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Accidental intraoperative hypothermia is defined as a core temperature
below 36.0°C. It is a common and avoidable adverse event of the
perioperative period and is associated with detrimental effects on
multiple organ systems and postoperative patient outcomes.[1] The
incidence of these adverse effects increases at core temperatures
below 34.5°C.[2] Shivering is an unpleasant experience, and negatively
contributes to a patient’s perioperative experience.[3] Hypothermia
increases the length of stay in the post-anaesthetic care unit, as well
as in hospital, and prolongs the recovery from surgery,[4,5] which
increases healthcare costs.[1] In addition, perioperative hypothermia is
associated with increased surgical-site infections, altered coagulation,
and altered drug metabolism.[4,6-8] The most serious adverse effects
of perioperative hypothermia are related to cardiac complications.
Dubick et al.[9] propose that hypothermia predisposes the heart to
ischaemia and reduces the threshold of the myocardium for arrythmias.
By maintaining normothermia, Frank et al.[10] found that there was a
reduction in perioperative morbid cardiac events, e.g. unstable angina,
cardiac arrest and myocardial ischaemia. In their recently published
multicentre trial, Sessler etal.[2] have shown no difference in the rate of
major adverse cardiac events between patients with intraoperative core
temperatures maintained at 35.5°C and those aggressively warmed to
37.0°C.[2] This provides a reasonable target temperature for perioperative
temperature management.
Considering the consequences and the incidence of perioperative
hypothermia, which may occur in up to 40% of patients,[6] it is
not surprising that the maintenance of normothermia is a specific
perioperative goal. The importance of this is reflected in a number of
local and international guidelines outlining the minimum level of care
for perioperative hypothermia. The overarching aims of these guidelines
are to guide best practice and ensure patient safety.
In their 2018 practice guidelines, The South African Society of
Anaesthesiologists (SASA),[11] specifically mention the need to monitor
patient temperature for procedures planned to take longer than 30
minutes, as well as active measures required to maintain the core
temperature between 36.0 and 37.0°C. A thermometer and a blood or
fluid warmer are listed as essential equipment that should be available at
all hospital levels, failing which the provision of an anaesthetic becomes
unsafe.[11] Similar recommendations regarding temperature monitoring
A comparison of the warming capabilities of
two Baragwanath rewarming appliances with the
Hotlinefluid warming device
K Wilson, BSc (Physio), MB BCh, DA(SA) ; M Fourtounas, MB ChB, DA (SA), Dip HIV, FCA, MMed (Anaesthesiol) ;
C Anamourlis, MB BCh, MSc (Med), DA (SA), FCA, MMed (Anaesthesiol)
Department of Anaesthesiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
Corresponding author: K Wilson (mostoman@gmail.com)
Background. Accidental intraoperative hypothermia is a common and avoidable adverse event of the perioperative period and is associated with
detrimental effects on multiple organ systems and postoperative patient outcomes. In a resource-limited environment, prevention of intraoperative
hypothermia is often challenging. Resourceful clinicians overcome these challenges through creative devices and frugal innovations.
Objective. To investigate the thermal performance of two Baragwanath Rewarming Appliances (BaRA) against that of the Hotline device to
describe an optimal setup for these devices.
Methods. This was a quasi-experimental laboratory study that measured the thermal performance of two BaRA devices and the Hotline device
under a number of scenarios. Independent variables including fluid type, flow rate, warming temperature and warming transit distance were
sequentially altered and temperatures measured along the fluid stream. Change in temperature (ΔT) was calculated as the difference between entry
and exit temperature for each combination of variables for each warming device.
Results. A total of 219 experiments were performed. At a temperature of 43.0°C and a transit distance of 200 cm, the BaRA A configuration
either matched or exceeded the ΔT of the Hotline over all fluid type and flowrate combinations. The BaRA B configuration does not provide
comparable thermal performance to the Hotline. Measured flowrates were noticeably slower than manufacturer-quoted values for all intravenous
(IV) cannulae used.
Conclusion. A warm-water bath at 43.0°C with 200 cm of submerged IV tubing provides thermal performance comparable to the Hotline device,
with all fluid type and flowrate combinations.
Keywords. perioperative hypothermia; frugal innovation; warming devices.
South Afr J Crit Care 2022;38(3):96-101. https://doi.org/10.7196/SAJCC.2022.v38i3.549
Contribution of the study. The present study provides an evidence-based method for warming intravenous fluid in resource-limited scenarios.
