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From the Department of Anaesthesia, University of Cape Town, Groote Schuur Hospital, Observatory, Cape Town, South Africa.
Dr. Niall R. Evans, Department of Anaesthesia, University of Cape Town, Groote Schuur Hospital, Observatory, Cape Town 7925, South Africa. Phone: +27-828986891; Fax: +27-821318986891; E-mail: niall{at}wol.co.za
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Abstract |
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Clinical features: A 32-yr-old man was electively scheduled for change of dressings and application of plaster of Paris to both legs. A size 5 PLMA was inserted on the first attempt and the patient allowed to breathe spontaneously. Twenty-five minutes into the procedure brown fluid was noticed in the drainage tube of the mask. There was no change in respiratory pattern nor any evidence of coughing retching or vomiting. Twenty-five millilitres of fluid were suctioned out of the tube which tested positive for acid. The PLMA was left in place and the procedure continued uneventfully. After removal of the mask pH testing showed the dorsum of the mask to have a pH of 7 and the ventrum/bowl of the mask to be dry with a pH of 7. The patient had no respiratory symptoms in the recovery room and the postoperative course was uneventful.
Conclusions: This case illustrates that passive regurgitation can occur unexpectedly intraoperatively and shows that the PLMA can protect the airway during such an event by allowing the regurgitated fluid to pass up the drainage tube without leaking into the glottis.
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Introduction |
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). A recent cadaver trial showed that a correctly placed PLMA isolated the airway by allowing fluid pumped into the esophagus from below to pass up the drainage tube without leaking into the glottis or oropharynx.4 We describe a case of intraoperative passive regurgitation where the PLMA successfully channelled fluid away from the respiratory tract.
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Case report |
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Anesthesia was induced with fentanyl 65 µg followed three minutes later by propofol 200 mg and maintained with isoflurane 1–2% in nitrous oxide and 33% oxygen at a fresh gas flow of 3 L•min-1 in a circle system with the patient breathing spontaneously. A size 5 PLMA was inserted easily on the first attempt using an introducer with the recommended technique as described by the manufacturer. The cuff of the mask was inflated with 35 mL of air to obtain an intracuff pressure of 60 cm H2O as measured by a calibrated aneroid manometre (Carron medical® control instruments RSA) and the lungs were ventilated easily, obtaining exhaled tidal volumes larger than 8 mL•kg-1. Adequate position of the mask was determined as recommended by Brain1 by sealing the proximal end of the drainage tube with lubricating jelly, pressurizing the breathing system, and noting the pressure at which gas leakage occurred. Leakage occurred from the mouth at 20 cm H2O with no leakage of air occurring up the drainage tube. Auscultation of the epigastrium revealed no gastric insufflation. A lubricated 16 G gastric tube was passed easily down the drainage tube into the stomach and 30 mL of fluid were aspirated using a 50-mL catheter tipped syringe. The fluid tested positive for gastric contents with litmus paper sensitive to changes of 1 pH unit from pH = 1 up to pH = 10 (Duotest® Macherey-Nagel Duren, Germany). The gastric tube was then removed.
Twenty-five minutes into the procedure brown fluid was noticed in the drainage tube of the mask. There was no corresponding change in respiratory pattern or any evidence of coughing, retching or vomiting. Exhaled tidal volume, respiratory rate, end-tidal carbon dioxide and percentage saturation of hemoglobin all remained constant. The mean arterial blood pressure and heart rate showed no change from maintenance levels of 70 mmHg and 80 beats•min-1 respectively. Twenty-five millilitres of fluid were suctioned out of the tube and tested positive for acid. The PLMA was left in place and the procedure continued uneventfully.
On awakening, when the patient could open his mouth to command, the PLMA was removed partially inflated and the dorsum and ventrum of the mask were tested with the litmus paper. The dorsum had a pH of 7 and the ventrum/bowl of the mask was dry with a pH of 7. The patient had no respiratory symptoms in the recovery room and the postoperative course was uneventful.
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Discussion |
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The potential for aspiration is the most limiting feature of the classic LMA5 and has been the subject of a recent editorial review.6 Studies involving esophageal manometry7 and lower esophageal pH studies8 suggest that lower esophageal relaxation occurs during LMA anesthesia. The incidence of silent regurgitation during LMA use is varyingly reported by different groups to be between 0%9,10 and 80%11,12 and it has been suggested that this incidence is technique dependent.13 Proper case selection and optimal techniques of placement as well as the maintenance of adequate levels of anesthesia throughout the procedure have been suggested as important contributory factors in the genesis of regurgitation during LMA anesthesia.14
The incidence of clinically detected regurgitation and aspiration derived from a meta-analysis of 547 LMA publications is approximately 1% and 0.02% respectively.5 This incidence of aspiration is similar to that reported for elective general anesthesia overall,15,16 although the two groups may not be comparable as "elective anesthesia" includes patients with potential full stomachs, a situation in which laryngeal masks are avoided.
