Thirteen RCTs were identified (686 participants, range 20 to 80). Sequence generation was unclear in nine studies. Two studies were single-blind, one was double-blind, one was observer blind and in other studies blinding was unclear. Three studies had incomplete outcome data. Allocation concealment, selective outcome reporting and other potential threats to validity were unclear in all studies. There were discrepancies between text and tables/figures; results here were reported in the tables/figures.
Nine of out of ten studies individually showed a significantly greater perioperative body temperature drop for room temperature fluid than for warmed fluid. There was significant heterogeneity (I2=87%), so the authors did not report the overall standardised mean difference.
Incidence of perioperative shivering was significantly higher in the room temperature fluid group versus the warmed fluid group (OR 5.13, 95% CI 2.59 to 10.19, I2=0%; five studies). Incidence of perioperative hypothermia was significantly higher in the room temperature fluid group versus the warmed fluid group (OR 20.01, 95% CI 2.03 to 197.08, I2=64%; three studies).
There was significantly lower intraoperative blood loss in the warmed fluid group versus the room temperature group (WMD 15.54mL, 95% CI 6.67 to 24.41, I2=0%; three studies).
One study measured the time taken to regain baseline temperature and found a significant benefit for the warmed fluid group when temperature was measured rectally (p=0.04). The effect was not significant when measured orally (p=0.07).
None of the studies reported significant negative side effects. A sensitivity analysis was reported. The authors recorded which other outcomes were reported in the studies, but did not provide relevant data.