RESUMO
BACKGROUND: Desflurane is known to augment central and systemic sympathetic nervous activity. The present study was aimed at examining the effects of desflurane on cardiovascular responses to intubation. METHODS: Seventy-five ASA physical status I patients (aged 35-60 yr) were assigned randomly to receive one of three treatment regimens (n = 25 each): 1 minimum alveolar concentration (MAC) of sevoflurane, 1 MAC of desflurane or 2 MAC of desflurane. Anesthesia was induced with IV thiopental (5 mg/kg), while patients were ventilated with 100% oxygen. Tracheal intubation was facilitated with IV vecuronium (0.12 mg/kg). After intubation, patients received each anesthetic gas in oxygen via a semiclosed anesthesia circuit. Systolic arterial blood pressure (SAP), heart rate (HR) and rhythm, and plasma catecholamine concentrations were measured. RESULTS: The intubation resulted in immediate increases of SAP and HR in all groups; peak effects occurred within 1 min of the intubation. In addition, 2 MAC desflurane elicited a secondary hemodynamic effect at 3 to 5 min after the intubation. The plasma concentrations of norepinephrine increased significantly when measured at 1 min after intubation in all groups, and returned to preintubation values at 5 min in the 1 MAC desflurane groups, but showed further increases at 5 min in the 2 MAC group. CONCLUSIONS: These results show that 2 MAC desflurane elicits a biphasic hemodynamic response along with an augmented norepinephrine release, where the first appears within 1 min and the second at 3 to 5 min after intubation.