Veterinary Anaesthesia and Analgesia, 2014, 41, 319–324
doi:10.1111/vaa.12122
CASE REPORT
Retrospective clinical evaluation of ultrasound guided transverse abdominis plane block in dogs undergoing mastectomy Diego A. Portela*, Marta Romano*† & Angela Briganti* *Department of Veterinary Sciences, Veterinary Teaching Hospital “Mario Modenato”, University of Pisa, San Piero a Grado, Italy †Clinica Veterinaria Apuana, Marina di Carrara, Italy
Correspondence: Dr. Diego A. Portela, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401, USA. E-mail: [email protected]
Abstract History Eleven female dogs of different breeds undergoing unilateral radical (n = 7) or regional abdominal mastectomy (n = 4) received an ultrasound guided transverse abdominis plane block (TAP-block). Physical examination Subjects showed single or multiple mammary tumours. Serum biochemistry, CBC and electrocardiogram were unremarkable. Eight animals were classified as ASA physical status II and 3 as ASA III. Management Dogs were premedicated with methadone [0.1 or 0.2 mg kg 1 intravenously (IV) or intramuscularly respectively] or fentanyl (2.5 lg kg 1 IV). Anaesthesia was induced with propofol and maintained with isoflurane or sevoflurane. Unilateral ultrasound guided TAP blocks were performed in the caudal and cranial abdomen with bupivacaine 0.25% (0.3 to 0.35 mL kg 1). Intercostal nerve blocks (T4 to T11) with bupivacaine 0.25% (0.013 to 0.04 mL kg 1) completed the blocked area in dogs undergoing radical mastectomy. Follow up The median (range) of end-expired isoflurane and sevoflurane necessary to maintain anaesthesia was 1.15 (1.07–1.22) and 2.07 (2.05–2.2) vol% respectively. A single administra-
tion of fentanyl (2.5 lg kg 1, IV) was administered to control nociception (defined as an increased heart rate or mean arterial blood pressure above 20% of the pre-incisional value) in four of 11 dogs. All dogs received carprofen (2 mg kg 1 subcutaneously) at the end of surgery. Post-operative pain, assessed for 120 minutes using the short form of Glasgow Composite Pain Scale (0–24), was always lower than 3. No rescue analgesia (allowed by the protocol) was required in this time. Conclusion Transverse abdominis plane block combined with intercostal nerve blocks may be useful to produce intraoperative anti-nociception and short term post-operative analgesia in dogs undergoing unilateral mastectomy. Keywords cancer pain, dog, mastectomy, regional anaesthesia, TAP block, ultrasound.
Introduction Transverse abdominis plane block (TAP block) is a regional anaesthetic technique used to provide local anaesthesia/analgesia to the abdominal wall in a wide range of human surgical procedures (Abdallah et al. 2012). Schroeder et al. (2010) reported the first clinical use of the TAP block in a Canadian Lynx and later in dogs under experimental conditions (Schroeder et al. 2011). 319
TAP block for mastectomy in dogs DA Portela et al.
Ventral branches of T11, T12, T13, L1, L2, and L3 spinal nerves supply innervation to the abdominal wall in dogs (Hermanson 2012). These nerves run distally into the fascial plane formed by the internal abdominal oblique muscle and the transversus abdominis muscle, supplying innervation to abdominal muscles, subcutaneous tissues, mammary glands, skin and the underling parietal peritoneum (Evans & de Lahunta 2010). Mastectomy is performed routinely in dogs suffering from mammary tumours. Many such dogs are old, and anaesthetic morbidity may increase with increasing age, due to decline in the organ function reserve. The additional use of regional anaesthesia may improve the outcome of surgical and anaesthetic procedures by reducing the amount of general anaesthetics and analgesics required (Kettner et al. 2011). Radical unilateral resection of the mammary gland is associated with high-level of perioperative stress and pain, which could enhance the morbidity associated to anaesthesia and surgery (Nakagawa et al. 2007). The present preliminary case series investigates the efficacy of ultrasound guided TAP block alone or combined to intercostal nerve blocks for regional abdominal or radical mastectomy respectively in dogs affected by mammary tumours. Case History Anaesthetic records of female dogs that had undergone unilateral radical mastectomy or regional abdominal mastectomy referred to the anaesthesia service of the Veterinary Teaching Hospital “Mario Modenato” – University of Pisa (VTHMM) and the Clinica Veterinaria Apuana (CVA) in the period of time between May 2012 and February 2013 were reviewed. Complete anaesthetic records of dogs that received ultrasound guided TAP block alone or combined to intercostal nerve blocks as analgesic protocol for unilateral regional abdominal or radical mastectomy were selected for the present study. Records of cases submitted to mastectomy combined to ovariohysterectomy were excluded from the analysis. Eleven anaesthetic records matched the inclusion criteria, five in the VTHMM and six in the CVA. Dogs were of different breeds, weighed 2.5 to 45 kg (median 25 kg) and were 7 to 16 (median 11) years old. Radical unilateral mastectomy and regional abdominal mastectomy were performed in seven and four cases respectively. 320
