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Educated Hand Publishing LLC 
“The Science Behind the Art” 
Volume 5 - No. 5 2017 

 Anesthesia eJournal - Online
ISSN 2333-2611

Page 30

Preoperative Interventions for the Prevention of Hypothermia

Trish Haley, MS(N), CRNA
Yejin Min, MS(N), CRNA
Shawn Collins, PhD, DNP, CRNA
Vallire Hooper, PhD, RN, CPAN, FAAN

Affiliation:
Trish Haley MS(N) CRNA was a graduate student in the Nurse Anesthesia Program at Western Carolina University, Asheville, North Carolina, at the time this paper was 
written.

Yejin Min MS(N) CRNA  was a graduate student in the Nurse Anesthesia Program at Western Carolina University, Asheville, North Carolina, at the time this paper was written.

Shawn Collins, PhD, DNP, CRNA  is a program director of the Nurse Anesthesia Program at Western Carolina University School of Nursing, Asheville, North Carolina.  Email: 
shawncollins@email.wcu.edu.

Vallire Hooper, RN, PhD, CPAN, FAAN is the nursing research manager at Mission Healths, Asheville, North Carolina. 

Funding/Conflict of Interest Disclosure: 
None 

KEYWORDS:  hypothermia, warming, preoperative, surgical population

INTRODUCTION
Perioperative hypothermia, defined by the American Society of PeriAnesthesia Nurses (ASPAN), is a core temperature below 
36 degrees Celsius, and is known to increase the risk of surgical wound infections, poor wound healing, blood loss, prolonged 
and altered drug effects, increased duration of hospital stay, cardiac events, and morbidity and mortality.1,2 Under normal 
physiologic conditions, the body can detect subtle drops in temperature. In response to a detected decrease in temperature, the 
hypothalamus will induce vasoconstriction and shivering mechanisms to maintain a core body temperature around 37 degrees 
Celsius. The induction of anesthesia blunts this response from the hypothalamus and contributes to perioperative hypothermia 
by inhibiting the body’s natural mechanisms for heat regulation and redistribution of core body temperature to the periphery 
from the resulting vasodilation.1-3 Anesthesia-induced redistribution of body heat is the process by which heat travels down 
a temperature gradient from warmer core tissues to cooler peripheral tissues. Patients undergoing surgery are at high risk of 
hypothermia due to thermoregulatory mechanisms becoming dysfunctional after the induction of anesthesia and exposure to 
surgical procedures, cold fluids, and low ambient room temperatures.3  

Abstract
Perioperative hypothermia can be a significant issue for surgical patients. Active warming methods initiated in the pre-
operative period may assist in the prevention of perioperative hypothermia. A literature review was conducted to provide 
a summary and resource for clinicians based on an evidence-based, practical, bedside approach to prewarming adult 
surgical populations and to highlight the further need for research. The literature review addressed preoperative warming 
recommendations, including warming methods and desired length of warming time. The literature supports the practice of 
preoperative warming for adult surgical patients to prevent or decrease the incidence of perioperative hypothermia.

AEJ



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Volume 5 - No. 5 2017 Page 31

