Influence of flow rate, fluid temperature, and extension line on Hotline and S-line heating capability: an in vitro study

doi:10.21203/rs.3.rs-69397/v3

Download PDF

Research article

Influence of flow rate, fluid temperature, and extension line on Hotline and S-line heating capability: an in vitro study

https://doi.org/10.21203/rs.3.rs-69397/v3

This work is licensed under a CC BY 4.0 License

Journal Publication

published 04 Jan, 2021

Read the published version in BMC Anesthesiology →

You are reading this latest preprint version

Background A fluid warmer can prevent hypothermia during the perioperative period. This study evaluated the heating capabilities of Hotline and Barkey S-line under different flow rates and initial fluid temperatures, as well as after the extension line installation.

Methods We measured the temperature of a 0.9% sodium chloride solution at the fluid warmer outlet (T_Prox) and the extension line end (T_Distal) with three different initial fluid temperatures (room, warm, and cold) and two flow rates (250 ml/hr and 100 mL/hr).

Results At a 250 ml/hr flow rate, the T_Prox and T_Distalvalues were observed to be higher in Hotline than in S-line when using room-temperature or cold fluid. Administering of the warm fluid at the same flow rate significantly increased the T_Prox and T_Distal values in S-line more than the cold and room-temperature fluids. At flow rates of 100 ml/hr, T_Distal values were significantly lower than T_Proxvalues in both devices regardless of the initial fluid temperature.

Conclusions Hotline outperformed S-line for warming fluids at a high flow rate with cold or room-temperature fluids. Administering warm fluid in S-line prevented a decrease in the fluid temperature at a high flow rate. However, at a low flow rate, the fluid temperature significantly decreased in both devices after passing through an extension line.

Anesthesiology & Pain Medicine

Hypothermia

Barkey S-line

Flow rate

Extension line

Fluid temperature

Heating capability

Inadvertent perioperative hypothermia commonly occurs in patients undergoing surgery on account of a cold operating room, anesthetic agents that weaken thermoregulatory control, and administration of un-warmed fluid [1-8]. Even mild hypothermia, defined as a core body temperature ranging from 34–36°C, is associated with complications, such as an increased need for a blood transfusion, increased length of hospitalization, a higher incidence of postoperative myocardial infarction, and the risk of developing a surgical wound infection [7-10]. Preventing perioperative hypothermia is therefore critical.

It is recommended that physicians assess the risk factors associated with perioperative hypothermia to reduce hypothermia-related complications [3, 11]. After assessing these risk factors, physicians should employ interventions that are appropriately designed for the specific patient population and type of operation [1-3, 10]. The use of cold intravenous fluids is one of the most potentially modifiable risk factors [5, 12]. The National Institute for Health and Care Excellence (NICE) published clinical guidelines in 2008 that support the use of intravenous fluid warmers to prevent perioperative hypothermia [13]. Using such a device to warm intravenous fluids before administering it to the patient has been shown to prevent inadvertent hypothermia [4, 5, 12]. However, there are various conditions during fluid administration that must be considered, such as the fluid warmer type, flow rate, fluid temperature, and the IV line length, because the conditions may affect the actual temperature of the administered fluid. Therefore, it is critical to investigate the performance of a fluid warmer in different circumstances.

Numerous commercially available fluid warmers, such as Ranger, ThermoSens, Mega Acer Kit, FT800, and Hotline HL-90, have been investigated under different flow rates and room temperatures [12, 14-16]. However, previous studies mainly focused on changing the flow rate [12, 14, 15]. To determine the clinical effectiveness, various clinical factors such as the initial fluid temperature and the use of extension lines should also be considered.

The purpose of this study was to evaluate the fluid heating capabilities of Barkey S-line and Hotline HL-90 according to different flow rates, fluid temperatures, and the presence of an extension line.

This study was performed in the designated spot next to the nursing station in the post-anesthesia care unit (PACU). The PACU room temperature was maintained at 23°C, and the humidity level was maintained at approximately 20%. Normal saline fluid (0.9% sodium chloride solution, CJ, Seoul, Republic of Korea) was used for all the experiments in this study. The fluid temperature was measured using a two-channel thermometer (ThermaQ; ThermoWorks, London, UK). For Barkey S-line (Barkey GmbH & Co. KG, Leopoldshöhe, Germany), the operating temperature was maintained at 39.5°C throughout the experiments. A standard infusion set was inserted in the 1.5-m heating profile of S-line according to the manufacturer instructions. For Hotline HL-90 (Smiths Medical, Minneapolis, MN), the operating temperature was set to 40°C. The REF L-70 disposable tubing system (length 2.4 m, volume load 20 ml; Level 1 Technologies Inc., MA, USA) was installed according to the manufacturer instructions.