Physical examination, complete blood count, serum biochemistry profile and electrocardiogram were performed in all subjects in the days prior to surgery. Eight dogs were classified as ASA physical status II and 3 as ASA III. Dogs in which heart murmurs (n = 3) could be heard at auscultation were submitted to echocardiographic examination and were all diagnosed with mitral valve endocardiosis. One of these dogs had received benazepril for two weeks prior to surgery, which was discontinued for the 24 hours before anaesthesia/surgery. As standard practice in both institutions, written detailed owner consent was obtained before performing anaesthesia and surgery in all dogs. Management Food but not water was withheld for approximately eight hours prior to the scheduled time of surgery. An intravenous (IV) catheter was placed in a cephalic vein for administration of fluids and drugs. All dogs received an opioid drug as anaesthetic premedication (Table 1). General anaesthesia was induced with a constant rate infusion of propofol (1.5 mg kg 1 minute 1, IV [Propofol Kabi 20 mg mL 1, Fresenius Kabi S.r.l., Italy]) using a syringe pump until orotracheal intubation was possible (total dose: 3.2 to 5.7 mg kg 1 IV). The endotracheal tube was then connected to a circle rebreathing system, and an oxygen/air mixture was delivered aiming to maintain a FiO2 > 60%. Respiratory rate and tidal volume were mechanically controlled (Ohmeda Ventilatore D’Anestesia 7750, UK; Datex-Ohmeda Aespire View, GE Healthcare, PA, USA; Multiflow 2002 Anaesthesia Ventilator, Hallowell EMC, MA, USA) during the entire procedure in order to maintain an end-tidal carbon dioxide (PE′CO2) between 35 and 45 mmHg (4.6 and 5.9 kPa). General anaesthesia was maintained with isoflurane (n = 9) or sevoflurane (n = 2). Warm lactated Ringer’s solution was administered (2.5 to 5 mL kg 1 hour 1 IV) throughout surgery. Body temperature was maintained above 37 °C using electrically heated and thermal foil blankets. An arterial catheter was placed in a dorsal pedal artery to monitor invasive arterial blood pressure throughout the procedure. Throughout the entire anaesthetic procedure, heart rate (HR), invasive mean arterial pressure (iMAP), PE′CO2, end-tidal isoflurane or sevoflurane (FE′ISO/FE′SEVO), oesophageal temperature, oxygen saturation (SpO2) and a lead II electrocardiogram
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
TAP block for mastectomy in dogs DA Portela et al. Table 1 Premedication and intraoperative rescue analgesia given to dogs submitted to radical or regional unilateral mastectomy that received ultrasound TAP block as analgesic protocol
Case Case Case Case Case Case Case Case Case Case Case
1* 2* 3* 4* 5* 6† 7† 8† 9† 10† 11†
Surgery
Premedication
Radical mastectomy Regional mastectomy Regional mastectomy Radical mastectomy Radical mastectomy Radical mastectomy Regional mastectomy Regional mastectomy Radical mastectomy Radical mastectomy Radical mastectomy
Methadone 0.2 mg Methadone 0.2 mg Methadone 0.2 mg Fentanyl 2.5 lg kg Fentanyl 2.5 lg kg Methadone 0.1 mg Methadone 0.1 mg Methadone 0.1 mg Fentanyl 2.5 lg kg Fentanyl 2.5 lg kg Fentanyl 2.5 lg kg
Intraoperative rescue analgesia kg 1, IM kg 1, IM kg 1, IM 1 , IV‡ 1 , IV‡ kg 1, IV kg 1, IV kg 1, IV 1 , IV 1 , IV 1 , IV
Fentanyl 2.5 lg kg 1, IV
Fentanyl 2.5 lg kg 1, IV
Fentanyl 2.5 lg kg 1, IV Fentanyl 2.5 lg kg 1, IV
*Cases referred to the Veterinary Teaching Hospital “Mario Modenato” – University of Pisa. †Cases referred to the Clinica Veterinaria Apuana. ‡Given 2 minutes before induction of general anesthesia.
were monitored continuously and recorded every five minutes. During surgery, fentanyl (2.5 lg kg 1, IV [Fentanest Pfizer Italia S.r.l., Italy]) was administered to control nociceptive responses defined as an increase of HR and/or MAP above 20% of the preincisional value. Multiparametric monitors (Mindray Beneview T5, China; Criticare Poet Plus 8100, WI) were used to measure the parameters described above. For iMAP measurements, a pre-calibrated transducer was zeroed to atmospheric pressure and positioned at the level of the left atrium. The entire abdominal wall was clipped and the skin of the abdominal flank was surgically prepared. Dogs were laid in lateral recumbency with the side to be blocked uppermost. A portable ultrasound machine (Venue 40, GE Medical Systems, China [used at the VTHMM] and a MyLabTM70 XVision Esaote, Italy [used at the CVA]) with a 12 MHz linear array transducer was used to identify the transverse abdominis plane and perform the TAP block as described elsewhere (Schroeder et al. 2011). Briefly, the US transducer was positioned in the dorsal abdominal flank, perpendicularly to the body long axis, cranially to the iliac crest (Fig. 1a). The transducer was slid gently until the three layers of the abdominal wall were identified (Fig. 2a). A 22 gauge, 90 mm spinal needle (Spinale Quincke, PicIndolor, Artesana S.p.A., Italy), connected to a 10 cm-long tubular extension prefilled with the local anaesthetic, was inserted with a dorso-ventral direction, perpendicular to the body long axis, using an “in-plane” technique (Fig. 1a). Thus the needle tip was advanced under ultrasound
guidance throughout the external layers of the abdominal wall towards the fascial plane between the internal abdominal oblique and transversus abdominis muscles (TAP space). Bupivacaine 0.25%, (Marcaina 5 mg mL 1; AstraZeneca S.p.A., Italy, diluted 1:1 with NaCl) 0.3 to 0.35 mL kg 1, was injected in each TAP block point. All dogs of this series received two TAP blocks, one in the caudal part of the middle abdominal region, cranially to the iliac crest and a second one in the cranial part of the middle abdominal region, caudally to the last rib (L5-L6 and L2-L3 intervertebral level respectively) (Fig. 1b). In case of radical unilateral mastectomy (n = 5), T4 to T12 intercostal nerves were blocked with bupivacaine 0.25% (0.03 to 0.04 mL kg 1) using a blind intercostal nerve block approach (Skarda & Tranquilli 2007). Cases submitted to complete mastectomy therefore received a total 0.25% bupivacaine volume of 0.87 to 1.06 mL kg 1 (2 TAP blocks + 9 intercostal blocks), which corresponds to a total dose of 2.1 to 2.6 mg kg 1. At the end of the procedure, carprofen (2 mg kg 1, subcutaneously, every 24 hours) was administered to all dogs. The short form of the Glasgow Composite Pain Scale (SF-GCPS) was used to assess pain scores in the post-anaesthetic period during 120 minutes after extubation (Reid et al. 2007). If pain score was above 5 out of 24, methadone (0.3 mg kg 1, IM) was administered as rescue analgesia. The transverse abdominal muscle and the internal abdominal oblique were visualized without problems
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
321
TAP block for mastectomy in dogs DA Portela et al.
