Dig Dis Sci (2014) 59:513–519 DOI 10.1007/s10620-013-2931-3
REVIEW
ERCP: The Unresolved Question of Endotracheal Intubation Basavana Goudra • Preet Mohinder Singh
Received: 14 September 2013 / Accepted: 18 October 2013 / Published online: 13 November 2013 Ó Springer Science+Business Media New York 2013
Abstract The anesthesia community is still divided as to the appropriate airway management in patients undergoing endoscopic retrograde cholangiopancreatography. Increasingly, gastroenterologists are comfortable with deep sedation (normally propofol) without endotracheal intubation. There are no comprehensive reviews addressing the various pros and cons of an un-intubated airway management. It is hoped that the present review will benefit both anesthesia providers and gastroenterologists. The reasons to avoid routine endotracheal intubation and the approaches for an un-intubated anesthetic management are discussed. The special situations where endotracheal intubation is the preferred approach are mentioned. Many special techniques to manage airway are illustrated. Keywords ERCP Sedation Airway Endoscopic retrograde cholangiopancreatography
Background A 59-year-old American Society of Anesthesiologists (ASA) physical status 2 male presented for an endoscopic retrograde cholangiopancreatography (ERCP). Past medical history was unremarkable apart from chronic atrial fibrillation. The ventricular rate was well controlled with medications. After
B. Goudra (&) Clinical Anesthesiology and Critical Care, Perelman School of Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA, USA e-mail: [email protected] P. M. Singh Department of Anesthesia, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India e-mail: [email protected]
providing an explanation of the MAC anesthesia and associated risks, an informed consent was obtained. The gastroenterologist explained in detail about the ERCP and the stone extraction. As per the standard practice, a decision was made to proceed with deep sedation without endotracheal intubation. During the procedure, desaturation set in that could not be treated quickly. This was followed by sudden onset of ventricular tachycardia. The patient was turned supine, intubated and CPR instituted. Although effective cardiac activity and circulation could be reestablished, the patient died a few hours later. Horrific experiences like this are bound to affect clinical practice of all anesthesia providers. Irrational and many times non-evidence based decisions can be made based on either personal experience like this one or experiences of others. However, as experienced and trained medical professionals, it is important that crucial practice decisions like endotracheal intubation are made based on the available evidence rather than a rare clinical event, however disastrous it might be. To highlight this statement consider another example. A 66-year-old male presented for a diagnostic upper gastrointestinal (GI) endoscopic procedure. History included severe aortic stenosis (valve orifice of 0.8 cm2). Again as per the standard practice, sedation was administered with propofol without endotracheal intubation. Hypoxemia (as evidenced by desaturation) led to cardiac arrest. CPR (cardio pulmonary resuscitation) was quickly instituted; however, the patient sustained anoxic brain injury. Although both of these unfortunate events were heralded by hypoxemia and possibly could have been prevented by elective endotracheal intubation (ETT), it is unlikely that anesthesia providers will be inclined to intubate all patients presenting for upper GI endoscopy, as much as they are likely to intubate all patents presenting for ERCP. In spite of adverse outcome in both situations, the prone positioning necessary for ERCP segregates this entity into a
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Table 1 Indications of endoscopic retrograde cholangiopancreatography (ERCP) in an outpatient center Indication
Occurrence
Chronic pancreatitis
6.25 %
Post hepatic transplant
41.43 %
Hepatic cancer (including metastasis)
8.56 %
Cholangiocarcinoma
8.56 %
Primary sclerosing cholangitis
4.62 %
Pancreatic cancer
20.83 %
Others
9.72 %
separate category. It is partly due to our long-held belief regarding the consequence of airway loss in an unintubated patient undergoing procedure in prone position. An important distinction has to be made regarding surgical procedure versus endoscopic procedure conducted in prone position. An intracranial procedure (with all its complexities in terms of positioning) or a spine procedure is entirely different than an ERCP, although both are conducted in prone position. First, endoscopic procedures can be aborted at any notice to facilitate airway management. The second difference, although depth of sedation for an ERCP is similar to or even greater than needed for a neurosurgical procedure, it is possible to titrate the anesthetic depth to maintain spontaneous ventilation. The intensity of stimulation for an ERCP is nowhere near a surgical incision and, apart from the phase of gastroscope insertion, is relatively constant. Further discussion on anesthetic approach and airway management of patients presenting for an ERCP will be based on these two factors.
laryngoscope is likely to change the landscape, intubationrelated injuries are common. Lip, dental and eye and other soft tissue injuries happen with a degree of frequency [2– 4]. Although these injuries are not life threatening, they are preventable and especially injuries to the eye can be disabling. More serious injuries like bronchial rupture can occur especially with the use of introducers [5]. Endotracheal intubation almost invariably requires administration of skeletal muscle relaxants. Due to the unexpected duration of this diagnostic and therapeutic procedure, it is sensible to use succinylcholine for this purpose. Apart from the well-known risks of muscle pain, myoglobulinemia myoglobinuria, succinylcholine is implicated in malignant hyperthermia [6, 7]. Depending on the endoscopic findings, sometimes it becomes necessary to administer a long acting relaxant along with the need for reversal agents. Apart from a significant increase in anesthesia times, use of muscle relaxants can increase the incidence of postoperative pulmonary complications [8, 9]. Use of reversal agents is associated with unwanted anticholinergic effects. Use of glycopyrrolate is not universal. Use of atropine for this purpose can potentially lead to central anticholinergic effects. Residual neuromuscular blockade is an important issue with nondepolarizing muscle relaxants [10, 11]. It can occur even 2 h after reversal. Inadequate reversal is an additional risk factor. It is hoped that advent of sugamedex [12] might change the role of nondepolarizing muscle relaxants in future.
