- Email: [email protected]
Use of the ProSeal™ laryngeal mask airway in a pregnant patient with a difficult airway during electroconvulsive therapy
Brown et al.
11 Hunt M. Syncope. In: Rosen P, Barkin R. Emergency Medicine: Concepts and Clinical Practice, 4th Edn. St Louis: Mosby-Year Book, 1998; 1570±82 12 Engl MR. The changes in bispectral index during a hypovolemic cardiac arrest. Anesthesiology 1999; 91: 1947±9 13 Merat S, Levecque J-P, Le Gulluche Y, Diraison Y, Brinquin L, Hoffmann J-J. BIS monitoring may allow the detection of severe cerebral ischemia. Can J Anaesth 2001; 48: 1066±9 14 Krumholz A. Nonepileptic seizures: diagnosis and management. Neurology 1999; 53 (5 Suppl 2): S76±83 15 Chabolla DR, Krahn LE, So EL, Rummans TA. Psychogenic nonepileptic seizures. Mayo Clin Proc 1996; 71: 493±500 16 Bruhn J, Bouillon TW, Shafer SL. Electromyographic activity falsely elevates the bispectral index. Anesthesiology 2000; 92: 1485±7 17 Kinsella SM, Tuckey JP. Perioperative bradycardia and asystole: relationship to vasovagal syncope and the Bezold±Jarisch re¯ex. Br J Anaesth 2002; 86: 859±68 18 VanLieshout JJ, Wieling W, Karemaker JM, Eckberg DL. The vasovagal response. Clin Sci 1991; 81: 575±86 19 Mercader MA, Varghese PJ, Potolicchio SJ, Venkatraman GK, Lee SW. New insights into the mechanism of neurally mediated syncope. Heart 2002; 88: 217±21
British Journal of Anaesthesia 91 (5): 752±4 (2003)
DOI: 10.1093/bja/aeg227
Use of the ProSealÔ Ô laryngeal mask airway in a pregnant patient with a dif®cult airway during electroconvulsive therapy N. Ivascu Brown1, P. Fogarty Mack1, D. M. Mitera2 and P. Dhar1* 1
Department of Anesthesiology and 2Department of Psychiatry, New York Presbyterian Hospital, Weill Medical College of Cornell University, New York, NY, USA *Corresponding author: 525 East 68th Street, Room M-323, New York, NY 10021, USA. E-mail: [email protected] We describe a patient at 20±22 weeks gestation, with a known dif®cult airway, who underwent eight sessions of electroconvulsive therapy using the ProSealÔ laryngeal mask airway and controlled ventilation. The airway management options for brief periods of general anaesthesia in patients with increased gastric volume are discussed. Br J Anaesth 2003; 91: 752±4 Keywords: airway, management; brain, electroconvulsive therapy; equipment, ProSealÔ laryngeal mask airway; pregnancy Accepted for publication: June 30, 2003
Electroconvulsive therapy (ECT) is an established treatment modality for various mood disorders. It requires a brief period of general anaesthesia and controlled ventilation during which an electrical stimulus is applied to the patient's head, inducing a grand mal seizure. The
American Psychiatric Association (APA) practice guidelines endorse the safety and ef®cacy of ECT for major depressive and bipolar disorders, and suggest ECT as a `primary treatment for these disorders during pregnancy'.1 The APA Task Force Report on ECT also acknowledges the
Ó The Board of Management and Trustees of the British Journal of Anaesthesia 2003
Downloaded from http://bja.oxfordjournals.org/ at UCSF Library on March 15, 2015
2 Hampl KF, Schneider MC. Vasovagal asystole before induction of general anaesthesia. Eur J Anaesthesiol 1994; 11: 131±3 3 Keane TK, Hennis PJ, Bink-Boelkens MT. Non-drug related asystole associated with anesthetic induction. Anaesthesia 1991; 46: 38±9 4 Barnett TP, Johnson LC, Naitoh P, et al. Bispectral analysis of electroencephalogram signals during waking and sleeping. Science 1971; 172: 401±2 5 Leslie K, Sessler DI, Schroeder M, Walters K. Propofol blood concentration and the bispectral index predict suppression of learning during propofol/epidural anesthesia in volunteers. Anesth Analg 1995; 81: 1269±74 6 Kearse LA, Rosow C, Zaslavsky A, et al. Bispectral analysis of the electroencephalogram predicts conscious processing of information during propofol sedation and hypnosis. Anesthesiology 1998; 88: 25±34 7 American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th Edn. Washington, DC: American Psychiatric Association, 1994 8 Martin RB. Anxiety, its manifestation and role in the dental patient. Dent Clin North Am 1995; 39: 523±39 9 Malamed SF. Managing medical emergencies. J Am Dent Assoc 1993; 124: 40±53 10 Verril PJ, Aelling WH. Vasovagal faint in the supine position. Br Med J 1970; IV: 348
ProSealTM laryngeal mask airway in a pregnant patient during ECT
safety of ECT during all three trimesters of pregnancy.2 We present a case of a pregnant patient (20±22 weeks) with a dif®cult airway who underwent a series of ECT using a ProSealÔ laryngeal mask airway (PLMA).
