Effect of PEEP Ventilation on Renal Function, Plasma Renin, Aldosterone, Neurophysins and Urinary ADH, and Prostaglandins

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Abstract
To explore the main factors which could be involved in the fluid retention induced by continuous positive pressure ventilation (CPPV), hemodynamic, renal and hormonal parameters were measured in 7 intensive care patients during 3 consecutive 60-min periods: 1 of intermittent positive pressure ventilation (IPPV), 1 of CPPV (PEEP 10 cm H2O), and finally 1 of IPPV. During CPPV, a 15% decrease in cardiac output was observed without alteration in arterial pressure or right atrial transmural pressure. In addition, decreases were observed in urinary output by 34%, glomerular filtration rate by 19%, renal blood flow by 32%, Na excretion by 33% and K excretion by 26%. There was no change in the fractional excretion of Na and free water. Institution of PEEP also led to a significant increase in plasma renin activity, plasma aldosterone and urinary antidiuretic hormone, without significant variation in plasma neurophysins and urinary prostaglandins E and F.alpha.. All of the changes that occurred during CPPV were reversed when PEEP was withdrawn. The short-term antidiuretic effect of PEEP is mainly due to a hemodynamic impairment of renal function. The water- and Na-retaining hormonal systems also are stimulated and could participate in the fluid retention during more prolonged respiratory support with PEEP.