However, no large retrospective or prospective studies are available examining the true incidence of aspiration with the LMA. The risk of unexpected regurgitation during anesthesia with a LMA remains, with no assurance of protection against aspiration.
Does the PLMA (particularly in view of its larger size) increase the risk of regurgitation? Although Vanner17 showed that the upper esophageal sphincter (UOS) is competent during spontaneous ventilation LMA anesthesia, Brain et al. in a pilot study of a prototype LMA point to the concern of a larger mask stretching and opening the UOS.18 Brimacombe and Keller found 2/60 patients to have an open UOS with the PLMA in place,2 and found the UOS to be open in the case of a regurgitation they documented.19 Opening of the UOS by the larger size of the PLMA may have been contributory in our case, although no fibreoptic visualization down the drainage tube was performed. Recent work by Brimacombe and Keller found that the PLMA had no effect on both UOS pressure and gastroesophageal barrier pressure in awake subjects.20 Further work should be done measuring the affect of the PLMA on the upper and lower esophageal sphincters during general anesthesia.
The ability of the PLMA to protect the airway during regurgitation depends on:19
The improved reliability of positioning of the PLMA is achieved by testing:1
These tests have been shown to predict effective isolation of the glottis from the esophagus while the mask is correctly positioned.2 In this case, the above tests predicted adequate alignment of the drainage tube and isolation of the glottis. Successful passage of the gastric tube also indicates that the tip of the mask has not folded posteriorly during insertion; this malposition may lead to gastric insufflation as described in a recent case report.21
Cadaver studies have investigated the barrier to regurgitated fluid created by the classic LMA22,23 and the PLMA4 by ligating the esophagus below the pharynx and infusing fluid into the esophagus using a continuous flow, pressure controlled pump. A fibreoptic bronchoscope was used to visualize when fluid appeared above and below the cuff of the mask. When inflated with 10 mL of air or more, the LMA and the PLMA with a clamped drainage tube were shown to prevent fluid leaking above and below the cuff until a pressure of 46–49 cm H2O was reached in the esophagus. This value increased to 63–68 cm H2O at higher cuff volumes for the clamped PLMA. With the drainage tube unclamped no leak above or below the cuff was found with the PLMA as fluid was successfully channelled upwards without any leak into the glottis or oropharynx.
The pressure generated during passive gastro-esophageal reflux is normally less than 10 cm H2O and rarely exceeds 30 cm H2O.24 The PLMA would be therefore expected to protect the glottis during passive regurgitation as occurred in this case. However, during retching or vomiting the pressure of the fluid can be expected to be higher, and the correct positioning of the mask itself is likely to be disrupted, resulting in the loss of the functional isolation of the respiratory tract.
An earlier prototype study in children25 had one episode of regurgitation in 50 cases; aspiration did not occur as the fluid passed up the drainage tube without leak into the bowl of the mask; the position (open/closed) of the UOS in this case is not documented.
Three reports have been published where an earlier prototype PLMA protected against aspiration in adults.26–28 Brimacombe describes more than 500 uses with one detectable incident of regurgitation in a recent report which describes a case where the PLMA successfully channelled regurgitated fluid away from the respiratory tract during the early postoperative phase.19 Another recent case is described where the PLMA protected against aspiration of fluid regurgitation which occurred intraoperatively.29
This case further illustrates that passive regurgitation of fluid can occur unexpectedly intraoperatively and shows that the PLMA can protect the airway during such an event.
Revision received January 18, 2002. Accepted for publication December 10, 2001.
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References |
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2 Brimacrombe J, Keller C. The proseal laryngeal mask airway: a randomised, crossover study with the standard laryngeal mask airway in paralysed, anaesthetised patients. Anesthesiology 2000; 93: 104–9.[Medline]
3
Keller C, Brimacrombe J. Mucosal pressure and oropharyngeal leak pressure with the Proseal vs. laryngeal mask airway in anaesthetized paralysed patients. Br J Anaesth 2000; 85: 262–6.
4
Keller C, Brimacrombe J. Does the proseal laryngeal mask airway prevent aspiration of regurgitated fluid? Anesth Analg 2000; 91: 1017–20.
5 Brimacrombe J, Brain AI, Berry AM. The Laryngeal Mask Airway, A Review and Practical Guide. WB Saunders, 1997: 117–22.
6
Sidaras G, Hunter J. Is it safe to ventilate a paralysed patient through the laryngeal mask? The jury is still out. Br J Anaesth 2001; 86: 749–53.
