Table 3 Studies included in the review

Henker et al. (1998) [16]

Descriptive comparison ICU USA

Severe head injury n = 8

Age: 18-58 GCS: 4-7

Site: right lateral ventricle Device: type T thermocouple (model no. 12983 Ventricular Catheter with Thermocouple; Radionics, Burlington, MA, USA)

Site 1: rectum Device: Hewlett-Packard Model 21090A probe (Hewlett-Packard Company, Androver, MA, USA) Site 2: bladder Device: bladder catheter (Bardex Lubricath, model 909116; CR Bard, Inc., Convington, GA, USA)

Yes

Random assignment to groups Hypothermia ('target' 32°C for 48 h, n = 5) Normothermia group (n = 3)

• Mean (SD) of T_br - T_r: 0.8 (0.8) °C

• Mean (SD) of T_br - T_bl: 1.0 (0.7) °C

Brain temperature is higher than rectal and higher than bladder temperature

Not possible to determine which patients reached the hypothermia 'target'

Rumana et al. (1998) [18]

Descriptive study ICU USA

Severe head injury n = 30

Mean (SD) age: 30.7 (13.0) GCS: ≤8 (n = 25); >8 (n = 5)

Site: intraparenchyma Device: Licox, Kiel-Mielkendorf, Germany

Site: rectum Device: 10-Fr thermistor probe (400 series, Sheridan Catheter Corporation, Argyle, NY, USA)

Yes

No

• Mean (SD) of T_br- T_r: 1.1 (0.6) °C

Brain temperature is higher than rectal temperature

Zhang et al. (2002) [21]

Descriptive study Unclear China

Severe head injury n = 18

Age: 20-73 GCS: ≤8

Site: frontal white matter Device: flexible Clark-type microcatheter (Licox-II system, GSM Co. Ltd, Germany)

Site: rectum Device: not reported

Unclear

Mild hypothermia on all patients

• Mean of T_br - T_r at 0 hours after cooling: 0.8°C

• Mean of T_br - T_r at 24 hours after cooling: 1.1°C

• Mean of T_br - T_r at 72 hours after cooling: 1.4°C

Brain temperature is consistently higher at 0, 24 and 72 hours after cooling

Soukup et al. (2002) [12]

Descriptive study ICU USA

Severe head injury n = 58

Age: ≥ 16 GCS: ≤8

Site: parenchyma Device: Paratrend 7, Diametrics Medical Inc., Roseville, MN, USA

Site: rectum Device: Hewlett Packard

Unclear

Mild hypothermia (n = 33);

Control (n = 25)

• Mean (SD) of T_br -T_r in the normothermic group: 0.0 (0.5)°C

• Mean (SD) of T_br-T_r in the hyperthermic group: 0.3 (0.5)°C

• Mean (SD) of T_br-T_r in the therapeutic 'cooled' group: -0.2 (0.6)°C

• Mean (SD) of T_br-T_r of spontaneous hypothermia group: -0.8 (1.4)C

Brain temperature is higher than rectal temperature at normothermia and hyperthermia conditions, but lower during therapeutic cooling and spontaneous hypothermia

Tokutomi et al. (2003) [13]

Descriptive study ICU Japan

Severe brain injury n = 31

Age: 15-69 GCS: 3-5

Site: subdural Device: Camino Direct Pressure monitor (Camino Laboratories, San Diego, CA, USA)

Site: rectum Device: Bi-Temp (RSP, Boston, MA, USA) Site 2: Jugular vein Device: fibreoptic catheter (manufacturer type not stated)

Unclear

Hypothermia therapy on all patients

• Mean (SD) of T_br- T_r: 0.5 (0.3) °C

• Mean (SD) of T_br- T_jv: 0.3(0.3) °C

Brain temperature is higher than both rectal and jugular vein temperature

Childs et al. (2005) [19]

Descriptive study ICU UK

Severe TBI n = 19

Age: 19-70 GCS: 3-13

Site: brain parenchyma Device: Camino 110-4BBT, 4 Fr, fibre-optic, transducer tipped sensor (Integra Neurosciences, Andover, UK)

Site: rectum Device: Mon-a- therm 400 series, 9 Fr, thermistor (Mallinckrodt Medical, Tyco Healthcare, Gosport, UK)

Yes

No

• Mean (SD) of T_br- T_r: -0.04 (0.9) °C

No evidence of systematic difference between brain and core temperature. Brain temperature is lower than rectal temperature

Kirk et al. (2009) [14]

Descriptive study ICU UK

Severe TBI n = 20

Age: 17-76 GCS: ≤8

Site: intraparenchyma Device: Neurovent-PTemp™, Raumedic AG, Münchberg, Germany

Site 1: tympanic membrane Device: Core-Check thermometer (model 2090 IVAC Corporation, San Diego, California, USA)

Site 2: temporal artery, Device: model TAT5000, Exergen, Watertown, MA, USA

Unclear

No

• Mean (SD) of T_br - T_tm: 0.9 (0.7) °C

• Mean (SD) of T_br - T_ta: 0.3 (0.4) °C

Brain temperature is higher than both tympanic membrane and temporal artery temperature

Temporal artery temperature is closer to brain than tympanic membrane temperature is

Puccio et al. (2009) [17]

Descriptive study Neurotrauma ICU USA

Severe TBI n = 42

Mean (SD) Age: 36.4 (14.8)

GCS: 3-8

Site: intraventricular Device: Licox^® (Integra LifeSciences Corp., Plainsboro, NJ, USA)

Site: rectum Device: not reported

Unclear

Induced normothermia (n = 21)

Control (n = 21)

• Mean of T_br - T_r in the control group: -0.4°C

• Mean of T_br - T_r in the induced normothermic group: -0.1°C

Brain temperature is lower than rectal temperature in both groups of patients

Kuo et al. (2011) [15]

Descriptive study ICU Taiwan

TBI n = 28

Age: 16-80 GCS: 6 (median)

Site: intraparenchyma Device: 110-4BT, Pressure-Temperature Monitoring Kit (Integra Camino, San Diego, CA, USA)

Site 1: rectum Device: Medi-Therm II Hyper-Hypothermia Machine (Gaymar Industries, Orchard Park, NY, USA) Site 2: temporal artery Device: Temporal Scanner™ TAT-5000 (EXERGEN, Boston, MA, USA)

Yes

No

• Mean (SD) of T_br - T_r: 0.23 (0.45) °C

• Mean (SD) of T_br - T_ta: 0.64 (0.60) °C

Brain temperature is higher than both rectal temperature and temporal artery temperature

Suehiro et al. (2011) [20]

Descriptive study Did not specify Japan

Severe TBI n = 11

Age: 15-73 GCS: ≤8

Site: intraparenchyma Device: Camino Laboratories, San Diego, California, USA

Site: bladder Device: thermocouple (Terumo, Tokyo, Japan)

Yes

Mild hypothermia on all patients

• Mean (SD) of T_br - T_bl: -0.17 (0.02) °C

Brain temperature is lower than bladder temperature

Fischer et al. (2011) [11]

Descriptive study Neuro-ICU Austria

Severe TBI n = 7

Age: 21-69 GCS: 3-8

Site: intraparenchyma Device: Neurovent-Temp-P (Raumedic AG, Muenchberg, Germany)

Site: bladder Device: Kendall Curity, Mansfield, Massachusetts, USA

Unclear

Induced normothermia (36.5°) on all patients

• Mean of T_br - T_bl: 0.1°C

Brain temperature is higher than bladder temperature during induced normothermia