[Safe handling of the laryngeal mask airway in eye surgery].

Background: We prospectively used the laryngeal mask airway (LM) in eye surgery to evaluate: 1) the limits of safe handling; 2) the feasibility of its use in long operative procedures, and 3) whether patients with higher anaesthetic risk (hypertension, asthma, children) may profit from the LM.

Methods: In 792 patients leak pressure, cuff volume, duration of anaesthesia, and complications were noted; 33 were children under 10 years of age, 100 had hypertension or severe asthma. In 54 patients cuff volume was increased to measure its influence on leak pressure; in 241 leak pressure was also measured at the end of the procedure; in 31 cuff pressure was measured under standard conditions over time; in 7 dead space was evaluated with the BANALYZER program; and in 300 blind endotracheal suction was attempted through the LM.

Results: Limits for the safe use of the LM were a leak pressure < 12 cm H2O combined with insufficient spontaneous ventilation (CO2et > 7 vol.%; n = 14), dislocation with gastric inflation (n = 2), and bronchial secretions (n = 1), as blind suctioning of the trachea through the LM was possible in only 1 out of 300 attempts. These limits could be recognised before the start of the operation in most cases. Laryngospasm or closure of the glottis (n = 36, 4.5%) was treatable and did not necessitate abandoning the use of the LM. Mean leak pressure was 17.7 +/- 4.8 cm H2O, showing a comparable distribution in adults and in children and being improved mainly by position changes of the LM, but not by changes in cuff volume. No gas leak occurred when the individual peak inspiratory pressure was equal to or lower than the measured leak pressure except in children. Dead space was almost halved by the LM compared to a face mask (90 +/- 13 vs. 162 +/- 31 ml; P < 0.05), allowing spontaneous breathing to be adequate even when manual assistance of ventilation was not possible (n = 14, 1.8%). In patients with sufficiently high leak pressures, the LM was safely used for long operations (up to 240 min), as leak pressure did not change over time. When only a low leak pressure could be achieved, deep breaths could be delivered by prolongation of the inspiratory time, thereby preventing atelectasis if tidal volume was limited. Cuff pressure rose to about 100 cm H2O within 60 min and should be monitored. In children, air was aspirated intermittently out of the stomach in procedures longer than 30 min; in adults, we monitored and buffered gastric contents where necessary. In patients at risk, the LM stimulates the circulation and bronchial reactivity less than an endotracheal tube. Children could be discharged earlier from the recovery room (0.45-1.5 h vs. > or = 2 h after neuromuscular relaxation and intubation).

Conclusion: Limits for the use of the LM in eye surgery are delineated. Within these limits, the LM offers control over the airway comparable to that of an endotracheal tube with less stimulation. The LM has to be applied by an experienced user, and has advantages in eye surgery.