Skip to main content
. Author manuscript; available in PMC: 2018 May 1.
Published in final edited form as: J Clin Anesth. 2017 Jan 31;38:93–104. doi: 10.1016/j.jclinane.2017.01.005

Appendix B.

Summary of study outcomes & limitations (n=25 included in qualitative review).

ACTIVE WARMING VS. PASSIVE WARMING
(n=11 included in meta-analysis; *excluded from meta-analysis due to outcome reporting)
AUTHOR/
YEAR 		RESULTS CONCLUSIONS LIMITATIONS
Mean
temperature
(°C)		 Mean
temperature
change (°C)		 Hypothermia
<36 °C or
specified (#;
%)
Benson et
al.
(2012)[35]		 PACU
admission
(p<0.001):

  • FAW: 36.5±0.3

  • Warm blanket: 36±0.8

 PACU
admission:

  • FAW: 1/15; 6.7%

  • Warm blanket: 3/15; 20%

 Preoperative with
intraoperative
FAW is more
effective than
warmed cotton
blankets.

  • Patient controlled FAW temperature not measured
Butwick et
al.
(2007)[22]		 (p=0.8):

  • FAW: −1.3±0.4

  • FAW off: −1.3±0.3

 <35.5 (p=0.5):

  • FAW: 8/15; 53%

  • FAW off: 10/15; 67%

 Intraoperative
FAW on lower
extremities is more
effective than no
FAW.

  • 10/15 passively warmed subjects received FAW at some point, effecting final temp reading
Casati et al.
(1999a)[36]		 End of surgery
(p<0.0005):

  • Temp 1 degree lower in reflective blanket group

 PACU
admission
(p<0.01):

  • FAW: 7/25; 24%

  • Reflective blanket: 16/25; 64%

 Intraoperative
FAW is more
effective than
reflective blanket.
Chakladar
et al.
(2014)[37]		 End of Surgery
(p=0.079):

  • Conductive heat mat: 36.5±0.4

  • Cotton sheet: 36.4±0.4

PACU
admission
(p=0.046):

  • Conductive heat mat: 36.5±0.5

  • Cotton sheet: 36.3±0.4

 PACU
admission
(p=0.043):

  • Conductive heat mat: 3/58; 5.2%

  • Cotton sheet: 11/58; 19%

 Intraoperative
conductive heat
mat warming
more effective
than a cotton
sheet.

  • 87.9% of conductive heat mat and 94.8% of cotton sheet group received warm IV fluids

  • Author consultant for manufacturer
*Chung et
al.
(2012)[40]		 Temp change
at 45 min
(p=0.004):

  • FAW: −0.6±0.4

  • Warm IV fluid: −0.5±0.3

  • FAW off: −0.9±0.4

 Preoperative with
intraoperative
FAW is as
effective as
warmed IV fluids,
and both are more
effective than
passive warming.

  • No temperature or hypothermia values reported or graphed
Cobb et al.
(2016)[33]		 PACU
admission
(p=0.006):

  • FAW + Warm IV fluids: 35.9±0.5

  • Cotton blankets: 35.5±0.5

 PACU
admission
(p=0.031):

  • FAW + Warm IV fluids: 14/22; 64%

  • Cotton blankets: 20/22; 91%

 Intraoperative
FAW in
combination with
warmed IV fluids
is more effective
than cotton
blankets.

  • Temp measurement site changed throughout study period

  • Measured temp through bladder during C-section
Fallis et al.
(2006)[24]		 End of surgery:

  • FAW: 36.1±0.4

  • Warm blankets: 35.9±0.4

  • FAW: −0.7±0.4

  • Warm blankets: −0.8±0.5

Significant
decrease in
temps for both
groups
(p<0.001), but
not between
groups		 When IV fluids
are warmed, there
is no difference in
effectiveness
between
intraoperative
FAW and cotton
blankets.

  • Room temp at end of operation significantly greater for FAW group (p<0.05)

  • Both groups received warm IV fluids
Grant et al.
(2015)[25]		 PACU
admission
(p=0.56):

  • Conductive heat mat: 36.3±0.6

  • Warm blanket: 36.3±0.6

 PACU
admission
(p=0.169):

  • Conductive heat mat: 88/243; 36%

  • Warm blanket: 102/241; 42%

 Conductive heat
mat warming is
more effective
than cotton
blankets.

  • Both groups received warm IV and irrigation fluids

  • n=17 subjects received general anesthesia, results not analyzed separately

  • Temp measurement site changed throughout study period

  • Measured temp through bladder during C-section
Horn et al.
(2002)[27]		 End of surgery
(p<0.01):

  • FAW: 37.1±0.4

  • Cotton blankets: 36±0.5

 FAW is more
effective than
cotton blankets.