Case report
Discussion Pregnant women are more prone to aspiration than nonpregnant patients for several reasons.4 First, the enlarged uterus increases intrabdominal and thus intragastric pressures. Secondly, gastric volume and the acidity of the gastric contents are increased by gastrin, which is produced by the placenta. Lower oesophageal sphincter tone may be reduced and complete gastric emptying is thought to be delayed; however, this continues to be controversial.5 Finally,
²
753
LMAâ is the property of Intavent Limited.
Downloaded from http://bja.oxfordjournals.org/ at UCSF Library on March 15, 2015
A 37-yr-old gravida 2, para 1 patient at 20 weeks gestation (63 kg, 160 cm), ASA physical status III, with psychotic depression, presented for ECT. Airway evaluation demonstrated a Mallampati class II airway, intact dentition, a small mandible, a high arched and narrow palate, anterior overriding of the maxillary teeth, and a thyromental distance of 5 cm. The patient denied any symptoms of gastroesophageal re¯ux disease. The patient was fasted overnight and sodium citrate (30 ml) was administered. She was positioned with left uterine displacement, and pre-oxygenated. Rapid sequence induction of anaesthesia was effected with thiopental 3 mg kg±1 and succinylcholine 1.6 mg kg±1. Laryngoscopy with a Macintosh 3 blade provided a Cormack grade III view.3 While maintaining cricoid pressure (Sellick manoeuvre), a 6.0 mm endotracheal tube was placed by an experienced anaesthetist, but with great dif®culty. As this patient was to undergo a series of such treatments, and had been a problematic intubation, an alternative means of controlling the airway was sought. The ProSealÔ LMA (PLMA) was chosen for airway management during the subsequent ECT sessions. Patient preparation and anaesthetic management remained the same except that a size 4 PLMA was inserted with the introducer after rapid sequence induction. Cricoid pressure was released for PLMA placement. The PLMA was in¯ated with 18 ml of air. With each treatment, bilateral breath sounds and the absence of sounds over the epigastrium were con®rmed. There was no appreciable air leak. Lubricant gel (1ml) was placed over the proximal ori®ce of the drainage tube to detect any gastric insuf¯ation or malposition. At each session, a ®breoptic bronchoscope was used to con®rm the absence of ¯uid in the glottic aperture and proper placement. When the patient regained consciousness and airway re¯exes were observed, the PLMA was removed in¯ated. The patient denied any sore throat. She underwent a series of eight ECT treatments in this manner, over a period of 3 weeks, without any adverse events.
