THE LARYNGEAL MASK AIRWAY REDUCES BLOOD-FLOW IN THE COMMON CAROTID-ARTERY BULB

Purpose: The introduction of the laryngeal mask airway (LMA) has had a major impact on anaesthetic practice in the last ten years, Previous authors have demonstrated pressures equivalent to mean arterial blood pressure within the cuff of the LMA. This study examined the effects o f cuff inflation on the cross sectional area, flow and velocity of blo od flow at the level of the carotid sinus. Methods: Seventeen patients scheduled to have LMAs inserted as part of routine anaesthetic manage ment were recruited into the study. Measurements of the common carotid artery bulb area, peak velocity and blood flow were performed upon LM A cuff inflation and deflation using a 5 MHz pulse wave Doppler probe. Results: Deflation of the cuff resulted in an increase in the cross s ectional area (from 0.58 +/- 0.05 to 0.64 +/- 0.04 cm(2); P < 0.005), an increase in blood flow (from 65.6 +/- 5.6 to 73.9 +/- 5.6 cm(3) . s ec(-1); P < 0.05) and a slight but non significant increase in velocit y of blood flow, Conclusion: This study demonstrates that inflation of the cuff on the LMA results in a decrease in carotid bulb cross secti onal area which results in a decrease in blood flow.