We evaluated the efficacy of the two fluid warmers under several conditions. Three different conditions were set for the initial fluid temperature: room temperature (22–23°C), cold (9–10°C), and warm (46–47°C.) The normal saline solutions were respectively maintained for 12 h in the operating room, in a refrigerator, and in a heating cabinet for each of the three different conditions. Two distinct flow rates were tested in this study: 100 ml/hr and 250 ml/hr. The roller clamp was fully open, and the flow rate was adjusted using a micro-flow regulator (I.V. Flow Control Line, Insung Medical Co., Seoul, Republic of Korea) attached to the infusion set at a flow rate of 100 or 250 ml/hr. The regulator tolerance ranged from −10% to 20% according to the manufacturer instructions. The height of the infusion bag was the same in all experiments (1.8 m.) One unit of a non-insulated extension set (DEHP-free Extension Plus, SBD Medical, Republic of Korea), which was 90 cm in length, was connected to the fluid warmer outlet. The fluid temperature was measured at two points, first at the fluid warmer outlet (T_Prox) and then at the end of the non-insulated extension line (T_Distal.) After starting each trial, the temperatures at the two positions (T_Prox and T_Distal) were recorded every minute until the end of the trial (Fig. 1).

T_Prox and T_Distal were carefully evaluated for the presence of a plateau in each trial. The plateau in each trial was defined as the time point at which the measured temperatures were the most stable without a noted fluctuation for 3 min. In each trial, only the T_Prox and T_Distal values from the middle time point of the plateau were used for the subsequent statistical analysis. Five trials were performed for an individual experimental condition to obtain five data points for T_Prox and T_Distal, respectively.

Statistical analysis was performed using SPSS v.20.0 for Windows (IBM SPSS, Inc., Armonk, NY) and R software version 3.4.4 (R Foundation for Statistical Computing, Austria). A data chart was produced using Microsoft Excel 2007. All fluid temperatures were reported as a median (interquartile [IQR] range). The Wilcoxon signed-rank test was used to test for a statistical difference between T_Prox and T_Distal values. The Hodges–Lehmann estimator was utilized to create the 95% confidence interval for the median difference between T_Prox and T_Distal. The Mann–Whitney U test was employed to compare T_Prox or T_Distal values under different flow rates using the same fluid warmer or between Hotline and S-line at the same flow rate. The bootstrap method was applied to form the 95% confidence interval for the analyses performed using the Mann–Whitney U test. Statistical significance was defined as a p-value < 0.05.

Room-temperature fluid

The room-temperature fluid was maintained at 21–23°C. T_Prox was higher in Hotline (38.7 [38.7-38.8]°C) than in S-line (28.2 [27.6-28.4]°C) based on the median difference of 10.5°C (95% CI 9.6–12.3) at the flow rate of 250 ml/hr. At the flow rate of 100 ml/hr, the T_Proxvalue was higher in Hotline (40.3 [40.1-40.4]°C) than S-line (38.7 [38.6-38.7]°C) according to the median difference of 1.6°C (95% CI 1.4–2.1. T_Distal measured higher in Hotline (37.6 [37.6-37.9]°C) than in S-line (27.8 [27.0-27.9]°C) based on the median difference of 9.8°C (95% CI 7.6–11.5) at the flow rate of 250 ml/hr. However, the T_Distal values were not significantly different between Hotline (25.6 [25.3-26.0]°C) and S-line (23.4 [23.4-23.5]°C) at 100 ml/hr (Fig. 2).

T_Proxin Hotline was slightly higher at 100 ml/hr than at 250 ml/hr based on the median difference of 1.6°C (95% CI 1.3–1.9). However, T_Prox in S-line was much higher at 100 ml/hr than at 250 ml/hr based on the median difference of 10.5°C (95% CI 9.6–12.3).