aspiration in pregnant patients is more likely during a dif®cult intubation.5 In this patient, airway management options included tracheal intubation, mask ventilation with constant cricoid pressure, the classic laryngeal mask airway (LMA)², or the ProSealÔ LMA. A rapid sequence induction and intubation is the most de®nitive means of airway protection at this stage of pregnancy. However, as the initial intubation was problematic, quick and atraumatic placement of a tracheal tube at each session could not be assured. Mask ventilation with cricoid pressure does not prevent gastric insuf¯ation. Proper mask ®t may be dif®cult to attain, as a bite block also has to be placed during the grand mal seizure. In a study comparing the LMA with the facemask, oxygen desaturation occurred in 13 and 52% of patients, respectively.6 The classic LMA has been used during elective Caesarean section in 1067 patients preferring general anaesthesia, but cricoid pressure was maintained until delivery.7 In a retrospective review of 11 910 patients, the incidence of aspiration with the LMA was 0.84/10 000.8 The PLMA was chosen in this scenario because it has design modi®cations that allow a better seal than the classic LMA, decreasing the likelihood of gastric insuf¯ation during positive pressure ventilation. The PLMA design includes a modi®ed cuff to isolate the glottis from the oesophagus, and a drainage tube alongside the airway tube, allowing ¯uid from the stomach and oesophagus to bypass the pharynx and mouth or to be suctioned;9 10 the connection also equilibrates the stomach and atmospheric pressures, reducing gastric insuf¯ation. The PLMA has several modi®cations that may protect against aspiration of regurgitated ¯uid. If properly placed, the drainage tube should be aligned with the oesophageal opening, and the distal cuff should be sealed against the hypopharynx.11 An accessory vent under the drainage tube in the bowl of the PLMA prevents pooling of secretions.12 Finally, the PLMA has a built-in bite block that proved to be effective in our patient during the induced grand mal seizure. In cadavers, even with a clamped drainage tube, the airway was protected from retrograde injection of ¯uid from the oesophagus until pressures of 68±73 cm H2O were reached inside the bowl of the PLMA.12 In a study of 103 patients, methylene blue in saline was injected down the drainage tube to ®ll the hypopharynx. A ®bre-optic bronchoscope, passed down the airway tube at the beginning and end of each case, demonstrated no leakage of methylene blue into the bowl of the mask or the oropharynx in all but two cases. These exceptions were attributed to light anaesthesia and mask displacement.13 Although we used a ®bre-optic scope for con®rmation of PLMA placement, this is not required in routine practice. ECT is a treatment that requires ef®cient and reliable control of the airway for short periods. If a prolonged
Brown et al.
intubation time or dif®culty in securing the airway is encountered, the patient may waken as the drug effects subside. Repeated bolus doses of the induction agent is not an option, as this will interfere with the seizure threshold and preclude completion of the procedure. The PLMA was used effectively in a pregnant patient deemed to be at increased risk of aspiration. Rapid sequence induction and insertion of the PLMA allowed immediate control of ventilation. The PLMA may be considered in circumstances where rapid but brief control of the airway is required in pregnant patients.
Acknowledgements The authors would like to thank Drs Cynthia Lien and Farida Gadalla for their assistance.
1 Weiner RD, Coffey CE, Fochtman LJ, et al. The Practice of Electroconvulsive Therapy: Recommendations for Treatment, Training and Privileging, 2nd Edn. Washington DC: American Psychiatric Association, 2001; 46 2 Echevarria Moreno M, Marin Munoz J, Sanchez Valderrabanos J, et al. Electroconvulsive therapy in the ®rst trimester of pregnancy. J ECT 1998; 14: 251±4 3 Cormack RS, Lehane J. Dif®cult tracheal intubation in obstetrics. Anesthesiology 1984; 39: 1105±11
754
Downloaded from http://bja.oxfordjournals.org/ at UCSF Library on March 15, 2015
References
4 Koffel BL. Physiologic adaptation to pregnancy; the healthy parturient. In: Norris MD, ed. Obstetric Anesthesia. Philadelphia: Lippincott, William & Wilkins, 1999; 16±8 5 Gibbs CP, Rolbin SH, Norien P. Cause and prevention of maternal aspiration. Anesthesiology 1984; 61: 111±2 6 Smith I, White PF. Use of the Laryngeal Mask Airway as an alternative to a face mask during outpatient arthroscopy. Anesthesiology 1992; 77: 850±5 7 Han T, Brimacrombe J, Lee E, et al. The laryngeal mask airway is effective and probably safe in selected healthy parturients for elective Caesarean section: a prospective study of 1067 cases. Can J Anesth 2001; 48: 1117±21 8 Verghese C, Brimacrombe J. Survey of laryngeal mask airway usage in 11,910 patients: safety and ef®cacy for conventional and nonconventional usage. Anesth Analg 1996; 82: 129±33 9 Brain AI, Verghese C, Strube PJ. The LMA ProsealÐa laryngeal mask with an oesphageal vent. Br J Anaesth 2000; 84: 650±4 10 Evans NR, Lewellyn RL, Gardner SV, et al. Aspiration prevented by the Proseal laryngeal mask airway: a case report. Can J Anesth 2002; 49: 413±6 11 Brimacombe J, Keller C. The proseal laryngeal mask airway: a randomized, crossover study with the standard laryngeal mask in paralyzed, anesthetized patients. Anesthesiology 2000; 93: 104±9 12 Keller C, Brimacombe J, Kleinsasser, et al. Does the Proseal laryngeal mask airway prevent aspiration of regurgitated ¯uid? Anesth Analg 2000; 91: 1017±20 13 Evans NR, Gardner SV, James MFM. Proseal laryngeal mask protects against aspiration of ¯uid in the pharynx. Br J Anaesth 2002; 88: 584±7
