Captopril reduces the dose requirement for sodium nitroprusside induced hypotension

The authors studied 12 patients who required deliberate hypotension for spinal fusion operations in order to investigate the efficacy of captopril for reducing dose requirement for sodium nitroprusside (SNP). Six patients, selected at random, were pretreated with captopril, 3 mg/kg po, and the remaining six patients served as controls. All patients received a similar anesthetic technique, consisting of thiopental 3 mg/kg, pancuronium 0.1 mg/kg, morphine 0.5 mg/kg, plus nitrous oxide 70% in oxygen. SNP was used to maintain mean arterial pressure (MAP) at 50-55 mmHg during deliberate hypotension lasting 140 +/- 13 minutes (mean +/- SE). Patients who received captopril required less SNP than untreated patients both early during hypotension (1.4 +/- 0.5 micrograms X kg-1 X min-1 vs. 4.8 +/- 0.8 micrograms X kg-1 X min-1, P less than 0.05), as well as late during hypotension (2.2 +/- 0.2 micrograms X kg-1 X min-1 vs. 5.6 +/- 0.6 micrograms X kg-1 X min-1, P less than 0.05). Whole blood cyanide was significantly lower in the patients pretreated with captopril than the untreated controls both early in the hypotensive period (2.7 +/- 0.6 mumol/l vs. 13 +/- 4 mumol/l, P less than 0.05) and also late in the hypotensive period (3.7 +/- 0.8 mumol/l vs. 30 +/- 10 mumol/l, P less than 0.05). MAP was reduced by captopril pretreatment both following induction of anesthesia (64 +/- 4 mmHg captopril vs. 80 +/- 4 mmHg control, P less than 0.05) and during surgery before deliberate hypotension (86 +/- 5 mmHg captopril vs. 100 +/- 4 control, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)