Prone Positioning and ETT The Intubation Dilemma Endoscopic retrograde cholangopancreatography poses unique challenges to both anesthesia provider and gastroenterologist. The last two decades have seen a phenomenal increase in the number of ERCPS. With the expanding indications, the patient population presenting for these procedures has also grown older and sicker. Some of the indications in our own hospital (from a retrospective review of 653 patients) are presented in Table 1 [1]. Although it is tempting to intubate all ERCPS and such is the practice in many centers around the world, the following considerations are to be borne in mind before committing all or a majority of patients to ETT.
Why Routine ETT Anesthesia Should Be Discouraged? How Safe is Laryngoscopy and Intubation? Laryngoscopy and endotracheal intubation itself is not an entirely innocuous procedure. Although the advent of video
123
Although all ERCP procedures involve prone positioning, patients are asked to position themselves when ETT is not involved. Turning prone after intubating in supine position presents significant challenges. Endoscopy units are not as well staffed as other surgical operating rooms. Injuries can occur during positioning and while positioned. Accidental extubation is risky, although can be managed either with bag-mask or a laryngeal mask airway (LMA) [13].
Efficiency Especially for very short procedures like change of stent, the endotracheal anesthesia adds significant additional time. In a retrospective study [14], we found that ‘‘anesthesia time’’ (total time minus procedural time) is a significant factor contributing to overall time in ERCP procedure. This time can be reduced by using dedicated anesthesiologists, and decreased incidence of endotracheal intubation is a contributing factor.
Dig Dis Sci (2014) 59:513–519
515
Why Anesthesiologists Intubate the Trachea? Fear of Losing Airway Fear of losing airway during the procedure is probably the most common reason for elective endotracheal intubation among the anesthesia providers. However, those fears are unfounded. Many publications during recent months have affirmed the safety of unintubated ERCP. Goudra et al. studied 653 consecutive patients undergoing elective ERCP in their outpatient center. Their intubation rate was \1 % and all the indications were fear of full stomach and history of aspiration. There were no instances of procedure interruption or emergency endotracheal intubation. Even while anesthetizing far sicker patients in their inpatient endoscopy center, the incidence of endotracheal intubation was \10 %. In a recent study, non-obese patients who underwent ERCP needed endotracheal intubation in about 10 % procedures [15]. Risk of Hypoxemia Many investigators have closely studied the risk of hypoxemia in patients undergoing advanced endoscopic procedures and ERCP [1, 14, 16]. In the study cited above [15], although incidence of endotracheal intubation for ERCP was \10 %, the incidence of oxygen desaturation was worryingly high. It is well known that hypoxemia (as evidenced by desaturation) is the most common precursor of more serious adverse events like cardiac arrhythmias and asystole. Part of the reasons for a striking difference in the intubation and desaturation rates might be the airway management technique. In one institution, airway management was geared towards preventing hypoxemia. By extensive use of either a nasal trumpet or an oral trumpet (both in turn connected to a mapelson breathing system, Figs. 1a, b, 2), one center could reduce the incidence of desaturation to negligible levels. However, if an anesthesia provider decides to embark on an unintubated approach while sedating these patients, certain precautions need to be undertaken [1]. Preoxygenation and timing of propofol administration along with the timing of endoscope insertion are all crucial. As it is well known, once the lungs are filled with 100 % oxygen by elective preoxygenation, it can take up to 11 min for pulse oximeter to register a desaturation to 90 %, in spite of no ventilation. Although, both preoxygenation for 3 min or four vital capacity breaths can provide at least 4 min of ‘‘safety time’’ before patients start desaturating, it is advised to use the former technique as the time available to deal with inadequate ventilation will be longer (up to 8 min) [17]. This is due to the nature of the oxygen desaturation curve. The arterial partial pressure of oxygen
Fig. 1 a A nasal trumpet placed in the nose and connected to a Mapelson C breathing system with an elective endotracheal intubation (ETT) adapter. b A nasal trumpet placed in the nose and connected to a Mapelson C breathing system, bag squeezed to assist
Fig. 2 A nasal trumpet placed in the mouth and connected to a Mapelson C breathing system with an ETT adapter
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appropriate airway manipulation. Assisting ventilation using a Mapelson breathing system (while depth of sedation is reduced appropriately) is useful [1, 14]. Many times, nothing more is required until spontaneous ventilation is established. However, the nature of the upper airway under propofol sedation with the gastroscope in situ is unpredictable and variable. As shown in the pictures, gastroscope might displace the tongue and help to establish the patency of the airway in many cases; however, by no means is it certain (Figs. 3 and 4). Risk of Aspiration
Fig. 3 A view from above taken from another fiber-optic bronchoscope with gastroscope in place; airway classification Mallampatti
