Atrial natriuretic factor in normothermic and hypothermic cardiopulmonary bypass

Background: To evaluate the plasmatic changes of atrial natriuretic factor (ANF) during and after cardiopulmonary bypass (CPB) in normothermia and hypothermia. Methods: Twenty-three patients (n = 23) undergoing coronary artery bypass graft surgery were randomly assigned to two groups. In Group I (n = 11), the patients underwent operation in normothermia; in Group II (n = 12), the operation was performed in hypothermia (26degreesC). Results: Plasma ANF levels were determined after induction of anaesthesia, at the end of CPB and one hour postoperatively. There were no demographic differences between the two groups, diuresis (p = 0.90) and natriuresis (p = 0.95). Plasma levels of ANF were significantly elevated during and after CPB in both groups (p < 0.01). The groups differed significantly for plasma levels of ANF during CPB and postoperatively (p < 0.05), but did not differ prebypass (p < 0.08). There was no correlation in either group between ANF release and central venous pressure, natriuresis and diuresis. There was only a borderline relationship between ANF concentration and diuresis after CPB in Group I. Conclusion: CPB triggers the production and release of ANF. The present study demonstrates a significantly enhanced ANF release during hypothermia and reperfusion after ischaemia. Thus, these data suggest the protective role of ANF on the hypoxic myocardium, and they confirm that ANF does not play a role in diuresis and natriuresis during and after hypothermic CPB.