Bretylium and diltiazem in porcine cardiac procedures

The use of miniature swine as a model for cardiovascular diseases of humans is becoming more popular for many reasons. One of the problems involved in using swine is their propensity for fatal cardiac arrhythmias during surgical procedures requiring general anesthetics, especially cardiac procedures. In preparation for use as a model of human atherosclerotic coronary artery disease, 30 three-month-old (15 kg) Hanford miniature swine underwent left heart catheterization, coronary angiography, and abrasion of the left anterior descending coronary artery. All pigs were treated with diltiazem HCl 30-60 mg (2-4 mg/kg) three times daily and aspirin 25 mg once daily, both given orally for three days before surgery. General anesthesia was induced with a combination of ketamine HCl 25 mg/kg, atropine sulfate 0.1 mg/kg, and acepromazine 0.22 mg/kg, all given intramuscularly. Halothane 1-2% and nitrous oxide 30% were used to maintain general anesthesia after endotracheal intubation. After successful cannulation of the femoral artery, all animals were given 200 units/kg heparin and 5 mg/kg bretylium tosylate intravenously. The electrocardiogram and mean blood pressure were monitored throughout the procedure. No significant change in blood pressure was noted during the procedure. Intracoronary nitroglycerin 200 micrograms was administered prior to abrasion of the left anterior descending with a 2.0-mm angioplasty balloon. The pigs were allowed to recover after routine closure of the incision. One pig (1/30) died during the abrasion procedure as a result of ventricular fibrillation. This represents a low, acceptable mortality using the present regimen compared with other regimens.