Date of Award

5-30-2017

Document Type

Dissertation

Degree Name

Master of Medicine (MMed)

First Supervisor/Advisor

Dr. David Nekyon

Second Supervisor/Advisor

Dr. Samina Mir

Third Supervisor/Advisor

Prof. Vitalis Mung’ayi

Department

Anaesthesiology (East Africa)

Abstract

Background: The Laryngeal Mask Airway (LMA) is one of several supra-glottic airway management devices used in anaesthesia. The scope of use of the LMA is progressively expanding to areas previously contraindicated, for instance laparoscopy and prone position surgery. Certain aspects of LMA use remain unsettled. Whether to remove the LMA when a patient is “awake” vs “deep” following anaesthesia is one such area. The manufacturer Ambu® recommends that the AuraOnce™ LMA be removed once the patient is fully awake and protective airway reflexes are active. Despite this, several studies have shown benefit in removal of the LMA while a patient is “deep” (anaesthetized). Current evidence is inconclusive as to which approach is preferable and safer in adults.

Primary Objective: To compare the impact of having LMA removal deep versus awake on the occurrence of airway complications following general anaesthesia in spontaneously breathing adult patients using Isoflurane as the sole volatile agent.

Secondary Objective: To compare the impact of deep versus awake LMA removal on anaesthesia theatre turn-around time.

Primary outcome measure(s): Airway complication(s), defined as; one or more of the following; Airway obstruction requiring airway manipulation; Laryngospasm; Desaturation to 90% or less on pulse oximetry.

Secondary outcome measure(s): Time to theatre exit

Study Setting: The Aga Khan University Hospital, Nairobi, Kenya.

Study Design: A prospective randomized control trial (open).

Sample size: A sample size of 116 participants, 58 in each arm.

Study population: ASA I and II patients aged 18-65 years scheduled for theatre for low to moderate risk, non-emergent surgery.

Procedure: 116 adult patients were randomly assigned to one of two groups. A standard anaesthesia protocol was used for induction and maintenance of anaesthesia. For the deep arm; The LMA was removed at the end of surgery after attaining an end tidal minimum alveolar concentration of Isoflurane of 1.15%. Occurrence of airway complication(s) (One or more of the following; Airway obstruction requiring airway manipulation; Laryngospasm; Desaturation to 90% or less on pulse oximetry) was noted until the subject was fully awake (appropriate response to command) in the post anaesthesia care unit.

For the awake arm; The LMA was removed on attaining an end tidal minimum alveolar concentration of Isoflurane of

Time to theatre exit was recorded for both groups from the point of attaining an end tidal minimum alveolar concentration of Isoflurane of 1.15% to the point of theatre exit, in both groups. These processes were in addition to standard care.

Data collection: Parameters of interest being; Airway obstruction requiring airway manipulation, laryngospasm, desaturation to 90% or less on pulse oximetry, all of which were composited to define ‘airway complication’. Time to theatre exit after attaining an end tidal of 1.15% Isoflurane.

Results: 116 ASA I & II patients scheduled to undergo elective surgery were included in this study, 58 (50%) subjects in the awake arm and 58 (50%) subjects in the deep arm. Baseline demographic characteristics were similar between the groups. More airway complications were encountered in the Deep arm - 13 (22.4%) relative to the Awake arm -5 (8.6%), this was found to be statistically and clinically significant, P value P=0.040, odds ratio 3.0622; 95% CI, 1.0139 to 9.2483.

Conclusion: The study concludes that there is a significant difference in the occurrence of airway complications when the laryngeal mask airway is removed deep (anaesthetized) compared to awake (appropriate response to command). In this regard, the removal of the LMA while the patient is still deeply anaesthetised is not as safe as or safer than awake laryngeal mask airway removal.

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