11 Hunt M. Syncope. In: Rosen P, Barkin R. Emergency Medicine: Concepts and Clinical Practice, 4th Edn. St Louis: Mosby-Year Book, 1998; 1570±82 12 Engl MR. The changes in bispectral index during a hypovolemic cardiac arrest. Anesthesiology 1999; 91: 1947±9 13 Merat S, Levecque J-P, Le Gulluche Y, Diraison Y, Brinquin L, Hoffmann J-J. BIS monitoring may allow the detection of severe cerebral ischemia. Can J Anaesth 2001; 48: 1066±9 14 Krumholz A. Nonepileptic seizures: diagnosis and management. Neurology 1999; 53 (5 Suppl 2): S76±83 15 Chabolla DR, Krahn LE, So EL, Rummans TA. Psychogenic nonepileptic seizures. Mayo Clin Proc 1996; 71: 493±500 16 Bruhn J, Bouillon TW, Shafer SL. Electromyographic activity falsely elevates the bispectral index. Anesthesiology 2000; 92: 1485±7 17 Kinsella SM, Tuckey JP. Perioperative bradycardia and asystole: relationship to vasovagal syncope and the Bezold±Jarisch re¯ex. Br J Anaesth 2002; 86: 859±68 18 VanLieshout JJ, Wieling W, Karemaker JM, Eckberg DL. The vasovagal response. Clin Sci 1991; 81: 575±86 19 Mercader MA, Varghese PJ, Potolicchio SJ, Venkatraman GK, Lee SW. New insights into the mechanism of neurally mediated syncope. Heart 2002; 88: 217±21
British Journal of Anaesthesia 91 (5): 752±4 (2003)
DOI: 10.1093/bja/aeg227
Use of the ProSealÔ Ô laryngeal mask airway in a pregnant patient with a dif®cult airway during electroconvulsive therapy N. Ivascu Brown1, P. Fogarty Mack1, D. M. Mitera2 and P. Dhar1* 1
Department of Anesthesiology and 2Department of Psychiatry, New York Presbyterian Hospital, Weill Medical College of Cornell University, New York, NY, USA *Corresponding author: 525 East 68th Street, Room M-323, New York, NY 10021, USA. E-mail: [email protected] We describe a patient at 20±22 weeks gestation, with a known dif®cult airway, who underwent eight sessions of electroconvulsive therapy using the ProSealÔ laryngeal mask airway and controlled ventilation. The airway management options for brief periods of general anaesthesia in patients with increased gastric volume are discussed. Br J Anaesth 2003; 91: 752±4 Keywords: airway, management; brain, electroconvulsive therapy; equipment, ProSealÔ laryngeal mask airway; pregnancy Accepted for publication: June 30, 2003
Electroconvulsive therapy (ECT) is an established treatment modality for various mood disorders. It requires a brief period of general anaesthesia and controlled ventilation during which an electrical stimulus is applied to the patient's head, inducing a grand mal seizure. The
American Psychiatric Association (APA) practice guidelines endorse the safety and ef®cacy of ECT for major depressive and bipolar disorders, and suggest ECT as a `primary treatment for these disorders during pregnancy'.1 The APA Task Force Report on ECT also acknowledges the
Ó The Board of Management and Trustees of the British Journal of Anaesthesia 2003
Downloaded from http://bja.oxfordjournals.org/ at UCSF Library on March 15, 2015
2 Hampl KF, Schneider MC. Vasovagal asystole before induction of general anaesthesia. Eur J Anaesthesiol 1994; 11: 131±3 3 Keane TK, Hennis PJ, Bink-Boelkens MT. Non-drug related asystole associated with anesthetic induction. Anaesthesia 1991; 46: 38±9 4 Barnett TP, Johnson LC, Naitoh P, et al. Bispectral analysis of electroencephalogram signals during waking and sleeping. Science 1971; 172: 401±2 5 Leslie K, Sessler DI, Schroeder M, Walters K. Propofol blood concentration and the bispectral index predict suppression of learning during propofol/epidural anesthesia in volunteers. Anesth Analg 1995; 81: 1269±74 6 Kearse LA, Rosow C, Zaslavsky A, et al. Bispectral analysis of the electroencephalogram predicts conscious processing of information during propofol sedation and hypnosis. Anesthesiology 1998; 88: 25±34 7 American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th Edn. Washington, DC: American Psychiatric Association, 1994 8 Martin RB. Anxiety, its manifestation and role in the dental patient. Dent Clin North Am 1995; 39: 523±39 9 Malamed SF. Managing medical emergencies. J Am Dent Assoc 1993; 124: 40±53 10 Verril PJ, Aelling WH. Vasovagal faint in the supine position. Br Med J 1970; IV: 348
ProSealTM laryngeal mask airway in a pregnant patient during ECT
safety of ECT during all three trimesters of pregnancy.2 We present a case of a pregnant patient (20±22 weeks) with a dif®cult airway who underwent a series of ECT using a ProSealÔ laryngeal mask airway (PLMA).
