[Cardiovascular effects of two dexmedetomidine doses: experimental study in dogs.]

There has been a growing interest in the anesthetic use of dexmedetomidine, a new alpha2-adrenergic agonist, due to decreased anesthetics consumption and better cardiovascular stability that it promoter. This study aimed at investigating cardiovascular effects of two different dexmedetomidine doses in anesthetized dogs.

The study involved 36 adult dogs anesthetized with propofol, fentanyl and isoflurane distributed in three groups which received: G1, 20 ml saline injection in 10 minutes, followed by 20 ml of the same solution infused in one hour; G2, 20 ml dexmedetomidine-containing saline (1 microg.kg-1) in 10 minutes, followed by 20 ml of the same solution infused one hour; and G3, of dexmedetomidine-containing saline (2 microg.kg-1) in 10 minutes, followed by 20 ml of the same solution infused in one hour. Cardiovascular attributes were evaluated in four moments: M1, control, M2, after initial 20 ml injection of the studied solution, coincident with the beginning of the same solution injection in one hour; M3, 60 minutes after M2 and M4, 60 minutes after M3.

G2 heart hate (HR) was decreased at M2, returning to baseline values at M3, while in G3 it was decreased at M2 but was kept so throughout the experiment. There has been progressive HR increase in G1. There were no significant changes in mean blood pressure in all group. Systemic vascular resistance (SVR) was maintained stable in G2 and G3, but was decreased in G1 at M3. Cardiac index (CI) was not significantly changed in G2 and G3, but has progressively increased in G1.

In dogs under these experimental conditions, dexmedetomidine has induced a dose-dependent HR decrease, has inhibited isoflurane-induced SVR decrease and has prevented hyperdynamic responses throughout the experiment.