Plasma noradrenaline levels in regular haemodialysis patients

Plasma concentrations of noradrenaline (NA), adrenaline (A) and renin (R) were measured in 29 regular haemodialysis patients (RHP) [13 normotensive, 10 hypertensive, 6 binephrectomised] and in 15 healthy control subjects (C) under various physiological conditions: supine-standing-walking. RHP had significant higher plasma levels of noradrenaline and adrenaline in the mean than C. All RHP responded to passive orthostasis with a significant increase in diastolic blood pressure, heart rate and plasma NA. In contrast to C, plasma NA did not drop after two hours of active orthostasis. Hypertensive RHP had significant higher plasma concentrations of R and A than normotensives. It is concluded that the sympathetic nervous system (SNS) plays a minor role in hypertensive blood pressure regulation of RHP. The adequate response to passive orthostasis in RHP with regard to diastolic blood pressure, heart rate and plasma NA indicates and intact function of the SNS under this condition. Hypertension in RHP not controllable by salt and volume depletion can be attributed to elevated levels of R, which in turn may stimulate adrenaline release from the adrenals. The mechanisms responsible for the elevated levels of circulating catecholamines remain unclear: an inhibition of re-uptake, disturbances in enzymatic metabolism or/and abolished renal clearance are suggested.