Case report
Discussion Pregnant women are more prone to aspiration than nonpregnant patients for several reasons.4 First, the enlarged uterus increases intrabdominal and thus intragastric pressures. Secondly, gastric volume and the acidity of the gastric contents are increased by gastrin, which is produced by the placenta. Lower oesophageal sphincter tone may be reduced and complete gastric emptying is thought to be delayed; however, this continues to be controversial.5 Finally,
²
753
LMAâ is the property of Intavent Limited.
Downloaded from http://bja.oxfordjournals.org/ at UCSF Library on March 15, 2015
A 37-yr-old gravida 2, para 1 patient at 20 weeks gestation (63 kg, 160 cm), ASA physical status III, with psychotic depression, presented for ECT. Airway evaluation demonstrated a Mallampati class II airway, intact dentition, a small mandible, a high arched and narrow palate, anterior overriding of the maxillary teeth, and a thyromental distance of 5 cm. The patient denied any symptoms of gastroesophageal re¯ux disease. The patient was fasted overnight and sodium citrate (30 ml) was administered. She was positioned with left uterine displacement, and pre-oxygenated. Rapid sequence induction of anaesthesia was effected with thiopental 3 mg kg±1 and succinylcholine 1.6 mg kg±1. Laryngoscopy with a Macintosh 3 blade provided a Cormack grade III view.3 While maintaining cricoid pressure (Sellick manoeuvre), a 6.0 mm endotracheal tube was placed by an experienced anaesthetist, but with great dif®culty. As this patient was to undergo a series of such treatments, and had been a problematic intubation, an alternative means of controlling the airway was sought. The ProSealÔ LMA (PLMA) was chosen for airway management during the subsequent ECT sessions. Patient preparation and anaesthetic management remained the same except that a size 4 PLMA was inserted with the introducer after rapid sequence induction. Cricoid pressure was released for PLMA placement. The PLMA was in¯ated with 18 ml of air. With each treatment, bilateral breath sounds and the absence of sounds over the epigastrium were con®rmed. There was no appreciable air leak. Lubricant gel (1ml) was placed over the proximal ori®ce of the drainage tube to detect any gastric insuf¯ation or malposition. At each session, a ®breoptic bronchoscope was used to con®rm the absence of ¯uid in the glottic aperture and proper placement. When the patient regained consciousness and airway re¯exes were observed, the PLMA was removed in¯ated. The patient denied any sore throat. She underwent a series of eight ECT treatments in this manner, over a period of 3 weeks, without any adverse events.
aspiration in pregnant patients is more likely during a dif®cult intubation.5 In this patient, airway management options included tracheal intubation, mask ventilation with constant cricoid pressure, the classic laryngeal mask airway (LMA)², or the ProSealÔ LMA. A rapid sequence induction and intubation is the most de®nitive means of airway protection at this stage of pregnancy. However, as the initial intubation was problematic, quick and atraumatic placement of a tracheal tube at each session could not be assured. Mask ventilation with cricoid pressure does not prevent gastric insuf¯ation. Proper mask ®t may be dif®cult to attain, as a bite block also has to be placed during the grand mal seizure. In a study comparing the LMA with the facemask, oxygen desaturation occurred in 13 and 52% of patients, respectively.6 The classic LMA has been used during elective Caesarean section in 1067 patients preferring general anaesthesia, but cricoid pressure was maintained until delivery.7 In a retrospective review of 11 910 patients, the incidence of aspiration with the LMA was 0.84/10 000.8 The PLMA was chosen in this scenario because it has design modi®cations that allow a better seal than the classic LMA, decreasing the likelihood of gastric insuf¯ation during positive pressure ventilation. The PLMA design includes a modi®ed cuff to isolate the glottis from the oesophagus, and a drainage tube alongside the airway tube, allowing ¯uid from the stomach and oesophagus to bypass the pharynx and mouth or to be suctioned;9 10 the connection also equilibrates the stomach and atmospheric pressures, reducing gastric insuf¯ation. The PLMA has several modi®cations that may protect against aspiration of regurgitated ¯uid. If properly placed, the drainage tube should be aligned with the oesophageal opening, and the distal cuff should be sealed against the hypopharynx.11 An accessory vent under the drainage tube in the bowl of the PLMA prevents pooling of secretions.12 Finally, the PLMA has a built-in bite block that proved to be effective in our patient during the induced grand mal seizure. In cadavers, even with a clamped drainage tube, the airway was protected from retrograde injection of ¯uid from the oesophagus until pressures of 68±73 cm H2O were reached inside the bowl of the PLMA.12 In a study of 103 patients, methylene blue in saline was injected down the drainage tube to ®ll the hypopharynx. A ®bre-optic bronchoscope, passed down the airway tube at the beginning and end of each case, demonstrated no leakage of methylene blue into the bowl of the mask or the oropharynx in all but two cases. These exceptions were attributed to light anaesthesia and mask displacement.13 Although we used a ®bre-optic scope for con®rmation of PLMA placement, this is not required in routine practice. ECT is a treatment that requires ef®cient and reliable control of the airway for short periods. If a prolonged
Brown et al.
