Abstract 177: A Multimodal Neuroprotection Strategy Using Ketamine, Melatonin, and Limited Initial Reoxygenation Following Cardiac Arrest Does Not Improve MRI Cytotoxic Injury in a Swine Model: A Pilot Study

Abstract

Introduction: Reperfusion/ischemic brain injury following arrest is a major cause of death/disability among patients surviving to admission. Aside from targeted temperature management, no proven neuroprotective strategies exist. Melatonin (anti-epileptic/antioxidant) and ketamine (glutamate inhibitor), along with controlled reintroduction of oxygenated blood have been proposed to reduce secondary injury. Hypothesis: We hypothesized that a combination of above therapies would reduce the ischemic burden measured on MRI following cardiac arrest if administered upon initial reperfusion. Methods: 6 swine underwent isoflurane anesthesia and control MRI (DTI b2000/20 directions, DSC). Swine were randomized to fixed periods of cardiac arrest (2 swine to 20 min and 1 to 30 min in both control and treated groups), and ECMO catheters placed in the distal aorta and right atrium, then ventricular fibrillation induced by a bipolar pacing catheter. Following ischemia, swine were reperfused at 2.8-3.5 L/min with either unblended oxygenated blood in the control group, or 21% oxygenated blood increased to 30% after 4 minutes and then titrated to maintain PaO2 of 80-100 mm Hg, melatonin 5 mg/kg bolus then 5 mg/kg/hr and ketamine 4 mg/kg/hr for 2 hours in the treated group. After 4 min swine were defibrillated until return of heartbeat. Animals were weaned from pump, decannulated, and epinephrine and fluid boluses administered for hemodynamic support, then re-imaged within 2 hours post-resuscitation using same protocol. Whole brain ADC measurements were performed on gray and white matter. Frontal lobe regions of interest drawn for DSC perfusion parameters. Results: Baseline hemodynamic parameters: BP, Heart Rate, End-Tidal CO2, and SpO2 were similar between animals. There was no difference in percent change ADC in gray or white matter between treated and untreated swine (p=0.9), or difference in CBV (p=0.67). CBF showed an upward trend in treated animals (p=0.17). Conclusions: A multimodal neuroprotective strategy of melatonin, ketamine, and controlled reoxygenation failed to demonstrate measurable impact on MRI markers of ischemia-reperfusion injury in this pilot study. The translation of promising neuroprotectants might be triaged using the employed model.