Furthermore, T_Distal in Hotline was higher at 250ml/hr than at 100ml/hr by 12.0°C (95% CI 9.8–14.2). T_Distal in S-line was higher at 250ml/hr than at 100ml/hr by 4.4°C (95% CI 2.6–5.3.) The T_Distal values were lower at 100 ml/hr than at 250ml/hr. In addition, T_Proxwas higher than T_Distal in both devices regardless of the flow rate. However, the differences were more substantial at 100 ml/hr. At a flow rate of 250 ml/hr, the median differences between T_Proxand T_Distal were 1.1°C (95% CI 0.9–2.2) in Hotline and 0.4°C (95% CI 0.3–0.6) in S-line. At 100 ml/hr, the median differences were 14.7°C (95% CI 14.3–16.7) in Hotline and 15.1°C (95% CI 13.9–16.0) in S-line.

Cold fluid

The initial temperature of the starting solution was maintained at 9–11°C in this group. T_Prox was higher in Hotline (37.2 [36.3-37.4]°C) than in S-line (18.2 [17.6-19.5]°C) by the median difference of 19.0°C (95% CI 16.7–20.2) at 250 ml/hr. However, the difference between Hotline (40.0 [39.8-40.0]°C) and S-line (38.6 [38.5-38.6]°C) was 1.4°C (95% CI 0.3–4.3) at 100 ml/hr. T_Distal at 250ml/hr was also higher in Hotline (36.2 [35.6-36.3]°C) than in S-line (19.1 [18.5-20.0]°C) based on the median difference of 17.1°C (95% CI 15.4–18.2). However, the T_Distal values from Hotline (23.5 [23.3-24.1]°C) and S-line (24.5 [24.1-24.7]°C) were not statistically different at 100 ml/hr (Fig. 2).

T_Prox measured in Hotline was slightly higher at 100ml/hr than at 250ml/hr by 2.8°C (95% CI 1.7–3.8). In S-line, the T_Proxvalue was significantly higher at 100 ml/hr than at 250ml/hr by 20.4°C (95% CI 17.5–21.4). For T_Distalin Hotline, the temperature at 250 ml/hr was higher than at 100 ml/hr, and the median difference was 12.7°C (95% CI 11.4–13.6). In contrast, T_Distal at 100 ml/hr was higher than at 250ml/hr in S-line, and the median difference was 5.4°C (95% CI 4.0–6.4). In both devices, the T_Distalvalues at 100 ml/hr were similar to the ambient temperature. The T_Proxwas higher than T_Distal in both devices regardless of the flow rate. The only exception was observed in S-line at 250 ml/hr; T_Prox is 18.2°C and T_Distalis 19.1°C. The difference between T_Prox and T_Distal was greater at 100 ml/hr than at 250 ml/hr. At 250 ml/hr, the median differences between T_Proxand T_Distal were 0.9°C (95% CI 0.6–1.2) in Hotline and 0.7°C (95% CI 0.5–0.9) in S-line. At 100 ml/hr, the median differences were 16.3°C (95% CI 15.8–16.6) in Hotline and 13.9°C (95% CI 11.2–14.6) in S-line. At 100 ml/hr, the extension line reversed most of the warming and substantially cooled the fluid as it traveled from T_Proxto T_Distal.

Warm fluid

The initial fluid temperature was maintained at 46–49°C in the warm temperature group. In this temperature group, the temperature of the initial fluid was higher than the operating temperatures of the fluid warmers themselves. The T_Proxvalue at 250 ml/hr in S-line (44.8 [44.7-45.4]°C) was higher than in Hotline (42.1 [42.1-42.1]°C) according to the median difference of 2.7°C (95% CI 2.4–3.8). At 100 ml/hr, the T_Proxvalue was higher in Hotline (40.5 [40.5-40.5]°C) than S-line (37.8 [37.8-37.9]°C) according to the median difference of 2.7°C (95% CI 1.6–3.7). T_Distalin S-line (43.9 [43.5-44.2]°C) at 250 ml/hr was higher than in Hotline (41.2 [41.0-41.2]°C) according to the median difference of 2.7°C (95% CI 2.2–3.2). At 100 ml/hr, no statistical difference existed between the T_Distalvalues in Hotline (27.6 [27.4-27.9]°C) and S-line (26.6 [26.5-26.8]°C) (Fig. 2).

