535428

research-article2014
CNRXXX10.1177/1054773814535428Clinical Nursing ResearchRowley et al.

Article
Clinical Nursing Research
2015, Vol. 24(4) 432­–441
Perioperative © The Author(s) 2014
Reprints and permissions:
Warming in sagepub.com/journalsPermissions.nav
DOI: 10.1177/1054773814535428
Surgical Patients: cnr.sagepub.com

A Comparison of
Interventions

Brenda Rowley, RN, BSN1, Marsi Kerr, CRNA,

MS1, Judy Van Poperin, RN, BSN1, Cindy Everett,
RN, CNOR, MBA1, Manfred Stommel, PhD2,
and Rebecca H. Lehto RN, PhD2

Abstract
The four arm study investigates how use of a preoperative forced-air
warming blanket and adjustment of ambient surgical room temperature may
contribute to prevention of perioperative hypothermia. Active warming
interventions may prevent the drop in core temperature that occur as a
result of surgical anesthesia. Core body temperatures from a convenience
sample of 220 adult surgical patients were sequentially monitored in the
preoperative, intraoperative, and post-anesthesia care units (PACU) while
receiving: (a) routine surgical care, (b) application of preoperative forced-air
warming blanket, (c) application of preoperative forced-air warming blanket
with adjustment of ambient surgical room temperatures, or (d) adjustment of
ambient surgical room temperature only. Sample characteristics were evenly
distributed among the four groups. There were no statistical differences
in PACU core body temperatures. The application of forced-air warming
blankets and room temperature adjustment interventions were not more
effective than current practice in preventing perioperative hypothermia.

1Allegiance Health System, Jackson, MI, USA

2Michigan State University, East Lansing, USA
Corresponding Author:
Brenda Rowley, Allegiance Health System, 205 N East Ave., Jackson, MI 49201, USA.
Email: brenda.rowley@allegiancehealth.org
Rowley et al. 433

Keywords
nursing, perioperative hypothermia, thermoregulation, surgical patients

Introduction
Unplanned perioperative hypothermia is associated with increased complica-
tions including infections, cardiac dysfunction, coagulopathies, increased
blood loss, altered drug metabolism, and delayed recovery (Association of
periOperative Registered Nurses, 2014; Burger & Fitzpatrick, 2009).
Although research has confirmed that unplanned perioperative hypothermia
can increase patients’ risk for serious postoperative complications, only a
limited number of studies have systematically investigated how dual patient
care environment factors contribute to changes in core body temperature in
perioperative patients (Burger & Fitzpatrick, 2009; Poveda, Clark, & Galvão,
2013). This study investigates how use of a preoperative forced-air warmer
and adjustment of surgical room ambient temperature may contribute to pre-
vention of unplanned perioperative hypothermia.

Problem
It is well documented that anesthetic agents decrease the vasoconstriction
threshold to levels below baseline body temperature as a result of heat flow
transfer from the body core to the periphery during surgery (Burger &
Fitzpatrick, 2009; Poveda et al., 2013). Surgical patients cannot actively
thermo-regulate and may experience a substantive drop in core temperature
within the first hour of surgery as a result of anesthesia-induced redistribution
of body heat (Lynch, Dixon, & Leary, 2010; Poveda et al., 2013). While peri-
operative staff routinely monitor patient changes in core body temperature in
the surgical environment, the application of forced-air warming systems and
adjustment of ambient surgical room temperatures are often in response to
unplanned perioperative hypothermia rather than as proactive preventive
measures (Knaepel, 2012; Lynch et al., 2010). The American Society of
PeriAnesthesia Nurses (ASPAN; 2010) guidelines advocate pre-warming
measures prior to operating room entry. Pre-warming interventions in surgery
patients have been shown to reduce need for pain medication, decrease recov-
ery and discharge time (Lista, Doherty, Backstein, & Ahmad, 2012). While
the benefits of preoperative warming is noted, research findings indicate that
there is continued need for evaluation and translation of research findings at
the local level (Moola & Lockwood, 2011). The optimal use of both forced-
air warming devices and ambient surgical room adjustment practices are
434 Clinical Nursing Research 24(4)

