to minimize the risk of laryngeal respiratory epithelium penetration to decrease airway irritation and potentially minimize webbing,1,34 as well as formation of a loop at the AAS‐end to prevent soft‐tissue injury during tunneling (Fig 1). We followed the recommendation to tie the AAS to a point that creates a final rima glottidis opening no larger than that with the endotracheal tube in place.26 This technique was practical and consistently provided adequate glottic opening, as determined by direct laryngoscopy. Its implementation may be beneficial, particularly since the importance of wide glottis opening in contrast to best arytenoid position has been questioned.17 Aspiration pneumonia has been reported in 0–33% of dogs after UCAL,3,4,7–9,20,36 although the true incidence may be higher.37 Major complication rates may even reach 58% when other surgical techniques are used to treat LP.26 It is possible that the soft‐tissue sparing steps of LI‐UCAL prevented such a high incidence of life‐threatening aspiration pneumonia in our dogs. Our overall incidence of aspiration pneumonia was 18%; 2 of these dogs (9%) developed mild aspiration pneumonia; neither required hospitalization and improved clinically within 3 days with no recurrence. Death secondary to aspiration pneumonia has been reported in up to 14%5 and occurred in 2 other dogs (9%) in our study. Just before death, 1 of these dogs was diagnosed with megaesophagus, a condition that has been associated with an increased mortality risk.5 Secondary megaesophagus is likely related to dysfunction of the para‐recurrent laryngeal nerves that supply the cervical and cranial thoracic esophagus.38–42 It is doubtful that the para‐recurrent nerve is endangered by either the standard UCAL or the LI‐UCAL surgical approach. Therefore, the low incidence of secondary megaesophagus in our study is likely not related to the surgical approach. Whereas esophageal contrast studies have been recommended to determine pre‐existing decreased esophageal function,9 the benefit of such a test in this dog would have been limited because the diagnosis of megaesophagus was established >2 years after LI‐UCAL. We believe that the risk for development of an acute life‐threatening respiratory emergency during presurgical esophagography because of the stress associated with this procedure or because of aspiration of contrast material is greater than the risk for development of possible post‐ surgical aspiration pneumonia. If pneumonia should occur, the prognosis seems favorable when treated in a timely fashion: 1 study showed that post‐surgical aspiration pneumonia was successfully treated in all cases.9 Idiopathic postoperative unilateral prosthesis failure after UCAL has been reported in 5% of cases.5 To decrease the risk of AAS failure, using 2 strands of 1 polypropylene suture and a horizontal mattress pattern have been suggested; however, it is unknown whether the tension required for failure of such suture (51 N) is generated in vivo.45 In addition, suture size, number and type were not associated with complications.5 Therefore and based on suggestions of others,23,24,26 we chose to use 1 single strand of 1 polypropylene suture. AAS failure was not
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diagnosed in any of our dogs, suggesting that use of 1 AAS strand is sufficient. Recurrence of stridor is reported in up to 33% of dogs after surgical treatment of LP.26 Causes include suspected prosthesis failure, development of regional neoplasia, right‐sided laryngeal collapse and webbing.5,34,43–45 In our study 2 dogs (9%) had recurrence of stridor. One of these was diagnosed with right‐sided laryngeal collapse and underwent successful right‐ sided LI‐UCAL. It is possible that this dog’s cartilage weakened over time. None of these dogs had been diagnosed with laryngeal collapse at initial examination; however, it cannot be ruled out that this developed after surgery. The owners of the other dog (13) opted not to pursue further diagnostics. As such, recurrence of stridor and associated decline in exercise tolerance in this dog could be associated to any of the causes listed above. Duration of hospitalization is often 1–3 days after laryngeal surgery3,4,8,9 and it has been suggested that earlier discharge of these frequently geriatric dogs may reduce postoperative stress.21,35 All of our dogs were discharged the day of surgery (median hospitalization, 6 hours), and owners consistently reported calm recoveries without adverse effects such as respiratory distress. Whereas recollection bias is possible, we believe that this risk is very low. Owners were contacted the day after surgery by telephone to ask about the status of their dogs and to remind them to inform us immediately if there should be any concerns. As such we do not believe that the reported calm recoveries are the result of bias, nor do we consider them incorrect. These observations suggest that LI‐UCAL could be performed as an outpatient procedure. Whereas direct comparison between this and previous retrospective reports is hindered by multiple different factors between studies (definition of complications, case numbers, amount and experience of surgeons, and collection of follow‐ up information),3–9,27 we feel that the complication rates and final outcome after LI‐UCAL are similar to those reported after conventional UCAL. Limitations of our study include its retrospective nature, small number of cases, subjective data obtained from owners, and lack of a control group. With the exception of 1 previous report,9 these are the same limitations as in all previous studies on UCAL.3,4,7,8,24 Preoperative blood work and radiographs were not available for all dogs because some presented in severe respiratory distress. Performing these diagnostics may have resulted in potential life‐threatening airway obstruction. Conducting a telephone interview for final follow‐up had limitations because of the subjective opinion of the owner. This effect was reduced by inclusion of objective referring veterinarian information. In addition, it has been shown that owner’s assessment of clinical signs and outcome of treatment, including assessment of breathing quality, can be very accurate.46–48 We conclude that LI‐UCAL results in appropriate airway opening, resolution of clinical signs, as well as clinical outcome similar to previous reports on UCAL. Early discharge from the hospital after LI‐UCAL does not seem to be associated with complications. We suggest LI‐UCAL is a feasible technique to treat LP.
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ACKNOWLEDGMENT We thank Kenneth Harkin, DVM, Diplomate ACVIM (Kansas State University), Nelson Priddy II, DVM, Diplomate ACVS (Anchorage), Colette Marshall (Anchorage) for editorial help as well as Dr. Bryden J. Stanley, BVMS, MACVSc, MVetSc, Diplomate ACVS (Michigan State University), and Michele C. Fritz, BSc, LVT (Michigan State University) for assistance with development of the questionnaire.
DISCLOSURE The authors report no financial or other conflicts related to this report.