In Hotline, the T_Prox value was higher at 250ml/hr than at 100 ml/hr, and the median difference was 1.6°C (95% CI 1.5–1.7). For the T_Distalvalue, the temperature measured at 250 ml/hr was again higher, and the median difference was 13.6°C (95% CI 13.1–14.9). Similarly, the T_Prox value in S-line was higher at 250 ml/hr than at 100 ml/hr; the median difference was 7.0°C (95% CI 5.9–8.1). For the T_Distal value, the measurement at 250 ml/hr was higher than at 100 ml/hr based on the median difference of 17.3°C (95% CI 16.7–18.6). T_Proxwas higher than T_Distal at the two flow rates in both Hotline and S-line. A flow rate of 100 ml/hr produced larger differences between T_Prox and T_Distal. At 250 ml/hr, the median differences between T_Proxand T_Distal were 1.0°C (95% CI 0.9–1.1) in Hotline and 1.2°C (95% CI 0.8–1.5) in S-line. At 100 ml/hr, the median differences were 12.9°C (95% CI 12.5–14.2) in Hotline and 11.3°C (95% CI 11.1–12.1) in S-line. The slower flow rate correlated with a more substantial difference in the median values.

This study showed that Hotline was superior to S-line for warming fluids when using room-temperature or cold saline at a high flow rate. However, at a low flow rate, the fluid temperature significantly decreased in both devices after passing through an extension line.

The difference in heating capacity between the two devices was likely due to the differences in their respective heating mechanisms, i.e., a coaxial circulating water bath (Hotline) versus a dry heating profile (S-line). The dry-heating system is expected to incur greater heat losses on account of the exposed portion of the extension line in ambient temperature. Thus, the Hotline coaxial warming system is apparently more effective than S-line in preventing hypothermia during rapid fluid administration. When administrating fluid rapidly, pre-warming fluid appears to be effective in maintaining fluid temperature warm especially in S-line. However, it would be important to check the warming temperature beforehand to avoid getting too hot fluid.

At 100 ml/hr, changing the initial temperature affected the T_Prox less in both Hotline and S-line. The slow flow rate would have provided sufficient time for both fluid warmers to affect the fluid temperatures. However, T_distal of the warm fluid seem to be slightly higher than those of the room-temperature or cold fluids at 100 ml/hr in both Hotline and S-line. This suggests that using pre-warmed fluid may have some role in maintaining fluid temperature even at the low flow rate when the extension line is used. Warm fluid could have influenced T_Distalthrough heating up the tube in which the fluid traveled down, however, the exact mechanism behind this finding remains to be further investigated.

There are several studies evaluating the performance of fluid warmers in literature [4, 12, 15, 16]. The previous studies produced detailed analyses on effect of changing one or two variables on the final fluid temperature among different fluid warmers. For example, the studies were descriptive of the effect of changing the flow rate or the initial fluid temperature. The current study has a strength that it analyzed how extension line, flow rate and initial fluid temperature interact to influence the final fluid temperature and presented comprehensive and clinically relevant performance profiles of Hotline and S-line.

It is clinically important to determine whether warmed fluids can be delivered to the patient without heat loss as they pass through a non-insulated extension line. Interestingly, in this study, a statistically significant change in fluid temperature was observed after the extension line in every experimental condition regardless of the fluid warmer type, initial fluid temperature, or flow rate. The change in fluid temperature was more pronounced at the low flow rate than at the high one. The fluid lost a significant amount of heat as it traveled an additional 90 cm at a rate of 100 ml/hr. This finding warrants the utilization of additional measures for hypothermia prevention when using an extension at the low flow rate, especially when administering fluids to patients with a high risk of developing hypothermia such as neonatal and older patients [17]. Furthermore, it is essential to minimize heat loss as the fluid travels down the extension line, which can be achieved by an extension line innovation or by applying supplemental measures against hypothermia.

Several limitations of this study should be noted. In an actual clinical setting, the fluid administration rate, initial fluid temperature, and extension line length may differ from the conditions used in this study. For example, during rapid fluid resuscitation, the infusion rate can be as high as 60 to 80 mL/kg per hour [18]. Also, in this study, the fluid temperature in the warm temperature group was greater than 45°C, which can be problematic because the proteins in red blood cells can degenerate at a temperature higher than 45°C [19]. Moreover, precautionary measures should be taken against preparing fluids that are excessively hot for clinical practice. Finally, extension lines longer than 90 cm can be employed in certain clinical scenarios. Longer extension lines could affect the fluid temperature more markedly than the line length employed in this study.

In summary, Hotline outperformed S-line for warming fluids at a high flow rate with cold or room-temperature fluids. Administering warm fluid in S-line prevented a decrease in the fluid temperature at a high flow rate. Finally, using an extension line can reduce the final fluid temperature delivered to the patient at a low flow rate in both devices.