The current standard of care for avoiding perioperative 
hypothermia consists of intraoperative and postoperative 
warming interventions, both active and passive, yet the incidence 
of perioperative hypothermia remains a significant risk.2 One 
of the primary interventions used to prevent perioperative 
hypothermia is prewarming before the induction of anesthesia. 
Hooper et al defined prewarming as the “warming of peripheral 
tissues or surface skin before induction of anesthesia.”1(p348)  
The literature suggests that preoperative warming with forced 
air reduces post-induction redistribution hypothermia, allows 
for faster rewarming after an initial post-induction drop 
in temperature intraoperatively, results in a higher average 
intraoperative temperature than non-prewarmed counterparts, 
and results in greater patient satisfaction.2,3 Additional benefits 
patients may experience include decreased blood loss, reduced 
total anesthesia costs, decreased incidence of intensive care 
unit (ICU) admission, reduction in myocardial infarctions, 
proper clotting, stable serum potassium levels, reduced need 
for postoperative mechanical ventilation, reduced incidence of 
surgical site infection, and an overall decrease in mortality.3 
METHODS
We used the PICO question model to guide our search for 
current literature. The PICO question is used to define the 
desired population (P), intervention (I), comparison (C), and 
outcome (O). The PICO question used to guide this review was 
as follows: “In adults undergoing general anesthesia, does the 
addition of preoperative warming devices for a specific length of 
time compared to no preoperative warming methods result in a 
decreased incidence of perioperative hypothermia?”  
The authors independently performed electronic searches for 
published literature in the Cumulative Index to Nursing and 
Allied Health Literature (CINAHL; EBSCO), MEDLINE 
(National Library of Medicine), and Cochrane Central Register 
of Controlled Trials (CENTRAL; Cochrane Collaboration) 
databases using the EBSCO search engine. The following 
keywords were used in varying combinations: “perioperative,” 
“peri-operative,” “preoperative,” “pre-operative,” “preoperative 
warming,” “hypothermia,” “warming methods,” “body 
temperature,” “forced-air warming,” “anesthesia,” “surgical,” and 
“active warming.” Boolean operators were used in the search 
engine to filter and combine terms.  
Included articles consisted of adult (18 years or older) surgical 
populations receiving general anesthesia for nonemergent surgery 
in which preoperative warming methods were studied. Other 
inclusion criteria were the availability of the full text of the article, 
articles that underwent peer review, and articles that were written 
in or translated into English. Articles published before January 
2008 or after October 2015 were excluded. Studies that included 
induced hypothermia were also excluded.  
The initial search resulted in 945 papers. After application of 
the inclusion and exclusion criteria previously defined and 
the removal of duplicate papers, 12 articles were identified for 
review. Study quality was determined based on the Grading of 
Recommendations Assessment, Development, and Evaluation 
(GRADE) system of review.4

REVIEW OF LITERATURE
Table 1 is a concise presentation of the studies reviewed and 
presents authors, study design, journal publication and date, 
sample size, warming device used, and conclusions.5-16 Table 2 
lists study quality and limitations.
Three studies5-7 produced results showing a significant effect 
of preoperative warming with forced-air warming gowns (Bair 
Paws) compared to a control group. Andrzejowski et al5 tested 68 
adult surgical patients with 31 patients receiving 60 minutes of 
prewarming with the warming gown system prior to induction 
of anesthesia compared to the control group of 37 patients. 
The study was not blinded but this is unlikely to have affected 
the results. The sample size was small and the type of general 
anesthetic (sevoflurane or propofol) was not controlled. The study 
concluded that 60 minutes of prewarming with the forced-air 
warming gown resulted in a decrease in both intraoperative 
hypothermia and perioperative hypothermia. Hooven6 reported 
that 11.7% of prewarmed patients were hypothermic on arrival 
to the post-anesthesia care unit compared to 48.6% of non-
prewarmed patients (P=0.026). The study failed to record 
intraoperative patient temperatures or to control ambient 
surgical suite temperatures and also noted a significant (P=0.048) 
difference in mean surgical durations between the prewarmed 
group and the non-prewarmed group. Kramer7 concluded that 
prewarming patients with a forced-air warming device was 
effective in reducing the amount of heat redistribution after 
the induction of anesthesia. Unfortunately, this study was quite 
limited and lacked sufficient literature review. The sample size 
was small (n=24) and there were many limitations and lack of 
controls, including failure to control both the prewarming device 
temperature setting and the ambient temperature of the operating 
suite. Different types of temperature devices were also used with 
no consistent timing of measurement.  
Two studies used Bair Hugger forced-air warming blankets 
to provide preoperative warming. Erdling and Johansson8 
studied 43 adult surgical patients and found that at 210 minutes 
after induction of anesthesia, esophageal temperatures in the 
prewarmed group increased by 0.65 degrees Celsius with a 
standard deviation of 0.63 (P=0.001). The group that did not 
receive prewarming had esophageal temperature increases of 0.27 
degrees Celsius with a standard deviation of 0.62, but the increase 
was not statistically significant (P=0.052). It was concluded that 
42 minutes of prewarming had a statistically significant effect 
(P=0.001) on preventing perioperative hypothermia. The authors 
noted the small sample size as a significant limitation. Shin et 
al9 studied 72 adult surgical patients. The prewarmed group had 
significantly (P<0.001) higher core temperatures than did the 
non-prewarmed group at 20, 40, 60, 80, 100, and 120 minutes 
after induction and intubation. The incidence of perioperative 
hypothermia was significantly lower in the prewarmed group 
than in the non-prewarmed group at all time periods previously 
mentioned (P=0.007 at 20 minutes and P=0.001 at all other 
times). The study noted a limitation in the inconsistency of 
measurement devices used (tympanic or esophageal) and possible 
inaccuracy of the tympanic measurements due to interference 
with the warming device.  



