Controlled Hypotension with Sodium Nitroprusside: Effects on Cerebral Blood Flow and Cerebral Venous Blood Gases in Patients Operated for Cerebral Aneurysms

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Abstract
The effect on cerebral haemodynamics of arterial hypotension induced by sodium nitroprusside infusion was studied in nine patients at the end of operations for intracranial aneurysms under N2O-O2-halothane anaesthesia. Cerebral blood flow (CBF), using the intraarterial 133Xe injection method, and cerebral jugular venous blood gases were monitored before, during and after the induced hypotension. CBF and jugular venous oxygen tension (PvO2) remained constant during the hypotensive period. Following its termination, a 13% increase in CBF occurred (P less than 0.05) and PvO2 showed the same trend, a 5% increase (P less than 0.30). Regional CBF recordings (rCBF) in 16 small areas within the cerebral hemisphere were obtained at each measurement. In four of the patients, rCBF abnormalities were present in the form of hyperaemic regions, probably induced by the operation or the disease itself. The focal abnormalities were not accentuated during hypotension nor were ischaemic regions disclosed. It is concluded that sodium nitroprusside has only a minor influence on cerebral haemodynamics in the anaesthetized state.