Reduced renal response to low-dose dopamine infusion in the elderly

Increasing age is associated with a number of changes in renal function, including a diminished capacity to excrete salt and water loads and an increased susceptibility to acute renal failure. Dopamine is a renal autocoid important in diuresis and natriuresis and may also serve to protect against ischemic renal injury. The aim of this study was to assess the renal response to a low-dose dopamine infusion in healthy young vs elderly individuals.

Five healthy young (28 +/- 2 yr) and elderly (68 +/- 3 yr) subjects underwent evaluation of renal function and blood pressure before, during, and after a 3-hour infusion of dopamine (1 microgram/kg/min) in the Clinical Research Center of Beth Israel Hospital.

Renal plasma flow, estimated by clearance of para-aminohippurate clearance, was significantly lower in the elderly than in the young subjects, but both groups increased estimated renal plasma flow by approximately 30% during dopamine infusion. Endogenous creatinine clearance was also significantly lower in the elderly. During dopamine infusion, creatinine clearance rose significantly only in the young. Both young and old had a similar natriuretic response to dopamine although urine flow and free water clearance were significantly lower in the old. Neither group had significant changes in blood pressure or heart rate.

Resistance to the actions of dopamine on creatinine clearance in the elderly may reflect an inability to respond to endogenous dopamine at times of physiologic stress with resulting susceptibility to azotemia.