The Effect of Captopril on Plasma Renin Activity , Aldosterone , Catecholamines and Electrolytes during Sodium Nitroprusside Induced Hypotension

Goo, Yeong Gwon; Kang, Ki Taeck; Woo, Sung; Cho, Kang Hee

Abstract

Sodium nitrorusside (SNP) is used for induced hypotension to decrease bleeding in operation site by direct relaxation of vascular smooth muscles. It is known that the infusion of SNP increases plasma renin activity (PRA) and this activation of renin-angiotensin system is one of physiologic mechanism opposing the hypotensive action. Captopril, the renin-angiotensin converting enzyme inhibitor, could reduced the dose of SNP during induced hypotension through blocking of the cardiovascular effect of renin-angiotensin system. The present study investigates the effect of captopril on PRA, aldosterone, elecholamines and electroytes and whether the pretreatment with captoril can reduce the dose of SNP. Forty patients who needed the induced hypotension for maxillofacial reconstructive surgery were studied. They were pertained to ASA class I and II and classified to 4 groups. Ten patients were pretreated with captopril 3 mg/kg, 10 min. before induction. And ten patients were 1 mg/kg, the other ten patients were 0.5 mg/kg and remainder served as control group. Blood samples for analysis were drawn according to the time sequence of SNP infusion; Stage 1; after the induction and before SNP infusion Stage 2; 30 min. after SNP (when mean arterial pressure was 60-70 torr) infusion Stage 3; before stopping infusion of SNP Stage 4; 30 min. after stopping infusion of SNP The results were as follows: 1) The duration of anesthesia were not stastically different among four groups. 2) Total dose of SNP were significantly decreased in each captopril group. 3) PRA and each value of control group were significantly increased compared with stage l. But there were no significant increase in stages 2, 3, 4 compared with control group PRA. 4) Aldosterone level of all captopril groups were decreased in all stage compared with control group. 5) Epinephrine and norepinephrine were significantly incerased in control group and returned to control level after stopping of SNP infusuon. In captopril group 3 mg/kg, norepinephrine of stage 2.3.4 were not significantly increased than stage l. Epinephrine in captopril 3 mg/ kg group, there were no significant changes except for stage 2. 6) While sodium was decreased in stage 3,4 compared with stage 1 in control group, potassium and chloride were not changed. In summary, captopril can reduce significantly the total dose of SNP required to produce induced hypotension during operation.