The role of volatile anesthetics in the inflammatory response to myocardial ischemia-reperfusion
Reedy, Roberta L
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Myocardial ischemia-reperfusion (IR) injury can result in major complications during the perioperative period. Experimental evidence demonstrates that inhaled volatile anesthetic administration enhances the recovery of the post-ischemic myocardium and reduces infarction size. There are few studies assessing 24 hours of in vivo reperfusion following coronary ischemia in the rat model. This study investigated the administration of the volatile anesthetic sevoflurane on the neutrophilic inflammatory response and postoperative myocardial IR damage and sought to broaden understanding of the role neutrophils play in IR injury through neutrophil depletion with vinblastine. Male Long-Evans rats were anesthetized via intraperitoneal injection of ketamine and xylazine (IP) and underwent two surgeries. The first survival surgery employed major coronary artery occlusion to induce cardiac damage followed by 24 hours of in vivo reperfusion. The second surgery consisted of cardiac harvesting. CONTROL received IP only (n=6). Sevoflurane (SEVO) received IP followed by twenty minutes 1% sevoflurane (n=6). Vinblastine (VIN) received brief sevoflurane four days preoperatively for IV injection and IP only for surgery. Postoperative cardiac damage was established by 1% triphenyl-tetrazolium chloride and 2% Evans blue staining. The area not affected appeared blue, the vulnerable myocardium red, and the infarcted area grey (MI). The area at risk (AAR) was vulnerable myocardium plus infarcted area. Infarcted area was calculated as percentage of total area affected (MI/AAR). Neutrophil count was obtained prior to vinblastine injection and each surgery for comparison. SEVO animals had significantly larger MI/AAR (0.33 ± .09) than CONTROL (0.17 ± 0.12), p = 0.027. Neutrophil change was greater in CONTROL than SEVO (p = 0.025) but did not reach a priori clinical significance. VIN data was incomplete due to mortality (n=2). The MI/AAR following coronary ischemia and 24 hours of in vivo reperfusion is not decreased by sevoflurane when preceded by IP ketamine and xylazine anesthesia in the rat model. Volatile anesthetics are rarely administered as the sole anesthetic agent and are rather administered in combination with other medications to facilitate amnesia and analgesia. Further research on combinations of medications utilized in clinical practice on cardioprotective outcomes is warranted. The role of the neutrophil in IR remains to be clarified.