SAJCC November 2022, Vol. 38, No. 3 99
ARTICLE
and the warming of intravenous (IV) fluids
are made by the Canadian Anesthesiologists’
Society,[12] National Institute of Health
and Care Excellence (NICE),[13] the World
Health Organization (WHO) and the World
Federation of Societies of Anaesthesiologists
(WFSA).[14]
Anaesthesia increases the risk of
hypothermia by inhibiting normal
homeostatic responses that maintain the
body’s core temperature. The mechanisms
involved in perioperative hypothermia include
inhibition of the central and peripheral
thermoregulatory responses by the anaesthetic
agents used, an increased loss of heat to
the environment through patient exposure,
altered behavioural responses to the cold and
administration of cold fluids internally.[1,3]
Yi etal.[15] have identified the administration
of unwarmed IV fluids in excess of 1 000 mL
as a risk factor for developing perioperative
hypothermia. It is commonly quoted that
infusing >1 L of room temperature (21°C)
fluid into an adult will reduce the core
body temperature by 0.25°C.[16,17] Sixteen
kilocalories of energy are needed to warm
a litre of fluid from room temperature to a
core body temperature of 37.0°C.[18] Various
methods have been described to prewarm IV
fluids before administration. These include
storing the fluid in a fluid-warming cabinet,[1]
prewarming the fluids in a warm-water bath[19]
or heating the fluid in a microwave.[20] These
methods have been shown to be superior at
maintaining core temperature (compared with
administering room-temperature fluid) and
are also comparable with the performance of
commercially available in-line fluid-warming
devices such as the Hotline apparatus (ICU
Medical Inc., USA).[1]
Resource-limited settings challenge the
delivery of acceptable levels of care and low-and
middle-income countries are most affected.
In response to these constraints, a number of
creative solutions have been constructed to
warm fluids. There are many anecdotal stories
of blood products being warmed in warm
blankets, buckets of warm water or even in
groins and axillae before being administered
to patients. Recommendations have been
published on the optimal use of these creative
solutions. Lindhoff and Palmer[20] described the
optimal use of a microwave for prewarming IV
fluids.[20] Shah etal.[21] described a novel fluid-
warming device using a non-sterile latex glove
filled with warmed water to heat a coil of IV
fluid being administered to the patient. Craig
etal.[22] described a method of prewarming IV
fluids using a warm air blower and a modified
cooler box. It is common practice at Chris Hani
Baragwanath Academic Hospital (CHBAH)
to warm IV fluid by passing the IV tubing
through a warm-water bath as it flows to the
patient. This sort of Baragwanath Rewarming
Appliance (BaRA) is an example of a novel
technology that addresses the need to provide
acceptable anaesthetic care in a resource-
limited setting; however, an assessment of the
performance of these devices is lacking.
The two BaRA configurations used in the
present study are shown in Fig. 1. BaRA A
consists of a warm-water bath with a variable
amount of IV extension tubing submerged in
it. BaRA B consists of a variable amount of IV
extension tubing wrapped around the tubing of
a forced-air warmer, Bair Hugger (3M, USA).
The aim of the present study was to describe
and compare the warming capabilities of
two BaRA devices and the Hotline device to
describe an optimal assembly of these devices
that approximates the warming capabilities
of the commercially available Hotline device.
Ethics
Ethical clearance was obtained from the Wits
Human Research Ethics Committee (Medical)
(ref. no. M2008107) and permission to use
human blood products was obtained from the
South African National Blood Services (ref.
no. 2019/0520).
Methods
A quasi-experimental, quantitative research
design was employed in the present study.
The study was conducted in an unused,
fully operational surgical theatre at CHBAH
using standardised 20 drops/min IV and 10
drops/min blood administration sets and
IV cannulae. Dextrose water was included
in the study as an electrolyte-free control
fluid. IV fluids were kept at a standard
1 m height above the warming device to
control driving pressure. Ambient air
temperature and fluid temperatures were
continuously monitored for fluctuations
during the experiments. Under experimental
conditions, independent variables relating
to the Hotline, BaRA A and BaRA B devices
were sequentially altered to assess the effect
on temperature at points T1 and T3, the
dependent variables. Fig. 2 illustrates the
experiment setup, the independent variables
related to each warming device and the
location of the temperature measurement
points. Actual flowrates for each cannula
were measured.
The independent variables for each BaRA
configuration were assigned a code which
described the warming device configuration,
e.g. Ba.43.200. Table 1 outlines the coding
system. Twelve combinations of independent
variables were tested for the Hotline and 48
combinations were tested for each BaRA
configuration, totalling 108 experimental
combinations.
