Prehospital therapeutic hypothermia after cardiac arrest: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Therapeutic hypothermia has been recommended for the treatment of cardiac arrest patients who remain comatose after the return of spontaneous circulation. However, the optimal time to initiate therapeutic hypothermia remains unclear. The objective of the present study is to assess the effectiveness and safety of prehospital therapeutic hypothermia after cardiac arrest.

METHODS: Databases such as MEDLINE, Embase, and Cochrane Library were searched from their establishment date to May of 2012 to retrieve randomized control trials on prehospital therapeutic hypothermia after cardiac arrest. Thereafter, the studies retrieved were screened based on predefined inclusion and exclusion criteria. Data were extracted and the quality of the included studies was evaluated. A meta-analysis was performed by using the Cochrane Collaboration Review Manager 5.1.6 software.

RESULTS: Five studies involving 633 cases were included, among which 314 cases were assigned to the treatment group and the other 319 cases to the control group. The meta-analysis indicated that prehospital therapeutic hypothermia after cardiac arrest produced significant differences in temperature on hospital admission compared with in-hospital therapeutic hypothermia or normothermia (patient data; mean difference=-0.95; 95% confidence interval -1.15 to -0.75; I(2)=0%). However, no significant differences were observed in the survival to the hospital discharge, favorable neurological outcome at hospital discharge, and rearrest. The risk of bias was low; however, the quality of the evidence was very low.

CONCLUSION: This review demonstrates that prehospital therapeutic hypothermia after cardiac arrest can decrease temperature on hospital admission. On the other hand, regarding the survival to hospital discharge, favorable neurological outcome at hospital discharge, and rearrest, our meta-analysis and review produces non-significant results. Using the Grading of Recommendations, Assessment, Development and Evaluation methodology, we conclude that the quality of evidence is very low.