Abstract 252: Older Brains vs. Younger Brains: Effect of Cardiac Arrest on Hemodynamic Fluctuations and Neurologic Impairment in a Rodent Model

Abstract

Introduction: The patient suffering from cardiac arrest (CA) is elderly. Numerous laboratory experimental studies of CA are based on the young rodent model. Post-CA patients are often hemodynamically unstable, hypotension is correlated with poor neurologic outcomes. To improve the clinical relevance of CA research in laboratory, we compared the effect of CA in retired breeder (RB) and young group (YG) rats. Hypothesis: The objective of this study was to investigate the effect of CA on systemic arterial blood pressure and neurologic impairment outcomes in RB and YG rats. We hypothesize that RB rats will demonstrate lower mean arterial pressure (MAP) and delayed restoration of electroencephalogram (EEG) associated with neurologic recovery. Methods: Male RB Wistar rats (10-12 months, n=7) and male YG Wistar rats (2-2.5 months, n=6) were subjected to 7 min of asphyxia CA. Multiple parameters including MAP, EEG were recorded. The neurological outcomes were evaluated via neurological deficit score (NDS). Results: There was no significant difference between the two groups’ pre-arrest baseline characteristics except for the body weights (RB vs YG as 581 ± 54 vs 395 ± 9 g). This includes baseline heart rate, MAP, EEG and time to CA. After CA, RB rats showed significantly longer time to achieve return of spontaneous circulation (ROSC) compared to the YG (123 ± 42 vs 81 ± 9 sec, p < 0.05). RB rats showed lower MAP post ROSC compared to YG (98.8 ± 19.0 vs 115.0 ± 16.2 mmHg, p < 0.05 during 0-30 min post ROSC). The recovery sequences of EEG post ROSC are as follows: non-detectable cortical activity (non-DCA); intermittent cortical activity (ICA); continuous cortical activity (CCA). Analysis of recovering EEG indicates a higher gamma fraction for the RB rats during CCA period (p<0.03). High gamma is a surrogate for better EEG recovery for complex cognitive function. NDS scores were no significant difference for both groups from 4 hours to 7 days post ROSC. Conclusion: It appears that older rats have slower hemodynamic recovery post ROSC compared to younger rats. The neurologic deficits are similar in both groups, but cognitive recovery by Gamma fraction seems better in RB. More study is needed to fully understand the effect of aging on the post ROSC brain.