(a)
(a)
(b)
(b)
Figure 1 Transverse abdominis plane (TAP) block in a dog. (a) A spinal needle is introduced through the lateral abdominal wall under ultrasound guidance using an “inplane” technique. (b) Schemathic representation of the US trasducer positioning (rectangular black figures) and the injection points to perform TAP blocks in the caudal and cranial abdomen and intercostal nerves blocks. The arrows represent the needle orientation. Black circles represent the intercostal nerve blocks.
in all dogs. The local anaesthetic injections caused the hydrodissection (separation of the muscular layers) of the TAP space (Fig. 2b) in all the cases. The elapsed time between TAP block and the beginning of surgery ranged from 10 to 45 (median 30) minutes. In all dogs FE′ISO or FE′SEVO was maintained below 1.3 (median: 1.15, range:1.07–1.22) vol% and 2.3 (median: 2.07, range 2.05–2.2)% respectively during the entire procedure (Fig. S1). No alterations in the cardiac rhythm were registered and mean arterial blood pressure remained between 60 and 95 mmHg in all dogs (Fig. S2). Anticholinergic, inotropic or vasoactive drugs were not required to support cardiovascular function in any case. In seven out of 11 cases fentanyl was not required during surgery. Four dogs required intraoperative rescue analgesia: cases 2, 5 and 10 during the ligation of the inguinal canal vessels; and case 8 at the level of the caudal thoracic 322
Figure 2 Ultrasonographic image of the muscular layers forming the abdominal wall in a dog. The ultrasound trasducer is positioned perpendicularly to the body long axis in the dorsal abdominal flank. (a) EO, external abdominal oblique muscle; IO, internal abdominal oblique muscle; TA, transversus abdominis muscle; P, peritoneum. (b) Local anaesthetic (LA) injected into the fascial plane between the internal abdominal oblique (IO) and transversus abdominis muscles (TA) using a spinal needle.
mammary gland (Table 1). In all four cases a single bolus of fentanyl (2.5 lg kg 1) was administered. Surgery time ranged from 25 to 65 (median 50) minutes. Recovery from anaesthesia was smooth and no complications were recorded. Ability to walk unassisted was regained in 15 to 45 (median 35) minutes after extubation. None of the dogs showed sings of discomfort after applying a gentle pressure on the wound zone and pain scores remained below 3 during the 120 minutes of post-operative evaluation. After that period, all dogs received methadone (0.3 mg kg 1 intramuscularly every 4–6 hours) for post-operative analgesia. Patients at the VTHMM were dismissed to the intensive care unit and discharged home around 30 hours after surgery, while those referred to the CVA were discharged home at least six hours after surgery. No complications related to the anaesthetic or surgical procedures were noted in the two weeks follow-up period in any patient. Discussion From our study, ultrasound TAP block provided intraoperative antinociception and post-operative
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
TAP block for mastectomy in dogs DA Portela et al. short-term analgesia in dogs undergoing unilateral regional mastectomy. Intercostal nerve blocks need to be combined with TAP block in order to supplement regional anaesthesia in dogs undergoing radical unilateral mastectomy. However, fentanyl might still be necessary to control nociception when structures contained in the inguinal canal are ligated. In female dogs, the inguinal canal contains the vaginal process (eversion of the peritoneum), external pudendal vessels, fat and the genitofemoral nerve, which arises from the 3rd lumbar nerve (Hermanson 2012). It is probable that the nociceptive response during ligation of this structure could be due to the lack of genitofemoral nerve blockade or to a visceral nociceptive component of the vaginal process. It is important to consider that TAP block only provides regional anaesthesia and analgesia of the abdominal wall with no effect on visceral components. Case 8 showed signs of nociception when the surgery involved the caudal thoracic mammary gland. The latter receives its nerve supply from the lateral cutaneous branches of the 6th and 7th thoracic nerves (Evans & de Lahunta 2012); therefore, the response, successfully controlled with a single dose of fentanyl (2.5 lg kg 1, IV), was probably due to a failure of the intercostal nerve block rather than TAP block. Methadone and fentanyl, administered as preanaesthetic medications, could have also produced antinociception and therefore participate in limiting the intraoperative fentanyl consumption. Considering their pharmacokinetics in dogs (Sano et al. 2006; Steagall et al. 2006; Credie et al. 2010; IngvastLarsson et al. 2010) and according to our clinical experience it is unlikely that at the doses used methadone and fentanyl produce such a degree of antinociception and post-operative analgesia. However, a prospective study including a control group could be useful to better assess the antinocieptive efficacy of the TAP block in dogs. The execution of a single TAP block at midway between the iliac crest and the caudal aspect of the last rib using bupivacaine-dye solution (10 mL) in 10 beagle cadavers (11.1 1.1 kg) resulted in 60%, 100%, 100% and 90% staining of T12, T13, L1 and L2, respectively. Nerve roots T11 and L3 were stained in 20% and 30% of the cadavers (Schroeder et al. 2011). In order to try to increase the percentage of blocking T11 and L3 we decided to use two injection sites: one in the caudal and one in the cranial aspect of the middle abdominal region (Fig. 1b). As the volume to be injected was relatively
