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Ann Thorac Surg 1991;51:739-746
© 1991 The Society of Thoracic Surgeons

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Articles

Pretreatment with nicardipine preserves ventricular function after hypothermic ischemic arrest

Surgery Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland USA

Accepted for publication November 28, 1990.

^_* Address reprint requests to Dr Clark, Department of Surgery, Allegheny General Hospital, 320 East North Ave, Pittsburgh, PA 15212.

Calcium antagonists have a protective effect on postischemic myocardial function when included in normothermic cardiopiegia solutions. This effect varies with the calcium antagonist, but is generally lost under hypothermic conditions. The hypothesis tested was that a calcium antagonist would increase postischemic myocardial performance if given before the onset of hypothermic arrest. Isolated working rat hearts were used with an oxygenated modified Krebs-Henseleit buffer solution as a perfusion media. Rats were pretreated with 1 of 9 doses of a nicardipine solution (0 to 100 µg/kg, intraperitoneally) 20 minutes before excision of the heart. Nicardipine is a light-stable, water-soluble calcium antagonist with minimal myocardial depressant effects. The hearts were arrested for 25 minutes at 37 °C or 93 minutes at 24 °C with 20 mL of cardiopiegia solution containing 0.05 mmol/L CaCl₂. Postischemic performance and adenosine triphosphate content were used as determinants of efficacy. Eighty-three percent of 101 treated hearts recovered in contrast to a mortality of 50% in the 24 nontreated hearts. Pretreatment with 25 µg/kg significantly increased (p < 0.05) the percent recovery (compared with the nontreated group) of the following variables of cardiac function: systolic pressure, 74% to 96% (37 °C), 76% to 90% (24 °C); cardiac output, 61% to 90% (37 °C), 62% to 84% (24 °C); stroke work, 49% to 95% (37 °C), 50% to 92% (24 °C); and adenosine triphosphate, 76% to 87% (37 °C), 58% to 68% (24 °C). Progressive increases in postischemic function at 37 ° and 24 °C were seen as the dose of nicardipine was increased from 0 to 25 µg/kg and decreased function was seen with a pretreatment dose greater than 25 µg/kg of nicardipine. Pretreatment with nicardipine significantly improved postischemic myocardial performance under hypothermic conditions and should be administered or at least not discontinued before cardiac operations.