Cardiac effects of carbon dioxide-consuming and carbon dioxide-generating buffers during cardiopulmonary...

Recent studies have demonstrated an increase in carbon dioxide (CO2) tension (PCO2) in both mixed venous and coronary vein blood early in the course of cardiac arrest and cardiopulmonary resuscitation. Because increased PCO2 in the myocardium correlates with both ischemic injury and depression of contractile function, the effects of hypertonic solutions of either the CO2-"generating" sodium bicarbonate (NaHCO3) buffer, a mixture of sodium carbonate (Na2CO3) and sodium bicarbonate (carbicarb) acting as a CO2-"consuming" buffer, or saline placebo (NaCl) were compared during cardiopulmonary resuscitation in 25 healthy minipigs. Both buffer agents significantly increased the pH and HCO3- of arterial, mixed venous and coronary vein blood. Bicarbonate increased whereas carbicarb reduced blood PCO2 in the systemic circuit as anticipated. However, neither the PCO2 nor the lactate content of coronary vein blood was favorably altered by buffer therapy. Four of eight animals treated with bicarbonate, five of eight treated with carbicarb and six of nine placebo-treated animals were successfully resuscitated and had a comparable 24 h survival rate. Coronary perfusion pressure during precordial compression, a critical determinant of resuscitability, was transiently decreased by each of the hypertonic solutions. Accordingly, neither CO2-generating nor CO2-consuming buffers mitigated increases in coronary vein PCO2 or improved the outcome of cardiopulmonary resuscitation under these experimental conditions.