Research ArticleEffect of Fluid Flow Rate on Efficacy of FluidWarmer: An In VitroExperimental Study

Vorasruang Thongsukh , Chanida Kositratana, and Aree Jandonpai

Department of Anesthesiology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok 10400, "ailand

Correspondence should be addressed to Vorasruang �ongsukh; ravts@yahoo.com

Received 1 November 2017; Accepted 30 May 2018; Published 8 July 2018

Academic Editor: Yukio Hayashi

Copyright © 2018Vorasruang�ongsukh et al.�is is an open access article distributed under the Creative CommonsAttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Introduction. In patients who require a massive intraoperative transfusion, cold fluid or blood transfusion can cause hypothermiaand potential adverse effects. One method by which to prevent hypothermia in these patients is to warm the intravenous fluidbefore infusion. �e aim of this study was to determine the effect of the fluid flow rate on the efficacy of a fluid warmer.Methods.�e room air temperature was controlled at 24°C. Normal saline at room temperature was used for the experiment. �e fluid wasconnected to an infusion pump and covered with a heater line, which constantly maintained the temperature at 42°C. �e fluidtemperature after warming was measured by an insulated thermistor at different fluid flow rates (100, 300, 600, 900, and1200mL/h) and compared with the fluid temperature before warming. Effective warming was defined as an outlet fluid tem-perature of >32°C. Results. �e room temperature was 23.6°C± 0.9°C. �e fluid temperature before warming was 24.95°C± 0.5°C.�e outlet temperature was significantly higher after warming at all flow rates (p< 0.001). �e increases in temperature were10.9°C± 0.1°C, 11.5°C± 0.1°C, 10.2°C± 0.1°C, 10.1°C± 0.7°C, and 8.4°C± 0.2°C at flow rates of 100, 300, 600, 900, and 1200mL/h,respectively. �e changes in temperature among all different flow rates were statistically significant (p< 0.001). �e outlettemperature was >32°C at all flow rates. Conclusions. �e efficacy of fluid warming was inversely associated with the increase inflow rate. �e outlet temperature was <42°C at fluid flow rates of 100 to 1200mL/h. However, all outlet temperatures reached>32°C, indicating effective maintenance of the core body temperature by infusion of warm fluid.

1. Introduction

�e normal core body temperature in humans is maintainedby the hypothalamus and typically ranges from 36.5°C to37.5°C. �e interthreshold range is usually only 0.2°C to0.4°C. Both general and regional anesthesia inhibit centralthermoregulation and increase the interthreshold range to2°C to 4°C, leading to hypothermia [1, 2]. Hypothermia isdefined as a decrease in the core body temperature to <36°C[1]. �e combination of hypothermia, acidosis, and coa-gulopathy has been identified as the “lethal triad” in traumapatients because it increases the risk of morbidity [3].Intraoperative hypothermia is associated with postoperativemyocardial ischemia, impaired coagulation, an increasedrisk of wound infection, and atrioventricular arrhythmia[3, 4]. Massive cold fluid or blood infusion is one cause ofhypothermia. One liter of fluid at room temperature will

reduce the mean body temperature by approximately 0.25°C[5]. Induction of mild hypothermia without extracorporealcirculation, a 30-min infusion of 2 L of normal saline at 4°C,decreases the core body temperature by 2.5°C [6]. �etheoretical impact of fluid infusion on the body temperaturecan be calculated as follows:

change in mean body temperature

�thermal stress of infused fluids

(weight × sp heat),

(1)

where thermal stress� difference between core body tem-perature and temperature of infused fluid (°C)× specific heatof infused fluid× volume of infused fluid (L/h), weight�

weight of patient (kg), and sp heat� specific heat of patient(0.83 kcal/L/°C). Sp heat of infused fluid: blood, 0.87 kcal/L/°C;saline, 1 kcal/L/°C [7, 8].

