The Annals of Thoracic Surgery, Vol 31, 558-563, Copyright © 1981 by The Society of Thoracic Surgeons
Substrate cardioplegia during hypothermic arrest in the alloxan diabetic dog
PE Clancy, AD Slater, D Brandt and MM Kirsh
In an experimental study, 26 mongrel dogs were treated with alloxan (50 mg
per kilogram) to induce fasting hyperglycemia and diabetes. The animals
were randomly subdivided into two groups, one of which received 100 mg of
propranolol in divided doses for two weeks. The animals underwent
sternotomy and were placed on total cardiopulmonary bypass. After aortic
cross-clamping, each animal received 10 ml per kilogram of cardioplegic
solution. Two different solutions were used, a standard hyperkalemic
solution and a high-energy glucose-insulin-potassium (GIK) substrate.
Baseline studies were made on the four groups of diabetic animals. Animals
given potassium cardioplegia but no propranolol showed statistically
significant decreases in cardiac index, heart rate, mean arterial pressure,
and minute left ventricular stroke work index after bypass. In contrast,
animals given GIK cardioplegia but no propranolol showed no changes in any
of these measurements. Animals administered propranolol and potassium
cardioplegia experienced decrease in mean arterial pressure from 77.5 +/-
14.1 mm Hg before bypass to 57.5 +/- 17.8 mm Hg after bypass. A similar
reduction occurred in animals given propranolol and GIK cardioplegia.
However, in this group, the cardiac index increased from 1.78 +/- 0.38
L/min/m2 before bypass to 2.96 +/- 0.73 L/min/m2 after bypass (p less than
.006). Similarly, the minute left ventricular stroke work index increased
after bypass in these animals. This study demonstrates the protective
effect against myocardial ischemia of the addition of substrate to the
cardioplegic solution in diabetic animals subjected to aortic
cross-clamping during cardiopulmonary bypass, one group receiving
propranolol and one group not receiving it.
