Hormonal response to fluid administration in cardiac surgery patients

Abstract

The effects of three different fluid regimes administered before surgery on stress-related hormones were studied in 36 patients undergoing elective aortocoronary bypass grafting. Low-dose Ringer's solution (10 ml/kg; low-dose crystalloid group [LDC]), high-dose Ringer's solution (20 ml/kg; high-dose crystalloid group [(HDC]). or a combination of Ringer's solution (10 ml/kg) with high-molecular weight hydroxyethylstarch (HES) (10 ml/kg) (crystalloid-HES group [C-HES]) were randomly administered prior to operation. Haemodynamic variables and plasma concentrations of ADH, ACTH, renin, aldosterone, cortisol and catecholamines were studied before volume load, before commencement of cardiopulmonary bypass (CPB), and immediately after weaning from CPB. Cardiac index and stroke volume index in the C-HES group increased by 20% and 18% respectively, systemic vascular resistance decreased by 25% after volume infusion. This was associated with a decrease in the plasma concentrations of ADH, renin and aldosterone. In contrast to this, in the LDC and HDC groups, haemodynamic parameters remained almost unchanged after volume load. This was associated with an increase in aldosterone (LDC 20%; HDC 58%) and renin (LDC 110%; HDC 44%). In all groups, plasma concentrations of catecholamines increased progressively during the time of surgery and were not influenced by the nature or volume of fluid administered. We conclude that the administration of a combination of crystalloid and colloid solutions during induction of anaesthesia effectively improves haemodynamics and attenuates the increase of the plasma levels of ADH, renin and aldosterone often associated with surgery.