  • Both groups received warm IV fluids

  • Industry funded
Horn et al.
(2014)[28]		 End of surgery
(p=0.0007):

  • FAW: 36.4±0.4

  • Warm blankets: 36±0.5

 End of surgery:

  • FAW: 1/19; 5%

  • Warm blankets: 10/21; 48%

 FAW is more
effective than
warmed cotton
blankets.
Paris et al.
(2014)[34]		 Intra-op
(p<0.05):

  • Conductive heat mat: 36.5±0.2

  • Warm IV fluids: 36.5±0.3

  • Warm blankets: 36.4±0.4

PACU (p<0.05):

  • Conductive heat mat: 36.2±0.4

  • Warm IV fluids: 36.1±0.4

  • Warm blankets: 35.9±0.5

 Intra-op:

  • Conductive heat mat: 36/77; 47%

  • Warm IV fluids: 28/73; 38%

  • Warm blankets: 50/76; 66%

PACU:

  • Conductive heat mat: 39/77; 51%

  • Warm IV fluids: 43/73; 59%

  • Warm blankets: 57/76; 75%

 Conductive heat
mat warming and
warmed IV fluids
are more effective
than cotton
blankets.
Conductive heat
mat warming is
more effective
than warmed IV
fluids at
maintaining
normothermia
outside of the
intraoperative
setting.

  • Measured temp through bladder during C-section
Salazar et
al.
(2011)[23]

  • Temps were significantly lower for the cotton blanket group before anesthesia induction (35.7±0.4 vs. 36.03±0.3; p<0.0001) and at all times during surgery (p<0.001) compared to the group receiving preoperative and intraoperative FAW in combination with warm IV fluids.

 During study
period:

  • FAW + warm IV fluids: 74.7% <36; 29.4% <35.5

  • Cotton sheet: 100% <36; 88% <35; 25.3% <34

 Preoperative and
intraoperative
FAW in
combination with
IV fluid warming
is more effective
than cotton
blankets.

  • Temp measurement site changed throughout study period
ACTIVE VS. ACTIVE WARMING (n=8 not included in meta-analysis)
AUTHOR/
YEAR 		RESULTS CONCLUSIONS LIMITATIONS
Mean
temperature
(°C)		 Mean
temperature
change (°C)		 Hypothermia
<36 °C or
specified (#;
%)
Casati et al.
(1999b)[32]		 End of surgery
(p>0.05):

  • Upper body FAW: 36.2±0.5

  • Lower body FAW: 36.3±0.5

 PACU arrival
(p>0.05):

  • Upper body FAW: 29%

  • Lower body FAW: 12.5%

 Upper body FAW
is more effective
than the lower
body FAW.
Fanelli et
al.
(2009)[26]		 End of surgery
(p>0.05):

  • FAW: 35.3±0.5

  • Conductive heat mat: 35.1±0.6

 FAW and
conductive heat
mat warming are
equally
ineffective.

  • Not powered

  • Both groups received warm IV fluids
Jo et al.
(2015)[43]		 Core
temperature
significantly
decreased in
both groups
(p<0.001), but
changes were
not significant
between
groups
(p=0.763)		 Intra-op <35.5
(p=0.02):

  • FAW pre-op + circulating water mattress: 0/25; 0%

  • Circulating water mattress: 8/24; 33%

PACU
admission <36
(p=0.32):

  • FAW pre-op + circulating water mattress: 10/25; 40%

  • Circulating water mattress: 13/24; 54%

 Prewarming with
FAW significantly
reduces the
severity of
hypothermia
(<35.5), but does
not maintain
normothermia
(>36) in
combination with
the circulating
water mattress

  • Circulating water mattress temperature set at 36°C

  • No temperatures reported
Kim et al.
(2014)[44]		 Changes in
core
temperature
were not
statistically
significant
(p>0.05)
between
groups		 No difference in
effectiveness
between
circulating water
mattress and
FAW.

  • Circulating water mattress warming initiated immediately prior to anesthesia induction, FAW applied after induction.

  • No temperature or hypothermia rates given

  • Both groups received warm IV fluids

  • Temp measurement site changed throughout study period
Koeter et al.
(2013)[45]		 Lowest core
(p>0.05):

  • FAW + reflective blanket: 35.7±0.4

  • FAW: 35.9±0.4

 No difference in
effectiveness
between FAW and
combination of
FAW and
reflective blanket.

