Hormonal response to volume depletion in non-nephrectomised patients on regular haemodialysis

The hormonal response to volume depletion by isolated ultrafiltration has been studied in seven non-nephrectomised haemodialysis patients. The mean reduction in blood volume was 14%, and pulmonary artery wedge pressure reduction averaged 77%. No increments in heart rate were observed in any of the patients. Cardiac output decreased while systemic vascular resistance increased. Mean arterial blood pressure remained stable in all but two patients. Significant increments in plasma vasopressin concentration were only found during hypotensive episodes, while in the whole group no significant increase was found. Both plasma renin activity, plasma aldosterone and plasma cortisol increased significantly during isolated ultrafiltration. The moderate increase in systemic vascular resistance indicates that the peripheral sympathetic nervous system - at least partly - was functioning. It was, however, not correlated with changes in any of the measured hormones. Furthermore the adrenal and cardiac response appeared to be absent.