Temperature was recorded at six points
and stored by a multichannel thermistor and
data capture software (BaRAGRABA 2.0),
both specifically designed for the experiment.
Full details on device and software
construction and calibration are available
as a supplement (https://www.samedical.
org/file/1952). In-stream temperatures were
recorded at T1 and T3. T2 was monitored
to maintain warming device temperature
for the BaRA A experiments. Hotline and
BaRA B temperatures were determined by the
Figure Error! No text of specified style in document.-1 BaRA device
c
onfigurations
BaRA A warm-water bather
Patient
BaRA B
Forced air warmer tubing
Patient
IV uids
IV uids
Fig.1. BaRA device congurations. (IV = intravenous.)
SAJCC November 2022, Vol. 38, No. 3 101
ARTICLE
individual devices. Ambient temperature and
in-line fluid temperature were also recorded
and monitored at two distal points to control
experimental conditions.
Temperature measurements were recorded
automatically at 500ms intervals for a period
equal to the transit period plus 5 seconds. The
transit period was calculated as the time taken
for an indicator bubble to travel from T1 to
T3. These temperature measurements were
automatically measured and saved digitally.
The warming capability of the device was
determined as the difference between the
mean exit temperature at T3 and the mean
entry temperature at T1 (ΔT).
Data analysis was carried out using SAS v9.4
for Windows (SAS, USA). A 5% significance
level was used. Each dependent variable, for
each warming device, was modelled in terms
of the relevant independent variables and
their two-way interactions using a general
linear model (GLM). Outliers were removed
as indicated by model diagnostics. Non-
significant interaction terms were removed
for model parsimony. A one-way ANOVA
was used for comparison of each dependent
variable for the Hotline to that of the eight
corresponding BaRA A and BaRA B device
conditions at a given combination of fluid type
and flowrate. Post hoc tests were conducted
using the Tukey-Kramer adjustment for
unequal group sizes to determine which BaRA
A and BaRA B combinations did not differ
significantly from the Hotline device readings.
Results
Experiments were conducted twice at each
combination of independent variables,
giving a total of 216 experiments. Data for
nine experiments were missing owing to
file errors. The estimated mean ΔT, with
associated 95% confidence intervals of the
warming devices at each combination of
the independent variables are shown in
the supplementary Table 1 (https://www.
samedical.org/file/1952) and Fig.3.
Table 2 shows the BaRA combinations,
marked in black, where ΔT matched or
exceeded the Hotline device. Ba.43.200
was the only configuration that provided
a similar ΔT to the Hotline device under
all fluid and flowrate combinations. Other
BaRA A configurations provided comparable
ΔT values but only under specific fluid
and flowrate combinations. When packed
red blood cells (PRBC) were utilised all
configurations of BaRA A had ΔT values
similar to the Hotline device.
The BaRA B devices only approximated
the ΔT of the Hotline in the Bb.43.200
configuration and only when PRBC were
used. No other combination of variables
of this device approximated the Hotline
ΔTreadings.
Table1. Experimental coding key
Code Interpretation
Ba BaRA A configuration
Bb BaRA B configuration
38 38.0°C (warming device temperature)
43 43.0°C (warming device temperature)
100 100 cm (transit distance)
200 200 cm (transit distance)
Figure-1 Experiment schematic
IV Fluids
Flowrate
T1 T3
Warming device
Independent
variable
IV uids
Flowrate
Warming device
temperature
Manufacturer determined
Warming transit
distance
Manufacturer determined
• 38 °C
• 43 °C
• 100 cm
• 200 cm
• 38 °C
• 43 °C
• 100 cm
• 200 cm
Hotline independent variables Baragwanath rewarming appliance (BaRA)
independent variables
BaRA A BaRA B
• Dextrose water (room temperature)
• PRBC (refrigerated)
• Ringer's lactate (room temperature)
• Voluven (room temperature)
• 22 G cannula (36 mL/min)
• 20 G cannula (60 mL/min)
• 18 G cannula (100 mL/min)
Fig.2. Experimental setup. (IV = intravenous; PRBC = packed red blood cells.)
Table2. BaRA configurations that matched or exceeded the Hotline device for ΔT (marked in red)*
Flowrate
(mL/min)
Dextrose water PRBC Ringer’s lactate Voluven
35 60 100 35 60 100 35 60 100 35 60 100
Ba.38.100
Ba.38.200
Ba.43.100
Ba.43.200
Bb.38.100
Bb.38.200
Bb.43.100
Bb.43.200
ΔT = warming capability of the device (determined as the difference between the mean exit temperature at T3 and the mean entry temperature at T1); PRBC = packed red blood cells.