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14. Pressman JL, Kelemen G: Physiology of the larynx. Physiol Rev 1955;35:506–554 15. Vogel PH: The innervation of the larynx of man and the dog. Am J Anat 1952;90:427–447 16. Monnet E: Laryngeal paralysis and devocalization, in Slatter D (ed): Small animal surgery (ed 3). Philadelphia, PA, Saunders, 2003, pp 837–845 17. White RAS: Canine laryngeal surgery: time to rethink? Vet Surg 2009;38:432–433 18. Konrad HR, Rattenborg CC: Combined action of laryngeal muscles. Acta Oto‐Laryngol 1967;67:646–649 19. Burbridge HM: A review of laryngeal paralysis in dogs. Br Vet J 1995;151:71–82 20. Burbridge HM, Goulden BE, Jones BR: Laryngeal paralysis: an evaluation of the bilateral arytenoid lateralization procedure. J Sm Anim Pract 1993;34:515–519 21. White RAS, Monnet E: The larynx, in Brockman DJ, Holt DE (eds): BSAVA manual of canine and feline head, neck and thoracic surgery. Quedgely, Gloucester, British Small Animal Veterinary Association, 2005, pp 94–104 22. Nelissen P, White RAS: Arytenoid lateralization for management of combined laryngeal paralysis and laryngeal collapse in small dogs. Vet Surg 2012;41:261–265 23. Bureau S, Monnet E: Effect of suture tension and surgical approach during unilateral arytenoid lateralization on the rima glottidis in the canine larynx. Vet Surg 2002;31:589–595 24. Greenberg MJ, Bureau S, Monnet E: Effect of suture tension during unilateral cricoarytenoid lateralization on canine laryngeal resistance in vitro. Vet Surg 2007;36:526–532
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32. Smith Hammond C, Davenport PW, Hutchison A, et al: Motor innervation of the cricopharyngeus muscle by the recurrent laryngeal. J Appl Physiol 1997;83:89–94 33. Hermanson JW, Evans HE: The muscular system, in Evans HE (ed): Miller’s anatomy of the dog (ed 3). Philadelphia, PA, Saunders, 1993, pp 296–297 34. Mehl ML, Kyles AE, Pypendop BH, et al: Outcome of laryngeal web resection with mucosal apposition for treatment of airway obstruction in dogs: 15 cases (1992–2006). J Am Vet Med Assoc 2008;233:738–742 35. Fingeroth JM: Canine laryngeal paralysis. Part 2. DVM Newsmagazine/dvm 360.com, 2011; August:10S,12S 36. Greenberg MJ, Reems MR, Monnet E: Use of perioperative metoclopramide in dogs undergoing surgical treatment of laryngeal paralysis: 43 cases (1999–2006). Vet Surg 2007;36:513– 608,E11 (abstr) 37. Hammel SP, Hottinger HA, Novo RE: Postoperative results of unilateral arytenoid lateralization for treatment of idiopathic laryngeal paralysis in dogs: 39 cases (1996–2002). J Am Vet Med Assoc 2006;228:1215–1220 38. Evans HE: The respiratory system, in Evans HE (ed): Miller’s anatomy of the dog (ed 3). Philadelphia, PA, Saunders, 1993, pp 463–493 39. Evans HE: The digestive apparatus and abdomen, in Evans HE (ed): Miller’s anatomy of the dog (ed 3). Philadelphia, PA, Saunders, 1993, pp 385–462 40. Negus VE: The comparative anatomy and physiology of the larynx. London, William Heinemann Medical Books Ltd., 1949 41. Stavroulaki P, Birchall M: Comparative study of the laryngeal innervation in humans and animals employed in laryngeal transplantation research. J Laryngol Otol 2001;115:257–266
25. Wignall JR, Baines SJ: Effects of unilateral arytenoid lateralization technique and suture tension on airway pressure in the larynx of canine cadavers. Am J Vet Res 2012;73:917– 924
42. Valic Z, Vidruk EH, Ruble SB, et al: Parasympathetic innervation of canine tracheal smooth muscle. J Appl Physiol 2001;90:23–28
26. Monnet E, Tobias KM: Larynx, in Tobias KM, Johnston SA (eds): Veterinary surgery small animal. St. Louis, MO, Elsevier, 2012, pp 1724–1729
43. Salisbury SK, Forbes S, Blevins WE: Peritracheal abscess associated with tracheal collapse and bilateral laryngeal paralysis in a dog. J Am Vet Med Assoc 1990;196:1273–1275
27. Lozier S, Pope E: Effects of arytenoid abduction and modified castellated laryngofissure on the rima glottidis in canine cadavers. Vet Surg 1992;21:195–200
44. Klein MK, Powers BE, Withrow SJ, et al: Treatment of thyroid carcinoma in dogs by surgical resection alone: 20 cases (1981– 1989). J Am Vet Med Assoc 1995;206:1007–1009
28. Lussier B, Flanders JA, Erb HN: The effect of unilateral arytenoid lateralization on rima glottidis area in canine cadavers. Vet Surg 1992;25:121–126
45. Mathews KG, Roe S, Stebbins M, et al: Biomechanical evaluation of suture pullout from canine arytenoid cartilages: effects of hole diameter, suture configuration, suture size and distraction rate. Vet Surg 2004;33:191–199
29. Griffiths LG, Sullivan M, Reid SWJ: A comparison of the effects of unilateral thyroarytenoid lateralization versus cricoarytenoid laryngoplasty on the area of the rima glottidis and clinical outcome in dogs with laryngeal paralysis. Vet Surg 2011;30:359–365 30. Batinger VF, Saks FF, Ettinger AP: Functional morphology of the cricopharyngeal muscle. Arkh Anat Gistol Embriol 1985;89:55–59 31. Ladlow J, Hardie RJ: Cricopharyngeal achalasia in dogs. Compend Contin Educ Pract Vet 2000;22:750–755
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46. Gerber V, Schott Ii HC, Robinson NE: Owner assessment in judging the efficacy of airway disease treatment. Equine Vet J 2011;43:153–158 47. Hudson JT, Slater MR, Taylor L, et al: Assessing repeatability and validity of a visual analogue scale questionnaire for use in assessing pain and lameness in dogs. Am J Vet Res 2004;65:1634– 1643 48. Innes JF, Barr AR: Can owners assess outcome following treatment of canine cruciate ligament deficiency? J Small Anim Pract 1998;39:373–378
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APPENDIX A Laryngeal Paralysis—Follow‐Up Survey
Date of surgery:
Date of follow-up:
Owner’s Name:
Phone number:
Em ail :
Primary Veterinarian (address, phone, fax, email): Dog’s call name:
Sex: M F M/N F/S
Breed:
Age at me of surgery:
1.
Birth date (mm/dd/yy):
Weight (kg)
By what percentage would you say have the below listed problems improved aer surgery? Increased panng:
labored breathing: increased/harsh respiratory noise (stridor):
Has there been improvement of exercise tolerance aer surgery?
Yes
No
If yes, by what percentage would you say has this improved? _____% 2.
