[Renal functions and extracorporeal circulation]

During 76 extracorporeal circulations (CEC) carried out for open heart operations using an identical protocol, the authors carried out renal function tests from the time of administration of the anesthetic to the post-operative period. Various periods may be distinguished: pre-operative, anesthesia induction (CEC 1, CEC 2) post induction (CEC 1, post CEC 2) finally, the post-operative period (post-operative 1 to 4). As far as renal hemodynamics are concerned, the authors made the following observations: constant reduction in thiosulphate clearance and endogenous creatinine clearance, which reflect glomerular filtration. Reduction in PAH clearance, which reflects renal perfusion. Taking into consideration changes in the hematocrit, one may consider that there is a reduction in renal blood flow at all stages of anesthesia. Taking into consideration concomitant variations in blood pressure, one may calculate that intrarenal resistances are increased. The diuresis/minute increases in very great proportions during induction of anesthesia. Plasma osmolality also increases, urinary osmolality becomes reduced and osmolar clearance rises. The ratio between osmolar clearance and creatinine clearance rises. The clearance of free water rises from negative values. The serum sodium becomes slightly reduced, and sodium diuresis increases. Serum potassium becomes slightly reduced and urinary potassium rises. The interpretation of these phenomena is difficult and should take into consideration the experimental conditions. Comparison with published results shows that there are definite differences depending on whether pure or diluted blood is used. It is however, possible to seek the role of the anesthetic, the thoracotomy or the extracorporeal circulation itself and its load, quite independent of prior changes due to decompensation or not of the congenital heart disease, whether or not it has been treated. The study of these changes in renal function permits one to understand better the precariousness of renal perfusion during extracorporeal circulation, imperfectly corrected by osmotic diuresis and responsible for transient and reversible renal hypofunction, liable to lead however, in cases of complications and prolonged low blood flow, to organic renal failure.