*Darkest shade indicates conditions under which the specified BaRA device matched the Hotline device.
102 SAJCC November 2022, Vol. 38, No. 3
ARTICLE
Table 3 shows the measured flowrates for each fluid through each
warming device. There was a large difference between the manufacturer-
stated flowrates and the measured flowrates for each cannula. Flowrates
also varied substantially between fluids in the case of PRBC. PRBC and
Voluven had the lowest flowrates of all fluids through all devices and
at all flowrates. PRBC had notably lower flowrates through the Hotline
device at all flowrates.
Discussion
The aim of the present study was to describe and compare the warming
capabilities of two BaRA devices with the commercially available
Hotline device to describe a configuration of the BaRA device that
would best approximate the warming capabilities of the Hotline device.
Table2 illustrates that Ba.43.200a provides a one-combination-fits-all
match for the thermal performance of the Hotline, i.e. the BaRA A
configuration with a warming temperature of 43.0°C and a transit
distance of 200 cm. There are a number of isolated conditions for the
BaRA A configuration which approximate the Hotline but only under
specific fluid and flowrate combinations. The BaRA B configuration
did not provide a comparable amount of heating compared with the
Hotline device under most fluid type and flowrate combinations;
however, the warming performance was similar to that of the Hotline
under condition Bb.43.200.
The transfer of heat energy from the warming device to the
fluid is proportional to the surface area available for heat transfer.
The entire surface area of the extension tubing is included in heat
transfer in both the Hotline and BaRA A devices as it is either
enveloped by or submerged in the warming device. This superior
warming effect by a co-axial system has been described in a previous
study by Shultz etal.[19] The BaRA B device has only a fraction of the
tubing surface area in contact with the warming device as it is coiled
on the outer surface of the Bair Hugger warmer conduit.
Fluid transit time is a function of the fluid flowrate and transit
distance. Longer transit times allow for greater heating of the fluid.
Thongsukh et al.[16] have previously shown the inverse relationship
between flowrate and warming device performance. Interestingly, the
100
60
35
Dextrose water
Flowrate (mL/min)
PRBC
Ringer's lactate
Voluven
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
25
20
15
10
5
0
Hotline
Ba.38.100
Ba.38.200
Ba.43.100
Ba.43.200
Bb.38.100
Bb.38.200
Ba.43.100
Bb.43.200
Hotline
Ba.38.100
Ba.38.200
Ba.43.100
Ba.43.200
Bb.38.100
Bb.38.200
Ba.43.100
Bb.43.200
Hotline
Ba.38.100
Ba.38.200
Ba.43.100
Ba.43.200
Bb.38.100
Bb.38.200
Ba.43.100
Bb.43.200
Estimated mean ΔT (°C)
Fig.3. Estimated mean ΔT for each warming device. (PRBC = packed red blood cells; ΔT = warming capability of the device (determined as the dierence between
the mean exit temperature at T3 and the mean entry temperature at T1).)
SAJCC November 2022, Vol. 38, No. 3 103
ARTICLE
measured flows were only ~5 - 55% of manufacturer-quoted flows.
Measured fluid flowrates were much higher with less viscous fluids
such as dextrose water and Ringer’s lactate, and decreased as viscosity
increased, i.e. when using PRBC and Voluven. The significance of this is
that more viscous fluids had longer transit times and resultant increased
heating. This may explain why PRBC were better heated compared with
other fluids under both BaRA A and B configurations. It is noteworthy
that the PRBC flowed slower through the Hotline than the other two
devices. Thermistors were mounted within the flow of fluids (https://
www.samedical.org/file/1952) and may have also affected flowrates.
These factors are important considerations when interpreting the results
of the present study. It is worth noting that the conclusions of the study
may no longer be valid at higher flowrates.
Study limitations
There were a few technical challenges with the conduct of the study. Firstly,
the study was quasi-experimental as no randomisation was performed. This
potentially allows repeat error to bias a particular experimental condition.
The reason for this design was to ensure efficient use of resources and
time and, most importantly, PRBC. Secondly, it was not anticipated that
the electrolyte solutions would alter the readings of the thermistors.
This was indeed the case – the thermistor leads required insulation and
recalibration. Dextrose water was included in the study as a control for the
effects of the electrolytes on the thermistors. After insulation there were
comparable readings at all temperature points with all fluids.