The risk of aspiration in patients undergoing colonoscopy under propofol mediated sedation was highlighted in a recent large retrospective study [20]. Even in the absence of gastric outlet obstruction, there is probably an increased risk of aspiration in patients undergoing ERCP (although no data are available). For procedures like drainage of pancreatic pseudocyst, endotracheal intubation is the airway management of choice. Single stage drainage of these cysts is common [21, 22] and the biochemical analysis has shown high protein content [23]. Like in other endoscopic procedures, silent aspiration of gastric contents cannot be ruled out during ERCP [24]. Lack of Reliable Monitoring in an Unintubated Patient
Fig. 4 A view from above taken from another fiber-optic bronchoscope with gastroscope in place; airway classification Mallampatti
has to fall from an initial 660 to about 90 mmHg for a fall in oxygen saturation. The patient needs to be either apneic or hypopneic for prolonged periods (depending on FRC and oxygen consumption) before the pulse oximeter can register desaturation. This period is difficult to detect without close observation. Although ASA has recommended the use of ECO2 monitoring for all patients undergoing GI endoscopic procedure under anesthesiaprovider provided sedation [18], its efficacy in the setting of GI endoscopy is far from satisfactory [19]. Close observation of the chest movement and alternative, more reliable means of ventilation (like acoustic respiratory monitor or impedance peumograpghy) are to be considered. The second issue is to have a means of assisting ventilation if (and when) hypoventilation is detected. Obviously, any airway obstruction needs to be corrected by
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ASA has recommended end tidal carbon dioxide monitoring in all patients undergoing these procedures with moderate to deep sedation [18]. However, practicalities of implementation are a major problem. End tidal carbon dioxide is not a reliable monitor in this setting [19]. There is nothing inherently wrong with the monitor, however practical obstacles prevent obtaining a reliable sample. Various devices to obtain such a sample are proposed, their reliability in the setting of upper GI endoscopy in general and ERCP in particular is not studied. Acoustic respiratory monitor and impedance pneumography are better respiratory monitoring alternatives. As impedance pneumography cannot detect breathing against an obstructed upper airway, acoustic respiratory monitoring may be preferable. Cardiac Arrest in Patients Undergoing ERCP and Upper GI Endoscopy The incidence of cardiac arrest in patients undergoing GI endoscpy is high compared to other forms of anesthesia. Interestingly, the cardiac arrests were all heralded by respiratory complications (much like pediatric anesthesia practice). However both the incidence and severity of such complications are no different between ERCP and other forms of upper GI endoscopy (like endoscopic ultrasound
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or therapeutic endoscopy). The incidence during colonoscopy was zero during the same period.
517 Fig. 5 Gastrolaryngeal tube
Airway Management for Prone ERCP As mentioned earlier, the oxygen dissociation curve is not an anesthesia provider’s friend. Due to the steep portion of the curve, it is very important (while anesthetizing any unintubated, spontaneously ventilating patient) to have a low threshold for endoscope withdrawal. Corrective airway maneuvers need to be instituted in anticipation of hypoxemia rather than as a response to hypoxemia. Waiting for pulse oximeter to display a saturation of 90–95 to respond might be too late. To facilitate such an approach, a patient’s ventilatory efforts need to be observed very closely. If the attending anesthesiologist (supervising the case) is doubtful of the abilities of his assistant, intubation might be a safer option. These skills can be easily taught and learnt. Especially in the initial stages of the procedure (endoscope insertion and recommencement of effective ventilation), documentation needs to be ignored and attention paid to monitor the patient. Inadequate levels of sedation can equally lead to severe cough and sometimes laryngospasm. In the absence of effective preoxygenation, hypoxemia can set in very quickly. As ERCP scopes have a side camera (rather than at the tip) insertion difficulties can lead to inadvertent stimulation of vocal cords triggering violent cough. Immediate endoscope withdrawal and deepening sedation is important. An anesthesia provider should not hesitate to express his concerns and request for a more experienced endoscopist to do the insertion. If the difficulties continue, it is prudent to reevaluate the plan and effect an endotracheal intubation after turning supine. At times, after commencement of the procedure, airway manipulations, insertion of nasal trumpet or bagging with the oral/nasal trumpet are insufficient to prevent hypoxemia. In such cases, withdrawal of the scope and bagging with a face mask to reoxygente is required. In the absence of any other difficulties, after appropriate adjustment of the depth of sedation, endoscope reinsertion can be permitted. There is increasing evidence as to the safety of LMA both as a primary airway in prone position and as a rescue method [13, 25, 26]. Although, a nasal trumpet connected to a Mapelson C breathing system (Fig. 1a, b) has been used as a standard in our hospital, it can also be used as a rescue measure. Another way to administer oxygen is by use of a modified nasal airway inserted into the mouth next to bite block and connected to a Mapelson C breathing system (Fig. 2). Both gastrolaryngeal tube (Fig. 5) and endoscopy mask (Fig. 6) could be used as support and possible ventilation during ERCP procedures [27]. However there is little
Fig. 6 Endoscopy mask
published literature with either of these airways during these procedures. Absence of a suction port is an obvious disadvantage with an endoscopy mask. Studies documenting the use of LMA for ERCP are lacking, but its use in prone position to administer anesthesia for other surgical procedures are plenty.
