Objectives: To determine whether hypothermic cardiopulmonary bypass (CPB) per se causes an increase in angiotensin II (A-ll) concentration in infants and to investigate the relationship between A-it concentration and gut mucosal 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, during, and after CPB. An orogastric tonometer allowed intermittent calculations of gastric intramucosal pH (pHi). Gastric mucosal blood flow (flux) was monitored using a laser Doppler flowmeter. Ten infants acted as controls (group 1): 10 infants received captopril, 0.9 mg/kg orally, 45 minutes before 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 remained at twice normal levels throughout surgery (median, 171 to 198 pg/mL post-CPB). A-ii concentrations remained normal (range, 52 to 120 pg/mL) during and after CPB in patients receiving enalaprilat (group 3). The authors found no significant correlation between A-ii concentration and pi-Ii or flux before, during, or after surgery. Conclusions: Acyanotic infants requiring cardiac surgery may have high perioperative concentrations of A-ii. Hypothermic CPB is associated with a decrease in A-ii concentration. Reductions in gut mucosal perfusion seen in some infants during hypothermic CPB are not related to increases in A-ii concentrations, Copyright (C) 1999 by W.B. Saunders Company.
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