Has your dog collapsed aer surgery? Yes
No
3.
Was your dog admied to an emergency clinic due to a respiratory crisis aer surgery: Yes
4.
How would you rate your dog’s current quality of breathing on a scale from 1 to 10, with 1 being poor and 10 being excellent?
No
Focus on your dog’s breathing. Please discount other medical condions such as arthris or other organ disease. Current breathing quality (circle): 1 2 3 4 5 6 7 8 9 10 5.
Did you noce recurrence of breathing problems aer surgery?
Yes
No
If yes, at approximately what me aer surgery did you noce recurrence (in months)? What kind of recurrent signs did you noce? O increased panng; O labored breathing; O stridor; O other: 6.
If your dog had trouble eang /chewing or take longer to eat before surgery – did this improve since surgery? Yes
No
If yes, by what percentage? ____% 7.
If your dog regurgitated (bringing up food without stomach contracons) aer eang /drinking before surgery – did this improve since surgery? Yes
8.
No
If yes, by what percentage? ____%
If your dog showed O coughing; O gagging; or O throat-clearing during eang/drinking before surgery – did this improve since surgery? Yes No If yes, by what percentage? ____%
9.
Has your dog developed aspiraon pneumonia or been treated for pneumonia aer surgery? Yes
a.
If yes, when (days or months) was aspiraon pneumonia diagnosed? ________________
b.
If yes, how many episodes of pneumonia were diagnosed aer surgery? ______________
c.
If yes, how fast did clinical signs resolve (approximately in days or weeks)? ____________
No
10. Were you sasfied with the surgical outcome in your dog (circle)? Yes No 11. If no, please explain ________________________________________________________
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Veterinary Specialists of Alaska P.C., Anchorage, AK and East Lansing, Michigan
Corresponding Author Dirsko J.F. von Pfeil, Dr Med Vet, DVM, Diplomate ACVS, Diplomate ECVS, Veterinary Surgical Centers, 140 Park St SE, Vienna, VA 22180. E‐mail: [email protected] Submitted December 2012 Accepted December 2013 DOI:10.1111/j.1532-950X.2014.12151.x
2
Department of Small Animal Clinical Sciences, Michigan State University,
Objective: To (1) describe a modification of conventional unilateral cricoarytenoid lateralization (UCAL), called less‐invasive unilateral cricoarytenoid lateralization (LI‐UCAL) for treatment of idiopathic laryngeal paralysis (LP); (2) report clinical outcome of LI‐UCAL; and (3) describe the effect of early discharge after surgery. Study Design: Retrospective clinical study. Animals: Dogs (n ¼ 22). Methods: Medical records (January 2009 to October 2011) of dogs diagnosed with idiopathic LP that had LI‐UCAL were reviewed. Signalment, clinical signs, laboratory tests, imaging, concurrent medical conditions, information from the anesthesia record, and hospitalization time were documented. Follow‐up was obtained by direct examination, questionnaire, and review of medical records from referring veterinarians. Results: Dogs included in the study had variable degrees and duration of respiratory distress before surgery. Median surgery time was 32 minutes. Median hospitalization was 6 hours, and median follow‐up was 427 days. Long‐term respiratory function, as reported by owners at last follow‐up, improved in 95.5% of dogs after surgery; exercise tolerance improved by 90%. Major complications included death secondary to aspiration pneumonia (9%), aspiration pneumonia from which dogs recovered within 3 days after administration of antimicrobials (9%), and development of right‐sided laryngeal collapse that required right sided LI‐UCAL (4.5%). At long‐term follow‐up, 95.5% of owners were satisfied with the surgical outcome. Conclusion: LI‐UCAL is a feasible surgical technique and resulted in improvement of clinical signs related to LP. Calm recoveries without adverse effects such as respiratory distress were associated with early discharge. LI‐UCAL could be considered an alternative to conventional UCAL.
Idiopathic laryngeal paralysis (LP) has been thoroughly described and surgical unilateral cricoarytenoid lateralization (UCAL) is considered the standard of care for alleviating secondary airway obstruction.1–8 The original UCAL surgical approach involves a 7.5–10 cm long skin incision over the left side of the larynx.3 After soft tissue dissection, the entire thyropharyngeus muscle is transected, the cricoarytenoideus dorsalis muscle is dissected from its attachment on the muscular process of the arytenoid cartilage and the cricopharyngeus muscle is retracted or transected to allow separation of the cricoarytenoid and cricothyroid articulations and transection of the sesamoid band.3 Next, 2 strands of suture are placed around the caudal end of the thyroid cartilage and then through the muscular process of the arytenoid cartilage.3 This allows Presented in part at the Annual Symposium of the American College of Veterinary Surgeons in San Antonio, TX, 2013.
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abduction of the arytenoid cartilage and subsequent opening of the rima glottidis.3,4,6–9 Careful attention to detail should allow every surgeon to identify the nerves around the larynx and inadvertent severance of these nerves must be avoided. However, according to previous anatomic studies, complete transection of the thyropharyngeus and the cricopharyngeus muscles may jeopardize the cranial laryngeal nerve and its branches, the ramus anastomoticus, the caudal laryngeal, and the para‐recurrent nerves.10–16 Indeed, compromised laryngeal muscle function and a potentially increased risk of aspiration pneumonia has been suggested to occur as a result of thyropharyngeus muscle transection.17 A less invasive approach could better preserve the local neurovascular anatomy and reduce the risk for aspiration pneumonia while maintaining a favorable surgical outcome of UCAL. Sparing soft‐tissue‐structures such as the cricothyroid muscle18,19 or splitting the thyropharyngeus muscle along the
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direction of its muscle fibers have been suggested as means to minimize laryngeal muscle damage, thus preserving laryngeal function and sensation.17,20–22 Whereas disarticulation of the cricoarytenoid articulation, caudal retraction of the cricopharyngeus muscle, and placement of a single arytenoid abduction suture (AAS) have been advocated and described in vitro,16,21,23–26 studies evaluating the clinical outcome of these combined soft‐tissue‐sparing techniques17 have not been conducted. An additional challenge is achieving sufficient opening of the rima glottidis to improve airflow, while minimizing the risk of aspiration pneumonia associated with excessive opening of the rima glottidis.23–25,27–29 Furthering this idea, White and Monnet suggested that optimal opening of the rima glottidis could be achieved by placement of an endotracheal tube of the largest possible diameter, followed by minimal tension applied to the AAS.21,26 To our knowledge, clinical evaluation of these techniques has not been reported. Finally, there is controversy on the most appropriate time of discharge from the hospital after UCAL. Whereas some surgeons prefer to monitor patients for 1–3 days after surgery,3,4,8,9 others suggest earlier discharge.21 Results of a study investigating the effect of early discharge after UCAL are lacking. Thus our purposes were: (1) to describe a less invasive alternative technique to UCAL; (2) report the clinical outcome of this technique in 22 dogs; and (3) evaluate the effect of early discharge from the hospital. We hypothesized that this less invasive UCAL (LI‐UCAL) would provide adequate lateralization of the arytenoid cartilage, minimize postoperative morbidity, result in clinical outcome similar to that reported with conventional UCAL, and that dogs recover well when discharged soon after surgery.
