Vitamin C compromises cardiac resuscitability in a rat model of ventricular fibrillation.

ABSTRACT

Resuscitation from cardiac arrest is partly limited by progressive reduction in left ventricular distensibility, leading to decreased hemodynamic efficacy of cardiopulmonary resuscitation (CPR). Reduction in left ventricular distensibility has been linked to loss of mitochondrial bioenergetic function that can result from oxidative injury. Attenuation of oxidative injury by administration of vitamin C during CPR may help maintain left ventricular distensibility and favor resuscitability and survival. Ventricular fibrillation was electrically induced in 2 series of 16 rats each and left untreated for 10 minutes. Resuscitation was attempted by 8 minutes of CPR and delivery of electrical shocks. Dehydroascorbate (DHA)-an oxidized form of vitamin C that enters the cell via glucose transporters-was used in series 1 and ascorbic acid (AA)-the reduced form of vitamin C that enters the cell via specialized AA transporters-in series 2. In each series, rats were randomized 11 to receive a 250 mg/kg right atrial bolus of DHA or AA or vehicle immediately before chest compression. Left ventricular distensibility-measured as the ratio between coronary perfusion pressure and compression depth-was numerically lower (not significant) in rats that received DHA (1.6 ± 0.2 vs. 1.9 ± 0.7 mm Hg/mm) and AA (1.8 ± 0.6 vs. 1.9 ± 0.3 mm Hg/mm). In addition, resuscitability was compromised by DHA (2/8 vs. 7/8; P = 0.041) and by AA (0/8 vs. 5/8; P = 0.026). AA levels in mitochondria were no different than control. Vitamin C failed to preserve left ventricular distensibility during CPR and had detrimental effects on resuscitability, suggesting possible disruption of protective signaling mechanisms during oxidative stress by vitamin C.