NEUROCIRCULATORY RESPONSES TO SEVOFLURANE IN HUMANS - A COMPARISON TO DESFLURANE

Background: Sevoflurane and desflurane are new volatile anesthetics with low blood solubilities that confer properties of rapid anesthetic induction and emergence. Desflurane has been associated with neurocirculatory excitation after the rapid increase in inspired concentrations. The current study evaluated and compared the sympathetic and hemodynamic responses associated with the administration of sevoflurane to those associated with administration of desflurane in humans. Methods: After Institutional Review Board approval, 21 healthy, young (19-32 yr) volunteers were randomly selected for participation. Arterial and central venous pressures were measured directly, and heart rate, forearm blood now, and plasma norepinephrine concentrations were determined indirectly. Efferent muscle sympathetic nerve activity was recorded by microneurography. After neurocirculatory recordings at conscious baseline, measurements were repeated beginning 2 min after 2 mg/kg propofol while the anesthetic was increased incrementally by mask over a 10-min period at 1%, 2%, and 3% sevoflurane (n = 12) or 3%, 6%, and 9% desflurane (n = 9). Responses to intubation were recorded and, 20 min later, recordings were evaluated during steady-state periods of 0.41, 0.83, and 1.24 MAC. Data also were obtained after steady-state 0.83 MAC measurements when the inspired gas concentration was rapidly increased to either 3% sevoflurane or 9% desflurane (''transition'' to 1.24 MAC). Results: Neurocirculatory variables did not differ between the two groups at conscious baseline, During the period of administration via mask and during the ''transition'' period, the significant increases in sympathetic nerve activity, heart rate, mean arterial pressure, and central venous pressure associated with desflurane were not observed with sevoflurane. Ten minutes after induction, mean arterial pressure and heart rate responses to intubation did not differ between groups, With increasing anesthetic concentration, there were progressive and similar decreases in mean arterial pressure in both groups and no changes in heart rate, Central venous pressure, sympathetic nerve activity, and plasma norepinephrine increased with the greater minimum alveolar concentration multiple of desflurane but not with that of sevoflurane. Conclusions: The neurocirculatory excitation seen with rapid increases in desflurane did not occur with sevoflurane. At steady-state, increasing the concentration of sevoflurane was associated with lower sympathetic nerve activity and central venous pressure and similar mean arterial pressure and heart rate with that of desflurane.