HindawiAnesthesiology Research and PracticeVolume 2018, Article ID 8792125, 4 pageshttps://doi.org/10.1155/2018/8792125

According to this equation, the temperature of the in-fused �uid should not be <36°C in a normothermic patientto prevent a decrease in the mean body temperature duringanesthesia. Jung et al. [9] developed a �uid warming deviceand suggested that e�ective warming was indicated bya warmed �uid temperature of >32°C. According to theabove equation, when infusing �uid at 32°C at a �ow rate of2 L/h to a normothermic patient whose core body tem-perature is 36°C and body weight is 50 kg, the mean bodytemperature will decrease by only 0.2°C.

Warm intravenous infusion is a direct, active method ofwarming the core body temperature and is suitable forpatients who require massive transfusion [10]. �e tem-perature of the warmed intravenous �uid should not exceed40°C to 42°C to avoid denaturation of plasma proteins [11].�e aim of this experimental study was to determine thee�ect of the infusion rate on the temperature of warmed�uid. Very high �ow rate may cause ine�ective �uidwarming due to short transit time. �e hypothesis was thatincreasing the infusion rate may decrease the e�cacy ofwarming by the heat line. �e �uid temperature beforewarming was the control variable, the di�erent infusion rateswere independent variables, and the di�erence in the �uidtemperature after warming was the dependent variable.

2. Methods

�is experimental study was performed in the general op-erating room at Ramathibodi Hospital. �e ambient tem-perature was controlled at 24°C via a room air conditioningsystem which was close to the operating condition in ourinstitution. Normal saline was used in this study because it iscommonly used as an isotonic solution for �uid replacementin operating rooms. �e �uid was maintained at the tem-perature of the operating room, then connected to the in-fusion pump (Terofusion; Terumo Europe, Leuven,Belgium), which was adjusted to �ow rates of 100, 300, 600,900, and 1200mL/h, and these ranges of �uid �ow rate were

commonly infused in major abdominal operation in localsetting. A 1.5m heater line (Barkey autocontrol 3XPT;Barkey, Leopoldshohe, Germany) covered the infusion line.�e heater line was set at 42°C. After rinsing the warmed�uid for 5min at each �ow rate to maintain a constanttemperature after warming, we recorded the room tem-perature by the electronic thermometer and the temperatureof the �uid before and after passing through the heater line.Each �ow rate was studied �ve times.�e outlet temperaturewas measured at the immediate end of the heater line with aninsulated digital thermistor (Life Scope i; Nihon Kohden,Tokyo, Japan) sealed in a 4mL test tube. Before the study, thereliability and accuracy of thermistor were checked by re-peatedly measuring the neonatal incubator temperature.E�ective warming was de�ned as an outlet temperature of>32°C [9]. �e experiment and data collection were com-pletely done in one day. �e schematic diagram is depictedin Figure 1.

Statistical analyses were performed using SPSS v.20.0 forWindows (IBM SPSS Inc., Armonk, NY), and a data chartwas produced using Microsoft Excel 2007. All �uid tem-peratures are reported as mean± standard deviation. �enormality assumption for continuous variables was assessedby the Shapiro–Wilk test. A paired t-test or Wilcoxon’s testwas used to assess the statistical signi�cance of the changesin temperature before and after warming, and an in-dependent t-test or the Mann–Whitney U test was used toassess the changes in temperature between each �ow rateand the next higher one. All statistical analyses were two-sided with a signi�cance level at p value< 0.05.

3. Results

�e room temperature during the experiment was 23.6°C±0.9°C. �e temperature of the �uid before warming was24.9°C± 0.5°C. �e outlet temperature signi�cantly in-creased after warming at all infusion rates (p< 0.001). �emaximum outlet temperature was 36.9°C at a �ow rate of

Room temperaturecontrol 24°C

Normalsaline

�ermistor 2

Temperaturea�er warming

�ermistor 1

Temperature before warming

Infusion pump Heater line 1.5 metersSet point 42°C

100 mL/h

Figure 1: Schematic diagram of the experimental set-up.

