Comparison of the effects of dexmedetomidine and esmolol on myocardial oxygen consumption in dogs.
OBJECTIVE
The beta-adrenergic blocker esmolol and the alpha 2-adrenergic agonist dexmedetomidine have the potential to decrease perioperative myocardial ischaemia. The pathophysiological mechanisms involved in these anti-ischaemic properties have not been thoroughly studied. We compared the effects of esmolol and dexmedetomidine on two indices of overall myocardial oxygen demand and on directly measured myocardial oxygen consumption of the left anterior coronary artery territory.


METHODS
Eleven mongrel dogs were instrumented to measure aortic and left ventricular pressure, aortic and left anterior coronary artery flow and myocardial wall thickening. Variables related to myocardial oxygen metabolism were also determined. Measurements were performed during four sequential experimental conditions in each dog (Control 1: esmolol; Control 2: dexmedetomidine).


RESULTS
Esmolol and dexmedetomidine decreased haemodynamic indices of myocardial oxygen demand to a similar extent: esmolol decreased the rate-pressure product by 16+/-3% and the pressure-work index (PWI) by 16+/-3%, dexmedetomidine decreased the rate-pressure product by 26+/-3% and the PWI by 16+/-7%. However, these similar decreases resulted from different haemodynamic effects of the two study drugs. Dexmedetomidine had a more pronounced bradycardic effect than esmolol (P = 0.01) and increased systolic aortic pressure (SAP) by 15+/-4% while esmolol decreased SAP by 8+/-2% (P < 0.01). dP/dt(max) and regional myocardial area decrease were lower after esmolol than after dexmedetomidine. Neither drug had an effect on myocardial oxygen consumption.


CONCLUSIONS
Esmolol and dexmedetomidine decreased two haemodynamic indices of overall myocardial oxygen demand to a similar extent but neither drug decreased directly measured myocardial oxygen consumption in the territory of the left anterior descending artery.
Willigers
H M M
HM
University Hospital Maastricht, Department of Anaesthesiology, The Cardiovascular Research Institute of Maastricht, Maastricht, The Netherlands.
Prinzen
F W
FW
Roekaerts
P M H J
PM
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002698:Chloralose / Q000008:administration & dosage; D003331:Coronary Vessels / Q000187:drug effects; D020927:Dexmedetomidine / Q000494:pharmacology*; D004285:Dogs; D006321:Heart / Q000187:drug effects; D006334:Heart Function Tests / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology; D011412:Propanolamines / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects; D018709:Statistics, Nonparametric; D014655:Vascular Resistance / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D018686:Anesthetics, Intravenous; D011412:Propanolamines; D002698:Chloralose; D020927:Dexmedetomidine; C036604:esmolol; D009638:Norepinephrine