Inadvertent hypothermia is when the body temperature falls below 36° C. This state is common in patients undergoing surgery. Hypothermia can lead to various complications. Many methods exist to keep the patient warm during surgery to avoid such complications. Warming methods can be divided into passive, which aim to isolate the patient to prevent heat loss, and active, which actively supply heat to the patient. What methods are preferred varies between different hospitals and different types of surgery.
Are there any systematic reviews which point to a specific method of warming being preferable during surgery?
We searched three electronic databases. We only included systematic reviews published in English. We identified 125 articles out of which 13 were considered potentially relevant. One person read these in full text. Five articles were included in the answer.
|Madrid et al (2016) Cochrane Database Syst Rev |
|67 RCTs comparing different active body surface warming systems (ABWS) with each other, or with passive warming methods, or different techniques of administering the same ABWS method.||Population:
Adult patients (<18 years) undergoing elective surgery with varying forms of anesthesia.
Comparison of the effectiveness of different active body surface warming systems (ABSW) which transfer heat through the skin. These included:
Electric heated mattresses and pads
Warm-water circulation systems
Other conductive warming systems
Forced air warming systems
|Core temperature in combination with one or more of the following:
Surgical site infection
Major cardiovascular complications
Intraoperative intravenous fluids infused
Other cardiovascular complications
“Forced-air warming (FAW), applied in the surgical pre- or intraoperative phases or both, seems to have a beneficial effect in terms of a lower rate of surgical site infection and complications, at least in people undergoing abdominal surgery with risk of infection, compared to not applying any active warming system. Intraoperative FAW also seems to have a beneficial effect in terms of lower rates of major cardiovascular complications when applied to people with documented substantial cardiovascular risk. It also improves patient comfort, as it maintains the core temperature within the normal range.”
|Alderson et al (2014) Cochrane Database Syst Rev |
|22 RCTs of which 16 contained data for analysis.||Population:
Adult patients (<18 years) undergoing elective and emergency surgery with general or regional anesthesia or both.
Comparison of the effectiveness of thermal insulation (reflective blankets or clothing) to:
1. Other methods of thermal insulation.
2. Warming of intravenous- and irrigation fluids.
3. Warming of inspired and insufflated gases.
4. Active warming systems.
Core temperature before, during and after surgery.
Major cardiovascular complications
“There is no clear benefit of extra thermal insulation compared with standard care. Forced air warming does seem to maintain core temperature better than extra thermal insulation, by between 0.5 ºC and 1 ºC, but the clinical importance of this difference is unclear.”
|Moola and Lockwood (2011) Int J Evid Based Healthc |
Adult patients (<18 years) undergoing different types of surgery.
The effectiveness of all passive and active warming systems and combined strategies.
“There are significant benefits associated with forced-air warming in terms of better outcomes such as higher core temperatures, reduced incidence of shivering and morbid cardiac events, increased thermal comfort, reduced blood loss, and reduced surgical site infections and shorter length of hospital stay. /…/ Single strategies such as forced-air warming were more effective than passive warming; however, combined strategies, including preoperative commencement, use of warmed fluids plus forced-air warming as other active strategies were more effective in vulnerable groups (age or durations of surgeries)”.
|Galvão, Liang and Clark (2010) J Adv Nurs |
Adult patients (<18 years) undergoing elective surgery with general, regional, epidural or spinal anesthesia.
The effectiveness of different types of cutaneous warming systems.
Forced air warming
Circulating water systems
Carbon fiber resistive heating
Energy transfer pads
Steri-drape cardiovascular sheet
Warm water and pulsating negative preassure
Warm air system
|Core temperature before, during and after surgery|
“Current evidence suggests that circulating water garments offer better temperature control than forced-air warming systems, and both are more effective than passive warming devices.”
“There is potential for the effectiveness of forced-air systems to be improved via the use of surgical access blankets, but currently there is insufficient evidence to determine whether this will elevate effectiveness to that of circulating water garments.”
|Mahoney and Odom (1999) AANA journal |
Patients of various ages (14-73 years) undergoing different types of elective surgery
Forced air warming
Circulating water blanket
Adverse effects related to excessive bleeding and resultant blood therapy
”Patients in whom normothermia has been maintained during the intraoperative period experience fewer adverse outcomes /…. / Intraoperative normothermia is more effectively maintained by using forced air warming.”
SBU Enquiry Service consists of systematic literature searches to highlight studies that can address questions received by the SBU Enquiry Service from Swedish healthcare or social service providers. Relevant references are compiled by an SBU staff member, in consultation with an external expert when needed. The quality of the studies identified is not systematically reviewed.
|Registration no:||SBU 2018/289|
Rebecka Björnfors and Christel Hellberg at SBU.