2 Anesthesiology Research and Practice

300mL/h.�e �uid temperature increased by 10.9°C± 0.1°C,11.5°C± 0.1°C, 10.2°C± 0.1°C, 10.1°C± 0.7°C, and 8.4°C±0.2°C at �ow rates of 100, 300, 600, 900, and 1200mL/h,respectively (Table 1 and Figure 2). For all �ow rates except300mL/h, the outlet temperature did not reach the idealtemperature of 36°C; however, all of the outlet temperatureswere >32°C. �e change in temperature was signi�cantlydi�erent among all �ow rates (p< 0.001) except the changebetween 600 and 900mL/h. A linear trend was found for theentire set of �ow rates (as shown in Figure 2), suggesting thatthe e�ectiveness of warming tended to be inversely corre-lated with the increase in �ow rate.

4. Discussion

One of themain factors that a�ected the warming capacity inthis experimental study was the ambient temperature. �eoperative room air conditioning system caused an ambienttemperature �uctuation of 23.6°C± 0.9°C, leading to varia-tion in the �uid temperature before warming. However, therecommended operating room temperature that can preventperioperative hypothermia ranges from 20°C to 24°C, whichwas within our range [12, 13]. �e initial temperature of the�uid before warming is 24.9°C± 0.5°C, higher than the roomtemperature may be from the di�erent location of mea-surement and not well distributed of air�ow. �e heater linewas constantly maintained at 42°C, but the outlet temper-ature at each �ow rate was <42°C. Only the outlet

temperature at a �ow rate of 300mL/h was >36°C. Never-theless, the outlet temperature at all �ow rates was >32°C,indicating e�ective warming. With respect to the warminge�cacy of other devices, the Hotline (SmithsMedical, St. Paul,MN) can warm the �uid to 34.8°C at a �ow rate of 80mL/h,and the Astotherm (Armstrong Medical, Coleraine, NorthernIreland) can warm the �uid to 30°C at the same �ow rate [7].In clinical practice, infusion of warmed �uid more e�ectivelymaintains the patient’s core body temperature than doesinfusion of room temperature �uid [14].

In the present study, the e�cacy of �uid warming de-creased as the �ow rate increased.�e change in temperaturewas dependent upon the duration of time that the venousline was in contact with the heater line for heat exchange.�erefore, the �uid can be completely heated at lower �owrates. However, we found that the e�cacy of warming waslower at a �ow rate of 100 than 300mL/h; this may have beendue to the higher rate of heat dispersal after warming to theatmosphere in the temperature measurement technique.

Based on our study, �uid warming with the heater line(Barkey autocontrol 3XPT®, Germany) can e�ectively in-crease infused �uid temperature for replacement therapy inuneventful abdominal operation. However, further researchis required to see if more rapid �ow rate can still generateoptimal temperature or not. It is also worthwhile to comparethe performance of some traditional �uid warming devicesbecause some devices can e�ectively warm the �uid at higher�ow rate than in our study.

5. Conclusion

Intravenous �uid warming is an alternative warmingmethod by which to prevent hypothermia in patients whorequired a massive �uid transfusion. In the present study,the e�ectiveness of warming was inversely associated withthe increase in the �ow rate. Although the outlet temper-ature was <42°C as the set point of the heater line, all tested�ow rates (100–1,200mL/h) were able to increase the outlettemperature to >32°C, which was considered to be e�ective�uid warming �uid.

Abbreviations

Sp heat: Speci�c heat.

Data Availability

�e datasets generated and/or analyzed during the currentstudy are available from the corresponding author. �e

Table 1: Fluid temperature before and after warming.