Who Should Provide Anesthesia for ERCP? Another way to increase both the safety and efficiency in ERCP sedation is to have a team of dedicated anesthesia providers. This approach is known to decrease desaturations and reduce the anesthesia time [14]. In this recently published study, a comparison was made between two naturally divided groups of anesthesia providers. Apart from an incidence of desaturation, a comparison was also made between the ‘‘anesthesia time’’ in the two groups. As a group, non-dedicated anesthesia providers took more time than dedicated providers. Moreover this amounted to an increase in the cost of anesthesia by about 760,000 US$
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in one hospital alone. Although no special fellowships and certifications are currently necessary, out-of-OR anesthesia might soon become frequent and complicated enough to require additional training. At the hospital of the University of Pennsylvania, dedicated out-of-operating-room resident anesthesia rotations are already in place to address this aspect of training. It is hoped that ASA and ABA will notice this expanding field of anesthesia and make appropriate provisions in the residency training curriculum. Frequently, the question arises about the nomenclature of sedation technique used for these procedures. Gastroenterologists are always competing with anesthesia providers to administer propofol. As observed in our institution, although the patients presenting for upper endoscopy (including ERCP) are told (and consented) that they will have moderate to deep sedation, 96 % of these patients were under deep general anesthesia as measured by brain function monitor (SEDLne). As a result, it is only appropriate that ‘‘sedation’’ for these procedures is provided by anesthesia providers. Having discussed the pros and cons of endotracheal intubation for ERCP, a low threshold to intubate is advised in the following subset of patients.
Obesity As stated earlier, emergency expert help in turning the patient supine to secure an airway may not be easy in an endoscopic suite. In a morbidly obese patient, such heroics could be fraught with dangers. With an already compromised FRC and increased oxygen consumption, time available to reestablish effective ventilation will be very limited. ETT is the preferred method of airway management, especially in the inexperienced.
Risk of Aspiration Suspicion of gastric outlet obstruction, full stomach and drainage of pseudocyst of pancreas are probably managed better with an ETT. Anticipated Difficult Ventilation Although anticipated difficult intubation may not be an indication for elective ETT, anticipated difficult ventilation should be. Additionally, other institution-specific factors like availability of anesthesia provider with experience in endoscopy anesthesia, location and size of the room, type and extent of help are important in this decision making.
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Conclusions Patients presenting for an ERCP can be safely and effectively sedated without the need for an elective endotracheal intubation. Close respiratory monitoring, ready availability of means of establishing ventilation and experience are important. Various airway techniques and adjuncts described can help in preventing and treating hypoxemia. Conflict of interest
None.
References 1. Goudra B, Singh P, Sinha A. Outpatient endoscopic retrograde cholangiopancreatography: safety and efficacy of anesthetic management with a natural airway in 653 consecutive procedures. Saudi J Anaesth. 2013;7:259. 2. Newland MC, Ellis SJ, Peters KR, et al. Dental injury associated with anesthesia: a report of 161,687 anesthetics given over 14 years. J Clin Anesth. 2007;19:339–345. 3. Vogel J, Stu¨binger S, Kaufmann M, Krastl G, Filippi A. Dental injuries resulting from tracheal intubation—a retrospective study. Dent Traumatol. 2009;25:73–77. 4. Yu H-D, Chou A-H, Yang M-W, Chang C-J. An analysis of perioperative eye injuries after nonocular surgery. Acta Anaesthesiol Taiwanica Off J Taiwan Soc Anesth. 2010;48:122–129. 5. Sahin M, Anglade D, Buchberger M, Jankowski A, Albaladejo P, Ferretti GR. Case reports: Iatrogenic bronchial rupture following the use of endotracheal tube introducers. Can J Anaesth J Can Anesth. 2012;59:963–967. 6. Dexter F, Epstein RH, Wachtel RE, Rosenberg H. Estimate of the relative risk of succinylcholine for triggering malignant hyperthermia. Anesth Analg. 2013;116:118–122. 7. Hopkins PM. Malignant hyperthermia: pharmacology of triggering. Br J Anaesth. 2011;107:48–56. 8. Tejada Artigas A, Bello Dronda S, Chaco´n Valle´s E, et al. Risk factors for nosocomial pneumonia in critically ill trauma patients. Crit Care Med. 2001;29:304–309. 9. Berg H, Roed J, Viby-Mogensen J, et al. Residual neuromuscular block is a risk factor for postoperative pulmonary complications. A prospective, randomised, and blinded study of postoperative pulmonary complications after atracurium, vecuronium and pancuronium. Acta Anaesthesiol Scand. 1997;41:1095–1103. 10. Debaene B, Plaud B, Dilly M-P, Donati F. Residual paralysis in the PACU after a single intubating dose of nondepolarizing muscle relaxant with an intermediate duration of action. Anesthesiology. 2003;98:1042–1048. 11. Varposhti MR, Heidari SM, Safavi M, Honarmand A, Raeesi S. Postoperative residual block in postanesthesia care unit more than two hours after the administration of a single intubating dose of atracurium. J Res Med Sci Off J Isfahan Univ Med Sci. 2011;16:651–657. 12. Soko´ł-Kobielska E. Sugammadex—indications and clinical use. Anaesthesiol Intensive Ther. 2013;45:106–110. 13. Raphael J, Rosenthal-Ganon T, Gozal Y. Emergency airway management with a laryngeal mask airway in a patient placed in the prone position. J Clin Anesth. 2004;16:560–561. 14. Goudra BG, Singh PM, Sinha AC. Anesthesia for ERCP: impact of anesthesiologist’s experience on outcome and cost. Anesth Res Pract. 2013;2013:570518.
