Adenosine for controlled hypotension: systemic compared with intracoronary infusion in dogs

We hypothesized that either through local myocardial or systemic effects, adenosine could be used to control hypotension during ischemia. Therefore, we compared the effects of systemic with intracoronary infusion of adenosine on myocardial hemodynamics and metabolism during ischemia in 27 dogs. Left anterior descending artery (LADa) flow was measured and the LADa constricted by a micrometer to restrict resting flow by 50%, 75%, and 100%. Adenosine was infused either systemically (n = 9), to maintain mean aortic pressure at 50-60 mm Hg, or directly into the LADa (n = 9), to create maximal coronary hyperperfusion; no adenosine was infused in the control group (n = 9). With systemic adenosine, during each constriction aortic pressure, left ventricular first derivative (LV dP/dt), and heart rate (HR) decreased: aortic pressure by 56.1% +/- 2.9% (mean +/- SEM), LV dP/dt by 36.2% +/- 2.2%, systemic resistance by 42.7% +/- 5%, and HR by 38.7% +/- 3% during 50% constriction (P less than 0.05 for each variable). Intracoronary adenosine decreased only aortic pressure, LV dP/dt, and HR, all to a lesser extent: aortic pressure by 5% +/- 2.8%, LV dP/dt by 15% +/- 1.2%, and HR by 4.6% +/- 1.7% (P less than 0.05, compared with systemic adenosine for each variable). With systemic adenosine only in the nonischemic area, regional myocardial blood flow increased and remained high, from 224.6 +/- 65.2 to 342 +/- 46.2 mL.min-1.100 g-1 during 50% constriction (P less than 0.05); with intracoronary adenosine, ischemic zone regional myocardial blood flow increased, but not consistently. In the ischemic area, O2 consumption was less with than without systemic adenosine; also, lactate flux production was less positive (-60.2 +/- 37.6 compared with 80.3 +/- 20.2 mmol.min-1.100 g-1 x 10(-3) during 50% constriction; P less than 0.05). Systemic infusion of adenosine during coronary hypoperfusion improves regional metabolism during ischemia and, thus, may mitigate myocardial ischemia. The mechanism by which systemic infusion improves metabolic status may be by decreases in both systemic pressure and systemic vascular resistance.