1. Calcium-entry blockers increase the intramyo-cardial pH and decrease the intramyocardial Pco2 of ischaemic canine myocardium. However, the evidence documenting improvements in myocardial acidosis and in myocardial resuscitability after administration of calcium-entry blockers during cardiac arrest is incomplete. We therefore compared the effects of verapamil (0.05 mg/kg) and diltiazem (0.075 mg/kg) with those of saline placebo in an established porcine model of cardiac arrest and cardiopulmonary resuscitation.

2. After verapamil, six of 11 animals were successfully resuscitated; after diltiazem, five of 10; and after saline placebo, six of 10. Coronary perfusion and mean aortic pressures together with end-tidal CO2 concentration during precordial compression were predictive of resuscitation, independently of the drug or placebo.

3. Coronary vein pH decreased to 6.91 ± 0.06 units (mean ± sem) with concurrent increases in Pco2 to levels exceeding 100 mmHg. Coronary vein lactate increased to a maximum of 7.5 ± 0.6 mmol/l. Coronary vein acidaemia was accompanied by decreases in intramyocardial pH to 6.64 ± 0.06 units. However, each of these differences between success and failure of resuscitation was unrelated to treatment with calcium-entry blockers.

4. Accordingly, neither verapamil nor diltiazem selectively altered coronary perfusion pressure, attenuated intramyocardial acidosis or improved resuscitability after porcine cardiac arrest and cardiopulmonary resuscitation.

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