REDUCED RENAL RESPONSE TO LOW-DOSE DOPAMINE INFUSION IN THE ELDERLY

Background. Increasing age is associated with a number of changes in r enal function, including a diminished capacity to excrete salt and wat er loads and an increased susceptibility to acute renal failure. Dopam ine is a renal autocoid important in diuresis and natriuresis and may also serve to protect against ischemic renal injury. The aim of this s tudy was to assess the renal response to a low-dose dopamine infusion in healthy young vs elderly individuals. Methods. Five healthy young ( 28 +/- 2 yr) and elderly (68 +/- 3 yr) subjects underwent evaluation o f renal function and blood pressure before, during, and after a 3-hour infusion of dopamine (1 mu g/kg/min) in the Clinical Research Center of Beth Israel Hospital. Results. Renal plasma flow, estimated by clea rance of para-aminohippurate clearance, was significantly lower in the elderly than in the young subjects, but both groups increased estimat ed renal plasma how by approximately 30% during dopamine infusion. End ogenous creatinine clearance was also significantly lower in the elder ly. During dopamine infusion, creatinine clearance rose significantly only in the young. Both young and old had a similar natriuretic respon se to dopamine although urine flow and free water clearance were signi ficantly lower in the old. Neither group had significant changes in bl ood pressure or heart rate. Conclusions. Resistance to the actions of dopamine on creatinine clearance in the elderly may reflect an inabili ty to respond to endogenous dopamine at times of physiologic stress wi th resulting susceptibility to azotemia.