Infusion rate (mL/h) Fluid temperaturebefore warming (°C)

Fluid temperatureafter warming (°C)

Di�erence in �uidtemperature (°C) p value

100 25.0± 0.1 35.9± 0.1 10.9± 0.1 <0.001∗300 24.8± 0.1 36.3± 0.2 11.5± 0.1 <0.001∗600 25.0± 0.2 35.2± 0.1 10.2± 0.1 <0.001∗900 24.1± 0.7 34.2± 0.0 10.1± 0.7 <0.001∗1,200 24.5± 0.2 33.0± 0.2 8.4± 0.2 <0.001∗

Data are presented as mean± standard deviation. ∗Statistically signi�cant at p< 0.001.

11.5 ± 0.1

13

12

11

10

100 300 600Infusion rate (mL/h)

Incr

ease

in fl

uid

tem

pera

ture

(°C)

900 1,200

9

8

7

10.9 ± 0.1 10.2 ± 0.110.1 ± 0.7

8.4 ± 0.2

Figure 2: Increasing temperatures after warming at di�erent in-fusion rates.

Anesthesiology Research and Practice 3

authors will personally share the data with academic in-stitutions upon a reasonable request.

Additional Points

Limitations. �e main limitation of the present study is thatby its inherent nature, it cannot be extrapolated to theclinical setting. �e effectiveness of the warming device andflow rate cannot represent the actual core body temperatureafter infusion of warmed fluid. However, the findings of thisstudy will serve as a baseline for future clinical studies. Leeet al. [15] suggested that both the flow rate and length of thecatheter from the warmer outlet to the patient influence theeffectiveness of the warmer. A longer catheter may be as-sociated with more heat loss to the ambient; thus, the outletfluid should be located as close as possible to the patient.

Disclosure

�e preliminary data of this study have been presented aspresentation abstract at �ai Journal of Anesthesiology Vol.40, 2014, p. 139-140 and was submitted as an abstract roundposter presentation at the European Society of Anesthesi-ology, 28–30 May 2016, London, United Kingdom.

Conflicts of Interest

�e authors declare that there are no conflicts of interestregarding the publication of this article.

Authors’ Contributions

Vorasruang �ongsukh conceived and designed the studyand critically revised the final draft for important intellectualcontent. Chanida Kositratana and Aree Jandonpai per-formed the experiment. Vorasruang �ongsukh and Cha-nida Kositratana performed the statistical analysis anddrafted the manuscript. All authors read and approved thefinal version of the manuscript.

Acknowledgments

�is study was supported by the general operating room staffof Ramathibodi Hospital. �e authors thank RojnarinKomonhirun for assisting with the statistical analysis and thepreparation and submission of our manuscript.

References

[1] D. I. Sessler, “Temperature monitoring and perioperativethermoregulation,” Anesthesiology, vol. 109, no. 2, pp. 318–338, 2008.

[2] J. F. Butterworth, D. C. Mackey, and J. D. Wasnick, “�er-moregulation hypothermia, & malignant hyperthermia,” inMorgan and Mikhail’s Clinical Anesthesiology, J. Butterworth,D. C. Mackey, and J. Wasnick, Eds., pp. 1183–1191, McGraw-Hill Medical, New York, NY, USA, 5th edition, 2013.

[3] E. E. Moore, “�omas G. Orr Memorial Lecture. Stagedlaparotomy for the hypothermia, acidosis, and coagulopathysyndrome,” American Journal of Surgery, vol. 172, no. 5,pp. 405–410, 1996.

[4] B. J. Tsuei and P. A. Kearney, “Hypothermia in the traumapatient,” Injury, vol. 35, no. 1, pp. 7–15, 2004.

[5] D. I. Sessler, “Temperature monitoring,” in Miller’s Anes-thesia, R. D. Miller, Ed., pp. 1571–1597, Elsevier ChurchillLivingstone, Philadelphia, PA, USA, 6th edition, 2005.

[6] A. Rajek, R. Greif, D. I. Sessler, J. Baumgardner, S. Laciny, andH. Bastanmehr, “Core cooling by central venous infusion ofice-cold (4 degrees C and 20 degrees C) fluid: isolation of coreand peripheral thermal compartments,” Anesthesiology,vol. 93, no. 3, pp. 629–637, 2000.