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Volume 5 - No. 5 2017 Page 32

The Mistral-Air premium warming suit (passive warming) and 
Mistral-Air forced-air warming unit were studied by Perl et al.10 
A sample size of 90 adult surgical patients was divided into 3 
groups. Thirty-two patients received only standard preoperative 
insulation (cotton blankets). Twenty-seven patients were warmed 
with the passive warming suit and 31 received the same passive 
preoperative warming combined with the forced-air warming 
device. A forced-air warming device with a reflective prewarming 
suit was significantly (P<0.05) effective in achieving higher 
core temperatures both intraoperatively and postoperatively 
compared to passive warming, which was shown to be ineffective 
at preventing perioperative hypothermia. Intraoperative 
warming alone was ineffective in the prevention of perioperative 
hypothermia. Prewarming durations varied greatly but all patients 
were warmed for at least 10 minutes.
De Witte et al11 looked at 27 adult surgical patients and 
prewarmed one group (n=9) with a forced-air warming device 
for 30 minutes and another group (n=9) with a carbon fiber 
warming device, also for 30 minutes. The control group consisted 
of 8 patients. After 30 minutes of prewarming with the carbon 
fiber device, patients had a core temperature that was significantly 
higher (P=0.05) than in the control group. There was no 
statistically significant difference between the forced-air and 
control groups. As seen with many of the available studies, the use 
of 2 methods to measure temperature (tympanic and esophageal) 
was noted as a limitation, as was the small population studied and 
inconsistent warmed body surface area. 
One study12 (n=200) focused on the duration of warming. 
Preoperative patients undergoing general anesthesia with an 
expected surgical duration of 30 to 90 minutes compared a 
control group to 3 other groups receiving varying durations 
of active prewarming. Fifty-two patients received 10 minutes 
of active warming. Forty-three received 20 minutes of active 
warming. Fifty received 30 minutes of active warming and 
55 were considered the control group and received no active 
preoperative warming. The authors concluded that the risk 
of perioperative hypothermia was considerably reduced after 
prewarming with forced air for 10, 20, or 30 minutes in 
comparison to no preoperative active warming.12 No significant 
difference (P=0.54) was found between the 3 groups that received 
active warming, which suggested that at least 10 minutes of 
preoperative active warming is enough to affect the incidence of 
perioperative hypothermia.12

The search produced several studies with varying limitations. 
Table 2 addresses the most significant recognized limitations 
and the quality of the studies based on the GRADE system of 
review. In contrast to other results, 4 trials found no statistical 
significance in relation to the addition of preoperative warming. 
Rowley13 reported a sample size of 220 patients divided into 4 
groups, each consisting of 55 individuals. The results showed no 
benefit of preoperative interventions compared to routine care 
(control group) in preventing perioperative hypothermia. The 
study compared forced-air warming in combination with routine 
care (cotton blanket) to routine care only. Routine care, forced-
air warming, and adjustment of the surgical suite temperature 
were combined as a study group as well as routine care and 

adjustment of surgical room temperature only. The study lacked 
randomization and failed to report P values clearly. The authors 
also noted a failure to achieve a temperature of 21.1 degrees 
Celsius in some of the surgical suites during the cases studied.13 

