Improved cerebral recovery from hypothermic circulatory arrest after remote ischemic preconditioning

Background: Remote ischemic preconditioning is a novel method of reducing ischemia-reperfusion injury in which a transient ischemic period of the limb provides systemic protection against a prolonged ischemic insult. This method of preconditioning has shown some potential in ameliorating ischemia-related injury in various organs and experimental settings. We hypothesized that remote ischemic preconditioning might also improve the recovery from hypothermic circulatory arrest (HCA).

Methods: Twenty-four juvenile pigs underwent 60 minutes of HCA at 18 degrees C with either transient right hind leg ischemic preconditioning or no ischemic preconditioning. Preconditioning was induced by four cycles of 5-minute ischemia periods with three 5-minute reperfusion periods in between. Microdialysis and electroencephalography (EEG) data were recorded to detect any possible changes during the recovery phase.

Results: The EEG data showed that the remote ischemic preconditioning group had significantly better EEG recovery time and a lower burst suppression ratio throughout the follow-up period. Cerebral extracellular glucose and glycerol content rose significantly immediately after HCA in the control group compared with the remote ischemic preconditioning group, and significantly higher lactate concentrations were measured in the control group at 5 and 6 hours after reperfusion, indicating a difference in cerebral metabolism.

Conclusions: Our data imply that remote ischemic preconditioning improves the recovery from HCA. It provides a faster recovery of cortical neuronal activity and protection against potential oxygen radical-mediated ischemia damage during and after HCA. In addition, it seems to protect from a late phase lactate and pyruvate burst, mitigating possible damage from an anaerobic metabolism phase.