MATERIAL AND METHODS Inclusion Criteria Medical records (January 2009 to October 2011) of dogs that had LI‐UCAL for treatment of LP were reviewed. All dogs were operated by 1 surgeon (D.V.P.). To be included in the study, the following information had to be available: signalment; body weight; clinical signs; duration of clinical signs; surgery‐, anesthesia‐, and hospitalization time; short‐ term follow‐up information obtained at our hospital or by the referring veterinarian; complications; and completed final questionnaire, including long‐term follow‐up information. Anesthesia Anesthesia was induced using propofol (4–6 mg/kg intravenously [IV]) to effect. Direct laryngoscopy was performed to confirm the diagnosis of LP. Dogs were intubated using the largest endotracheal tube that could be placed without damaging the larynx. After intubation, anesthesia was maintained using isoflurane in oxygen. Then acepromazine (0.5 mg/kg IV), butorphanol (0.2 mg/kg IV), atropine
Less Invasive Unilateral Arytenoid Lateralization in Dogs
(0.02 mg/kg IV), metoclopramide (0.2 mg/kg subcutaneously), dexamethasone‐SP (0.5 mg/kg IV), cefazolin (10 mg/kg IV), and Normosol‐R (22 mL/kg/hr IV) were administered. Surgical Procedure Dogs were positioned in right lateral recumbency with the neck extended and supported with a vacuum bag so that the left side of the larynx was facing upward and laterally. The thoracic limbs were retracted caudodorsally. After aseptic preparation, a 2–3 cm long skin incision, made immediately ventral and parallel to the jugular vein, was centered over the caudal edge of the cricoid cartilage. After connective tissue dissection including the platysma muscle, the thyropharyngeus muscle was exposed and then incised transversely to the direction of its muscle fibers over the area medial to the muscular process of the arytenoid cartilage along the dorsocaudal edge of the thyroid cartilage. The extent of the dissection line was limited to 25% of thyropharyngeus muscle length. A single stay suture of 2‐0 polyamide was inserted through the freed thyroid cartilage to facilitate ventrolateral retraction. The fascial membrane of the larynx was incised. Using bipolar electrosurgery, bundles of the frequently atrophied cricoarytenoideus dorsalis muscle were dissected as needed from the muscular process of the arytenoid cartilage to improve its exposure. Care was taken to remain as close to the muscular process as possible to minimize the risk of inadvertent damage to the surrounding soft tissue structures. A curved Halsted mosquito forceps was used to dissect the cricoarytenoid articulation, preserving the cricopharyngeus muscle. The caudodorsal aspect of the cricoid cartilage was palpated and a Kelly hemostatic forceps was used to create a small opening through the connective tissues at the dorsolateral cricotracheal junction. Although not visible during dissection, the anatomic structures bordering this area may aid the reader to understand the precise location of this opening. These borders include dorsally the esophagus, rostrally the cricopharyngeus muscle, and ventrally the sternothyroideus muscle. Caudally the opening was bordered by the ventral aspect of the esophagus and dorsal aspect of the sternothyroideus muscle. A Kelly hemostatic forceps was placed caudal to the edge of the cricoid cartilage with its tip pointing rostrally. The hemostat was then “hooked” behind the caudal edge of the cricoid cartilage. The swaged‐on taper needle of a 1 polypropylene suture was bent slightly to reduce its curvature. The needle was passed between the opened jaws of the preplaced Kelly hemostatic forceps and pushed craniolaterally to exit 2 mm caudal to the muscular process of the arytenoid cartilage. While passing the needle, care was taken to maintain the tip of the needle against the medial wall of the cricoid cartilage. This was done in an effort to minimize the risk for penetration of the laryngeal respiratory epithelium. The Kelly hemostatic forceps was removed and the area immediately caudal to the muscular process exposed. The suture was then driven through the center of the articular surface of the muscular process. This was facilitated by lifting the muscular process with a Brown‐Adson tissue forceps. A Senn retractor, placed cranial to the muscular
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Postoperative Follow‐Up
Figure 1 Tunneling of hemostat to grasp AAS. 1 ¼ intact cricopharyngeus muscle, 2 ¼ caudal end of the AAS. Note formation of loop before being grasped in an effort to reduce soft tissue damage when pulling rostrally. 3 ¼ stay suture, 4 ¼ thyropharyngeus muscle, 5 ¼ muscular process, 6 ¼ cranial end of AAS, 7 ¼ cricoarytenoideus dorsalis muscle.
process, was used to direct the tip of the needle laterally without incorporating surrounding soft tissue structures. A Kelly hemostatic forceps was used to create a tunnel underneath the cricopharyngeus muscle and its associated neurovascular bundle starting caudal to the muscular process and exiting at the caudodorsal edge of the cricoid cartilage. The free end of the AAS was then pulled rostrally through the tunnel (Fig 1). The suture ends were then pulled alternately to check for drag, which could be indicative of endotracheal tube entrapment. If entrapment was suspected, the endotracheal tube was moved by the anesthesiologist. If the surgeon felt movement of the AAS, it was removed and repositioned. A surgeon’s knot was used to tie the suture with minimal tension and 4 additional single interrupted knots were added. After lavage, routine closure with 3‐0 polyglactin 910, simple continuous pattern interrupted by Aberdeen knots, was used to conclude the procedure. The degree of left arytenoid cartilage abduction and patency of the rima glottidis were evaluated after surgery by direct laryngoscopy. Dogs were re‐intubated before anesthetic recovery. Postoperative Care After extubation, dogs were closely monitored for signs of respiratory distress. Dogs were released from the hospital as soon as possible—once ambulatory and showing normal breathing pattern. Postoperative medications included cefpodoxime (5–10 mg/kg orally once daily for 14 days) as preventative measure to decrease the risk of infection in these geriatric dogs and tramadol (1–4 mg/kg orally twice daily as needed for 5 days) for analgesia.
