Table 1.

Summary of studies included in meta-analysis, OR operating room.

Author	Groups and method of warming	Other heating methods	Anaesthetic technique/dose	Temperature device
Butwick and colleagues14	Forced air warming (n=15) - placed over the upper thighs just distal to the inguinal fold (set to 43°C) Control group (n=15) - warming blanket only (switched off)	Both groups have cotton blanket covering warmer	Spinal: 12 mg bupivacaine + fentanyl 10 mcg + morphine 200 mcg	Oral digital thermometer (Medichoice, Portsmouth, VA)
Chan and colleagues21	Warmed fluid (n=21) - through a Fenwal blood warmer set at 36.5°C (no preload in either group), warmed cleaning solutions (38–42°C) and extra gowns, socks, blankets, covered as much as possible during epidural insertion and for the following 20 min Control group (n=19) – room temperature crystalloids, prep solution and single hospital gown. Epidural medications were room temperature		Epidural: 3 ml lidocaine with 1:200000 adrenaline test dose followed by titrated doses to T4-T6	Aural canal thermistors (Mon-A-Therm, Inc., St. Louis, MO) and temperature sensing Foley catheter in bladder
Chung and colleagues22	Forced air warming (n=15) - Bair hugger set at 43°C to upper body 15 min before spinal and room temperature fluid pre-load with 10 ml kg−1 Hartmann's solution pre-spinal. Warmed fluid (n=15) - from warming cabinet set at 37–38°C. Preload of 10 ml kg−1 Hartmann's solution Control group (n=15) – 10 ml kg−1 Hartmann's solution pre spinal at room temperature		Spinal: 10 mg hyperbaric bupivacaine	Core temp-thermoscan® (infrared tympanic thermometer IRT 4020; Braun, Bethlehem, PA, USA)
Fallis and colleagues23	Forced air warming (n=32) - Bair hugger set at 43°C to upper body until mother exited operating room Control group (n=30) warmed cotton blankets as needed	Both groups had warmed fluid from the warming cupboard set at 39°C.	Spinal: Local anaesthetic not stated; Intrathecal morphine 150 mcg Fentanyl 32±39 mcg in control; 14±4 mcg in warmed group	IVAC TempPLUS II electronic thermometer (Alaris Medical Systems, San Diego, CA)
Goyal and colleagues15	Warmed fluid (n=32) - through a Asotherm plus AP220 Futuremed fluid warmer set at 39°C Control (n=32) – fluids at OR temperature (22°C) Both groups preloaded with 10 ml kg−1 0.9% Normal Saline		Spinal: 2.5 ml heavy bupivacaine 0.5%	Tympanic membrane thermometer - model not presented
Horn and colleagues24	Forced air warming (n=15) - Bair hugger set to 43°C over upper body 15 min before epidural insertion. Control group (n=15) - Single cotton blanket	All patients received warmed fluids to 37°C (device not stated)	Epidural: 3 ml ropivacaine 0.75% test dose then 4 ml boluses until block to T4 bilaterally (no opioids)	Tympanic membrane temp Mon-a-Therm thermocouples (Mallinckrodt Anesthesiology Product, Inc., St. Louis, MO)
Horn and colleagues14	Forced air warming (n=19) - Level 1 Equator warmer over upper body immediately set to 44°C after spinal Control group (n=21) – pre warmed cotton blankets taken from 40°C heating cabinet		Spinal: 1.4 to 1.6 ml 0.5% bupivacaine + sufentanil 5 mcg	Skin temperature on chest of mother (Infrared Temperature Scanner, Model Dermatemp DT-1001, Exergen Corporation, Watertown, MA). Sublingual temperature probe (Temp-Plus II, Model 2080, Alaris™; Carefusion, San Diego, CA) into posterior sublingual pocket
Jorgensen and colleagues17	Warmed fluid (n=57) – 37°C stored in thermostat control. Preload (20 ml kg−1 during the 15 min preceding spinal injection) and maintenance (10 ml kg−1 during the 20 min after spinal injection) Control group (n=56) - 21°C fluid. Volumes as with warmed group		Spinal: 2.7 ml bupivacaine 0.5%	Not described
Paris and colleagues16	Warmed fluid (n=73) - fluid warmed to 41°C via infusion pump and fluid warmer. Three fluid warmers utilized for study (type and manufacturer not stated) Control group (n=76) - one warm blanket applied to lower extremities and one warm blanket applied across maternal upper chest and arms		Not stated	Temperature sensing Foley catheters (make and manufacturer not stated)
Smith and colleagues12	Warmed fluid (n=35) - via Hotline, set point 42°C Control group (n=32) – room temperature fluids at 20–22°C		Spinal lidocaine or bupivacaine or epidural lidocaine to achieve block to T4-T6 (technique not dictated by protocol)	Mon-a-therm thermocouple temperature probes (Mallinkrodt Medical Inc, St Louis MO) at tympanic membrane
Woolnough and colleagues7	Warmed fluid - either from: a) Warmed cabinet (n=25) set at 45°C (distal end 37–38°C) b) Hotline (n=25; Smiths Medical) set to 42°C Control group (n=25) - fluid through Hotline warmer switched off		Spinal: 2.3 ml bupivacaine 0.5% + diamorphine 350 mcg	Infrared tympanic thermometer (ThermoScan Exac-Temp, Braun, Weybridge, UK)
Workhoven and colleagues19	Warmed fluid (n=22) – from heated cabinet and administered immediately 30–33.9°C Control group (n=22) – fluid at room temperature Both groups received 1Litre Hartmann's solution over 10–15 min		Epidural: 2% lidocaine with epinephrine 1:200000. 3 ml test dose + 17–22 ml, small doses of fentanyl and thiopental or both given pre and post-delivery for sedation as necessary	Oral temperature (device not stated)
Yokoyama and colleagues20	Warmed fluid (n=15) – heated for 3 days at 41°C and then infused through i.v. tube warmer coil at 38°C Control group (n=15) - fluid maintained at room temperature (25°C) Both groups received preload of 400 mls Hydroxyethlated starch	All patients had reflective blanket on shoulders, upper extremities and lower extremities	Spinal: 12.5 mg hyperbaric bupivacaine; 0.5 mg midazolam after delivery	Thermocouple probe (Monatherm; Covidien, Mansfield, MA)