Effects of lidocaine and epinephrine on myocardial preservation following cardiopulmonary bypass in the dog.

The effect of lidocaine infusion on the ultrastructural damage to cardiac muscle by normothermic cardiopulmonary bypass was assessed in nine dogs. Three dogs received no medication other than pentobarbital (30 mg. per kilogram, administered intravenously), and six dogs were treated with lidocaine after anesthesia. Lidocaine was given as a 2 mg. per kilogram loading dose 10 minutes prior to ischemic arrest, followed by a 2 mg. per minute continuous infusion throughout the experimental period. Three of the lidocaine-treated animals received a single injection of epinephrine (0.5 c.c., 1:10,000) immediately after the start of coronary reperfusion. Biopsies of the left ventricular apex were taken after thoracotomy and 5 minutes after the start of coronary reperfusion. In the nontreated dogs, mitochondria were swollen, cristae disrupted, matrix cleared, sarcomeres fragmented, and glycogen was reduced or absent. Ultrastructural damage to dogs receiving lidocaine alone was limited to some swelling of mitochondria, with focal clearing of matrix and disruption of cristae. Generally, sarcomeres were intact and glycogen was present. Ultrastructural changes in dogs receiving lidocaine with epinephrine generally was similar to those in dogs receiving lidocaine alone, with the exception of the mitochondria. In the lidocaine-epinephrine group, the clearing of mitochondrial matrix and disruption of cristae resembled that seen in the nontreated dogs. The results suggest that lidocaine can protect the integrity of the ischemic myocardium and that, even in therapeutic doses, ionotropic drugs can produce ultrastructural changes which might increase the extent of myocardial ultrastructural damage.