Hemodynamic responses induced by dopamine and dobutamine in anesthetized patients premedicated with clonidine

To test the hypothesis that the pharmacological effects of dopamine (DOA) a nd dobutamine (DOB) are altered when there is inhibition of the release of norepinephrine from nerve endings, we examined the hemodynamic responses to DOA and DOE in anesthetized patients premedicated with oral clonidine. Sev enty adult patients were assigned to one of two groups (oral premedication with clonidine 5 mu g/kg or no premedication). After the induction of gener al anesthesia, heart rate and systemic blood pressure (BP) were measured fo r 10 min after each of five IV infusions (3 and 5 mu g.kg(-1).min(-1) of DO A; 0.5, 1, and 3 mu g.kg(-1).min(-1) of DOE) in a randomized, double-blind manner. Ln patients given clonidine, the mean BP increases induced by DOA 5 mu g.kg(-1).min(-1) were significantly attenuated (P < 0.01), whereas the mean BP increases induced DOB-0.5, 1, or 3 mu g.kg(-1).min(-1) were signifi cantly enhanced (P < 0.01 or 0.05). The heart rate responses to DOA and DOE did not differ between patients with or without clonidine. Premedication w ith clonidine alters the effects on BP to both DOA and DOE. When small dose s of DOA or DOE are used in clonidine-premedicated patients, differences of pharmacological profiles need to be considered for perioperative managemen t. Implications: Our randomized, double-blind study suggests that premedica tion with clonidine may enhance the effect on blood pressure response to a small dose of dobutamine (direct-acting) and attenuate that to a small dose of dopamine (mixed direct- and indirect-acting) in patients anesthetized w ith fentanyl and nitrous oxide.