Dig Dis Sci (2014) 59:513–519 15. Barnett SR, Berzin T, Sanaka S, Pleskow D, Sawhney M, Chuttani R. Deep sedation without intubation for ERCP is appropriate in healthier, non-obese patients. Dig Dis Sci. (Epub ahead of print). doi:10.1007/s10620-013-2783-x. 16. Berzin TM, Sanaka S, Barnett SR, et al. A prospective assessment of sedation-related adverse events and patient and endoscopist satisfaction in ERCP with anesthesiologist-administered sedation. Gastrointest Endosc. 2011;73:710–717. 17. Gambee AM, Hertzka RE, Fisher DM. Preoxygenation techniques: comparison of three minutes and four breaths. Anesth Analg. 1987;66:468–470. 18. Weaver J. The latest ASA mandate: CO2 monitoring for moderate and deep sedation. Anesth Prog. 2011;58:111–112. 19. Goudra BG. Comparison of acoustic respiration rate, impedance pneumography and capnometry monitors for respiration rate accuracy and apnea detection during GI endoscopy anesthesia. Open J Anesth. 2013;03:74–79. 20. Cooper GS, Kou TD, Rex DK. Complications following colonoscopy with anesthesia assistance: a population-based analysis. JAMA Intern Med. 2013;173:551–556. 21. Ahlawat SK, Charabaty-Pishvaian A, Jackson PG, Haddad NG. Single-step EUS-guided pancreatic pseudocyst drainage using a
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large channel linear array echoendoscope and cystotome: results in 11 patients. JOP J Pancreas. 2006;7:616–624. Ahn JY, Seo DW, Eum J, et al. Single-step EUS-guided transmural drainage of pancreatic pseudocysts: analysis of technical feasibility, efficacy, and safety. Gut Liver. 2010;4:524–529. Mo¨nkemu¨ller KE, Harewood GC, Curioso WH, et al. Biochemical analysis of pancreatic fluid collections predicts bacterial infection. J Gastroenterol Hepatol. 2005;20:1667–1673. Raksakietisak M. Unrecognised aspiration pneumonitis during enteroscopy: two cases report. J Med Assoc Thail Chotmaihet Thangphaet. 2009;92:869–871. Abrishami A, Zilberman P, Chung F. Brief review: airway rescue with insertion of laryngeal mask airway devices with patients in the prone position. Can J Anaesth J Can Anesth. 2010;57: 1014–1020. Osborn IP, Cohen J, Soper RJ, Roth LA. Laryngeal mask airway—a novel method of airway protection during ERCP: comparison with endotracheal intubation. Gastrointest Endosc. 2002;56:122–128. Fabbri C, Luigiano C, Cennamo V, et al. The gastro-laryngeal tube for interventional endoscopic biliopancreatic procedures in anesthetized patients. Endoscopy. 2012;44:1051–1054.
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REVIEW
ERCP: The Unresolved Question of Endotracheal Intubation Basavana Goudra • Preet Mohinder Singh
Received: 14 September 2013 / Accepted: 18 October 2013 / Published online: 13 November 2013 Ó Springer Science+Business Media New York 2013
Abstract The anesthesia community is still divided as to the appropriate airway management in patients undergoing endoscopic retrograde cholangiopancreatography. Increasingly, gastroenterologists are comfortable with deep sedation (normally propofol) without endotracheal intubation. There are no comprehensive reviews addressing the various pros and cons of an un-intubated airway management. It is hoped that the present review will benefit both anesthesia providers and gastroenterologists. The reasons to avoid routine endotracheal intubation and the approaches for an un-intubated anesthetic management are discussed. The special situations where endotracheal intubation is the preferred approach are mentioned. Many special techniques to manage airway are illustrated. Keywords ERCP Sedation Airway Endoscopic retrograde cholangiopancreatography
Background A 59-year-old American Society of Anesthesiologists (ASA) physical status 2 male presented for an endoscopic retrograde cholangiopancreatography (ERCP). Past medical history was unremarkable apart from chronic atrial fibrillation. The ventricular rate was well controlled with medications. After
B. Goudra (&) Clinical Anesthesiology and Critical Care, Perelman School of Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA, USA e-mail: [email protected] P. M. Singh Department of Anesthesia, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India e-mail: [email protected]
providing an explanation of the MAC anesthesia and associated risks, an informed consent was obtained. The gastroenterologist explained in detail about the ERCP and the stone extraction. As per the standard practice, a decision was made to proceed with deep sedation without endotracheal intubation. During the procedure, desaturation set in that could not be treated quickly. This was followed by sudden onset of ventricular tachycardia. The patient was turned supine, intubated and CPR instituted. Although effective cardiac activity and circulation could be reestablished, the patient died a few hours later. Horrific experiences like this are bound to affect clinical practice of all anesthesia providers. Irrational and many times non-evidence based decisions can be made based on either personal experience like this one or experiences of others. However, as experienced and trained medical professionals, it is important that crucial practice decisions like endotracheal intubation are made based on the available evidence rather than a rare clinical event, however disastrous it might be. To highlight this statement consider another example. A 66-year-old male presented for a diagnostic upper gastrointestinal (GI) endoscopic procedure. History included severe aortic stenosis (valve orifice of 0.8 cm2). Again as per the standard practice, sedation was administered with propofol without endotracheal intubation. Hypoxemia (as evidenced by desaturation) led to cardiac arrest. CPR (cardio pulmonary resuscitation) was quickly instituted; however, the patient sustained anoxic brain injury. Although both of these unfortunate events were heralded by hypoxemia and possibly could have been prevented by elective endotracheal intubation (ETT), it is unlikely that anesthesia providers will be inclined to intubate all patients presenting for upper GI endoscopy, as much as they are likely to intubate all patents presenting for ERCP. In spite of adverse outcome in both situations, the prone positioning necessary for ERCP segregates this entity into a
