Low-dose dopamine in critically ill oliguric patients: the influence of the renin-angiotensin system.

OBJECTIVE

To assess the effect of low-dose dopamine on urine output and natriuresis in critically ill oliguric patients and the relationship of this response to the renin-angiotensin aldosterone system.

DESIGN

A prospective, controlled study.

SETTING

A multidisciplinary intensive care unit of a teaching hospital.

SUBJECTS

Critically ill, volume-resuscitated, oliguric patients.

INTERVENTION

Dopamine was infused at a rate of 2 micrograms/kg/min. The change in urine output and sodium excretion was measured over a 6-hour period. Plasma Renin Activity (PRA) and serum aldosterone were measured before commencing low-dose dopamine.

OUTCOME MEASURE

Patients whose mean urine output increased by greater than 20 ml/hour were considered to have responded to low-dose dopamine.

RESULTS

Nine patients were studied. Five of the nine patients responded to low-dose dopamine. The mean increase in urine volume was 58.4 ml/hr in the responders compared with 5.0 ml/hr in the nonresponders. The mean PRA (normal, 0.8 to 2.5 ng/ml/hr) was 5.7 ng/ml/hr in the responders compared with 26.8 ng/ml/hr in the nonresponders (p = 0.042). A significant inverse correlation existed between the PRA and the increase in urinary output (r = -0.75; p = 0.019).

CONCLUSION

The response to renal dopamine in critically ill patients appears to be dependent on the interaction between the vasodilating-natriuretic effect of dopamine and the vasoconstricting antinatriuretic effect of the renin-angiotensin aldosterone system.