The grades of evidence (I-III) and levels of recommendations (I-III) are defined at the end of the "Major Recommendations" field.
Level I
There are insufficient data to support a Level I recommendation for this topic.
Level II
There are insufficient data to support a Level II recommendation for this topic.
Level III*
Pooled data indicate that prophylactic hypothermia is not significantly associated with decreased mortality when compared with normothermic controls. However, preliminary findings suggest that a greater decrease in mortality risk is observed when target temperatures are maintained for more than 48 hours.
Prophylactic hypothermia is associated with significantly higher Glasgow Outcome Scale (GOS) scores when compared to scores for normothermic controls.
Note: In this meta-analysis, although all included studies were Class II, the sub-analyses findings introduced sufficient concern about unknown influences to render the recommendation a Level III.
Summary
Evidence from six moderate quality randomized controlled trials (RCTs) did not clearly demonstrate that hypothermia was associated with consistent and statistically significant reductions in all-cause mortality. However, patients treated with hypothermia were more likely to have favorable neurological outcomes, defined as GOS scores of 4 or 5. Preliminary findings suggest that hypothermia may have higher chances of reducing mortality when cooling is maintained for more than 48 hours. Interpretation of results from this and other subgroup analyses based on different aspects of the hypothermia treatment protocols were limited due to small sample sizes. Potential confounding and effect modifying factors that are not accounted for in the trials included in this analysis, such as patients' temperature at admission, limit these recommendations to Level III.
Definitions:
Grades of Evidence
Class I - Good quality randomized controlled trial (RCT)
Class II - Moderate quality RCT, good quality cohort, or good quality case-control
Class III - Poor quality RCT; moderate or poor quality cohort; moderate or poor case-control; case series, databases or registries
Levels of Recommendation
Levels of recommendation are Level I, II, and III, derived from Class I, II, and III evidence, respectively.
Level I - recommendations are based on the strongest evidence for effectiveness, and represent principles of patient management that reflect a high degree of clinical certainty.
Level II - recommendations reflect a moderate degree of clinical certainty.
Level III - recommendations for which the degree of clinical certainty is not established.