high, 0.25% bupivacaine was used in order to avoid possible local anaesthetic toxicity. Although, the total bupivacaine dose was close to, or even higher than the maximal recommended dose for dogs in some textbooks (i.e. 1.5 to 3 mg kg 1) (Hellyer et al. 2007), it remained under the toxic dose (i.e. 5 mg kg 1) reported in dogs (Liu et al. 1983). Although no cardiovascular or neurologic complications were observed in the cases reported here, the clinician must be aware of the total administered dose in order to avoid potential complications related to local anaesthetic toxicity. It is possible that lower bupivacaine concentrations (e.g. 0.125%) could still provide a good analgesic effect (Abdallah et al. 2012; Thackeray et al. 2013), however further studies are required to confirm this hypothesis. During the first two post-operative hours the animals studied did not show any signs of pain as no reaction was elicited following palpation of the surgical wound and SF-GCPS was always lower than 3. In human, post-operative pain delays recovery time, return to normal activities and depresses the immune system (Desborough 2000). Stress associated to surgery and post-operative pain could increase the incidence of cancer recurrence or distant metastasis in humans undergoing breast cancer surgery (Exadaktylos et al. 2006). At the moment we don’t know if this is applicable to dogs undergoing mastectomy, however TAP block with or without intercostals nerve block might be considered to provide antinociception and postoperative analgesia in such animals. In summary, these preliminary evaluations suggest that the TAP block might be effective to provide regional anaesthesia and analgesia to the abdominal wall in dogs undergoing unilateral mastectomy. TAP blocks should be combined with intercostal nerve blocks in dogs undergoing radical unilateral mastectomy. It is probable that TAP block will reduce the amount of systemic analgesic requirements in a balanced multimodal analgesic protocol. Prospective controlled studies are required to: 1) define the minimal local anaesthetic dose and concentration necessary to promote an efficient regional block; 2) to establish if postoperative opioid consumption could be reduced by adding a TAP block to a multimodal analgesic protocol; 3) to determine the role of regional anaesthesia in perioperative stress response and cancer recurrence after regional or radical mastectomy in dogs.
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
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Acknowledgment Authors would like to thank Prof. Gloria Breghi and Dr. Luciano Borghetti for supporting this study. References Abdallah FW, Chan VW, Brull R (2012) Transversus abdominis plane block: a systematic review. Reg Anesth Pain Med 37, 193–209. Credie RG, Teixeira Neto FJ, Ferreira TH et al. (2010) Effects of methadone on the minimum alveolar concentration of isoflurane in dogs. Vet Anaesth Analg 37, 240–249. Desborough JP (2000) The stress response to trauma and surgery. Brit J Anaesth 85, 109–117. Evans HE, de Lahunta A (2010) The abdomen, pelvis, and pelvic limb. In: Guide to the Dissection of the Dog. 7th edn). Evans HE, de Lahunta A, (ed). Saunders, Elsevier Inc, Philadelphia. pp. 136–207. Evans HE, de Lahunta A (2012) The urogenital system. In: Miller’s Anatomy of the Dog - (4th edn). Evans HE, de Lahunta A (eds). Elsevier - Saunders, Missouri. pp. 361– 405. Exadaktylos AK, Buggy DJ, Moriarty DC et al. (2006) Can anesthetic technique for primary breast cancer surgery affect recurrence or metastasis? Anesthesiology 105, 660–664. Hellyer PW, Robertson SA, Fail AD (2007) Pain and its managment. In: Lumb & Jones’ Veterinary Anesthesia – (4th edn). Thurmon JC, Tranquilli WJ, Benson GJ (eds). Blackwell Publishing Ltd, Iowa. pp. 31–57. Hermanson JW (2012) The muscular system. In: Miller’s Anatomy of the Dog - (4th edn). Evans HE, de Lahunta A (eds). Elsevier - Saunders, Missouri. pp. 185–280. Ingvast-Larsson C, Holgersson A, Bondesson U et al. (2010) Clinical pharmacology of methadone in dogs. Vet Anaesth Analg 37, 48–56. Kettner SC, Willschke H, Marhofer P (2011) Does regional anaesthesia really improve outcome? Brit J Anaesth. 107 (suppl 1), 90–95. Liu PL, Feldman HS, Giasi R et al. (1983) Comparative CNS toxicity of lidocaine, etidocaine, bupivacaine, and tetracaine in awake dogs following rapid intravenous administration. Anesth Analg 62, 375–379. Nakagawa K, Miyagawa Y, Takemura N et al. (2007) Influence of preemptive analgesia with meloxicam before resection of the unilateral mammary gland on