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Owners were contacted the day after discharge to check the status of the dog. Clinical re‐examination was performed 2 weeks postoperatively or earlier if necessary. During these conversations, owners were also asked whether they felt that their dogs had been anxious or calm the first days after surgery. At the time of final data collection, owners were contacted again and asked to complete a questionnaire and report on the improvement of clinical signs of their dogs (Appendix A). If the dog had died, owners were asked whether the cause of death was related to respiratory disease, whether clinical signs or a diagnosis of recurrence had been made before death, and whether they could still provide information listed in the questionnaire. Complications were recorded as major or minor. Major complications were defined as: (1) those requiring a 2nd laryngeal surgery; (2) infection; (3) aspiration pneumonia; and (4) death related to complications of the procedure. Aspiration pneumonia was defined as a radiographic alveolar pattern in the presence of clinical signs and supportive laboratory findings. Other complications were considered minor. Occasional coughing, gagging, throat‐clearing, and panting were not identified as complications because such behaviors are frequently encountered after UCAL and can be expected.3,5,9 Data Analysis Descriptive statistics (median, range, and percentage) were used to report data.
RESULTS Twenty‐two dogs (10 castrated and 2 intact males, 9 spayed and 1 intact female; median age, 12 years [range, 9–14 years], median weight, 35.2 kg [range, 14.1–53.6 kg]) fulfilled the inclusion criteria. There were 14 Labrador Retrievers (64%), 3 dogs of mixed breeding (13.5%), 2 Golden Retrievers (9%), 2 Brittany Spaniels (9%), and 1 Chesapeake Bay Retriever (4.5%). History and Clinical Findings Duration of respiratory distress varied between acute onset and progressive worsening over a period up to 17 months (mean, 6.1 months). Clinical signs included (1) exercise intolerance in 18 dogs (82%); (2) coughing, gagging, or throat clearing while eating in 6 dogs (27%); (3) slower than normal eating in 4 dogs (18%); and (4) mild occasional regurgitation of small amounts of food after eating in 2 dogs (9%). As reported by the owners, these 2 dogs had shown mild regurgitation for most of their lives, usually associated with exciting events, such as greeting the owner when he/she returned home after a longer time of absence, preparing for longer hikes, playing hard and rough, or when receiving rare treats. Thoracic radiographs of these dogs were normal. Before surgery, these 2 owners were informed about the increased risk for development of aspiration
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pneumonia and permanent tracheostomy was offered as a treatment. Both owners declined permanent tracheostomy but opted for LI‐UCAL. Acute episodes of collapse and cyanosis were reported in 9 dogs (41%). Six of these had been admitted to an emergency hospital before referral. The other 3 dogs were referred after they had recovered at home and been examined by a veterinarian. Before surgery, using a 1 (worse) to 10 (best) scale, clients subjectively rated the quality of breathing to be a median of 2 (range, 1–5). The main respiratory signs during pre‐surgical physical examination were stridor of variable severity in 22 dogs (100%), panting in 7 dogs (32%), and labored breathing in 7 dogs (32%).
Laboratory Tests and Diagnostic Imaging Preoperative hematologic and serum biochemical profiles (16 dogs; 73%) had no abnormalities. Preoperative thoracic radiographs (11 dogs; 50%) demonstrated a typical geriatric bronchointerstitial lung pattern, without evidence of aspiration pneumonia or megaesophagus. Perioperative Data All dogs had a laryngeal examination performed immediately after induction of anesthesia and before left‐sided LI‐UCAL. Findings were consistent with bilateral LP in all dogs. Additional surgical procedures were performed in 9 dogs (41%) and included excision of benign skin masses in 8 dogs. One dog was castrated after LI‐UCAL. Median surgery time for LI‐UCAL was 32 minutes (range, 24–64 minutes). Median total anesthesia time, including additional procedures was 95 minutes (range, 72–168 minutes). As expected, duration of anesthesia increased with the number of additional procedures. Endotracheal entrapment was not noted in any dog. Left arytenoid cartilage abduction and patency of the rima glottidis were judged appropriate in all dogs. Median hospitalization time was 6 hours (range, 4– 8 hours). Postoperative Clinical Evaluation Owners of all dogs (100%) were called the day after the surgery. Eighteen dogs (82%) were examined 2 weeks postoperatively at our clinic and the other 4 dogs (18%) were examined by the referring veterinarian. All owners reported calm recoveries without adverse effects such as respiratory distress. Compared to preoperative respiratory clinical signs, 19 dogs (86%) had marked improvement by 2 weeks, whereas increased frequency of coughing remained in 3 dogs (14%). By 4 weeks, coughing in these dogs had noticeably improved.
Outcome Median follow‐up was 427 days (range, 214–866 days). Six dogs (27%) died or were euthanatized for reasons unrelated to
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surgery at a median of 320 days after surgery (range, 183–762 days). Causes of death in these dogs included severe weakness and ataxia (2), sudden death without any prior signs of respiratory dysfunction (2), pancreatic neoplasia (1), nasal neoplasia, and simultaneous kidney failure (1). Fourteen dogs (64%) were alive at final follow‐up. Clinical signs as reported by the owner at last follow‐up or before death revealed that stridor, labored breathing, and panting had improved in 21 dogs (95.5%). One dog (4.5%; dog 13) had recurrence of stridor at 8 months and had associated relapse of decreased exercise tolerance; the owner declined further evaluation and treatment. Based on the same 1–10 scale used preoperatively, owners subjectively rated the quality of breathing at final follow‐up or before death to be a median of 8 (range, 2–10). None of the dogs collapsed or needed to be admitted to an emergency hospital for respiratory distress or cyanosis at any time after surgery. All 18 dogs that had exercise intolerance before surgery had improved exercise tolerance by 20–100% (median, 90%); 14 dogs (78%) had returned to 80–100% activity level. The owner of dog 13 reported that exercise improvement was 70–80% for the first 8 months after surgery, then declined to 20% (laryngeal examination and additional treatment were declined). The owners of the other 3 dogs (4, 11, 16) reported improvement of 50%, 60%, and 60%, respectively, but felt that osteoarthritis, not airway disease, was the major factor limiting exercise. The 6 dogs that had coughing, gagging, and throat clearing while eating before surgery showed improvement of these clinical signs (median, 80%; range, 20–90%) after surgery. Slow eating in the 4 dogs with this as an initial complaint improved (median, 85%; range, 60–95%). Improvement by 70% and 80%, respectively, was reported for the 2 dogs that had presurgical regurgitation. Major complications occurred in 5 dogs (22%). Four dogs (18%) developed aspiration pneumonia; 2 dogs (9%) died as a consequence at 346 and 858 days, respectively. One of these dogs was concurrently diagnosed with megaesophagus, which was not evident on preoperative radiographs. The other 2 dogs (9%) developed a cough secondary to aspiration pneumonia, confirmed on clinical examination and thoracic radiography by the referring veterinarian at 2 and 671 days postoperatively, respectively. Both dogs were administered clavamox (13.75 mg/kg orally twice daily) and clinical signs resolved within 3 days. One dog (4.5%) that developed right‐sided laryngeal collapse, associated with recurrent cough and marked stridor at 9 months, was treated with right‐sided LI‐UCAL, and clinical signs resolved. Minor complications consisting of recurrent, chronic cough were reported in 2 dogs (9%). One dog developed coughing episodes 2 months postoperatively; thoracic radiographs at 2 and 5 months did not reveal signs of pneumonia. Supportive treatment (hydrocodone, 0.2 mg/kg orally every 8 hours) was initiated and resolution of the cough occurred within 4 weeks. The other dog developed chronic cough 1 year postoperatively unassociated with pneumonia as confirmed by thoracic radiography. The owner declined further investigation
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or treatment because of the absence of signs other than cough. Dog 13 developed recurrence of stridor 8 months after surgery but the owners opted not to pursue further diagnostics so the cause was not identified. Overall, 21 owners (95.5%) reported they were satisfied with the surgical outcome at last follow‐up, and 1 owner (4.5%) of the 1 dog that developed recurrent stridor at 8 months was not satisfied.