Another study14 consisted of 128 subjects undergoing general 
anesthesia for a variety of surgical cases with no mention of 
case duration. The study compared only prewarmed patients to 
non-prewarmed patients. Ambient surgical suite temperatures 
were not controlled for and the investigators failed to regulate the 
timing of temperature measurements. Intraoperative temperature 
measurements were also not evaluated. The findings were not 
significant (P=0.314) for any difference in mean temperatures 
between the 2 groups.14  
Adriani et al15 is yet another study that found no significant 
difference with the addition of preoperative warming in 
preventing or lessening the incidence of perioperative 
hypothermia. Adriani et al15 reported no significant difference 
(P=0.755) of body temperature over time between groups. 
Study quality was low and had extensive limitations such as 
failure to control for operating room mattress temperature, 
ambient temperature, and the device used to measure patient’s 
temperature. No consistency was found in devices used for 
measurement (esophageal or oral), and many issues regarding 
intraoperative warming existed, including no criteria for initiation 
of intraoperative warming, failure to control ambient temperature, 
and surgical table underbody mattress that may or may not have 
been warmed.15

One additional study listed an inability to produce a lower rate 
of perioperative hypothermia with the addition of preoperative 
warming. The study had many flaws and limitations. The study 
was unable to effectively evaluate prewarming compared to 
non-prewarming interventions, which was its stated purpose.16 
Three of the 4 studies were of low quality due to varying levels 
of inconsistency, numerous limitations, small sample sizes, and 
inability to draw reliable conclusions. These studies were not 
considered for final recommendations concerning prewarming for 
the prevention of perioperative hypothermia.
DISCUSSION
Under normal physiologic states, the body can maintain core 
temperatures between 36 and 37 degrees Celsius. The 2 main 
areas of the brain responsible for regulating body temperature 
are the preoptic area and the anterior hypothalamus. These 
areas can trigger thermoregulatory responses when an increase 
or decrease in core temperature is detected by afferent sensing. 
Vasodilation and sweating are induced to prevent hyperthermia, 
whereas vasoconstriction and shivering are induced to prevent 
hypothermia.17  
The induction of general anesthesia creates a redistribution of 
body heat from core to periphery due to vasodilation and also 
blunts the response of the hypothalamus. Without diligent 
warming, hypothermia is near unavoidable depending on 
numerous factors including room temperature, equipment used, 
type of procedure, length of procedure, and intravenous fluid 
temperature. Over time, the anesthetized patient continues to 
lose heat and achieve a lower core body temperature. Because 
anesthetic drugs hinder proper hypothalamic responses to 



hypothermia, the body is unable to induce vasoconstriction 
and shivering mechanisms for warming.17 Once a patient’s core 
temperature becomes hypothermic, intraoperative active warming 
with forced-air devices likely will not be sufficient to restore 
normothermia due to the considerable amount of time it takes for 
the heat to reach the core tissues.1 Because of this, it is important 
to incorporate interventions necessary to prevent or lessen the 
degree of hypothermia experienced after induction of anesthesia.  
Of the studies reviewed, 8 of 12 reported prewarming to be 
effective in decreasing or preventing perioperative hypothermia. 
Because 2 of the studies15,16 that found prewarming to be 
ineffective and 2 of the studies7,11 that found it to be effective 
were of poor quality, recommendations will be drawn from the 
remaining 8 studies.  
Six of the remaining 8 studies concluded that preoperative 
warming was effective in varying durations ranging from 10 
minutes to more than 60 minutes. Forced-air warming devices, 
specifically Bair Paws gowns, were most consistently studied and 
shown to be effective with very minimal associated risks.
 
 

CONCLUSION
The findings of this review suggest that adult surgical patients 
benefit from as little as 10 to 60 minutes of active prewarming 
to reduce perioperative hypothermia and that intraoperative 
warming alone is likely not adequate. Because there are few 
risks involved in the addition of prewarming and the available 
literature suggests that it is effective, it is recommended as 
a standard of care for all adult surgical patients prior to the 
induction of general anesthesia. While 10 minutes of forced-air 
warming is an effective option that may reduce hypothermia in 
the perioperative period, it is likely that additional time may be 
more beneficial.
There are an inadequate number of quality studies available to 
answer all of the questions surrounding preoperative warming 
interventions to prevent perioperative hypothermia. A need 
exists for randomized controlled trials testing current warming 
methods as well as newer technology. New studies should be 
consistent between groups and only use the most proven method 
of temperature measurement and reduce limitations. Specific 
populations should also be further studied to identify those that 
may benefit from these interventions.

