NEUROCIRCULATORY RESPONSES TO INTUBATION WITH EITHER AN ENDOTRACHEAL-TUBE OR A LARYNGEAL MASK AIRWAY IN HUMANS

Study Objective: To compare the sympathetic and hemodynamic responses to intubation with either an endotracheal tube (ETT) or laryngeal mask airway (LMA). Design: Prospective, randomized, single-blinded study. Setting: The in vitro study was carried out in an experimental laborat ory. Patients: 16 healthy male consenting volunteers, ages 20 to 31 ye ars, were studied. Interventions: After placement of a radial artery c atheter, ECG electrodes, and a recording needle in the peroneal nerve, subjects were anesthetized with propofol 2.5 mg/kg, paralyzed with ve curonium 0.15 mg/kg, and ventilated vial mask for 5 minutes with oxyge n and 0.5 MAC desflurane or 0.5 MAC isoflurane. A LMA or ETT was inser ted and neurocirculatory responses were continuously recorded. Measure ments and Main Results: Measurements of heart rate (HR), mean arterial pressure (MAP), and sympathetic nerve activity (SNA) were made at pre intubation baseline and at the peak response after airway manipulation . The time to recovery to 20% and 10% of baseline MAP and HR also was measured. Neurocirculatory variables did not differ in either the LMA (n = 7) or ETT (n = 9) groups immediately prior to intubation. The ETT group demonstrated a 27% HR increase in the LMA group. Muscle SNA inc reased 600% in the ETT group versus 66% in the LMA group (p < 0.01). T he time to return MAP and HR to 20% and 10% of preintubation baseline was significantly longer in the ETT than the LMA group (p < 0.01). Con clusions: Because of the substantial reduction in the neurocirculatory responses to the LMA versus ETT, the LMA may prove advantageous in pa tients in whom HR and MAP increases may predispose to adverse cardiac or cerebrovascular events.