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Table 1 Indications of endoscopic retrograde cholangiopancreatography (ERCP) in an outpatient center Indication
Occurrence
Chronic pancreatitis
6.25 %
Post hepatic transplant
41.43 %
Hepatic cancer (including metastasis)
8.56 %
Cholangiocarcinoma
8.56 %
Primary sclerosing cholangitis
4.62 %
Pancreatic cancer
20.83 %
Others
9.72 %
separate category. It is partly due to our long-held belief regarding the consequence of airway loss in an unintubated patient undergoing procedure in prone position. An important distinction has to be made regarding surgical procedure versus endoscopic procedure conducted in prone position. An intracranial procedure (with all its complexities in terms of positioning) or a spine procedure is entirely different than an ERCP, although both are conducted in prone position. First, endoscopic procedures can be aborted at any notice to facilitate airway management. The second difference, although depth of sedation for an ERCP is similar to or even greater than needed for a neurosurgical procedure, it is possible to titrate the anesthetic depth to maintain spontaneous ventilation. The intensity of stimulation for an ERCP is nowhere near a surgical incision and, apart from the phase of gastroscope insertion, is relatively constant. Further discussion on anesthetic approach and airway management of patients presenting for an ERCP will be based on these two factors.
laryngoscope is likely to change the landscape, intubationrelated injuries are common. Lip, dental and eye and other soft tissue injuries happen with a degree of frequency [2– 4]. Although these injuries are not life threatening, they are preventable and especially injuries to the eye can be disabling. More serious injuries like bronchial rupture can occur especially with the use of introducers [5]. Endotracheal intubation almost invariably requires administration of skeletal muscle relaxants. Due to the unexpected duration of this diagnostic and therapeutic procedure, it is sensible to use succinylcholine for this purpose. Apart from the well-known risks of muscle pain, myoglobulinemia myoglobinuria, succinylcholine is implicated in malignant hyperthermia [6, 7]. Depending on the endoscopic findings, sometimes it becomes necessary to administer a long acting relaxant along with the need for reversal agents. Apart from a significant increase in anesthesia times, use of muscle relaxants can increase the incidence of postoperative pulmonary complications [8, 9]. Use of reversal agents is associated with unwanted anticholinergic effects. Use of glycopyrrolate is not universal. Use of atropine for this purpose can potentially lead to central anticholinergic effects. Residual neuromuscular blockade is an important issue with nondepolarizing muscle relaxants [10, 11]. It can occur even 2 h after reversal. Inadequate reversal is an additional risk factor. It is hoped that advent of sugamedex [12] might change the role of nondepolarizing muscle relaxants in future.
Prone Positioning and ETT The Intubation Dilemma Endoscopic retrograde cholangopancreatography poses unique challenges to both anesthesia provider and gastroenterologist. The last two decades have seen a phenomenal increase in the number of ERCPS. With the expanding indications, the patient population presenting for these procedures has also grown older and sicker. Some of the indications in our own hospital (from a retrospective review of 653 patients) are presented in Table 1 [1]. Although it is tempting to intubate all ERCPS and such is the practice in many centers around the world, the following considerations are to be borne in mind before committing all or a majority of patients to ETT.
Why Routine ETT Anesthesia Should Be Discouraged? How Safe is Laryngoscopy and Intubation? Laryngoscopy and endotracheal intubation itself is not an entirely innocuous procedure. Although the advent of video
123
Although all ERCP procedures involve prone positioning, patients are asked to position themselves when ETT is not involved. Turning prone after intubating in supine position presents significant challenges. Endoscopy units are not as well staffed as other surgical operating rooms. Injuries can occur during positioning and while positioned. Accidental extubation is risky, although can be managed either with bag-mask or a laryngeal mask airway (LMA) [13].
Efficiency Especially for very short procedures like change of stent, the endotracheal anesthesia adds significant additional time. In a retrospective study [14], we found that ‘‘anesthesia time’’ (total time minus procedural time) is a significant factor contributing to overall time in ERCP procedure. This time can be reduced by using dedicated anesthesiologists, and decreased incidence of endotracheal intubation is a contributing factor.