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postoperative cardiovascular parameters in dogs. J Vet Med Sci 69, 939–944. Reid J, Nolan A, Hughes J et al. (2007) Development of the short-form Glasgow Composite Measure Pain Scale (CMPS-SF) and derivation of an analgesic intervention score. Anim Welf 16, 97–104. Sano T, Nishimura R, Kanazawa H et al. (2006) Pharmacokinetics of fentanyl after single intravenous injection and constant rate infusion in dogs. Vet Anaesth Analg 33, 266–273. Schroeder CA, Schroeder KM, Johnson RA (2010) Transversus abdominis plane block for exploratory laparotomy in a Canadian lynx (Lynx canadensis). J Zoo Wildl Med 41, 338–341. Schroeder CA, Snyder LBC, Tearney CC et al. (2011) Ultrasound-guided ransversus abdominis plane block in the dog: an anatomical evaluation. Vet Anaesth Analg 38, 267–271. Skarda RT, Tranquilli WJ (2007) Local and Regional Anesthetic and Analgesic Techniques: Dogs. In: Lumb & Jones’ Veterinary Anesthesia – (4th edn). Thurmon JC, Tranquilli WJ, Benson GJ (eds). Blackwell Publishing Ltd, Iowa. pp. 561–594. Steagall PVM, Teixeira Neto FJ, Minto BW et al. (2006) Evaluation of the isoflurane-sparing effects of lidocaine and fentanyl during surgery in dogs. J Am Vet Med Assoc 229, 522–527. Thackeray EM, Swenson JD, Gertsch MC et al. (2013) Diaphragm function after interscalene brachial plexus block: a double-blind, randomized comparison of 0.25% and 0.125% bupivacaine. J Shoulder Elbow Surg 22, 381–386. Received 18 March 2013; accepted 28 May 2013.
Supporting Information Additional Supporting Information may be found in the online version of this article: Figure S1. Median and range of the end-tidal isoflurane concentration (FE′ISO) and end-tidal sevoflurane concentration (FE′SEVO) in vol% of dogs undergoing unilateral mastectomy. Figure S2. Mean and SD of heart rate (HR) and invasive mean arterial pressure (iMAP) of dogs undergoing unilateral mastectomy.
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
doi:10.1111/vaa.12122
CASE REPORT
Retrospective clinical evaluation of ultrasound guided transverse abdominis plane block in dogs undergoing mastectomy Diego A. Portela*, Marta Romano*† & Angela Briganti* *Department of Veterinary Sciences, Veterinary Teaching Hospital “Mario Modenato”, University of Pisa, San Piero a Grado, Italy †Clinica Veterinaria Apuana, Marina di Carrara, Italy
Correspondence: Dr. Diego A. Portela, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401, USA. E-mail: [email protected]
Abstract History Eleven female dogs of different breeds undergoing unilateral radical (n = 7) or regional abdominal mastectomy (n = 4) received an ultrasound guided transverse abdominis plane block (TAP-block). Physical examination Subjects showed single or multiple mammary tumours. Serum biochemistry, CBC and electrocardiogram were unremarkable. Eight animals were classified as ASA physical status II and 3 as ASA III. Management Dogs were premedicated with methadone [0.1 or 0.2 mg kg 1 intravenously (IV) or intramuscularly respectively] or fentanyl (2.5 lg kg 1 IV). Anaesthesia was induced with propofol and maintained with isoflurane or sevoflurane. Unilateral ultrasound guided TAP blocks were performed in the caudal and cranial abdomen with bupivacaine 0.25% (0.3 to 0.35 mL kg 1). Intercostal nerve blocks (T4 to T11) with bupivacaine 0.25% (0.013 to 0.04 mL kg 1) completed the blocked area in dogs undergoing radical mastectomy. Follow up The median (range) of end-expired isoflurane and sevoflurane necessary to maintain anaesthesia was 1.15 (1.07–1.22) and 2.07 (2.05–2.2) vol% respectively. A single administra-
tion of fentanyl (2.5 lg kg 1, IV) was administered to control nociception (defined as an increased heart rate or mean arterial blood pressure above 20% of the pre-incisional value) in four of 11 dogs. All dogs received carprofen (2 mg kg 1 subcutaneously) at the end of surgery. Post-operative pain, assessed for 120 minutes using the short form of Glasgow Composite Pain Scale (0–24), was always lower than 3. No rescue analgesia (allowed by the protocol) was required in this time. Conclusion Transverse abdominis plane block combined with intercostal nerve blocks may be useful to produce intraoperative anti-nociception and short term post-operative analgesia in dogs undergoing unilateral mastectomy. Keywords cancer pain, dog, mastectomy, regional anaesthesia, TAP block, ultrasound.
Introduction Transverse abdominis plane block (TAP block) is a regional anaesthetic technique used to provide local anaesthesia/analgesia to the abdominal wall in a wide range of human surgical procedures (Abdallah et al. 2012). Schroeder et al. (2010) reported the first clinical use of the TAP block in a Canadian Lynx and later in dogs under experimental conditions (Schroeder et al. 2011). 319
TAP block for mastectomy in dogs DA Portela et al.