T_Prox: temperature at the fluid warmer point

T_Distal: temperature at the extension line point

PACU: post-anesthesia care unit

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request

Competing interests

The authors declare that they have no competing interests

Funding

Support was provided solely from departmental resources of the Department of Anesthesiology and Pain Medicine, Seoul National University Hospital.

Authors' contributions

HK and TKK collected and analyzed the study data. SY and J-TK designed the study and interpreted the study data. HK and TKK was a major contributor in writing the manuscript. All authors read and approved the final manuscript.

Acknowledgements

Not applicable

Diaz M, Becker DE: Thermoregulation: physiological and clinical considerations during sedation and general anesthesia. Anesth Prog 2010, 57(1):25-32; quiz 33-24.
Matika R, Ibrahim M, Patwardhan A: The importance of body temperature: An anesthesiologist's perspective. Temperature (Austin) 2017, 4(1):9-12.
Sessler DI: Temperature monitoring and perioperative thermoregulation. Anesthesiology 2008, 109(2):318-338.
Tansey EA, Johnson CD: Recent advances in thermoregulation. Adv Physiol Educ 2015, 39(3):139-148.
Wax DB, Tyson W, Smith N: Avoidance of Inadvertent Hypothermia With a Fluid-Warming/Infusion System. J Cardiothorac Vasc Anesth 2018, 32(5):e4-e5.
Moola S, Lockwood C: Effectiveness of strategies for the management and/or prevention of hypothermia within the adult perioperative environment. Int J Evid Based Healthc 2011, 9(4):337-345.
Billeter AT, Hohmann SF, Druen D, Cannon R, Polk HC, Jr.: Unintentional perioperative hypothermia is associated with severe complications and high mortality in elective operations. Surgery 2014, 156(5):1245-1252.
Flores-Maldonado A, Medina-Escobedo CE, Rios-Rodriguez HM, Fernandez-Dominguez R: Mild perioperative hypothermia and the risk of wound infection. Arch Med Res 2001, 32(3):227-231.
Mahoney CB, Odom J: Maintaining intraoperative normothermia: a meta-analysis of outcomes with costs. AANA J 1999, 67(2):155-163.
Tsuei BJ, Kearney PA: Hypothermia in the trauma patient. Injury 2004, 35(1):7-15.
Moran DS, Mendal L: Core temperature measurement: methods and current insights. Sports Med 2002, 32(14):879-885.
Zoremba N, Bruells C, Rossaint R, Breuer T: Heating capabilities of small fluid warming systems. BMC Anesthesiol 2018, 18(1):98.
National Institute for Health and Care Excellence (2008) Hypothermia: prevention and management in adults having surgery. https://www.nice.org.uk/guidance/cg65. Accessed 23 March 2020.
Xu X, Lian C, Liu Y, Ding H, Lu Y, ShangGuan W: Warming efficacy of Ranger and FT2800 fluid warmer under different room temperatures and flow rates. J Clin Monit Comput 2020, 34(5):1105-1110..
Thongsukh V, Kositratana C, Jandonpai A: Effect of Fluid Flow Rate on Efficacy of Fluid Warmer: An In Vitro Experimental Study. Anesthesiol Res and Pract 2018, 2018:4.
Kim DJ, Kim SH, So KY, An TH: Mega Acer Kit(R) is more effective for warming the intravenous fluid than Ranger and ThermoSens(R) at 440 ml/h of infusion rate: an experimental performance study. Korean J Anesthesiol 2017, 70(4):456-461.
Macario A, Dexter F: What are the most important risk factors for a patient's developing intraoperative hypothermia? Anesth Analg 2002, 94(1):215-220, table of contents.
Santry HP, Alam HB: Fluid resuscitation: past, present, and the future. Shock 2010, 33(3):229-241.
Gershfeld NL, Murayama M: Thermal instability of red blood cell membrane bilayers: temperature dependence of hemolysis. J Membr Biol 1988, 101(1):67-72.

Download PDF

Journal Publication

published 04 Jan, 2021

Read the published version in BMC Anesthesiology →

Editorial decision: Accept
21 Dec, 2020
Editor assigned by journal
07 Dec, 2020
Submission checks completed at journal
07 Dec, 2020
Editor invited by journal
07 Dec, 2020

You are reading this latest preprint version

Influence of flow rate, fluid temperature, and extension line on Hotline and S-line heating capability: an in vitro study

Status:

Journal Publication

Version 3

Abstract

Figures

Background

Methods

Results

Discussion

Conclusions

List Of Abbreviations

Declarations

References

Status:

Journal Publication

Version 3