The use of an analogue electronic system, such as the multichannel
thermistor, poses a number of challenges. As the system increases in
complexity, and more thermistors are added, electrical interference
within the system increases and calibration becomes more difficult and
less reliable. This may affect the measurement of absolute temperatures,
as they are calculated indirectly through the Steinhart-Hart equation.
The relative changes between temperatures such as ΔT should not be
affected as the relationship between temperature and resistance remains
fixed within the system, however, a digital temperature monitoring device
would be an ideal upgrade over the analogue system employed in the
present study. Finally, the BaRAGRABA 2.0 corrupted 9 (of 216) data
sets. Despite this loss, many data points were available for statistical
comparison.
Conclusion
Despite a number of technical challenges, the findings of the study
provide valuable insights into the use of the BaRA devices as
alternatives to the Hotline device. To the best knowledge of the authors,
this is the first study that compares the warming capabilities of the
Hotline with the BaRA devices. Resource-limited settings challenge
the provision of adequate levels of perioperative care. Sessler etal.[2]
have shown that a reasonable target core temperature is between 35.5
and 37.0°C. Providing adequately warmed IV fluids forms a major part
of maintaining this target range in the perioperative period. The BaRA
A can be constructed easily from basic consumables found in most
clinical settings and at a fraction of the cost of the Hotline device and
its consumables. This device is not limited to the warming of fluids
during the perioperative period but can be constructed in any setting
requiring the provision of warmed IV fluids. The requirements for
constructing the BaRA A are a container of water warmed to 43.0°C
and 200 cm of IV extension tubing. With this length of IV extension
tubing submerged in the container of warm water, the configuration
should provide warming of dextrose water, Ringer’s lactate, PRBC and
Voluven through IV cannulae at flowrates of 36, 60 and 100 mL/min,
respectively, that is comparable with the Hotline device. The challenges
outlined in the study may assist in the future design of a similar study.
Declaration. is study was performed in partial fullment of the
requirements of KW’s MMed degree.
Acknowledgements. We acknowledge the statistical consultation services of
Data Management and Statistical Analysis (DMSA) in the preparation of the
results. We would like to thank the CHBAH Department of Anaesthesiology
for access to valuable resources to complete this study.
Author contributions. KW: conceptualisation, methodology, soware,
investigation, writing (original dra); MF: supervision, methodology, writing,
review and editing; CA: supervision, methodology, writing, review and editing.
Funding. e CHBAH Department of Anaesthesiology bore the cost of
printing and paper for the postgraduate approval as well as the consumables,
excluding the blood products for the experiments. e blood products were
supplied by SANBS at no additional cost. KW provided the funds for the
multichannel thermistor, statistician and data capture soware.
Conicts of interest. None.
1. John M, Ford J, Harper M. Peri-operative warming devices: Performance and clinical application.
Anaesthesia 2014;69(6):623-638. https://doi.org/10.1111/anae.12626
2. Sessler DI, Pei L, Li K, et al. Aggressive intraoperative warming versus routine thermal
management during non-cardiac surgery (PROTECT): A multicentre, parallel group, superiority
trial. Lancet 2022;399(10337):1799-1808. https://doi.org/10.1016/S0140-6736(22)00560-8
3. Campbell G, Alderson P, Smith AF, Warttig S. Warming of intravenous and irrigation fluids for
preventing inadvertent perioperative hypothermia. Cochrane Database Syst Rev 2015;2015(4):1-
62. https://doi.org/10.1002/14651858.CD009891.pub2
4. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-
wound infection and shorten hospitalisation. Study of Wound Infection and Temperature Group.
N Engl J Med 1996;334(19):1209-1215. https://doi.org/10.1056/NEJM199605093341901
5. Lenhardt R, Marker E, Goll V, Mild intraoperative hypothermia prolongs postanesthetic recovery.
Anesthesiology 1997;87(6):1318-1323. https://doi.org/10.1097/00000542-199712000-00009
6. Melling AC, Ali B, Scott EM, Leaper DJ. Effects of preoperative warming on the incidence of
wound infection after clean surgery: A randomised controlled trial. Lancet 2001;358(9285):876-
880. https://doi.org/10.1016/S0140-6736(01)06071-8
7. Heier T, Caldwell JE. Impact of hypothermia on the response to neuromuscular blocking drugs.
Anesthesiology 2006;104(5):1070-1080. https://doi.org/10.1097/00000542-200605000-00025
8. Rajagopalan S, Mascha E, Na J, Sessler DI. The effects of mild perioperative hypothermia on blood
loss and transfusion requirement. Anesthesiology 2008;108(1):71-77. https://doi.org/10.1097/01.
