Premedication with oral dexmedetomidine alters hemodynamic actions of intravenous anesthetic agents in chronically instrumented dogs.
Dexmedetomidine (the D-stereoisomer of medetomidine), a highly selective alpha 2-adrenoceptor agonist, has been demonstrated to produce analgesia and sedation and attenuate hemodynamic responses to emergence from inhalational anesthetics, which suggests a potential use for this drug as a premedicant for general anesthesia. The authors examined hemodynamic interactions between dexmedetomidine and three commonly used intravenous anesthetic agents with markedly different hemodynamic effects. Conscious, chronically instrumented dogs received intravenous induction doses of ketamine, propofol, or etomidate, followed by continuous infusions of each drug at four different doses for 15-min intervals on different days. Studies in six separate groups (range, 9-12 dogs/group) with and without pretreatment with oral dexmedetomidine (20 micrograms/kg) were completed. Heart rate, arterial pressure, left ventricular pressure, rate of increase of left ventricular pressure at 50 mmHg (dP/dt50), and cardiac output were continuously recorded. Dexmedetomidine administration caused a significant (P less than 0.05) decrease in heart rate, rate-pressure product, left ventricular dP/dt50, and cardiac output. Dexmedetomidine abolished or attenuated the increase in heart rate, rate-pressure product, cardiac output, and arterial pressure produced during induction of anesthesia with ketamine. After the dexmedetomidine pretreatment, continuous infusion of ketamine caused no increase in heart rate or rate-pressure product. However, ketamine significantly reduced left ventricular dP/dt50 compared to control in dogs premedicated with dexmedetomidine. Except for a significant reduction in systemic vascular resistance, dexmedetomidine did not significantly affect the hemodynamic response to induction of anesthesia with propofol. Similarly, dexmedetomidine did little to alter the hemodynamic response to induction of anesthesia with etomidate.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226.
L T
LT
Proctor
W T
WT
Schmeling
D C
DC
Warltier
D000284:Administration, Oral; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000771:Anesthesia, Intravenous; D000818:Animals; D004285:Dogs; D005045:Etomidate; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D007262:Infusions, Intravenous; D007649:Ketamine; D008297:Male; D020926:Medetomidine; D011229:Preanesthetic Medication; D015742:Propofol
D000316:Adrenergic alpha-Agonists; D007093:Imidazoles; D007649:Ketamine; D020926:Medetomidine; D015742:Propofol; D005045:Etomidate