often based on site practices and/or incomplete evidence (Galvão, Marck,

Sawada, & Clark, 2009; Lynch et al., 2010), and studies in this area are often
heterogeneous and of questionable reliability (Sajid, Shakir, Khatri, & Baig,
2009). Furthermore, there are few studies that have tested two or more warm-
ing interventions simultaneously for efficacy (Knaepel, 2012). Systematic
research is needed to develop empirically based unplanned perioperative
hypothermia protocols and targeted screening sequences for vulnerable hos-
pital patients (Sajid et al., 2009). This study, a quality management activity,
organized by perioperative nursing staff with academic partnership collabo-
ration, was guided by Melnyk’s Advancing Research and Clinical Practice
through Close Collaboration Model that was developed to improve the inte-
gration of research and clinical practices in acute-care settings (Melnyk &
Fineout-Overholt, 2002). The model incorporates mentorship, expert knowl-
edge, outcomes management, time, patient care, and institutional factors as a
broad strategy to promote evidence-based practice.

Purpose of the Study

The purpose of the exploratory study was to investigate how the use of a
preoperative forced-air warmer and adjustment of surgical room ambient
temperature may contribute to core body temperature changes. The primary
research question is:

Research Question: What are the differential core body temperature ben-
efits derived from the systematic application of a forced-air warming blan-
ket and/or adjustment of ambient room temperatures for surgical hospital
patients?

The study hypothesis is:

Hypothesis: The application of a preoperative forced-air warming blanket

and the adjustment of the surgical room ambient temperature will be most
effective in maintaining or improving pre- to post-operative core body
temperatures in surgical patients.

Method
This was a quasi-experimental exploratory study with four arms. For logisti-
cal reasons, patients were not randomly assigned to the four different expo-
sure conditions. Instead, the enrollment of eligible study patients occurred
sequentially until a total of 55 patients were recruited in each study arm with
Rowley et al. 435

a total sample of 220 adult surgical patients. Treatment exposure in the study
arms were as follows: Study Arm I, routine care (control group); Study Arm
II, routine surgical care and application of a preoperative forced-air warming
blanket; Study Arm III, routine surgical care, application of preoperative
forced-air warming blanket, and adjustment of ambient surgical room tem-
perature; and Study Arm IV, routine surgical care with adjustment of ambient
surgical room temperature only.
Study inclusion criteria included adult patients of at least 18 years old that
were scheduled to undergo surgical procedures of a minimum of 1 hour in
duration. The procedures included major (open) abdominal surgery, total hip
replacements, total knee replacements, and lumbar spinal fusion surgery.
Exclusion criteria included (a) body mass index (BMI) greater than 30 kg/m2;
(b) febrile, greater than 38°C (100.4°F); and (c) comorbidities including doc-
umented history of impaired respiratory function (e. g., chronic obstructive
pulmonary disease, asthma, pulmonary fibrosis), and vascular disease (e. g.,
coronary artery disease, peripheral arterial disease, venous insufficiency). To
maintain patient safety and satisfaction, patients who required or requested
additional warming measures during the perioperative period would be
excluded from the study; however, no subjects were excluded for this
reason.
All study procedures were approved by the hospital Institutional Review
Board prior to study initiation. Potential eligible candidates were identified
during the pre-admission interview or on arrival to the preoperative surgical
unit. On arrival to the preoperative unit, current weight and BMI were
assessed. After verification of eligibility status, patients received study infor-
mation including potential risks and benefits and then provided consent.
Study documents were placed in the patients’ tagged chart including signed
consent forms, data collection tools, and a white bouffant hat to identify the
patient as a study participant.

Instruments
Medical grade temporal lobe infrared probe thermometers were used to mea-
sure temperature readings to provide less intrusion and ease of operation.
According to Barringer, Evans, and Ingram (2011), temporal lobe measure-
ments closely correlate with electronic oral temperatures. The same thermom-
eter accompanied the patient throughout the study testing duration providing
for consistency and accuracy. Patients’ body temperatures were sequentially
monitored and documented in the preoperative, intraoperative, and post-anes-
thesia care unit (PACU) areas. The temporal thermometers and forced-air
warming devices were tested by the Bio-Medical Department to confirm
436 Clinical Nursing Research 24(4)

function, safety, and measurement standards. In addition, instrument verifica-

tion of accuracy was performed periodically during the 18-month study.
A data collection tool was developed for the nurses to record demographic
information, temperature values, and times. Other data, including type of sur-
gery, BMI calculation, duration of surgery, and intravenous fluids, received
were obtained by chart review.

