الفهرس 
THE CEREBRAL CIRCULATIONOnly 14 pages are availabe for public view
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Abstract
Most of volatile anesthetics are considered to be cerebral vasodilators, although it is controversial whether the increase, if any, of cerebral blood flow (CBF) by volatile anesthetics is maintained during the whole period of anesthesia.
This study was designed to estimate and compare between the effects of sevoflurane and isoflurane at different concentrations on middle cerebral artery (MCA) flow velocity during the maintenance of general anesthesia. It is was also to ascertain the effect of prolonged steady state concentrations of sevoflurane and isoflurane on the cerebrovascular circulation.
The study involved 60 adult patients of either male or female gender, aged 25-60 years, ASA I or II physical states and all of them gave a written informed consent to be enrolled in the study and to receive general anesthesia. The patients did not have an overt cerebrovascular disease and their surgeries did not involve manipulations of head or neck nor associated with fluctuations in blood pressure.
These patients were randomly and equally divided in two groups (n=30 in each group) to receive either sevoflurane (G-I) or isoflurane (G-II).
Patients were hydrated by 1500 ml of Ringer lactate solution over 2 hours prior to the beginning and during the study it was adjusted to 4 ml/kg/hr.
All patients received a standardized general anesthetic technique consisting of pre-oxygenation then intravenous induction of sleeping dose of propofol 2-2.5 mg/Kg, fentanyl 2ug/kg and atracurium 0.5mg/kg, followed by endotracheal intubation and mechanical ventilation with an air/oxygen mixture (at FiO2 = 0.4), with zero positive end expiratory pressure, then the ventilator rate and peak inspiratory pressures were adjusted at normocapnia (ETCO2=35-40mmHg) throughout the study.
Normothermia (36.5o-37.7o C) was maintained by using conductive water mattress, conductive air warmer and I.V. fluid warmer. During the study routine monitoring were done including E.C.G, NBP, pulse oximetery, nasopharyngeal temperature probe and capnography.
Cerebral blood flow velocity was measured in awake patients (baseline) and it was 64.83±12.72 cm/sec. in GI and 64.43±12.01 cm/sec. in GII.
It was measured again five minutes after reaching the steady state of inspired and end-expired concentration of 0.5 MAC and it was 41.77±8.44 cm/sec. in GI and 46.00±7.52 cm/sec. in GII. At 1.0 MAC it was 46.43±8.57 cm/sec. in GI and 51.43±8.11 cm/sec. in GII. Then at 1.5 MAC it was 54.50±10.3 cm/sec. in GI and 58.57±9.95 cm/sec. in GII.