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Rabey PG, Murphy PJ, Langton JA, Barker P, Rowbotham DJ. Effect of the laryngeal mask airway on lower oesophageal sphincter pressure in patients during general anaesthesia. Br J Anaesth 1992; 69: 346–8.
8 Owens TM, Robertson P, Twomey C, Doyle M, Mcdonald N, Mcshane AJ. The incidence of gastrooesophageal reflux with the laryngeal mask: a comparison with the facemask using oesophageal lumen PH electrodes. Anesth Analg 1995; 80: 980–4.[Abstract]
9 Bapat P, Verghese C. LMA and incidence of reguritation during gynae laparoscopies. Anesth Analg 1997; 85:139–43.[Abstract]
10
Agro F, Brimacrombe J, Verghese C, Carassiti M, Cataldo R. Laryngeal mask airway and incidence of gastro-esophageal reflux in paralysed patients undergoing ventilation for elective orhtopaedic surgery. Br J Anaesth 1998; 81: 537–9.
11
Roux M, Drolet P, Girard M, Grenier Y, Petit B. Effect of the laryngeal mask airway on oesophageal pH: influence of the volume and pressure inside the cuff. Br J Anaesth 1999; 82: 566–9.
12
Mcrory C, Mcshane AJ. Gastroesophageal reflux during spontaneous respiration with the laryngeal mask airway. Can J Anesth 1999; 46: 268–70.
13
Illing L, Duncan PG, Yip R. Gastro-oesophageal reflux during anaesthesia. Can J Anaesth 1992; 39: 466–70.
14 Brain AIJ. The laryngeal mask and the oesophagus. Anaesthesia 1991; 46: 701–2.
15 Warner MA, Warner ME, Weber G. Clinical significance of pulmonary aspiration during the perioperative period. Anesthesiology 1993; 78: 56–62.[Medline]
16
Engelhardt T, Webster NR. Pulmonary aspiration of gastric contents in anaesthesia. Br J Anaesth 1999; 83: 453–60.
17 Vanner RG, Pryle BJ, O'Dwyer JP, Reynolds F. Upper oesophageal sphincter pressure during inhalational anaesthesia. Anaesthesia 1992; 47: 950–4.[Medline]
18 Brain AIJ, Verghese C, Strube P, Brimacombe J. A new laryngeal mask prototype. Anaesthesia 1995; 50: 42–8.[Medline]
19 Brimacombe J, Keller C. Airway protection with the proseal laryngeal mask airway: a case report. Anaesth Intensive Care 2001; 29: 288–91.[Medline]
20
Keller C, Brimacombe J. Resting esophageal sphincter pressures and deglutition frequency in awake subjects after oropharyngeal topical anesthesia and laryngeal mask device insertion. Anesth Analg 2001; 93: 226–9.
21
Brimacombe J, Keller C, Berry A. Gastric insufflation with the proseal laryngeal mask. Anesth Analg 2001; 92: 1614–5.
22
Keller C, Brimacombe J, Radler C, Puhringer F. Do laryngeal mask devices attenuate liquid flow between the esophagus and pharynx? A randomized controlled cadaver study. Anesth Analg 1999; 88: 904–7.
23
Brimacrombe J, Keller C. Water flow between the upper oesophagus and pharynx for the LMA and COPA in fresh cadavers. Can J Anesth 1999; 46: 1064–66.
24 Holloway RH, Hongo M, Berger K, McCallum RW. Gastric distension: a mechanism for postprandial gastroesophageal reflux. Gastroenterology 1985; 89: 779–84.[Medline]
25
Lopez-Gil, Brimacombe J, Brian AIJ. Preliminary evaluation of a new prototype laryngeal mask in children. Br J Anaesth 1999; 82: 132–4.
26 Brimacombe J. Airway protection with the new laryngeal mask prototype. Anaesthesia 1996; 51: 602–3.
27 Agro F, Brain A, Gabbrielli A, et al. Prevention of tracheal aspiration in a patient with a high risk of regurgitation using a new double-lumen gastric laryngeal mask airway. Gastrointestinal Endoscopy 1997; 46: 257–8.[Medline]
28 Agro F, Brimacombe J, Brain AIJ, Carassiti M, Cataldo R. Awake use of a new laryngeal mask prototype in a non fasted patient requiring urgent peripheral vascular surgery. Resuscitation 1999; 40: 187–9.[Medline]
29 Dalgleish DJ, Dolgner M. The proseal laryngeal mask airway (Letter). Anaesthesia 2001; 56: 1010.
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