Study Procedures
Routine care for the study arm I (control group) consisted of covering the
patient with a room temperature flannel bath blanket after changing into the
hospital gown. On request, patients were given warmed flannel bath blankets.
Once anesthesia induction was finished, a forced-air warming blanket was
placed on the patient and the device was set at 43°C (109.4°F). Once the case
was finished, the forced-air device was removed and the patient covered with
a warmed flannel bath blanket. The patient was then transferred to the PACU.
Study arm II participants received routine care with the addition of the forced-
air warming blanket applied in the preoperative area. Based on the time spent
in the preoperative area, the warming device was on for approximately 20 to
30 min prior to leaving for surgery. Study arm III participants received rou-
tine care with the preoperative forced-air warming blanket and the addition of
adjustment of the ambient surgical room temperature. The digital thermostat
was adjusted to 21.1°C (70°F) prior to the patient operating room arrival.
Once the patient was prepped, positioned, and surgical incision complete, the
room temperature could be decreased as needed to meet comfort needs of the
surgical staff. Prior to finishing the surgical procedure and undraping the
patient, the room thermostat was re-adjusted to 21.1°C (70°F). Study arm IV
participants received routine care with adjustment of the ambient room tem-
perature in the operating room only, as described above.

Data Analysis
The sample size for the study was calculated using G*Power 3.1 power anal-
ysis software (Faul, Erdfelder, Buchner, & Lang, 2009). It was determined
that 220 patients (55 patients per arm) were needed to provide a 0.80 level of
statistical power to detect meaningful between-group differences in the four
study arms. The priori calculations were based on a moderate 0.25 effect size
and a two-tailed 0.05 level of statistical significance (Cohen, 1992).
The primary study measurements were core body temperatures measured
at six different times: preoperative (immediately following consent in the
preoperative unit), on entrance to the operating room, at incision time, at the
Rowley et al. 437

Table 1.  Demographic and Health Characteristics of the Sample (N = 220).

Characteristic, M ± SD/ Overall Arm 1 (control) Arm 2 Arm 3 Arm 4
(minimum − maximum) (n = 220) (n = 55) (n = 55) (n = 55) (n = 55)

Age (years), M ± SD 65.5 ± 14.8 65.3 ± 15.3 64.6 ± 12.4 64.8 ± 16.1 67.5 ± 15.4
(minimum − maximum) (21 − 90)
Body mass index, M ± SD 25.82 ± 3.0 25.56 ± 2.8 25.8 ± 3.3 25.8 ± 2.6 26.1 ± 3.3
(minimum − maximum) (16 − 30)
IV fluids in liters, M ± SD 1.6 ± 1.1 1.7 ± 1.3 1.5 ± 0.6 1.6 ± 0.7 1.6 ± 1.4
(minimum − maximum) (0.4 − 11.2)
Admit temperature 36.4 ± 0.35 36.4 ± 0.31 36.3 ± 0.32 36.3 ± 0.36
(Celsius), M ± SD
PACU temp (Celsius), 36.4 ± 0.45 36.4 ± 0.36 36.4 ± 0.35 36.2 ± 0.54
M ± SD
Type of surgery
  Open abdominal 70 (32%) 19 16 16 19
 Hip 38 (17%)  9 12  8  9
 Knee 72 (33%) 18 16 20 18
 Lumbar/spine 40 (18%)  9 11 11  9

Note. PACU = post-anesthesia care unit.

end of surgery, at the time of admission to PACU, and at the time of dis-
charge. With a continuous outcome variable like patient body temperature,
we adopted a repeated-measures analysis of variance (ANOVA) model, using
the four arms as the between-group factor (Winer, Brown, & Michels, 1991).
Use of the repeated-measures ANOVA accounts for systematic effects associ-
ated with the manipulated factors from individual unexplained variations in
outcomes (Winer et al., 1991). Additional data collected were sex, age, BMI,
and type of operation as control variables. All analyses were carried out using
STATA 12.0 software.