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Why Anesthesiologists Intubate the Trachea? Fear of Losing Airway Fear of losing airway during the procedure is probably the most common reason for elective endotracheal intubation among the anesthesia providers. However, those fears are unfounded. Many publications during recent months have affirmed the safety of unintubated ERCP. Goudra et al. studied 653 consecutive patients undergoing elective ERCP in their outpatient center. Their intubation rate was \1 % and all the indications were fear of full stomach and history of aspiration. There were no instances of procedure interruption or emergency endotracheal intubation. Even while anesthetizing far sicker patients in their inpatient endoscopy center, the incidence of endotracheal intubation was \10 %. In a recent study, non-obese patients who underwent ERCP needed endotracheal intubation in about 10 % procedures [15]. Risk of Hypoxemia Many investigators have closely studied the risk of hypoxemia in patients undergoing advanced endoscopic procedures and ERCP [1, 14, 16]. In the study cited above [15], although incidence of endotracheal intubation for ERCP was \10 %, the incidence of oxygen desaturation was worryingly high. It is well known that hypoxemia (as evidenced by desaturation) is the most common precursor of more serious adverse events like cardiac arrhythmias and asystole. Part of the reasons for a striking difference in the intubation and desaturation rates might be the airway management technique. In one institution, airway management was geared towards preventing hypoxemia. By extensive use of either a nasal trumpet or an oral trumpet (both in turn connected to a mapelson breathing system, Figs. 1a, b, 2), one center could reduce the incidence of desaturation to negligible levels. However, if an anesthesia provider decides to embark on an unintubated approach while sedating these patients, certain precautions need to be undertaken [1]. Preoxygenation and timing of propofol administration along with the timing of endoscope insertion are all crucial. As it is well known, once the lungs are filled with 100 % oxygen by elective preoxygenation, it can take up to 11 min for pulse oximeter to register a desaturation to 90 %, in spite of no ventilation. Although, both preoxygenation for 3 min or four vital capacity breaths can provide at least 4 min of ‘‘safety time’’ before patients start desaturating, it is advised to use the former technique as the time available to deal with inadequate ventilation will be longer (up to 8 min) [17]. This is due to the nature of the oxygen desaturation curve. The arterial partial pressure of oxygen
Fig. 1 a A nasal trumpet placed in the nose and connected to a Mapelson C breathing system with an elective endotracheal intubation (ETT) adapter. b A nasal trumpet placed in the nose and connected to a Mapelson C breathing system, bag squeezed to assist
Fig. 2 A nasal trumpet placed in the mouth and connected to a Mapelson C breathing system with an ETT adapter
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appropriate airway manipulation. Assisting ventilation using a Mapelson breathing system (while depth of sedation is reduced appropriately) is useful [1, 14]. Many times, nothing more is required until spontaneous ventilation is established. However, the nature of the upper airway under propofol sedation with the gastroscope in situ is unpredictable and variable. As shown in the pictures, gastroscope might displace the tongue and help to establish the patency of the airway in many cases; however, by no means is it certain (Figs. 3 and 4). Risk of Aspiration
Fig. 3 A view from above taken from another fiber-optic bronchoscope with gastroscope in place; airway classification Mallampatti
The risk of aspiration in patients undergoing colonoscopy under propofol mediated sedation was highlighted in a recent large retrospective study [20]. Even in the absence of gastric outlet obstruction, there is probably an increased risk of aspiration in patients undergoing ERCP (although no data are available). For procedures like drainage of pancreatic pseudocyst, endotracheal intubation is the airway management of choice. Single stage drainage of these cysts is common [21, 22] and the biochemical analysis has shown high protein content [23]. Like in other endoscopic procedures, silent aspiration of gastric contents cannot be ruled out during ERCP [24]. Lack of Reliable Monitoring in an Unintubated Patient
Fig. 4 A view from above taken from another fiber-optic bronchoscope with gastroscope in place; airway classification Mallampatti
has to fall from an initial 660 to about 90 mmHg for a fall in oxygen saturation. The patient needs to be either apneic or hypopneic for prolonged periods (depending on FRC and oxygen consumption) before the pulse oximeter can register desaturation. This period is difficult to detect without close observation. Although ASA has recommended the use of ECO2 monitoring for all patients undergoing GI endoscopic procedure under anesthesiaprovider provided sedation [18], its efficacy in the setting of GI endoscopy is far from satisfactory [19]. Close observation of the chest movement and alternative, more reliable means of ventilation (like acoustic respiratory monitor or impedance peumograpghy) are to be considered. The second issue is to have a means of assisting ventilation if (and when) hypoventilation is detected. Obviously, any airway obstruction needs to be corrected by
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ASA has recommended end tidal carbon dioxide monitoring in all patients undergoing these procedures with moderate to deep sedation [18]. However, practicalities of implementation are a major problem. End tidal carbon dioxide is not a reliable monitor in this setting [19]. There is nothing inherently wrong with the monitor, however practical obstacles prevent obtaining a reliable sample. Various devices to obtain such a sample are proposed, their reliability in the setting of upper GI endoscopy in general and ERCP in particular is not studied. Acoustic respiratory monitor and impedance pneumography are better respiratory monitoring alternatives. As impedance pneumography cannot detect breathing against an obstructed upper airway, acoustic respiratory monitoring may be preferable. Cardiac Arrest in Patients Undergoing ERCP and Upper GI Endoscopy The incidence of cardiac arrest in patients undergoing GI endoscpy is high compared to other forms of anesthesia. Interestingly, the cardiac arrests were all heralded by respiratory complications (much like pediatric anesthesia practice). However both the incidence and severity of such complications are no different between ERCP and other forms of upper GI endoscopy (like endoscopic ultrasound
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or therapeutic endoscopy). The incidence during colonoscopy was zero during the same period.
