1 Department of Anesthesiology and 2 Department 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: panchalidhar@msn.com LMA® is the property of Intavent Limited.
Accepted for publication: June 30, 2003
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Abstract |
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Br J Anaesth 2003; 91: 7524
Keywords: airway, management; brain, electroconvulsive therapy; equipment, ProSealTM laryngeal mask airway; pregnancy
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Introduction |
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Case report |
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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 kg1 and succinylcholine 1.6 mg kg1. 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 difficulty.
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 ProSealTM 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 inflated with 18 ml of air. With each treatment, bilateral breath sounds and the absence of sounds over the epigastrium were confirmed. There was no appreciable air leak. Lubricant gel (1ml) was placed over the proximal orifice of the drainage tube to detect any gastric insufflation or malposition. At each session, a fibre-optic bronchoscope was used to confirm the absence of fluid in the glottic aperture and proper placement. When the patient regained consciousness and airway reflexes were observed, the PLMA was removed inflated. 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.
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Discussion |
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In this patient, airway management options included tracheal intubation, mask ventilation with constant cricoid pressure, the classic laryngeal mask airway (LMA), or the ProSealTM LMA. A rapid sequence induction and intubation is the most definitive 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 insufflation. Proper mask fit may be difficult 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 modifications that allow a better seal than the classic LMA, decreasing the likelihood of gastric insufflation during positive pressure ventilation.
The PLMA design includes a modified cuff to isolate the glottis from the oesophagus, and a drainage tube alongside the airway tube, allowing fluid 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 insufflation. The PLMA has several modifications that may protect against aspiration of regurgitated fluid. 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 fluid from the oesophagus until pressures of 6873 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 fill the hypopharynx. A fibre-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 fibre-optic scope for confirmation of PLMA placement, this is not required in routine practice.
ECT is a treatment that requires efficient and reliable control of the airway for short periods. If a prolonged intubation time or difficulty 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.
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Acknowledgements |
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References |
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