Intra-arrest therapeutic hypothermia with combined helium-mixed gas and cold fluid infusion significantly augments brain cooling efficiency: An experimental study in pigs.

Objective: This study aimed to develop a more efficient method for intra-arrest therapeutic hypothermia (IATH) and demonstrate its usefulness in cardiopulmonary cerebral resuscitation. Methods and results: The following experiments were performed in pigs while measuring the brain temperature, introducing cardiac arrest, and performing cardiopulmonary resuscitation. In experiment 1, the use of helium gas mixtures in cardiac arrest intra-arrest lung cooling (IALC) increased brain cooling efficiency. When the IATH method was performed by adding cold fluid infusion to IALC, a decrease in brain temperature of approximately 0.8 °C within 10 min was observed. In experiment 2, cerebral microdialysis (CMD) during the IATH method of cardiopulmonary resuscitation showed a slight elevation of glutamate and significantly lower glutamate levels than those in the normally resuscitated group. Finally, the IATH method achieved return of spontaneous circulation equivalent to conventional resuscitation involving adrenaline administration and number of defibrillation attempts, without a statistically significant difference between the groups. Conclusion: The IATH method with IALC using a helium gas mixture and cold fluid infusion rapidly decreased brain temperature by approximately 0.8 °C within 10 min after the start of resuscitation. CMD with IATH showed no increase in glutamate levels, suggesting a possible cerebroprotective effect, and cardiac resuscitation could be performed without complications. These facts suggest that this IATH method of rapidly decreasing brain temperature may be more effective for mitigating post-CA brain injury.