[Cerebral effects of isoflurane-induced or PGE1-induced hypotension in dogs].

The cerebral effects of hypotension induced by inhalation of increasing concentrations of isoflurane or intravenous administration of prostaglandin E1 (PGE1) were studied in 15 dogs anesthetized with 1% isoflurane and 50% nitrous oxide during normocarbic (PaCO2 approximately 39 mmHg) and normothermic (37.5 degrees C) condition. Mean arterial pressure (MAP) was decreased stepwise to 25, 40, and 55% of its baseline values. Cerebral blood flow (CBF) was measured using the venous outflow technique. Cerebral metabolic rate for oxygen (CMRO2), cerebral metabolic rate for glucose (CMRgl) and oxygen/glucose index (OGI) were calculated, and cerebrospinal fluid pressure (CSFP) and EEG were also recorded at each decrement in MAP and after resuming the control condition. The CBF, CMRO2, CMRgl, OGI and CSFP responses related to hypotension showed no significant changes from baseline values in both methods. However, CBF values in isoflurane-induced hypotension at 25% and 40% reduction of MAP were significantly higher than those in PGE1-induced hypotension. By increasing concentration of isoflurane, EEG changed from continuous fast wave to high amplitude (100 microV) slow wave (4-6 Hz) and typical burst suppression observed in 3 of 8 dogs. In contrast, no significant EEG changes were seen during PGE1-induced hypotension. These results suggest no adverse effect of isoflurane- and PGE1-induced hypotension on cerebral metabolism or function.