Buffer solutions may compromise cardiac resuscitation by reducing coronary perfusion presssure

Abstract

Objective: --To investigate the effects of hypertonic buffer solutions on coronary perfusion pressure (CPP) and resuscitability during experimental closed-chest cardiac resuscitation.

Design: --Randomized, placebo-controlled trial.

Setting: --Mammalian research laboratory.

Participants: --Forty-four domestic pigs.

Interventions: --Cardiac arrest was induced by ventricular fibrillation in mechanically ventilated pigs anesthetized with pentobarbital sodium. Precordial compression was started at the third minute of untreated ventricular fibrillation and maintained for an interval of 8 minutes. A hypertonic solution of sodium bicarbonate, Carbicarb (an equimolar mixture of sodium bicarbonate and sodium carbonate [International Medication Systems, Ltd]), or sodium chloride or an isotonic solution of sodium chloride was infused into the right atrium over a 1-minute interval starting at the sixth minute of ventricular fibrillation. Restoration of spontaneous circulation was attempted by DC transthoracic countershock after 11 minutes of ventricular fibrillation.

Main outcome measures: --Plasma osmolality, CPP, and cardiac resuscitability.

Results: --Infusion of hypertonic buffer and sodium chloride solutions increased plasma osmolality from an average of 280 to 330 mOsm/kg. This was accompanied by a significant decrease in the aortic pressures and CPPs generated during precordial compression. No such changes occurred after infusion of isotonic sodium chloride. Restoration of spontaneous circulation, as in earlier studies, was contingent on the levels of CPP prior to attempted defibrillation. Accordingly, none of 13 animals in which the CPP declined to less than 10 mm Hg after infusion of the hypertonic solutions were successfully resuscitated. This contrasted with nine animals that received isotonic sodium chloride and served as controls. Coronary perfusion pressure consistently exceeded 10 mm Hg in these control animals, and spontaneous circulation was restored in each instance.

Conclusions: --Hypertonic solutions and specifically buffer solutions administered in the absence of vasopressor agents may adversely affect cardiac resuscitation efforts by reducing CPP below critical thresholds.