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Volume 5 - No. 5 2017 Page 33



 
Table 1. Overview of the Articles Included in the Literature Review
Author, Date, Journal, 
Design

Population,
Sample Size (n)

Type of Preoperative 
Warming Device, 
Duration

Conclusions

Adriani & Moriber (2013)

AANA Journal

Quasi-experimental

Nonrandomized Trial

n=60

Women undergoing general 
anesthesia for a variety of 
surgical types

ASA class I-III 

Bair Paws, forced-air warming 
gown

Minimum of 30 minutes with a 
mean time of 51 minutes

Temperature controlled by 
patient

Active prewarming with Bair Paws 
gown demonstrated no significant 
effect on preventing perioperative 
hypothermia.

Body temperature over time showed 
no statistically significant difference 
between groups.

Andrzejowski et al
(2008)

British Journal of Anaes-
thesia

Randomized Controlled 
Trial

n=68

Adults
undergoing general anes-
thesia for spinal surgery

ASA class I & II

Bair Paws, forced-air warming 
gown

60 minutes 

60 minutes of prewarming with Bair 
Paws gown yielded a decrease in both 
intraoperative hypothermia and periop-
erative hypothermia.

De Witte et al
(2010)

Anesthesia and Analgesia

Randomized Controlled 
Trial

n=27

Adults undergoing general 
anesthesia for laparoscopic 
colorectal surgery

Forced-air warming
Carbon fiber warming

30 minutes

30 minutes of prewarming with 
resistive heating produced significantly 
higher core temperatures than in the 
control group.

No significant difference between the 
forced-air and control group. 

Erdling & Johansson (2015)

AANA Journal

Experimental

Randomized Controlled 
Trial

n=43

Adults undergoing general 
anesthesia in combination 
with regional analgesia for 
colorectal surgery

ASA class I&II 

Pre-warmed group: Forced-air 
warming device

Warm Touch, Nellcor, or Gay-
mar, Smiths Medic

32-52 minutes

Prewarming for 42 minutes had 
a positive effect in preventing 
perioperative hypothermia and even 
shorter prewarming times may be of 
benefit for hypothermia prevention.

Fettes et al (2013)

AORN Journal

Experimental

Randomized Controlled 
Trial

n=128

Adults undergoing general 
anesthesia for a variety of 
surgical cases

ASA class I-III 

Forced-air warming blanket

Approximately 60 minutes

 

Prewarming did not significantly affect 
patient temperature on arrival to the 
PACU or the length of time spent in 
the PACU.

Hooven (2011)

Journal of Peri-Anesthesia 
Nursing

Quasi-experimental

Nonrandomized Trial

n=148

Adults undergoing general 
anesthesia for colorectal 
surgery

Bair Paws forced-air warming 
gown

60 minutes

11.7% of prewarmed patients were 
hypothermic compared with 48.6% of 
non-prewarmed patients (P=0.026).

Prewarming with the Bair Paws 
forced-air warming blanket decreased 
the incidence of perioperative 
hypothermia in patients undergoing 
colorectal surgery. 

Horn et al (2012)

Anaesthesia

Experimental

Randomized Controlled 
Trial

n=200

Adults undergoing general 
anesthesia with a variety of 
surgical cases with ex-
pected durations of 30-90 
minutes

ASA class I-II

Snuggle Warm Upper Body 
Blanket, forced-air warming 
blanket covered by cotton 
blanket, connected to Level 1 
Equator warmer

10, 20, or 30 minutes 

Forced-air prewarming of 10, 20, or 
30 minutes considerably decreased 
the incidence of perioperative 
hypothermia.

There was no significant difference 
(P=0.540) between the 3 prewarmed 
groups.

Kramer (2013)

Journal of Peri-Anesthesia 
Nursing

Quasi-experimental

Nonrandomized Trial

n=24

Women undergoing general 
anesthesia for breast recon-
struction

Forced-air warming gown

Minimum of 30 minutes

Forced-air prewarming gown was 
effective in decreasing post-induction 
redistribution hypothermia. 

Nicholson (2013)

AORN Journal

Experimental

Randomized Controlled 
Trial

n=66

Adults undergoing general 
anesthesia for colorectal 
surgery

ASA class I-IV 

Forced-air warming gown

Minimum 30 minutes

Prewarming with a forced-air 
warming gown was unable to decrease 
the number of patients who had 
perioperative hypothermia.

