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Angiotensin II concentrations and gut mucosal perfusion in infants undergoing cardiopulmonary bypass
P D Booker1, A J Davis, M J Diver
1Royal Liverpool Children's Hospital, United Kingdom.
Insights
Hypothermic cardiopulmonary bypass (CPB) in infants may be associated with high angiotensin II (A-II) levels, but CPB itself appears to decrease A-II. Gut mucosal perfusion is not directly linked to A-II concentrations during this procedure.
Area of Science:
- Cardiovascular Surgery
- Pediatric Cardiology
- Renal Physiology
Background:
- Perioperative angiotensin II (A-II) levels in infants undergoing cardiac surgery are not well understood.
- Hypothermic cardiopulmonary bypass (CPB) is a critical procedure in infant cardiac surgery.
- The impact of CPB on A-II and its relation to gut perfusion requires investigation.
Purpose of the Study:
- To determine if hypothermic CPB increases angiotensin II (A-II) concentration in infants.
- To explore the relationship between A-II concentration and gut mucosal perfusion during CPB.
- To assess the effect of ACE inhibitors on A-II levels during CPB.
Main Methods:
- Prospective observational study in 30 acyanotic infants undergoing CPB.
- A-II concentrations measured pre-, during, and post-CPB.
- Gastric intramucosal pH (pHi) and mucosal blood flow (flux) monitored; ACE inhibitors (captopril, enalaprilat) administered to subgroups.
Main Results:
- Elevated A-II concentrations (>450 pg/mL) were present in most infants pre-CPB.
- A-II levels decreased during CPB but remained elevated in control and captopril groups.
- Enalaprilat effectively normalized A-II levels during and after CPB; no correlation found between A-II and gut perfusion parameters.
Conclusions:
- Acyanotic infants undergoing cardiac surgery often exhibit high perioperative A-II concentrations.
- Hypothermic CPB is associated with a reduction in A-II levels, not an increase.
- Observed decreases in gut mucosal perfusion during CPB are independent of A-II concentration changes.
Objectives:
To determine whether hypothermic cardiopulmonary bypass (CPB) per se causes an increase in angiotensin II (A-II) concentration in infants and to investigate the relationship between A-II concentration and gut mucosal perfusion.
Design:
Prospective, open, nonrandomized, observational study.
Setting:
Children's teaching hospital.
Participants:
Thirty acyanotic infants requiring CPB.
Interventions:
A-II 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-II 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 pHi 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.