The laryngeal mask airway: anesthetic gas leakage and fiberoptic control of positioning.
OBJECTIVE
To examine the anesthetic gas leakage and prelaryngeal position of the laryngeal mask airway (LMA).


METHODS
Clinical trial evaluating LMA ventilation conditions.


METHODS
Lithotripsy room of a urology clinic at a university hospital.


METHODS
100 adult ASA physical status I and II patients undergoing general anesthesia for kidney stone lithotripsy.


METHODS
Anesthesia was induced with propofol 1.5 to 2.5 mg/kg intravenously (IV) and fentanyl 1 to 1.5 micrograms/kg IV and maintained with isoflurane plus nitrous oxide in oxygen.


RESULTS
Waste anesthetic gas concentration, an indicator of mask tightness during intermittent positive-pressure ventilation, was measured using an infrared oxide analyzer. LMA position in relation to laryngeal skeleton was assessed using fiberoptic laryngoscopy. The LMA was found to be gastight in 62% of patients, with a peak airway pressure up to 25 cmH2O. During peak airway pressure ventilation less than 10 cmH2O and during spontaneous ventilation, waste anesthetic gas contamination in the anesthesiologist's breathing zone was within legal limits in every case. During peak airway pressure ventilation up to 30 cmH2O, contamination was found within legal limits in 78% of all cases. Fiberoptic control showed a central position in 59% of cases, lateral deviations to the left or right in 29%, dorsal positions in 8%, and ventral positions in 4%. Incorrect ventral or dorsal positioning was related to forced reclining or forced flexion of the patient's head. There was no correlation between LMA position and tightness. The esophageal entrance was visible in 15 patients using high peak airway pressure greater than 25 cmH2O.


CONCLUSIONS
The LMA is a new airway management technique with good qualities of tightness and ventilation conditions. However, contraindications such as patients with a full stomach, intra-abdominal surgery, high peak airway pressure, prolonged operation, and an inexperienced anesthesiologist apply.
Füllekrug
B
B
Department of Anesthesiology, University Hospital Eppendorf, Hamburg, Germany.
Pothmann
W
W
Werner
C
C
Schulte am Esch
J
J
D000328:Adult; D000769:Anesthesia, Inhalation / Q000379:methods*; D005260:Female; D005336:Fiber Optic Technology; D006801:Humans; D007385:Intermittent Positive-Pressure Ventilation; D007530:Isoflurane; D007669:Kidney Calculi / Q000628:therapy*; D017214:Laryngeal Masks; D007828:Laryngoscopy; D008096:Lithotripsy; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide
D007530:Isoflurane; D009609:Nitrous Oxide