  • Not powered for spinal anesthesia alone
Ng et al.
(2006)[30]		 End of surgery
(p>0.05):

  • FAW: 36.8±0.4

  • Conductive heat mat: 36.9±0.4

 No patients
were <36 °C in
either group at
the end of
surgery		 Intraoperative
FAW and
conductive heat
warming are
equally effective.

  • Both groups received warm IV fluids

  • Temp measurement site changed throughout study period
Torrie et al.
(2005)[31]		 End of surgery
(p=0.03):

  • FAW: 36.4±0.6

  • Radiant warmer: 36.1±0.5

 On PACU
arrival (p=0.3):

  • FAW: 33%

  • Radiant warmer: 46%

 FAW is more
effective than
radiant warming.

  • Both groups received warm IV and irrigation fluids

  • Temp measurement site changed throughout study period
Winkler et
al.
(2000)[46]		 Average intra-op
(p<0.001):

  • Titrated: 36.5±0.3

  • Conventional: 36.1±0.3

 Intra-op:

  • Titrated FAW: 4/75 (5%)

 Titrating FAW
based on patient
temperature is
more effective
than conventional
FAW.

  • Room temp significantly greater in titrated FAW group (p=0.004)

  • Both groups received warm IV fluids

  • Industry funded
ACTIVE WARMING VS. ACTIVE WARMING VS. PASSIVE WARMING (n=2 not included in meta-
analysis)
AUTHOR/
YEAR 		RESULTS CONCLUSIONS LIMITATIONS
Mean
temperature
(°C)		 Mean
temperature
change (°C)		 Hypothermia
<36 °C or
specified (#;
%)
Vanni et al.
(2007)[38]		 End of
prewarming
(p<0.05):

  • Pre-op FAW temp higher than intra-op FAW and cotton blanket group

After anesthesia
induction
(p>0.05):

  • No difference in group temps

End of surgery
(p<0.05):

  • FAW groups temp greater than cotton blanket group

 End of surgery:

  • FAW groups: 50%

  • Cotton blanket: 100%

PACU
admission:

  • FAW groups: 100%

  • Cotton blanket:100%

 Intraoperative
FAW is more
effective than
cotton blankets.
Preoperative FAW
does not increase
the effectiveness
of intraoperative
FAW.
Yamakage
et al.
(1995)[29]		 At 40 min
intraop
(p<0.05):

  • Upper body FAW: −0.52±0.30

  • Lower body FAW: unchanged

  • Cotton blanket: −0.40±0.28

 Lower body FAW
blanket is more
effective than
upper body FAW
blanket or cotton
blanket.

  • Not powered

  • Both groups received IV warm fluids

  • No temperature or hypothermia values reported or graphed
PASSIVE VS. PASSIVE WARMING (n=3 not included in meta-analysis)
AUTHOR/
YEAR 		RESULTS CONCLUSIONS LIMITATIONS
Mean
temperature
(°C)		 Mean
temperature
change (°C)		 Hypothermia
<36 °C or
specified (#;
%)
Dyer &
Heathcote
(1986)[41]		 Greatest mean:

  • Cotton blanket (I): −1.3 (at 75 min)

  • Reflective blanket (II): −1.1 (at 60 min)

  • Warm irrigation fluid (III): −1.1 (at 45 min)

  • Group II + III (IV): −0.8 (at 60 min)

I & IV:
(p<0.01–0.05)
I & II & III:
(p>0.05)		 Reflective
blankets are more
effective than
cotton blankets.

  • Not powered

  • Group IV group had significantly shorter procedure (p<0.05)

  • No temperature or hypothermia values reported or graphed
Hindsholm
et al.
(1992)[42]

  • Temperature decreased significantly (p<0.05) in both groups; decreased significantly less (p<0.05) in reflective blanket group

 Reflective
blankets are more
effective than
cotton blankets.

  • No temperature or hypothermia values reported

  • Both groups received IV warm fluids
    • Temp measurement site changed throughout study period
Hirvonen &
Niskanen
(2011)[21]		 End of surgery
(p=0.077):

  • Reflective suit: 35.8±0.4

  • Cotton clothing: 35.6±0.5

PACU arrival
(p=0.03):

  • Reflective suit: 35.7±0.4

  • Cotton clothing: 35.2±0.5

 PACU
admission
(p<0.001):

  • Reflective suit: −0.56

  • Cotton clothing: −1.31

 PACU
admission
(<35°C):

  • Reflective suit: 1/20; 5%

  • Cotton clothing: 7/20; 35%

 Reflective
blankets are more
effective than
cotton blankets.

  • Both groups received warm IV & irrigation fluids

  • Industry funded