Mild protective and resuscitative hypothermia for asphyxial cardiac arrest in rats

It has been shown in dogs that mild hypothermia (34 degrees C) during or immediately after ventricular fibrillation cardiac arrest can improve cerebral outcome. The effect of mild hypothermia on outcome after 8 minutes of asphyxiation (5 minutes' cardiac arrest) was studied for the first time in rats. Restoration of spontaneous circulation was with external cardiopulmonary resuscitation and observation to 72 hours. Three groups of 10 rats each were studied. At 72 hours postarrest, compared with the normothermic control group 1, final overall performance categories (OPC) and neurological deficit scores (NDS) were numerically better in the resuscitative (post-arrest) hypothermia group 2 and significantly better in the protective (pre-intra-arrest) hypothermia group 3 (P < .05). Total brain histopathological damage scores (HDS) were 17 +/- 5 in group 1, 14 +/- 6 in group 2 (NS), and 6 +/- 2 in group 3 (P < .001 versus group 1). HDS correlated with OPC (r = .6, P < .05) and NDS (r = .7, P < .05). Mild hypothermia improved cerebral outcome after asphyxial cardiac arrest in rats, more when induced before than after arrest. The model's insult is within the therapeutic window, which makes it also suitable for screening other cerebral resuscitation potentials.