Ventral branches of T11, T12, T13, L1, L2, and L3 spinal nerves supply innervation to the abdominal wall in dogs (Hermanson 2012). These nerves run distally into the fascial plane formed by the internal abdominal oblique muscle and the transversus abdominis muscle, supplying innervation to abdominal muscles, subcutaneous tissues, mammary glands, skin and the underling parietal peritoneum (Evans & de Lahunta 2010). Mastectomy is performed routinely in dogs suffering from mammary tumours. Many such dogs are old, and anaesthetic morbidity may increase with increasing age, due to decline in the organ function reserve. The additional use of regional anaesthesia may improve the outcome of surgical and anaesthetic procedures by reducing the amount of general anaesthetics and analgesics required (Kettner et al. 2011). Radical unilateral resection of the mammary gland is associated with high-level of perioperative stress and pain, which could enhance the morbidity associated to anaesthesia and surgery (Nakagawa et al. 2007). The present preliminary case series investigates the efficacy of ultrasound guided TAP block alone or combined to intercostal nerve blocks for regional abdominal or radical mastectomy respectively in dogs affected by mammary tumours. Case History Anaesthetic records of female dogs that had undergone unilateral radical mastectomy or regional abdominal mastectomy referred to the anaesthesia service of the Veterinary Teaching Hospital “Mario Modenato” – University of Pisa (VTHMM) and the Clinica Veterinaria Apuana (CVA) in the period of time between May 2012 and February 2013 were reviewed. Complete anaesthetic records of dogs that received ultrasound guided TAP block alone or combined to intercostal nerve blocks as analgesic protocol for unilateral regional abdominal or radical mastectomy were selected for the present study. Records of cases submitted to mastectomy combined to ovariohysterectomy were excluded from the analysis. Eleven anaesthetic records matched the inclusion criteria, five in the VTHMM and six in the CVA. Dogs were of different breeds, weighed 2.5 to 45 kg (median 25 kg) and were 7 to 16 (median 11) years old. Radical unilateral mastectomy and regional abdominal mastectomy were performed in seven and four cases respectively. 320
Physical examination, complete blood count, serum biochemistry profile and electrocardiogram were performed in all subjects in the days prior to surgery. Eight dogs were classified as ASA physical status II and 3 as ASA III. Dogs in which heart murmurs (n = 3) could be heard at auscultation were submitted to echocardiographic examination and were all diagnosed with mitral valve endocardiosis. One of these dogs had received benazepril for two weeks prior to surgery, which was discontinued for the 24 hours before anaesthesia/surgery. As standard practice in both institutions, written detailed owner consent was obtained before performing anaesthesia and surgery in all dogs. Management Food but not water was withheld for approximately eight hours prior to the scheduled time of surgery. An intravenous (IV) catheter was placed in a cephalic vein for administration of fluids and drugs. All dogs received an opioid drug as anaesthetic premedication (Table 1). General anaesthesia was induced with a constant rate infusion of propofol (1.5 mg kg 1 minute 1, IV [Propofol Kabi 20 mg mL 1, Fresenius Kabi S.r.l., Italy]) using a syringe pump until orotracheal intubation was possible (total dose: 3.2 to 5.7 mg kg 1 IV). The endotracheal tube was then connected to a circle rebreathing system, and an oxygen/air mixture was delivered aiming to maintain a FiO2 > 60%. Respiratory rate and tidal volume were mechanically controlled (Ohmeda Ventilatore D’Anestesia 7750, UK; Datex-Ohmeda Aespire View, GE Healthcare, PA, USA; Multiflow 2002 Anaesthesia Ventilator, Hallowell EMC, MA, USA) during the entire procedure in order to maintain an end-tidal carbon dioxide (PE′CO2) between 35 and 45 mmHg (4.6 and 5.9 kPa). General anaesthesia was maintained with isoflurane (n = 9) or sevoflurane (n = 2). Warm lactated Ringer’s solution was administered (2.5 to 5 mL kg 1 hour 1 IV) throughout surgery. Body temperature was maintained above 37 °C using electrically heated and thermal foil blankets. An arterial catheter was placed in a dorsal pedal artery to monitor invasive arterial blood pressure throughout the procedure. Throughout the entire anaesthetic procedure, heart rate (HR), invasive mean arterial pressure (iMAP), PE′CO2, end-tidal isoflurane or sevoflurane (FE′ISO/FE′SEVO), oesophageal temperature, oxygen saturation (SpO2) and a lead II electrocardiogram
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
TAP block for mastectomy in dogs DA Portela et al. Table 1 Premedication and intraoperative rescue analgesia given to dogs submitted to radical or regional unilateral mastectomy that received ultrasound TAP block as analgesic protocol
Case Case Case Case Case Case Case Case Case Case Case
1* 2* 3* 4* 5* 6† 7† 8† 9† 10† 11†
Surgery
Premedication
Radical mastectomy Regional mastectomy Regional mastectomy Radical mastectomy Radical mastectomy Radical mastectomy Regional mastectomy Regional mastectomy Radical mastectomy Radical mastectomy Radical mastectomy
Methadone 0.2 mg Methadone 0.2 mg Methadone 0.2 mg Fentanyl 2.5 lg kg Fentanyl 2.5 lg kg Methadone 0.1 mg Methadone 0.1 mg Methadone 0.1 mg Fentanyl 2.5 lg kg Fentanyl 2.5 lg kg Fentanyl 2.5 lg kg
Intraoperative rescue analgesia kg 1, IM kg 1, IM kg 1, IM 1 , IV‡ 1 , IV‡ kg 1, IV kg 1, IV kg 1, IV 1 , IV 1 , IV 1 , IV
Fentanyl 2.5 lg kg 1, IV
Fentanyl 2.5 lg kg 1, IV
Fentanyl 2.5 lg kg 1, IV Fentanyl 2.5 lg kg 1, IV
*Cases referred to the Veterinary Teaching Hospital “Mario Modenato” – University of Pisa. †Cases referred to the Clinica Veterinaria Apuana. ‡Given 2 minutes before induction of general anesthesia.
