Angiotensin II concentrations and gut mucosal perfusion in infants undergoing cardiopulmonary bypass

Objectives: To determine whether hypothermic cardiopulmonary bypass (CPB) p er se causes an increase in angiotensin II (A-ll) concentration in infants and to investigate the relationship between A-it concentration and gut muco sal perfusion. Design: Prospective, open, nonrandomized, observational study. Setting: Children's teaching hospital. Participants: Thirty acyanotic infants requiring CPB. Interventions: A-it concentrations were measured on six occasions before, d uring, and after CPB. An orogastric tonometer allowed intermittent calculat ions of gastric intramucosal pH (pHi). Gastric mucosal blood flow (flux) wa s monitored using a laser Doppler flowmeter. Ten infants acted as controls (group 1): 10 infants received captopril, 0.9 mg/kg orally, 45 minutes befo re induction of anesthesia (group 2), and 10 infants received enalaprilat, 0.06 mg/kg intravenously, just before CPB (group 3). Measurements and Main Results: A-ii concentrations were abnormally high in 28 of 30 patients before CPB (median, 450 pg/mL (range, 83 to 5,787 pg/mL). A-Il concentrations in groups 1 and 2 decreased during CPB, but values rem ained at twice normal levels throughout surgery (median, 171 to 198 pg/mL p ost-CPB). A-ii concentrations remained normal (range, 52 to 120 pg/mL) duri ng and after CPB in patients receiving enalaprilat (group 3). The authors f ound no significant correlation between A-ii concentration and pi-Ii or flu x before, during, or after surgery. Conclusions: Acyanotic infants requiring cardiac surgery may have high peri operative concentrations of A-ii. Hypothermic CPB is associated with a decr ease in A-ii concentration. Reductions in gut mucosal perfusion seen in som e infants during hypothermic CPB are not related to increases in A-ii conce ntrations, Copyright (C) 1999 by W.B. Saunders Company.