517 Fig. 5 Gastrolaryngeal tube
Airway Management for Prone ERCP As mentioned earlier, the oxygen dissociation curve is not an anesthesia provider’s friend. Due to the steep portion of the curve, it is very important (while anesthetizing any unintubated, spontaneously ventilating patient) to have a low threshold for endoscope withdrawal. Corrective airway maneuvers need to be instituted in anticipation of hypoxemia rather than as a response to hypoxemia. Waiting for pulse oximeter to display a saturation of 90–95 to respond might be too late. To facilitate such an approach, a patient’s ventilatory efforts need to be observed very closely. If the attending anesthesiologist (supervising the case) is doubtful of the abilities of his assistant, intubation might be a safer option. These skills can be easily taught and learnt. Especially in the initial stages of the procedure (endoscope insertion and recommencement of effective ventilation), documentation needs to be ignored and attention paid to monitor the patient. Inadequate levels of sedation can equally lead to severe cough and sometimes laryngospasm. In the absence of effective preoxygenation, hypoxemia can set in very quickly. As ERCP scopes have a side camera (rather than at the tip) insertion difficulties can lead to inadvertent stimulation of vocal cords triggering violent cough. Immediate endoscope withdrawal and deepening sedation is important. An anesthesia provider should not hesitate to express his concerns and request for a more experienced endoscopist to do the insertion. If the difficulties continue, it is prudent to reevaluate the plan and effect an endotracheal intubation after turning supine. At times, after commencement of the procedure, airway manipulations, insertion of nasal trumpet or bagging with the oral/nasal trumpet are insufficient to prevent hypoxemia. In such cases, withdrawal of the scope and bagging with a face mask to reoxygente is required. In the absence of any other difficulties, after appropriate adjustment of the depth of sedation, endoscope reinsertion can be permitted. There is increasing evidence as to the safety of LMA both as a primary airway in prone position and as a rescue method [13, 25, 26]. Although, a nasal trumpet connected to a Mapelson C breathing system (Fig. 1a, b) has been used as a standard in our hospital, it can also be used as a rescue measure. Another way to administer oxygen is by use of a modified nasal airway inserted into the mouth next to bite block and connected to a Mapelson C breathing system (Fig. 2). Both gastrolaryngeal tube (Fig. 5) and endoscopy mask (Fig. 6) could be used as support and possible ventilation during ERCP procedures [27]. However there is little
Fig. 6 Endoscopy mask
published literature with either of these airways during these procedures. Absence of a suction port is an obvious disadvantage with an endoscopy mask. Studies documenting the use of LMA for ERCP are lacking, but its use in prone position to administer anesthesia for other surgical procedures are plenty.
Who Should Provide Anesthesia for ERCP? Another way to increase both the safety and efficiency in ERCP sedation is to have a team of dedicated anesthesia providers. This approach is known to decrease desaturations and reduce the anesthesia time [14]. In this recently published study, a comparison was made between two naturally divided groups of anesthesia providers. Apart from an incidence of desaturation, a comparison was also made between the ‘‘anesthesia time’’ in the two groups. As a group, non-dedicated anesthesia providers took more time than dedicated providers. Moreover this amounted to an increase in the cost of anesthesia by about 760,000 US$
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in one hospital alone. Although no special fellowships and certifications are currently necessary, out-of-OR anesthesia might soon become frequent and complicated enough to require additional training. At the hospital of the University of Pennsylvania, dedicated out-of-operating-room resident anesthesia rotations are already in place to address this aspect of training. It is hoped that ASA and ABA will notice this expanding field of anesthesia and make appropriate provisions in the residency training curriculum. Frequently, the question arises about the nomenclature of sedation technique used for these procedures. Gastroenterologists are always competing with anesthesia providers to administer propofol. As observed in our institution, although the patients presenting for upper endoscopy (including ERCP) are told (and consented) that they will have moderate to deep sedation, 96 % of these patients were under deep general anesthesia as measured by brain function monitor (SEDLne). As a result, it is only appropriate that ‘‘sedation’’ for these procedures is provided by anesthesia providers. Having discussed the pros and cons of endotracheal intubation for ERCP, a low threshold to intubate is advised in the following subset of patients.
Obesity As stated earlier, emergency expert help in turning the patient supine to secure an airway may not be easy in an endoscopic suite. In a morbidly obese patient, such heroics could be fraught with dangers. With an already compromised FRC and increased oxygen consumption, time available to reestablish effective ventilation will be very limited. ETT is the preferred method of airway management, especially in the inexperienced.
Risk of Aspiration Suspicion of gastric outlet obstruction, full stomach and drainage of pseudocyst of pancreas are probably managed better with an ETT. Anticipated Difficult Ventilation Although anticipated difficult intubation may not be an indication for elective ETT, anticipated difficult ventilation should be. Additionally, other institution-specific factors like availability of anesthesia provider with experience in endoscopy anesthesia, location and size of the room, type and extent of help are important in this decision making.
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Conclusions Patients presenting for an ERCP can be safely and effectively sedated without the need for an elective endotracheal intubation. Close respiratory monitoring, ready availability of means of establishing ventilation and experience are important. Various airway techniques and adjuncts described can help in preventing and treating hypoxemia. Conflict of interest
None.
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