ObjectivesDopamine is currently used in the ICU for its vasopressor, renal vasodilating, and cardiac inotropic properties. Animal studies have shown both endocrine and T-lymphocyte alterations with dopamine agonist administration. The relationships between exogenous dopamine and patient hormonal and lymphocyte proliferative responses have not been evaluated in the critically ill patient. These findings furnished the impetus for the present study.DesignProspective, controlled, clinical study.Patients and MethodsAll patients admitted to the ICU at Truman Medical Center were evaluated for admission into the protocol, excluding patients whose medications or diseases produced effects in the study-dependent variables. Before institution of dopamine therapy, blood samples were taken for T-cell analysis and prolactin measurement. Daily, early morning blood samples were taken if the dopamine infusion was >5 μg/kg/min for 4 hrs during that 24-hr period. An early morning postdopamine sample was taken on the first day after dosage discontinuation. Control blood samples for determination of T-cell and prolactin responses were drawn from ICU patients who did not receive dopamine. A severity-of-disease score (Acute Physiology and Chronic Health Evaluation [APACHE II] score) was recorded for all patients.Main ResultsSerum prolactin concentrations decreased >90% (p< .001) within hours in all patients receiving dopamine infusions at study dose limit or above. Thein vitroT-cell proliferative response to concanavalin A decreased (a transitory response) in patients receiving a dopamine infusion (p< .001). Dopamine infusions in medical ICU patients produced an immediate and profound reduction in serum prolactin concentrations in both males and females. An immediate transitory decrease in patient T-cell response to concanavalin A stimulationin vitrowas seen in patients receiving dopamine.ConclusionsThe data suggest the possibility of altered endocrine and immune function as a corollary of therapeutic concentrations of dopamine in critically ill patients. (Crit Care Med 1992; 20:1644–1649)