Results
The participants mean age was 65.53 years, SD 14.82, range 21 to 90 years.
Most of the patients were female (n = 135, 61%). Additional demographic
and health characteristics are listed in Table 1. Patient characteristics were
well-randomized among the four arms. There were no statistical significances
in study results as a result of patient factors including sex (χ2 = 3.27; p > .05);
age (F = .44, p > .05), height (F = 1.51, p > .05), weight (F = .87, p > .05),
BMI (F = .32, p > .05), intravenous fluids (F = .20, p > .05), and type of sur-
gery (χ2 = 18.32, p > .05). Figure 1 provides the mean temperature trends for
all four arms across the perioperative time points. There were no significant
statistical differences (p > .05) in postoperative core body temperatures
among the four groups.
438 Clinical Nursing Research 24(4)

37
36.9 Arm I
Paent Temperatures

36.8
Arm II
36.7
36.6 Arm III
36.5 Arm IV
36.4
36.3
36.2
36.1

Time Points

Figure 1.  Arm I-IV mean temperatures over perioperative time points.
Note. OR =Operating Room; PACU = post-anesthesia care units.

Discussion
Recognizing the severity of consequences associated with unplanned periop-
erative hypothermia, the study purpose was aimed at testing interventions that
could potentially lead to the standardization of care to prevent this untoward
occurrence in susceptible patients. Although enrolled patients temperatures
varied over the perioperative time period, we cannot claim that the application
of a forced-air warming blanket or adjustment of ambient room temperature
made a significant difference in patients’ tendency to experience hypothermia.
According to ASPAN (2010), the patients’ temperature goal must be greater
than or equal to 36°C (96.8°F) within the first 15 min of entering PACU.
Findings showed no significant difference between pre- to post- core body
temperatures. Thus, the additional interventions were not more effective than
the current routine surgical care in preventing unplanned perioperative hypo-
thermia and the study hypothesis was not confirmed. It is important to con-
sider that routine surgical care in each of the four arms consisted of application
of an intraoperative forced-air warming device, which may have contributed
to subjects’ ability to maintain normothermic postoperative temperatures.
A limitation of the study was utilizing a convenience sample rather than
randomization of patients to the study conditions. The sequential enrollment
design ensured compliance of the interventions for the four arms and accu-
racy of data collection for a study that was conducted in a busy complex
treatment environment involving a multidisciplinary team. There were little
Rowley et al. 439

differences in patient characteristics among the four arms, which improves

the credibility of the study findings. A second limitation was procedural,
there were challenges in achieving the desired ambient surgical room tem-
perature of 21.1°C (70°F) for some study cases in Arms III and IV; thus, we
needed to statistically correct for a room temperature of 20°C (68°F) in data
analysis. Estimated blood loss (EBL) was not included in the data collection,
which could have affected a patient’s tendency to experience hypothermia.
However, since all subjects were normothermic on entering PACU, it is less
likely that EBL would change the study outcomes. Another limitation was
including stringent exclusion criteria of patients with BMIs greater than 30
kg/m2. Many surgical candidates were excluded from the study due to obesity
and co-morbid conditions. It is plausible that patients with higher BMI’s and
co-morbid vulnerabilities may have had differing trends with thermoregula-
tion than what were found in this study.

Application
The study findings contribute to what is known about evidence-based periop-
erative warming practices. Importantly, it offers the contribution of testing
two or more warming interventions in the same study. The study did not sup-
port changing current standard of practice during the perioperative phase at
the institution under study. Further research that examines bundled patient
care factors in the prevention of unplanned perioperative hypothermia using
randomized control designs are warranted. It is essential that clinical staff are
involved in evidence-based practice and quality management activities that
incorporate mentorship, expert knowledge, outcomes management, patient
care, and institutional factors as a broad strategy to further promote evidence-
based practice in this area.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research,
authorship, and/or publication of this article.

Funding
The author(s) received no financial support for the research, authorship, and/or publi-
cation of this article.

