Corory vasodilatation following diazepam (Valium)

Area of Science:

• Cardiology
• Pharmacology
• Anesthesiology

Background:

• Diazepam's effects on cardiovascular function require further elucidation, particularly its impact on myocardial contractility and coronary circulation.
• Previous studies suggested a positive inotropic effect of diazepam, but the underlying mechanisms remained unclear.

Purpose of the Study:

• To investigate the specific effects of diazepam on coronary and systemic vascular resistance in anesthetized dogs.
• To determine whether diazepam's influence on myocardial contractility is mediated by changes in coronary blood flow.

Main Methods:

• Anesthetized dogs on cardiopulmonary bypass were used, with controlled heart rate and aortic pressure.
• Coronary and systemic vascular resistance were measured following diazepam administration.
• Myocardial contractility was assessed using various hemodynamic parameters under conditions of constant and variable coronary blood flow.
• A double pump-oxygenator system was employed to achieve complete separation of coronary and systemic circulations for direct intracoronary administration of diazepam.

Main Results:

• Diazepam consistently induced coronary vasodilation and decreased systemic vascular resistance.
• When coronary blood flow was held constant, diazepam did not alter left ventricular contractility.
• Direct intracoronary administration of diazepam caused coronary vasodilation, while systemic administration did not affect coronary pressure or flow.

Conclusions:

• Diazepam augments myocardial contractility by increasing coronary blood flow.
• This effect is independent of extracardiac humoral mechanisms.
• The delivery of diazepam to the coronary circulation is essential for its positive inotropic effect.