anes.0000296719.73450.52
9. Dubick MA, Brooks DE, Macaitis JM, Bice TG, Moreau AR, Holcomb JB. Evaluation of
commercially available fluid-warming devices for use in forward surgical and combat areas. Mil
Med 2005;170(1):76-82. https://doi.org/10.7205/milmed.170.1.76
Table3. Measured flowrates of IV cannulae
Flowrate (mL/min) and device*
35 60 100
Fluid Hotline BaRA A BaRA B Hotline BaRA A BaRA B Hotline BaRA A BaRA B
Dextrose water 18 19.5 19.5 24 26.25 24 33 36 33
PRBC 3 6 6 3.99 15 15 4.5 16.5 16.5
Ringer’s lactate 24 18 15 34.5 21 21 43.5 27 24
Voluven 11.1 7.5 6 14.25 9 11.25 16.5 16.5 15
IV = intravenous; PRBC = packed red blood cells.
*BaRA devices had the same measured flowrates for both 100 and 200 cm transit distances.
104 SAJCC November 2022, Vol. 38, No. 3
ARTICLE
10. Frank SM, Fleisher LA, Breslow MJ, etal. Perioperative maintenance of normothermia reduces the
incidence of morbid cardiac events. A randomised clinical trial. JAMA 1997;277(14):1127-1134.
https://doi.org/10.1001/jama.1997.03540380041029
11. South African Society of Anaesthesiologists. Practice Guidelines 2018 Revision. SAJAA
2018;24(2):1-58. https://sasaapi.sasaweb.com/Document/SAJAA(V24N1)2061SASAPracticeGuidel
ines_V12_636803016948256880.pdf (accessed June 2020).
12. Dobson G, Chow L, Flexman A, etal. Guidelines to the Practice of Anesthesia – Revised Edition
2019. Can J Anesthesia 2019,66(1):75-108. https://doi.org/10.1007/s12630-018-1248-2
13. National Institute for Health and Care Excellence. Hypothermia: Prevention and Management in
Adults Having Surgery (NICE Guideline 65). London: NICE, 2008. http://nice.org.uk/guidance/
cg65 (accessed 5 March 2020).
14. Gelb AW, Morriss WW, Johnson W, etal. World Health Organization-World Federation of Societies
of Anaesthesiologists (WHO-WFSA) International Standards for a Safe Practice of Anesthesia. Can
J Anaesth 2018;65(6):698-708. https://doi.org/10.1007/s12630-018-1111-5
15. Yi J, Lei Y, Xu S,etal. Intraoperative hypothermia and its clinical outcomes in patients undergoing
general anesthesia: National study in China. PLoS ONE 2017;12(6):1-13. https://doi.org/10.1371/
journal.pone.0177221
16. Thongsukh V, Kositratana C, Jandonpai A. Effect of fluid flow rate on efficacy of fluid
warmer: An in vitro experimental study. Anesthesiol Res Pract 2018;2018:1-4. https://doi.
org/10.1155/2018/8792125
17. Sessler DI. Mild perioperative hypothermia. N Engl J Med 1997;336(24):1730-1737. https://doi.
org/10.1056/nejm199706123362407
18. Horosz B, Malec-Milewska M. Methods to prevent intraoperative hypothermia. Anaesthesiol
Intensive Ther 2014;46(2):96-100. https://doi.org/10.5603/AIT.2014.0019
19. Schultz J, Sims C, Bissonnette B. Methods for warming intravenous fluid in small volumes. Can J
Anaesth 1998;45(11):1110-1115. https://doi.org/10.1007/BF03012402
20. Lindhoff G, Mac G Palmer J. An assessment of the thermal safety of microwave warming of
crystalloid fluids. Anaesthesia 2000;55(3):251-254. https://doi.org/10.1046j.1365-2044.2000.01319.x
21. Shah S, Hariharan U, Bhargava A. A novel fluid-and blood-warming technique for the developing
world. Int J Health Allied Sci 2015;4(1):58-59. https://doi.org/10.4103/2278-344x.149278
22. Craig R, Peoples GE. A novel device developed, tested, and used for warming and maintaining
intravenous fluids in a forward surgical team during Operation Enduring Freedom. Mil Med
2006;171(6):500-503. https://doi.org/10.7205/milmed.171.6.500
Accepted 11 August 2022.
