[Clinical evaluation of controlled hypotensive anesthesia with MR7S1]

Efficacy, safety and the optimal dose of MR7S1, an injectable preparation of sodium nitroprusside, were studied in 37 patients (ASA class I and II) under nitrous oxide-oxygen-enflurane anesthesia. MR7S1 was administered by intravenous infusion. The dose of MR7S1 was increased gradually starting from 0.25 micrograms.kg-1.min-1 to the dose which could achieve the target value of systolic blood pressure (80-100 mmHg). Thereafter this dose level was maintained. During the period in which the dose was increased, the blood pressure was reduced in proportion to the rate of administration. With the rate of administration of 1.0 to 3.0 micrograms.kg-1.min-1, a significant decrease in systolic blood pressure (SBP) was observed compared with the pretreatment level of SBP. During the maintenance period, the SBP was maintained around 80 to 100 mmHg at a rate of administration of 0.25 to 3.5 micrograms.kg-1.min-1. Two out of 37 patients showed a slight decrease in PaO2, but these values returned to normal without any treatment. These findings suggest that MR7S1 is a useful agent to control blood pressure for the hypotensive anesthesia.