DISCUSSION LI‐UCAL was developed in an effort to minimize regional soft tissue injury, to achieve appropriate rima glottidis opening, and to accomplish outcomes similar to previous reports on UCAL. Our findings demonstrate that those goals were achieved. Quality of breathing increased from a median of 2 (range, 1–5) before surgery to a median of 8 (range, 2–10) after surgery. Owners were satisfied with the surgical outcome in 95.5% of dogs. We attempted to implement previous recommendations to protect regional muscles and nerves during UCAL7,17,20 as follows. First, the transverse incision of the thyropharyngeus muscle was limited to 25% of its entire length. This muscle was neither retracted nor transected. Dysfunction of this muscle, possibly secondary to regional nerve damage, can result in dysphagia, regurgitation, aspiration, coughing, or cricopharyngeal achalasia.30,31 To prevent these possible complications, the innervation to the cricopharyngeus muscle, arising from the glossopharyngeal and branches of the vagus nerves32,33 should be preserved during laryngeal surgery. Splitting the thyropharyngeus muscle along its fibers17 may have been even less invasive but because of poor visualization when having attempted this technique in other cases, this was not performed. Second, based on previous anatomic descriptions,10–16 it can be hypothesized that additional regional nerve damage is minimized with LI‐UCAL. Protection of the intrinsic branches as well as the ramus anastomoticus of the cranial laryngeal nerve preserves the sensory supply to the laryngeal mucosa.12 Similarly, protection of the recurrent laryngeal nerve is essential as it not only innervates the laryngeal muscles but also receives sensory fibers from trachea, esophagus, and laryngeal mucosa.11–12 Finally, damage to the 1st cervical nerve16 may also be decreased during LI‐UCAL. Nerve velocity conduction and anatomic evaluation of nerve damage, performed in purpose bred dogs as part of a comparative laboratory study would be necessary to evaluate the potential benefits of LI‐UCAL compared to UCAL. Such investigations were beyond the scope of our clinical study. Third, the cricothyroid joint was preserved. Its disarticulation might increase the risk for laryngeal collapse27; however, it may facilitate more precise suture position.7,16 In our study, accurate suture placement was achieved while maintaining this joint’s integrity. We suggest cricothyroid joint disarticulation is not necessary during LI‐UCAL. Fourth, the sesamoid band was preserved to reduce the risk for esophageal injury and aspiration pneumonia3,7,25,27,28
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and because its transection neither significantly changes rima glottidis opening nor reduces airway pressure.25,28 Other less invasive surgical steps included an attempt to minimize the risk of laryngeal respiratory epithelium penetration to decrease airway irritation and potentially minimize webbing,1,34 as well as formation of a loop at the AAS‐end to prevent soft‐tissue injury during tunneling (Fig 1). We followed the recommendation to tie the AAS to a point that creates a final rima glottidis opening no larger than that with the endotracheal tube in place.26 This technique was practical and consistently provided adequate glottic opening, as determined by direct laryngoscopy. Its implementation may be beneficial, particularly since the importance of wide glottis opening in contrast to best arytenoid position has been questioned.17 Aspiration pneumonia has been reported in 0–33% of dogs after UCAL,3,4,7–9,20,36 although the true incidence may be higher.37 Major complication rates may even reach 58% when other surgical techniques are used to treat LP.26 It is possible that the soft‐tissue sparing steps of LI‐UCAL prevented such a high incidence of life‐threatening aspiration pneumonia in our dogs. Our overall incidence of aspiration pneumonia was 18%; 2 of these dogs (9%) developed mild aspiration pneumonia; neither required hospitalization and improved clinically within 3 days with no recurrence. Death secondary to aspiration pneumonia has been reported in up to 14%5 and occurred in 2 other dogs (9%) in our study. Just before death, 1 of these dogs was diagnosed with megaesophagus, a condition that has been associated with an increased mortality risk.5 Secondary megaesophagus is likely related to dysfunction of the para‐recurrent laryngeal nerves that supply the cervical and cranial thoracic esophagus.38–42 It is doubtful that the para‐recurrent nerve is endangered by either the standard UCAL or the LI‐UCAL surgical approach. Therefore, the low incidence of secondary megaesophagus in our study is likely not related to the surgical approach. Whereas esophageal contrast studies have been recommended to determine pre‐existing decreased esophageal function,9 the benefit of such a test in this dog would have been limited because the diagnosis of megaesophagus was established >2 years after LI‐UCAL. We believe that the risk for development of an acute life‐threatening respiratory emergency during presurgical esophagography because of the stress associated with this procedure or because of aspiration of contrast material is greater than the risk for development of possible post‐ surgical aspiration pneumonia. If pneumonia should occur, the prognosis seems favorable when treated in a timely fashion: 1 study showed that post‐surgical aspiration pneumonia was successfully treated in all cases.9 Idiopathic postoperative unilateral prosthesis failure after UCAL has been reported in 5% of cases.5 To decrease the risk of AAS failure, using 2 strands of 1 polypropylene suture and a horizontal mattress pattern have been suggested; however, it is unknown whether the tension required for failure of such suture (51 N) is generated in vivo.45 In addition, suture size, number and type were not associated with complications.5 Therefore and based on suggestions of others,23,24,26 we chose to use 1 single strand of 1 polypropylene suture. AAS failure was not
