Spinal anesthesia attenuates myocardial ischemia during coronary artery spasm induced by intraaortic methacholine in rats

Coronary artery spasm is not rare in patients with coronary artery disease, but the influence of regional anesthesia on spasm-induced myocardial ischemia is not known. We investigated the effects of spinal anesthesia on myocardial ischemia during coronary artery spasm in rats, and compared these with the effects of an alpha- and beta-adrenergic antagonist, and an alpha-adrenergic agonist. An intraaortic catheter was inserted via the right internal carotid artery so that the tip of the catheter was placed near the coronary ostium. An intrathecal catheter was placed at lumbar level. Coronary spasm was induced by the intraaortic injection of methacholine, and we identified the thresholds of myocardial ischemia, defined as the dose of methacholine that induced ST-segment elevation. Subsequently, the thresholds were determined after spinal anesthesia, and after the intraaortic injection of phentolamine and propranolol. The thresholds of myocardial ischemia increased significantly after intrathecal bupivacaine. In contrast, the threshold did not change after the injection of phentolamine. The thresholds increased significantly after the injection of propranolol. Methoxamine significantly decreased the threshold of ischemia. These results demonstrated that spinal anesthesia attenuated myocardial ischemia during methacholine-induced coronary spasm. This effect was equivalent to that of propranolol.