BEYOND HYPERKALEMIA - BETA-BLOCKER-INDUCED CARDIAC-ARREST FOR NORMOTHERMIC CARDIAC OPERATIONS

Background. Four experimental protocols were carried out to assess the ability of esmolol to induce and maintain reversible cardiac arrest u nder continuous normothermic (37 degrees C) perfusion. Methods and Res ults. In the first protocol, 8 perfused rat hearts were subjected to 2 0, 60, 90, and 120 minutes of esmolol arrest, after which positive and negative first derivative of pressure, heart rate, left ventricular d eveloped pressure, and left ventricular end-diastolic pressure were ev aluated. Arrest was achieved 45 to 60 seconds after beginning the infu sion of esmolol. Mechanical arrest was achieved before electrical arre st. In the second protocol, dose-response curves were obtained using i solated (Langendorff) rat and rabbit (n = 6) hearts. The concentration s of esmolol varied from 0.084 to 6.7 mmol/L and from 0.12 to 1.45 mmo l/L in the rat and rabbit heart experiments, respectively. In the thir d protocol, the effects of 20 minutes of normothermic (37 degrees C) i schemia on the function of isolated rat hearts perfused with esmolol-c ontaining Krebs solution were compared with those using high-potassium (25 mmol/L) Krebs solution. Group A subjects (n = 9) received the isc hemic injury after being perfused (and arrested) for 20 minutes with e ither esmolol or potassium (KCl, 25 mmol/L). Group B subjects (n = 10) received the same ischemic insult before being perfused with either e smolol or potassium. Esmolol-treated hearts showed better recovery tha n those receiving potassium, in terms of +/-dP/dt (p < 0.01), left ven tricular systolic pressure (p < 0.01), and left ventricular developed pressure (p < 0.009). Finally, the fourth protocol was done to evaluat e the effects of esmolol in a clinically relevant experimental model. Pigs were divided into esmolol (n = 6) and potassium (n = 5) groups an d subjected to normothermic cardiopulmonary bypass and a 1-hour period of cardiac arrest. Twenty minutes after stopping infusion of the card ioplegic agents, all animals were weaned off bypass. There were no sta tistically significant differences between the groups. Conclusions. Es molol hydrochloride can be used as effectively as potassium for induci ng and maintaining predictable and reversible cardiac arrest during no rmothermic cardiac operations. (C) 1997 by The Society of Thoracic Sur geons.