RESUMO
BACKGROUND: The reduction is cerebral blood flow (CBF) caused by hypocapnia is an important element of anesthetic techniques for neurosurgery as well as for nonneurologic surgery in patients with reduced intracranial compliance. Accordingly, the impact of anesthetic agents on the CO2 responsiveness of the cerebral circulation has important implications with regard to anesthetic selection. The purpose of this study was to investigate the effects of isoflurane-N2O and propofol-N2O anesthesia on the CBF response to changes in end-tidal CO2 in healthy patients. METHODS: 19 healthy patients with nonneurological operation were selected. In group 1, anesthesia was induced with thiopental sodium 4 mg/kg, fentanyl 1 g/kg, succinylcholine 1~1.5 mg/kg and was maintained with isoflurane 0.5~1.5 vol%. In group 2, anesthesia was induced with propofol 2~2.5 mg/kg, fentanyl 1 g/kg, succinylcholine 1~1.5 mg/kg and was maintained with a propofol infusion of 10 mg/kg/h for 10 min and then 8 mg/kg/h for 10 min and then was reduced 3~6 mg/kg/h of the remainder of the study. All patients were ventilated with N2O in O2 (FIO2 0.5) and measured end-tidal CO2 (PETCO2). Mean blood flow velocity of middle cerebral artery was measured using transcranial Doppler in PETCO2 45, 40, 35, 30, 25, 20 mmHg. RESULT: CO2 reactivity of MCA flow velocity during isoflurane-N2O and propofol-N2O anesthesia was 5.1 +/- 1.8 %/mmHg, 4.4 +/- 1.0 %/mmHg respectively. CONCLUSION: The cerebral vasculature in healthy patients remains responsive to changes in PETCO2 during isoflurane-N2O and propofol-N2O anesthesia.