[7] C. E. Smith and W. Karl, “Principles of fluid and bloodwarming in trauma,” ITACCS, vol. 8, no. 1, pp. 71–79, 2008.

[8] P. E. Horowitz, M. A. Delagarza, J. J. Pulaski, and R. A. Smith,“Flow rates and warming efficacy with Hotline and Rangerblood/fluid warmers,” Anesthesia and Analgesia, vol. 99, no. 3,pp. 788–792, 2004.

[9] S. W. Jung, T. H. Han, J. Y. Lee et al., “Performance char-acteristics of high efficiency fluid and blood warmer usingprint circuit board heater at various flow rates,” KoreanJournal of Anesthesiology, vol. 51, no. 5, pp. 598–605, 2006.

[10] S. Kumar, P. F. Wong, A. C. Melling, and D. J. Leaper, “Effectsof perioperative hypothermia and warming in surgicalpractice,” International Wound Journal, vol. 2, no. 3,pp. 193–204, 2005.

[11] R. Vazquez and D. F. Larson, “Plasma protein denaturationwith graded heat exposure,” Perfusion, vol. 28, no. 6,pp. 557–559, 2013.

[12] AORN Recommended Practices Committee, “Recommendedpractices for the prevention of unplanned perioperative hy-pothermia,” AORN Journal, vol. 85, no. 5, pp. 972–974, 2007.

[13] Pennsylvania Patient Safety Advisory Group, “Prevention ofinadvertent perioperative hypothermia,” Patient Safety Au-thority, vol. 5, no. 2, pp. 44–52, 2008.

[14] C. E. Smith, E. Geddes, S. Swede et al., “Warming intravenousfluids reduces perioperative hypothermia in women un-dergoing ambulatory gynecology surgery,” Anesthesia andAnalgesia, vol. 87, no. 1, pp. 37–41, 1998.

[15] S. H. Lee, H. K. Kim, S. C. Park, E. S. Kim, T. K. Kim, andC. S. Kim, “�e effect of infusion rate and catheter length onthe temperature of warming fluid,” Korean Journal of Anes-thesiology, vol. 58, no. 1, pp. 31–37, 2010.

4 Anesthesiology Research and Practice

Stem Cells International

Hindawiwww.hindawi.com Volume 2018

Hindawiwww.hindawi.com Volume 2018

MEDIATORSINFLAMMATION

of

EndocrinologyInternational Journal of

Hindawiwww.hindawi.com Volume 2018

Hindawiwww.hindawi.com Volume 2018

Disease Markers

Hindawiwww.hindawi.com Volume 2018

BioMed Research International

OncologyJournal of

Hindawiwww.hindawi.com Volume 2013

Hindawiwww.hindawi.com Volume 2018

Oxidative Medicine and Cellular Longevity

Hindawiwww.hindawi.com Volume 2018

PPAR Research

Hindawi Publishing Corporation http://www.hindawi.com Volume 2013Hindawiwww.hindawi.com

The Scientific World Journal

Volume 2018

Immunology ResearchHindawiwww.hindawi.com Volume 2018

Journal of

ObesityJournal of

Hindawiwww.hindawi.com Volume 2018

Hindawiwww.hindawi.com Volume 2018

Computational and Mathematical Methods in Medicine

Hindawiwww.hindawi.com Volume 2018

Behavioural Neurology

OphthalmologyJournal of

Hindawiwww.hindawi.com Volume 2018

Diabetes ResearchJournal of

Hindawiwww.hindawi.com Volume 2018

Hindawiwww.hindawi.com Volume 2018

Research and TreatmentAIDS

Hindawiwww.hindawi.com Volume 2018

Gastroenterology Research and Practice

Hindawiwww.hindawi.com Volume 2018

Parkinson’s Disease

Evidence-Based Complementary andAlternative Medicine

Volume 2018Hindawiwww.hindawi.com

Submit your manuscripts atwww.hindawi.com