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diagnosed in any of our dogs, suggesting that use of 1 AAS strand is sufficient. Recurrence of stridor is reported in up to 33% of dogs after surgical treatment of LP.26 Causes include suspected prosthesis failure, development of regional neoplasia, right‐sided laryngeal collapse and webbing.5,34,43–45 In our study 2 dogs (9%) had recurrence of stridor. One of these was diagnosed with right‐sided laryngeal collapse and underwent successful right‐ sided LI‐UCAL. It is possible that this dog’s cartilage weakened over time. None of these dogs had been diagnosed with laryngeal collapse at initial examination; however, it cannot be ruled out that this developed after surgery. The owners of the other dog (13) opted not to pursue further diagnostics. As such, recurrence of stridor and associated decline in exercise tolerance in this dog could be associated to any of the causes listed above. Duration of hospitalization is often 1–3 days after laryngeal surgery3,4,8,9 and it has been suggested that earlier discharge of these frequently geriatric dogs may reduce postoperative stress.21,35 All of our dogs were discharged the day of surgery (median hospitalization, 6 hours), and owners consistently reported calm recoveries without adverse effects such as respiratory distress. Whereas recollection bias is possible, we believe that this risk is very low. Owners were contacted the day after surgery by telephone to ask about the status of their dogs and to remind them to inform us immediately if there should be any concerns. As such we do not believe that the reported calm recoveries are the result of bias, nor do we consider them incorrect. These observations suggest that LI‐UCAL could be performed as an outpatient procedure. Whereas direct comparison between this and previous retrospective reports is hindered by multiple different factors between studies (definition of complications, case numbers, amount and experience of surgeons, and collection of follow‐ up information),3–9,27 we feel that the complication rates and final outcome after LI‐UCAL are similar to those reported after conventional UCAL. Limitations of our study include its retrospective nature, small number of cases, subjective data obtained from owners, and lack of a control group. With the exception of 1 previous report,9 these are the same limitations as in all previous studies on UCAL.3,4,7,8,24 Preoperative blood work and radiographs were not available for all dogs because some presented in severe respiratory distress. Performing these diagnostics may have resulted in potential life‐threatening airway obstruction. Conducting a telephone interview for final follow‐up had limitations because of the subjective opinion of the owner. This effect was reduced by inclusion of objective referring veterinarian information. In addition, it has been shown that owner’s assessment of clinical signs and outcome of treatment, including assessment of breathing quality, can be very accurate.46–48 We conclude that LI‐UCAL results in appropriate airway opening, resolution of clinical signs, as well as clinical outcome similar to previous reports on UCAL. Early discharge from the hospital after LI‐UCAL does not seem to be associated with complications. We suggest LI‐UCAL is a feasible technique to treat LP.
Less Invasive Unilateral Arytenoid Lateralization in Dogs
ACKNOWLEDGMENT We thank Kenneth Harkin, DVM, Diplomate ACVIM (Kansas State University), Nelson Priddy II, DVM, Diplomate ACVS (Anchorage), Colette Marshall (Anchorage) for editorial help as well as Dr. Bryden J. Stanley, BVMS, MACVSc, MVetSc, Diplomate ACVS (Michigan State University), and Michele C. Fritz, BSc, LVT (Michigan State University) for assistance with development of the questionnaire.
DISCLOSURE The authors report no financial or other conflicts related to this report.
REFERENCES 1. Harvey CE, Venker‐van Haagen AJ: Surgical management of pharyngeal and laryngeal airway obstruction in the dog. Vet Clin North Am 1975;5:515–535 2. Gaber CE, Amis TC, Lecouteur RA: Laryngeal paralysis in dogs: a review of 23 cases. J Am Vet Med Assoc 1985;86:377–380 3. La Hue TR: Treatment of laryngeal paralysis in dogs by unilateral cricoarytenoid laryngoplasty. J Am Anim Hosp Assoc 1989;25:317–324 4. White RAS: Unilateral arytenoid lateralization: an assessment of technique and long term results in 62 dogs with laryngeal paralysis. J Small Anim Pract 1989;30:543–549 5. MacPhail CM, Monnet E: Outcome and postoperative complications in dogs undergoing surgical management of laryngeal paralysis: 140 cases (1992–2000). J Am Vet Med Assoc 2001;218:1949–1956 6. Snelling SR, Edwards GA: A retrospective study on unilateral arytenoid lateralization in the treatment of laryngeal paralysis in 100 dogs (1992–2000). Aust Vet J 2003;81:464–468 7. Demetriou JL, Kirby BM: The effect of two modifications of unilateral arytenoid lateralization on rima glottidis area in dogs. Vet Surg 2003;32:62–68 8. Weinstein J, Weisman D: Intraoperative evaluation of the larynx following unilateral arytenoid lateralization for acquired idiopathic laryngeal paralysis in dogs. J Am Anim Hosp Assoc 2010;46:241–248 9. Stanley BJ, Hauptman JG, Fritz MC, et al: Esophageal dysfunction in dogs with idiopathic laryngeal paralysis: a controlled cohort study. Vet Surg 2010;39:139–149 10. Bowden REM, Scheuer JL: Comparative studies of the nerve supply of the larynx in eutherian mammals. Proc Zool Soc London 1961;136:325–330 11. Lemere F: Innervation of the larynx; I. Innervation of laryngeal muscles. Am J Anat 1932;51:417–437 12. Lemere F: Innervation of the larynx; II. Ramus anastomoticus and ganglion cells of the superior laryngeal nerve. Anat Rec 1932;54:389 13. Lemere F: Innervation of the larynx; III. Experimental paralysis of the laryngeal nerves. Arch Otolaryngol 1933;18:413–424