were monitored continuously and recorded every five minutes. During surgery, fentanyl (2.5 lg kg 1, IV [Fentanest Pfizer Italia S.r.l., Italy]) was administered to control nociceptive responses defined as an increase of HR and/or MAP above 20% of the preincisional value. Multiparametric monitors (Mindray Beneview T5, China; Criticare Poet Plus 8100, WI) were used to measure the parameters described above. For iMAP measurements, a pre-calibrated transducer was zeroed to atmospheric pressure and positioned at the level of the left atrium. The entire abdominal wall was clipped and the skin of the abdominal flank was surgically prepared. Dogs were laid in lateral recumbency with the side to be blocked uppermost. A portable ultrasound machine (Venue 40, GE Medical Systems, China [used at the VTHMM] and a MyLabTM70 XVision Esaote, Italy [used at the CVA]) with a 12 MHz linear array transducer was used to identify the transverse abdominis plane and perform the TAP block as described elsewhere (Schroeder et al. 2011). Briefly, the US transducer was positioned in the dorsal abdominal flank, perpendicularly to the body long axis, cranially to the iliac crest (Fig. 1a). The transducer was slid gently until the three layers of the abdominal wall were identified (Fig. 2a). A 22 gauge, 90 mm spinal needle (Spinale Quincke, PicIndolor, Artesana S.p.A., Italy), connected to a 10 cm-long tubular extension prefilled with the local anaesthetic, was inserted with a dorso-ventral direction, perpendicular to the body long axis, using an “in-plane” technique (Fig. 1a). Thus the needle tip was advanced under ultrasound
guidance throughout the external layers of the abdominal wall towards the fascial plane between the internal abdominal oblique and transversus abdominis muscles (TAP space). Bupivacaine 0.25%, (Marcaina 5 mg mL 1; AstraZeneca S.p.A., Italy, diluted 1:1 with NaCl) 0.3 to 0.35 mL kg 1, was injected in each TAP block point. All dogs of this series received two TAP blocks, one in the caudal part of the middle abdominal region, cranially to the iliac crest and a second one in the cranial part of the middle abdominal region, caudally to the last rib (L5-L6 and L2-L3 intervertebral level respectively) (Fig. 1b). In case of radical unilateral mastectomy (n = 5), T4 to T12 intercostal nerves were blocked with bupivacaine 0.25% (0.03 to 0.04 mL kg 1) using a blind intercostal nerve block approach (Skarda & Tranquilli 2007). Cases submitted to complete mastectomy therefore received a total 0.25% bupivacaine volume of 0.87 to 1.06 mL kg 1 (2 TAP blocks + 9 intercostal blocks), which corresponds to a total dose of 2.1 to 2.6 mg kg 1. At the end of the procedure, carprofen (2 mg kg 1, subcutaneously, every 24 hours) was administered to all dogs. The short form of the Glasgow Composite Pain Scale (SF-GCPS) was used to assess pain scores in the post-anaesthetic period during 120 minutes after extubation (Reid et al. 2007). If pain score was above 5 out of 24, methadone (0.3 mg kg 1, IM) was administered as rescue analgesia. The transverse abdominal muscle and the internal abdominal oblique were visualized without problems
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
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(a)
(a)
(b)
(b)
Figure 1 Transverse abdominis plane (TAP) block in a dog. (a) A spinal needle is introduced through the lateral abdominal wall under ultrasound guidance using an “inplane” technique. (b) Schemathic representation of the US trasducer positioning (rectangular black figures) and the injection points to perform TAP blocks in the caudal and cranial abdomen and intercostal nerves blocks. The arrows represent the needle orientation. Black circles represent the intercostal nerve blocks.
in all dogs. The local anaesthetic injections caused the hydrodissection (separation of the muscular layers) of the TAP space (Fig. 2b) in all the cases. The elapsed time between TAP block and the beginning of surgery ranged from 10 to 45 (median 30) minutes. In all dogs FE′ISO or FE′SEVO was maintained below 1.3 (median: 1.15, range:1.07–1.22) vol% and 2.3 (median: 2.07, range 2.05–2.2)% respectively during the entire procedure (Fig. S1). No alterations in the cardiac rhythm were registered and mean arterial blood pressure remained between 60 and 95 mmHg in all dogs (Fig. S2). Anticholinergic, inotropic or vasoactive drugs were not required to support cardiovascular function in any case. In seven out of 11 cases fentanyl was not required during surgery. Four dogs required intraoperative rescue analgesia: cases 2, 5 and 10 during the ligation of the inguinal canal vessels; and case 8 at the level of the caudal thoracic 322
Figure 2 Ultrasonographic image of the muscular layers forming the abdominal wall in a dog. The ultrasound trasducer is positioned perpendicularly to the body long axis in the dorsal abdominal flank. (a) EO, external abdominal oblique muscle; IO, internal abdominal oblique muscle; TA, transversus abdominis muscle; P, peritoneum. (b) Local anaesthetic (LA) injected into the fascial plane between the internal abdominal oblique (IO) and transversus abdominis muscles (TA) using a spinal needle.
