Effects of dexmedetomidine on coronary hemodynamics and myocardial oxygen balance.
OBJECTIVE
alpha 2-adrenergic agonists decrease central sympathetic outflow and maintain normal transmural myocardial blood flow distribution, but intravenous bolus doses of these agents can also induce excessive coronary vasoconstriction and myocardial ischemia. The hypothesis of the present study was that a rapid intravenous bolus of dexmedetomidine, a specific alpha 2-adrenergic agonist, will cause coronary vasoconstriction and accompanying myocardial ischemia in young pigs.


METHODS
Prospective, controlled study on experimental animals.


METHODS
Animal laboratory of a university cardiorespiratory research center.


METHODS
Twelve domestic 8-week-old open-chest pigs, anesthetized with high-dose fentanyl. Another six pigs served as controls.


METHODS
Sequential intravenous dexmedetomidine boluses of 3, 10, and 30 mg/kg were administered, and responses were measured during peak changes (2 minutes after injection) and during recovery after each dose.


RESULTS
Left anterior descending coronary artery blood flow, calculated regional coronary vascular resistance, myocardial extraction of oxygen and lactate, plasma catecholamine levels, and conventional central hemodynamic parameters were measured. The two higher doses of dexmedetomidine induced 21% and 29% immediate increases in left anterior descending coronary artery blood flow. At the same time mean systemic blood pressure and pulmonary capillary wedge pressure increased, and calculated regional coronary vascular resistance increased. Myocardial extraction of oxygen and lactate remained unchanged.


CONCLUSIONS
Large intravenous doses of dexmedetomidine caused moderate regional coronary vasoconstriction without metabolic signs of myocardial ischemia in young domestic pigs at the same time as a marked vasoconstrictive response in the systemic circulation.
Jalonen
J
J
Department of Anesthesiology, University of Turku, Finland.
Halkola
L
L
Kuttila
K
K
Perttilä
J
J
Rajalin
A
A
Savunen
T
T
Scheinin
M
M
Valtonen
M
M
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects*; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D020926:Medetomidine; D017202:Myocardial Ischemia / Q000139:chemically induced; D009206:Myocardium / Q000378:metabolism; D010100:Oxygen / Q000097:blood*; D010865:Pilot Projects; D011446:Prospective Studies; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D007093:Imidazoles; D020926:Medetomidine; D010100:Oxygen