Introduction: The neuroprotective effects of hypothermia have been proven to be partly dependent on the speed of cooling. Recent clinical cases reported that rapid hypothermia using continuous renal replacement therapy (CRRT) was feasible and further facilitated the recovery of cardiac and cerebral function. Here we investigated the efficacy of cooling by CRRT and its effects on brain injury and neuronal apoptosis after CPR in a porcine model.
Hypothesis: CRRT cooling would induce ultrafast hypothermia so as to produce more potent protective effects against post-resuscitation brain injury.
Methods: Twenty-seven male domestic pigs weighing 36 ± 2 kg were utilized. The animals underwent 8 mins of untreated VF followed by 5 mins of CPR. At 5 mins after resuscitation, the animals were randomized to receive either normothermic life support (NT group) or hypothermia implemented by either a combination of earlier 8-hr CRRT and later 16-hr surface cooling (CRRT group) or the whole 24-hr surface cooling (SC group). The rate of blood flow of CRRT was initially set at 180 ml/min with the infusion line submerged in 4 °C of ice water to rapidly decrease the blood temperature.
Results: The resuscitated animals were rapidly cooled in the hypothermic two groups. However, the time to target temperature of 33 °C was significantly shorter in the CRRT group than the SC group (28±7 mins vs. 185±35 mins, p<0.001). Consequently, significantly milder cerebral injury after resuscitation was observed in the hypothermic two groups than the NT group. Additionally, post-resuscitation cerebral injury was further significantly alleviated in animals treated with CRRT when compared to the SC group. Similarly, significantly lesser neuronal apoptosis was detected in all hypothermic animals, and this was more obvious in the CRRT group than the SC group(Table).
Conclusion: Ultrafast cooling was successfully induced by CRRT in swine, which reduced post-resuscitation brain injury and neuronal apoptosis.