mammary gland (Table 1). In all four cases a single bolus of fentanyl (2.5 lg kg 1) was administered. Surgery time ranged from 25 to 65 (median 50) minutes. Recovery from anaesthesia was smooth and no complications were recorded. Ability to walk unassisted was regained in 15 to 45 (median 35) minutes after extubation. None of the dogs showed sings of discomfort after applying a gentle pressure on the wound zone and pain scores remained below 3 during the 120 minutes of post-operative evaluation. After that period, all dogs received methadone (0.3 mg kg 1 intramuscularly every 4–6 hours) for post-operative analgesia. Patients at the VTHMM were dismissed to the intensive care unit and discharged home around 30 hours after surgery, while those referred to the CVA were discharged home at least six hours after surgery. No complications related to the anaesthetic or surgical procedures were noted in the two weeks follow-up period in any patient. Discussion From our study, ultrasound TAP block provided intraoperative antinociception and post-operative
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
TAP block for mastectomy in dogs DA Portela et al. short-term analgesia in dogs undergoing unilateral regional mastectomy. Intercostal nerve blocks need to be combined with TAP block in order to supplement regional anaesthesia in dogs undergoing radical unilateral mastectomy. However, fentanyl might still be necessary to control nociception when structures contained in the inguinal canal are ligated. In female dogs, the inguinal canal contains the vaginal process (eversion of the peritoneum), external pudendal vessels, fat and the genitofemoral nerve, which arises from the 3rd lumbar nerve (Hermanson 2012). It is probable that the nociceptive response during ligation of this structure could be due to the lack of genitofemoral nerve blockade or to a visceral nociceptive component of the vaginal process. It is important to consider that TAP block only provides regional anaesthesia and analgesia of the abdominal wall with no effect on visceral components. Case 8 showed signs of nociception when the surgery involved the caudal thoracic mammary gland. The latter receives its nerve supply from the lateral cutaneous branches of the 6th and 7th thoracic nerves (Evans & de Lahunta 2012); therefore, the response, successfully controlled with a single dose of fentanyl (2.5 lg kg 1, IV), was probably due to a failure of the intercostal nerve block rather than TAP block. Methadone and fentanyl, administered as preanaesthetic medications, could have also produced antinociception and therefore participate in limiting the intraoperative fentanyl consumption. Considering their pharmacokinetics in dogs (Sano et al. 2006; Steagall et al. 2006; Credie et al. 2010; IngvastLarsson et al. 2010) and according to our clinical experience it is unlikely that at the doses used methadone and fentanyl produce such a degree of antinociception and post-operative analgesia. However, a prospective study including a control group could be useful to better assess the antinocieptive efficacy of the TAP block in dogs. The execution of a single TAP block at midway between the iliac crest and the caudal aspect of the last rib using bupivacaine-dye solution (10 mL) in 10 beagle cadavers (11.1 1.1 kg) resulted in 60%, 100%, 100% and 90% staining of T12, T13, L1 and L2, respectively. Nerve roots T11 and L3 were stained in 20% and 30% of the cadavers (Schroeder et al. 2011). In order to try to increase the percentage of blocking T11 and L3 we decided to use two injection sites: one in the caudal and one in the cranial aspect of the middle abdominal region (Fig. 1b). As the volume to be injected was relatively
high, 0.25% bupivacaine was used in order to avoid possible local anaesthetic toxicity. Although, the total bupivacaine dose was close to, or even higher than the maximal recommended dose for dogs in some textbooks (i.e. 1.5 to 3 mg kg 1) (Hellyer et al. 2007), it remained under the toxic dose (i.e. 5 mg kg 1) reported in dogs (Liu et al. 1983). Although no cardiovascular or neurologic complications were observed in the cases reported here, the clinician must be aware of the total administered dose in order to avoid potential complications related to local anaesthetic toxicity. It is possible that lower bupivacaine concentrations (e.g. 0.125%) could still provide a good analgesic effect (Abdallah et al. 2012; Thackeray et al. 2013), however further studies are required to confirm this hypothesis. During the first two post-operative hours the animals studied did not show any signs of pain as no reaction was elicited following palpation of the surgical wound and SF-GCPS was always lower than 3. In human, post-operative pain delays recovery time, return to normal activities and depresses the immune system (Desborough 2000). Stress associated to surgery and post-operative pain could increase the incidence of cancer recurrence or distant metastasis in humans undergoing breast cancer surgery (Exadaktylos et al. 2006). At the moment we don’t know if this is applicable to dogs undergoing mastectomy, however TAP block with or without intercostals nerve block might be considered to provide antinociception and postoperative analgesia in such animals. In summary, these preliminary evaluations suggest that the TAP block might be effective to provide regional anaesthesia and analgesia to the abdominal wall in dogs undergoing unilateral mastectomy. TAP blocks should be combined with intercostal nerve blocks in dogs undergoing radical unilateral mastectomy. It is probable that TAP block will reduce the amount of systemic analgesic requirements in a balanced multimodal analgesic protocol. Prospective controlled studies are required to: 1) define the minimal local anaesthetic dose and concentration necessary to promote an efficient regional block; 2) to establish if postoperative opioid consumption could be reduced by adding a TAP block to a multimodal analgesic protocol; 3) to determine the role of regional anaesthesia in perioperative stress response and cancer recurrence after regional or radical mastectomy in dogs.
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Supporting Information Additional Supporting Information may be found in the online version of this article: Figure S1. Median and range of the end-tidal isoflurane concentration (FE′ISO) and end-tidal sevoflurane concentration (FE′SEVO) in vol% of dogs undergoing unilateral mastectomy. Figure S2. Mean and SD of heart rate (HR) and invasive mean arterial pressure (iMAP) of dogs undergoing unilateral mastectomy.
© 2014 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia, 41, 319–324
