ACADEMIC EMERGENCY MEDICINE • October 2001, Volume 8, Number 10
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BASIC INVESTIGATIONS Post-resuscitative Hypothermic Bypass Reduces Ischemic Brain Injury in Swine KAZUHISA MORI, MD, YASUSHI ITOH, MD, PHD, JOTA SAITO, MD, YOSHIHIRO TAKEYAMA, MD, YOSHIAKI KURATA, MD, MASAMITSU KANEKO, MD, PHD, YASUFUMI ASAI, MD, PHD, TOSHIHIKO TORIGOE, MD, PHD, ERIC W. DICKSON, MD
Abstract. Objectives: Increasing human and laboratory evidence suggests that post-resuscitative brain hypothermia reduces the pathologic consequences of brain ischemia. Using a swine model of prolonged cardiac arrest, this investigation sought to determine whether unilateral hypothermic carotid bypass was capable of inducing selective brain hypothermia and reducing neurohistologic damage. Methods: Ventricular fibrillation was induced in common swine (n = 12). After 20 minutes of cardiopulmonary arrest (without ventilatory support or cardiopulmonary resuscitation), systemic extracorporeal bypass was instituted to restore coronary and cerebral perfusion, followed by restoration of normal sinus rhythm. Animals randomized to the normal brain temperature (NBT) cohort received mechanical ventilation and intravenous fluids for 24 hours. The selective brain hypothermia (SBH) cohort received 12 hours of femoral/ carotid bypass at 32⬚C. The bypass temperature was then increased one degree per hour until reaching 37⬚C and continued at this temperature until completion of the protocol (24 hours). Histopathologic dam-
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ILD TO moderate brain hypothermia has been shown to reduce neuropathologic damage in models of stroke and traumatic brain injury.1–3 Preliminary results from our group and From the Departments of Traumatology and Critical Care Medicine (KM, YI, JS, YT, YK, MK, YA) and Pathology (TT), Sapporo Medical University School of Medicine. Sapporo, Japan; and the Departments of Emergency Medicine, Physiology, and Anesthesiology (EWD), University of Massachusetts Medical School, Worcester, MA. Received March 14, 2001; revision received June 26, 2001; accepted June 27, 2001. Presented in part at the American College of Emergency Physicians Research Forum, Las Vegas, NV, October 1999. Supported in part by a grant from the Cardiovascular Division, Medtronic, Inc. Address for correspondence and reprints: Eric W. Dickson, MD, Department of Emergency Medicine, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester MA 01655. Fax 508-856-6902; e-mail:
[email protected]
age was evaluated in two areas of the hippocampus. Results: Normal sinus rhythm was restored in all animals after the systemic (femoral/femoral) bypass was initiated. Nasal temperature (surrogate measure of brain temperature) remained higher than 37.0⬚C throughout the 24-hour recovery period in the NBT animals. In the SBH cohort, right nasal temperature dropped to the mild hypothermic range (