Perl et al (2014)

Minerva Anestesiologica

Experimental

Prospective, randomized, 
multi-center, controlled 
study

n=90

Adults undergoing general 
anesthesia for a variety of 
surgical cases scheduled 
for 30-120 minutes

ASA class I-III

Mistral-Air premium warming 
suit (passive warming)

Mistral-Air premium warming 
suit and Mistral-Air forced-air 
warming unit

30-60 minutes

A forced-air warming device with 
a reflective prewarming suit was 
effective in achieving higher core 
temperatures both intraoperatively and 
postoperatively compared to passive 
warming, which was ineffective at 
preventing perioperative hypothermia.

Intraoperative warming alone was 
ineffective in preventing perioperative 
hypothermia.

Rowley et al (2015)

Clinical Nursing Research

Quasi-experimental

Nonrandomized Trial

n=220

Adults undergoing general 
anesthesia for a variety of 
surgical procedures lasting 
a minimum of 60 minutes.

Forced-air warming blanket

Approximately 20-30 minutes

No significant difference was found 
between preoperative to postoperative 
core body temperatures for each group.

Prewarming interventions were 
not more effective in preventing 
perioperative hypothermia.

Shin et al (2015)

BMC Anesthesiology

Experimental

Randomized Controlled 
Trial

n=72

Adults undergoing general 
anesthesia for endovascular 
coiling to treat cerebral 
aneurysm

Bair Hugger, forced-air 
warming full-body blanket 
connected to warm-air-blower

30 minutes 

The prewarmed group had 
significantly higher core temperatures 
than those of the non-prewarmed 
group at 20, 40, 60, 80, 100, and 120 
minutes post intubation (P<0.001).

Incidence of perioperative 
hypothermia was significantly lower in 
the prewarmed group than in the non-
prewarmed group at 20, 40, 60, 80, 
100, and 120 minutes after intubation 
(P=0.002 at 20 min, P<0.001 at other 
times).

Conclusion: prewarming should be 
considered as part of the anesthetic 
management for patients undergoing 
coiling of aneurysm at risk of 
hypothermia in a cold environment. 

Abbreviations: ASA, American Society of Anesthesiologists; PACU, post-anesthesia care unit.

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Volume 5 - No. 5 2017 Page 34



Table 2. Article Limitations
Author, Date, 
Journal, Design

Quality Limitations

Adriani & Moriber 
(2013)

AANA Journal

Quasi-experimental

Nonrandomized Trial

Strength: Level 2

Quality: Low

Oral and esophageal probe was used to obtain temperature readings

Extraneous variables not controlled: ambient temperature, OR mattress temperature, 
and staff taking temperature readings

Non-blinded, nonrandomized, small sample size

Andrzejowski et al
(2008)

British Journal of 
Anaesthesia

Randomized Con-
trolled Trial

Strength: Level 1

Quality: Moderate 

Not all patients had same method of anesthesia maintenance

Non-blinded

Actual mean duration of prewarming longer than the target of 60 minutes

De Witte et al
(2010)

Anesthesia and Anal-
gesia

Randomized Con-
trolled Trial

Strength: Level 2

Quality: Low

Small population studied

Warmed body surface area inconsistent between forced-air group and carbon fiber 
group

Duration of anesthesia 90-260 minutes

2 methods were used to measure core temperature: tympanic and esophageal probe

Clinical setting was inappropriate to study heat balance and the quantification of redis-
tribution of heat 

Erdling & Johansson 
(2015)

AANA Journal

Experimental

Randomized Con-
trolled Trial

Strength: Level 1

Quality: High

Limitations in sample size, type of surgery, and anesthesia technique limiting general-
izability

Beta-blockers and vasopressor medications were used in both prewarmed and non-pre-
warmed group during anesthesia

Patient conditions such as perfusion and tissue disorders may have affected results

Varied placement of temperature probes in patients

Outflow temperature in the warming device varied from -1°C to +5°C from the preset 
value of 43°C

Fettes et al (2013)

AORN Journal

Experimental

Randomized Con-
trolled Trial

Strength: Level 1

Quality: Moderate

Small sample size

Both groups received warmed cotton blankets preoperatively

Lack of patients with hypothermia in both groups throughout the study

Intraoperative temperature measurements were not evaluated

Imprecise time intervals for temperature measurements
Hooven (2011)

