The effects of clonidine premedication on the blood pressure and tachycardiac responses to ephedrine in elderly and young patients during propofol anesthesia

Abstract

We studied the pressor and tachycardiac responses to ephedrine in elderly and young patients given either clonidine or midazolam during propofol anesthesia. In the first experiment, elderly (>60 yr) and young (20-45 yr) patients were randomly allocated to one of four groups according to age and premedicated regimens (n = 16 each; elderly-clonidine [EC], elderly-midazolam [EM], young-clonidine [YC], and young-midazolam [YM]). Under propofol anesthesia, ephedrine was injected, and hemodynamic measurements were made. In the second experiment, with clonidine premedication, elderly patients (n = 16) were given a reduced dose of propofol (EC-LP) and young patients (n = 16) were given an increased dose of propofol (YC-HP). Ephedrine was injected, and he- modynamic measurements were performed. The in-creases in mean blood pressure and heart rate were larger in the EC group than in the EM, YM, and EC-LP groups (P < 0.05). In the YC-HP group, the pressor response to ephedrine tended to be augmented as compared with the YC group but was not statistically significant. These results suggest that clonidine premedication augmented the pressor and tachycardiac responses to ephedrine, especially in elderly patients during a standard dose of propofol anesthesia, and that clonidine, age, and propofol could be involved in the augmentation of the blood pressure and tachycardiac responses to ephedrine.

Implications: Clonidine premedication augments the pressor and tachycardiac responses to ephedrine in elderly patients during standard or large doses of propofol anesthesia but does not augment during small doses of propofol anesthesia. Clonidine, age, and propofol could be involved in the augmentation of the pressor and tachycardiac responses to ephedrine.