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14. Pressman JL, Kelemen G: Physiology of the larynx. Physiol Rev 1955;35:506–554 15. Vogel PH: The innervation of the larynx of man and the dog. Am J Anat 1952;90:427–447 16. Monnet E: Laryngeal paralysis and devocalization, in Slatter D (ed): Small animal surgery (ed 3). Philadelphia, PA, Saunders, 2003, pp 837–845 17. White RAS: Canine laryngeal surgery: time to rethink? Vet Surg 2009;38:432–433 18. Konrad HR, Rattenborg CC: Combined action of laryngeal muscles. Acta Oto‐Laryngol 1967;67:646–649 19. Burbridge HM: A review of laryngeal paralysis in dogs. Br Vet J 1995;151:71–82 20. Burbridge HM, Goulden BE, Jones BR: Laryngeal paralysis: an evaluation of the bilateral arytenoid lateralization procedure. J Sm Anim Pract 1993;34:515–519 21. White RAS, Monnet E: The larynx, in Brockman DJ, Holt DE (eds): BSAVA manual of canine and feline head, neck and thoracic surgery. Quedgely, Gloucester, British Small Animal Veterinary Association, 2005, pp 94–104 22. Nelissen P, White RAS: Arytenoid lateralization for management of combined laryngeal paralysis and laryngeal collapse in small dogs. Vet Surg 2012;41:261–265 23. Bureau S, Monnet E: Effect of suture tension and surgical approach during unilateral arytenoid lateralization on the rima glottidis in the canine larynx. Vet Surg 2002;31:589–595 24. Greenberg MJ, Bureau S, Monnet E: Effect of suture tension during unilateral cricoarytenoid lateralization on canine laryngeal resistance in vitro. Vet Surg 2007;36:526–532
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32. Smith Hammond C, Davenport PW, Hutchison A, et al: Motor innervation of the cricopharyngeus muscle by the recurrent laryngeal. J Appl Physiol 1997;83:89–94 33. Hermanson JW, Evans HE: The muscular system, in Evans HE (ed): Miller’s anatomy of the dog (ed 3). Philadelphia, PA, Saunders, 1993, pp 296–297 34. Mehl ML, Kyles AE, Pypendop BH, et al: Outcome of laryngeal web resection with mucosal apposition for treatment of airway obstruction in dogs: 15 cases (1992–2006). J Am Vet Med Assoc 2008;233:738–742 35. Fingeroth JM: Canine laryngeal paralysis. Part 2. DVM Newsmagazine/dvm 360.com, 2011; August:10S,12S 36. Greenberg MJ, Reems MR, Monnet E: Use of perioperative metoclopramide in dogs undergoing surgical treatment of laryngeal paralysis: 43 cases (1999–2006). Vet Surg 2007;36:513– 608,E11 (abstr) 37. Hammel SP, Hottinger HA, Novo RE: Postoperative results of unilateral arytenoid lateralization for treatment of idiopathic laryngeal paralysis in dogs: 39 cases (1996–2002). J Am Vet Med Assoc 2006;228:1215–1220 38. Evans HE: The respiratory system, in Evans HE (ed): Miller’s anatomy of the dog (ed 3). Philadelphia, PA, Saunders, 1993, pp 463–493 39. Evans HE: The digestive apparatus and abdomen, in Evans HE (ed): Miller’s anatomy of the dog (ed 3). Philadelphia, PA, Saunders, 1993, pp 385–462 40. Negus VE: The comparative anatomy and physiology of the larynx. London, William Heinemann Medical Books Ltd., 1949 41. Stavroulaki P, Birchall M: Comparative study of the laryngeal innervation in humans and animals employed in laryngeal transplantation research. J Laryngol Otol 2001;115:257–266
25. Wignall JR, Baines SJ: Effects of unilateral arytenoid lateralization technique and suture tension on airway pressure in the larynx of canine cadavers. Am J Vet Res 2012;73:917– 924
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26. Monnet E, Tobias KM: Larynx, in Tobias KM, Johnston SA (eds): Veterinary surgery small animal. St. Louis, MO, Elsevier, 2012, pp 1724–1729
43. Salisbury SK, Forbes S, Blevins WE: Peritracheal abscess associated with tracheal collapse and bilateral laryngeal paralysis in a dog. J Am Vet Med Assoc 1990;196:1273–1275
27. Lozier S, Pope E: Effects of arytenoid abduction and modified castellated laryngofissure on the rima glottidis in canine cadavers. Vet Surg 1992;21:195–200
44. Klein MK, Powers BE, Withrow SJ, et al: Treatment of thyroid carcinoma in dogs by surgical resection alone: 20 cases (1981– 1989). J Am Vet Med Assoc 1995;206:1007–1009
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APPENDIX A Laryngeal Paralysis—Follow‐Up Survey
Date of surgery:
Date of follow-up:
Owner’s Name:
Phone number:
Em ail :
Primary Veterinarian (address, phone, fax, email): Dog’s call name:
Sex: M F M/N F/S
Breed:
Age at me of surgery:
1.
Birth date (mm/dd/yy):
Weight (kg)
By what percentage would you say have the below listed problems improved aer surgery? Increased panng:
labored breathing: increased/harsh respiratory noise (stridor):
Has there been improvement of exercise tolerance aer surgery?
Yes
No
If yes, by what percentage would you say has this improved? _____% 2.
Has your dog collapsed aer surgery? Yes
No
3.
Was your dog admied to an emergency clinic due to a respiratory crisis aer surgery: Yes
4.
How would you rate your dog’s current quality of breathing on a scale from 1 to 10, with 1 being poor and 10 being excellent?
No
Focus on your dog’s breathing. Please discount other medical condions such as arthris or other organ disease. Current breathing quality (circle): 1 2 3 4 5 6 7 8 9 10 5.
Did you noce recurrence of breathing problems aer surgery?
Yes
No
If yes, at approximately what me aer surgery did you noce recurrence (in months)? What kind of recurrent signs did you noce? O increased panng; O labored breathing; O stridor; O other: 6.
If your dog had trouble eang /chewing or take longer to eat before surgery – did this improve since surgery? Yes
No
If yes, by what percentage? ____% 7.
If your dog regurgitated (bringing up food without stomach contracons) aer eang /drinking before surgery – did this improve since surgery? Yes
8.
No
If yes, by what percentage? ____%
If your dog showed O coughing; O gagging; or O throat-clearing during eang/drinking before surgery – did this improve since surgery? Yes No If yes, by what percentage? ____%
9.
Has your dog developed aspiraon pneumonia or been treated for pneumonia aer surgery? Yes
a.
If yes, when (days or months) was aspiraon pneumonia diagnosed? ________________
b.
If yes, how many episodes of pneumonia were diagnosed aer surgery? ______________
c.
If yes, how fast did clinical signs resolve (approximately in days or weeks)? ____________
No
10. Were you sasfied with the surgical outcome in your dog (circle)? Yes No 11. If no, please explain ________________________________________________________
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