Journal of Peri-Anes-
thesia Nursing

Quasi-experimental

Nonrandomized Trial

Strength: Level 2

Quality: Moderate

 Temperature measurements only obtained for preoperative and postoperative periods

Mean surgical duration time differed significantly between the 2 groups (P=0.048)

Significant difference in preoperative temperatures in both groups (P=0.008)

Temperature measurement intervals unclear and staff training on correct equipment 
use unclear

Horn et al (2012)

Anaesthesia

Experimental

Randomized Con-
trolled Trial

Strength: Level 1

Quality: High 

Distribution of surgery types was not equal among groups

4% of patients were already hypothermic on arrival to preoperative unit

Patients not blinded

Kramer (2013)

Journal of Peri-Anes-
thesia Nursing

Quasi-experimental

Nonrandomized Trial

Strength: Level 2

Quality: Low

Nonrandomized

Oral and esophageal temperature measurement instruments used in the study

Not clear on prewarming device set temperature, ambient OR room temperature, cor-
rect use of temperature measurement instruments and other equipment

Nicholson (2013)

AORN Journal

Experimental

Randomized Con-
trolled Trial

Strength: Level 1

Quality: Low

Both study groups received prewarming before induction of general anesthesia

Few participants were hypothermic on arrival to preoperative area; no mention of 
distribution in the study groups

No mention of prewarming device temperature and staff training on equipment use

Various temperature measurement instruments used throughout the study: oral, nasal, 
esophageal, or rectal temperature probe or temperature-sensing urinary catheter

Lack of dedicated research assistants or co-investigators, the facility policy to warm 
patients intraoperatively before induction, and difficulty obtaining oral temperatures in 
the immediate postoperative period

Perl et al (2014)

Minerva Anestesio-
logica

Experimental

Prospective, random-
ized, multi-center, 
controlled study

Strength: Level 1

Quality: Moderate

22 patients had to be excluded due to protocol violations

A wide range of prewarming durations (but all patients received greater than 10 min-
utes of prewarming)

A relevant number of patients were hypothermic on arrival to the OR

No mention of prewarming device temperature or staff training on equipment use

Oral and esophageal probe used for temperature measurement in the study

Rowley et al (2014)

Clinical Nursing 
Research

Quasi-experimental

Nonrandomized Trial

Strength: Level 2

Quality: High

No randomization (convenience sample)

Unable to achieve desired ambient surgical room temperature of 21.1°C/70°F for some 
study cases in samples III and IV

EBL not included in the data collection

Many surgical candidates excluded from the study due to obesity and comorbidities
Shin et al (2015)

BMC Anesthesiology

Experimental

Randomized Con-
trolled Trial

Strength: Level 1

Quality: High

Oral and esophageal probe used for temperature measurement in the study

Warming device indirectly affected tympanic membrane temperature and caused inac-
curacy of core temperature measurement with the infrared tympanic thermometer, so 
the highest value of 3 consecutive measurements were recorded to decrease error and 
the study relied more heavily on the esophageal temperature as the accurate measure-
ment of core temperature

No mention of prewarming device temperature and staff training on equipment use
Abbreviations: EBL, estimated blood loss; OR, operating room.

 

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Volume 5 - No. 5 2017 Page 35



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Anesthesia eJournal                         www.anesthesiaejournal.com
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https://doi.org/10.1093/bja/aen272
https://doi.org/10.1016/j.jopan.2010.07.013
https://doi.org/10.1016/j.jopan.2013.04.144
https://doi.org/10.1016/j.jopan.2013.04.144
https://doi.org/10.1186/1471-2253-15-8
https://doi.org/10.1213/ANE.0b013e3181cb3ebf
https://doi.org/10.1111/j.1365-2044.2012.07073.x
https://doi.org/10.1111/j.1365-2044.2012.07073.x
https://doi.org/10.1177/1054773814535428
https://doi.org/10.1016/j.aorn.2012.12.011
https://doi.org/10.1016/j.aorn.2012.12.018
https://doi.org/10.2344/0003-3006-57.1.25

