Chronic angiotensin converting inhibition does not influence renal hemodynamic and function during cardiac surgery

Treatment with angiotensin-converting enzyme (ACE) inhibitors affects the autoregulation of renal blood flow and glomerular filtration and provides renal protective effects. The purpose of this case-control study was to investigate the effects of chronic ACE inhibition on perioperative renal hemodynamics and function.

We prospectively studied renal function in two groups of patients, chronically treated or not, with ACE inhibitors (ACEI and control; n = 16, in each group) who underwent elective cardiac surgery under hypothermic cardiopulmonary bypass. Glomerular filtration rate, effective renal plasma flow, osmolar clearance and fractional excretion of sodium and potassium were determined before, during and after CPB. Additional measurements included plasma atrial natriuretic factor (ANF) as well as plasma and urinary cyclic GMP (cGMP), thromboxane B2 (TxB2) and 6-keto-PGF1.

Renal functional and hemodynamic variables did not differ between the two groups, at any period. Cardiopulmonary bypass induced increases in urinary flow, osmolar clearance and fractional excretion of sodium and potassium in both groups. Plasma and urinary ratio of 6-keto-PGF to TxB2 increased markedly and reflected a predominant systemic and renal release of vasodilatory prostaglandins. Intraoperatively, ANF was higher in ACEIs than in control patients.

Long term treatment with ACE inhibitors does not influence the perioperative changes in renal hemodynamics and function. During cardiopulmonary bypass, a transient impairment in solute reabsorption is associated with renal release of vasodilatory mediators (nitric oxide and prostacyclin).