Combined effects of buffer and adrenergic agents on postresuscitation myocardial function

Although buffer agents alone have failed to improve the success of resuscit ation, we now examine the widely held concept that it is the combined effec t of alkaline buffer and adrenergic agents that improves outcomes of cardio pulmonary resuscitation. In the present report, the effects of both CO2-con suming and CO2-generating buffer agents in combination with adrenergic vaso pressor drugs were investigated. Ventricular fibrillation was electrically induced in Sprague-Dawley rats weighing between 450 and 550 g. Precordial c ompression and mechanical ventilation were initiated after 8 min of untreat ed ventricular fibrillation. Animals were then randomized to receive bolus injections of either inorganic sodium bicarbonate buffer, organic trometham ine buffer, or saline placebo. The beta(1) adrenergic effects of epinephrin e were blocked with esmolol. The vasopressor amine was injected 2 min after injection of the buffer agent. Electrical defibrillation was attempted at the end of 8 min of precordial compression. In 15 additional animals, the s equence of administration of the adrenergic vasopressor and buffer agents w as reversed such that the adrenergic vasopressor was injected before the bu ffer agents. All animals were restored to spontaneous circulation. Both bic arbonate and tromethamine significantly decreased coronary perfusion pressu re from 26 to 15 mm Hg and reduced the magnitude of the vasopressor effect of the adrenergic vasopressor. When the vasopressor preceded the buffer, de clines in coronary perfusion pressure after administration of buffer agents were prevented. In each instance, however, greater impairment of postresus citation myocardial function and decreased postresuscitation survival were observed after treatment with buffer agents.