Active body surface warming systems for preventing complications caused by inadvertent perioperative hypothermia in adults

Forced-air warming seems to have a beneficial effect in terms of a lower rate of surgical site infection and complications, at least in those undergoing abdominal surgery, compared to not applying any active warming system. It also has a beneficial effect on major cardiovascular complications in people with substantial cardiovascular disease, although the evidence is limited to one study. It also improves patient's comfort, although we found high heterogeneity among trials. While the effect on blood loss is statistically significant, this difference does not translate to a significant reduction in transfusions. Again, we noted high heterogeneity among trials for this outcome. The clinical relevance of blood loss reduction is therefore questionable. The evidence for other types of ABSW is scant, although there is some evidence of a beneficial effect in the same direction on chills/shivering with electric or resistive-based heating systems. Some evidence suggests that extending systemic warming to the preoperative period could be more beneficial than limiting it only to during surgery. Nothing suggests that ABSW systems pose a significant risk to patients.The difficulty in observing a clinically-relevant beneficial effect with ABSW in outcomes other than temperature may be explained by the fact that many studies applied concomitant procedures that are routinely in place as co-interventions to prevent hypothermia, whether passive or active warming systems based in other physiological mechanisms (e.g. irrigation fluid or gas warming), as well as a stricter control of temperature in the context of the study compared with usual practice. These may have had a beneficial effect on the participants in the control group, leading to an underestimation of the net benefit of ABSW.