intubation time or dif®culty in securing the airway is encountered, the patient may waken as the drug effects subside. Repeated bolus doses of the induction agent is not an option, as this will interfere with the seizure threshold and preclude completion of the procedure. The PLMA was used effectively in a pregnant patient deemed to be at increased risk of aspiration. Rapid sequence induction and insertion of the PLMA allowed immediate control of ventilation. The PLMA may be considered in circumstances where rapid but brief control of the airway is required in pregnant patients.
Acknowledgements The authors would like to thank Drs Cynthia Lien and Farida Gadalla for their assistance.
1 Weiner RD, Coffey CE, Fochtman LJ, et al. The Practice of Electroconvulsive Therapy: Recommendations for Treatment, Training and Privileging, 2nd Edn. Washington DC: American Psychiatric Association, 2001; 46 2 Echevarria Moreno M, Marin Munoz J, Sanchez Valderrabanos J, et al. Electroconvulsive therapy in the ®rst trimester of pregnancy. J ECT 1998; 14: 251±4 3 Cormack RS, Lehane J. Dif®cult tracheal intubation in obstetrics. Anesthesiology 1984; 39: 1105±11
754
Downloaded from http://bja.oxfordjournals.org/ at UCSF Library on March 15, 2015
References
4 Koffel BL. Physiologic adaptation to pregnancy; the healthy parturient. In: Norris MD, ed. Obstetric Anesthesia. Philadelphia: Lippincott, William & Wilkins, 1999; 16±8 5 Gibbs CP, Rolbin SH, Norien P. Cause and prevention of maternal aspiration. Anesthesiology 1984; 61: 111±2 6 Smith I, White PF. Use of the Laryngeal Mask Airway as an alternative to a face mask during outpatient arthroscopy. Anesthesiology 1992; 77: 850±5 7 Han T, Brimacrombe J, Lee E, et al. The laryngeal mask airway is effective and probably safe in selected healthy parturients for elective Caesarean section: a prospective study of 1067 cases. Can J Anesth 2001; 48: 1117±21 8 Verghese C, Brimacrombe J. Survey of laryngeal mask airway usage in 11,910 patients: safety and ef®cacy for conventional and nonconventional usage. Anesth Analg 1996; 82: 129±33 9 Brain AI, Verghese C, Strube PJ. The LMA ProsealÐa laryngeal mask with an oesphageal vent. Br J Anaesth 2000; 84: 650±4 10 Evans NR, Lewellyn RL, Gardner SV, et al. Aspiration prevented by the Proseal laryngeal mask airway: a case report. Can J Anesth 2002; 49: 413±6 11 Brimacombe J, Keller C. The proseal laryngeal mask airway: a randomized, crossover study with the standard laryngeal mask in paralyzed, anesthetized patients. Anesthesiology 2000; 93: 104±9 12 Keller C, Brimacombe J, Kleinsasser, et al. Does the Proseal laryngeal mask airway prevent aspiration of regurgitated ¯uid? Anesth Analg 2000; 91: 1017±20 13 Evans NR, Gardner SV, James MFM. Proseal laryngeal mask protects against aspiration of ¯uid in the pharynx. Br J Anaesth 2002; 88: 584±7