References
The American Society of PeriAnesthesia Nurses. (2010). ASPAN’s evidence-based
clinical practice guideline for the promotion of perioperative normothermia.
Journal of PeriAnesthesia Nursing, 25, 346-350.
440 Clinical Nursing Research 24(4)

Association of periOperative Registered Nurses. (2014). Perioperative standards

and recommended practice for inpatient and ambulatory settings. Denver, CO:
Author.
Barringer, L., Evans, C., & Ingram, L. (2011). Agreement between temporal artery,
oral, and axillary temperature measurements in the perioperative period. Journal
of PeriAnesthesia Nursing, 26, 143-150.
Burger, L., & Fitzpatrick, J. (2009). Prevention of perioperative hypothermia. British
Journal of Nursing, 18, 1114-1119.
Cohen, J. (1992). A power primer. Psychology Bulletin, 112, 155-159.
Faul, F., Erdfelder, E., Buchner, A., & Lang, A. G. (2009). Statistical power analyses
using G*Power 3.1. Behavior Research Methods, 41, 1149-1160.
Galvão, C. M., Marck, P. B., Sawada, N. O., & Clark, A. M. (2009). A systematic
review of the effectiveness of cutaneous warming systems to prevent hypother-
mia. Journal of Clinical Nursing, 18, 627-636.
Knaepel, A. (2012). Inadvertent perioperative hypothermia: A literature review.
Journal of Perioperative Practice, 22, 86-90.
Lista, F., Doherty, C. D., Backstein, R. M., & Ahmad, J. (2012). The impact of peri-
operative warming in an outpatient aesthetic surgery setting. Aesthetic Surgery
Journal, 32, 613-620.
Lynch, S., Dixon, J., & Leary, D. (2010). Reducing the risk of unplanned periopera-
tive hypothermia. AORN Journal, 92, 553-565.
Melnyk, B. M., & Fineout-Overholt, E. (2002). Rochester ARCC: Putting research
into practice. Reflections on Nursing Leadership, 28, 22-25.
Moola, S., & Lockwood, C. (2011). Effectiveness of strategies for the management
and/or prevention of hypothermia within the adult perioperative environment.
International Journal of Evidence-Based Healthcare, 9, 337-345.
Poveda, V. D., Clark, A. M., & Galvão, C. M. (2013). A systematic review on the
effectiveness of prewarming to prevent perioperative hypothermia. Journal of
Clinical Nursing, 22, 906-918.
Sajid, M. S., Shakir, A. J., Khatri, K., & Baig, M. K. (2009). The role of periopera-
tive warming in surgery: A systematic review. Sao Paulo Medical Journal, 127,
231-237.
Winer, B. J., Brown, D. R., & Michels, K. M. (1991). Statistical principles in experi-
mental design (3rd ed.). New York, NY: McGraw-Hill.

Author Biographies
Brenda Rowley is the unit-based educator for Surgical Services at Allegiance Health
in Jackson, Michigan. She has an Associate Degree in Nursing from Jackson
Community College and a Bachelor of Science in Nursing from Eastern Michigan
University. Brenda was the principal investigator for the research study.
Marsi Kerr is a Nurse Anesthetist at Allegiance Health in Jackson Michigan. She
earned her Bachelor of Science in Nursing from Madonna University in Livonia,
Michigan and her Masters in Nurse Anesthetist from the University of Detroit Mercy
Rowley et al. 441

in Detroit Michigan. Marsi has been involved in professional practice, advocating for
evidence-based practice, and development of research projects throughout her nursing
career.
Judy Van Poperin earned her diploma in nursing from St Luke’s School of Nursing
in Marquette Michigan. She received her Bachelor of Science in Nursing from
Northern Michigan University. Judy began her nursing career at St Francis Hospital
in Escanaba, Michigan prior to joining Allegiance Health, Jackson Michigan in 2006
as a staff nurse in the Surgical Services Department.
Cindy Everett is the Director of Surgical Services at Allegiance Health in Jackson,
Michigan. She has an Associate in Nursing from Ferris State University and a Masters
in Business Administration from the University of Phoenix. Cindy is also Certified in
the Operating Room, CNOR.
Manfred Stommel, PhD is a Professor in the College of Nursing at Michigan State
University. Dr. Stommel, a biostatistician and sociologist, served as the statistical
consultant on the current study.
Rebecca H. Lehto, PhD, MS, RN is an Assistant Professor at Michigan State
University College of Nursing. Dr. Lehto has served as a research liaison and consul-
tant as part of academic partnership with the Allegiance Health System for the past
three years.