An Experimental Study of Warming Intravenous Fluid in a Cold Environment☆

Warming of blood and intravenous fluids using low-power infra-red light-emitting diodes

Non-contact warming of blood and intravenous (IV) fluids with temperature drop compensation is an unmet clinical need till now, for management of hypothermia in patients with urgent requirement of blood. Currently available technologies provide wet warming or dry warming with direct contact using hot water or with a hot plate, respectively. These conventional technologies need disposable cartridges to be used in conjunction with the warmer. The warmed fluids lose their temperature when passing through long IV lines and fails in its purpose at low flow rates. In this paper, a distributed non-contact warming method is introduced using infra-red radiations. The method incorporates a bag warming unit and an inline cartridge unit. Bag warming unit provides uniform distribution of infra-red thermal energy liberated from low cost infra-red light emitting diodes (IR LEDs) in horizontal and vertical planes of the fluid carrying bag. An inline cartridge, through which the IV line passes, reduces the drop in temperature just before the transfusion site using a cluster of IR LEDs. As per the In Vitro tests are carried out in to establish the safety and efficacy, the bag warming unit steadily rises the temperature to attain the cut off value with a temperature rise coefficient of 0.7 °C/min and the inline cartridge warms the fluid within 10 min at a thermal transfer rate of more than 1.5 °C/min. The fluid temperature is uniformly distributed within a narrow range of 36-38 °C. When the inline warmer is powered on, the drop-in temperature is reduced to zero for flow up to 5 ml/min. For flow rates more than 8 ml/min, the temperature drop is reduced more than half. For massive transfusion range, the temperature of the fluid remains within 38.5 ± 1.2 °C for flow rates in the range of 100-1500 ml/min.

Heating Intravenous Fluid Tubing in an Experimental Setting for Prehospital Hypothermia

OBJECTIVE

Hypothermia secondary to environmental exposure is a serious condition. Active external warming measures to treat it may prove challenging in the prehospital setting. We conducted an experimental study to measure the ability of commercially available heating elements to warm intravenous (IV) fluids during infusion.

METHODS

250-milliliter bags of dextrose 10% solution were suspended inside a refrigerator. IV tubing was coiled, and the tubing output was placed inside a thermally insulated cup. The tubing was heated directly with a hand warmer, a meals ready-to-eat heater, or a heating blanket. Fluids were run through the IV line. The temperature of the fluid at the tubing output was measured. The initial and final infusion temperatures for the methods were compared.

RESULTS

The use of hand warmers, meals ready-to-eat heaters, and heating blankets to warm IV tubing did increase the temperature of the fluids but was ineffective at achieving the desired mean infusion temperature of 35°C to 42°C.

CONCLUSION

Although the mean temperature increase did not meet the established experimental threshold, further research is needed to determine whether the fluid warming effect of these commercial heating elements used in the prehospital environment is significant enough to limit heat loss while repleting the dextrose of a hypothermic, hypoglycemic patient.

Warming blood prior to transfusion using latent heat

OBJECTIVE

Major trauma is associated with blood loss and hypothermia. It is common to replace lost fluid with red cells stored at 2-6°C, and/or colloid/crystalloid fluid stored at ambient temperature, thus increasing hypothermia risk. At trauma and medical retrieval sites, mains electricity powered fluid warmers cannot be generally used. Latent heat provides an alternate practical method of portable temperature-controlled intravenous fluid warming. This work investigates the safety and efficacy of a fluid warmer powered by latent heat.

METHODS

Twenty-five haematology patients received red cell transfusions, one through a fluid warmer, using latent heat from a super-cooled liquid and one without warming. Temperature of donor red cell units was measured after passing through fluid warmers. Blood samples were collected from red cell units and patients, prior and after each transfusion. These were tested for haemolysis markers (plasma haemoglobin, potassium, lactate dehydrogenase, bilirubin) and for traces of super-cooled liquid. Patient physiological parameters (oxygen saturation, pulse, temperature, blood pressure, respiration) were monitored during each transfusion.

RESULTS

Patient's physiological signs remained stable and no transfusion reactions were observed during warm transfusions. Latent heat fluid warmers increased the temperature of red cell units to approximately 35°C. There were no significant differences in haemolysis markers following warmed and unwarmed transfusions, and no contamination of red cell units by super-cooled liquid was detected.

CONCLUSION

The latent heat fluid warmer was shown to safely warm transfused blood in a controlled clinical setting.

The prehospital management of hypothermia - An up-to-date overview

BACKGROUND

Accidental hypothermia concerns a body core temperature of less than 35°C without a primary defect in the thermoregulatory system. It is a serious threat to prehospital patients and especially injured patients, since it can induce a vicious cycle of the synergistic effects of hypothermia, acidosis and coagulopathy; referred to as the trauma triad of death. To prevent or manage deterioration of a cold patient, treatment of hypothermia should ideally begin prehospital. Little effort has been made to integrate existent literature about prehospital temperature management. The aim of this study is to provide an up-to-date systematic overview of the currently available treatment modalities and their effectiveness for prehospital hypothermia management.

DATA SOURCES

Databases PubMed, EMbase and MEDLINE were searched using the terms: "hypothermia", "accidental hypothermia", "Emergency Medical Services" and "prehospital". Articles with publications dates up to October 2017 were included and selected by the authors based on relevance.

RESULTS

The literature search produced 903 articles, out of which 51 focused on passive insulation and/or active heating. The most effective insulation systems combined insulation with a vapor barrier. Active external rewarming interventions include chemical, electrical and charcoal-burning heat packs; chemical or electrical heated blankets; and forced air warming. Mildly hypothermic patients, with significant endogenous heat production from shivering, will likely be able to rewarm themselves with only insulation and a vapor barrier, although active warming will still provide comfort and an energy-saving benefit. For colder, non-shivering patients, the addition of active warming is indicated as a non-shivering patient will not rewarm spontaneously. All intravenous fluids must be reliably warmed before infusion.

CONCLUSION

Although it is now accepted that prehospital warming is safe and advantageous, especially for a non-shivering hypothermic patient, this review reveals that no insulation/heating combinations stand significantly above all the others. However, modern designs of hypothermia wraps have shown promise and battery-powered inline fluid warmers are practical devices to warm intravenous fluids prior to infusion. Future research in this field is necessary to assess the effectiveness expressed in patient outcomes.

The effect of infusion rate and catheter length on the temperature of warming fluid

Background

We used warming fluid for maintenance of body temperature in operating room or intensive care unit. This study was aimed to investigate the effect of infusion rate and catheter length on the temperature of warming fluid.

Methods

Normal saline was used for testing infusion and temperature of infusion was maintained by a warmer as 40℃. The temperatures of solution in infusion line were measured at 0, 25, 50, 75, and 100 cm apart from warmer at six different flow rates (100, 200, 300, 700, 1,400, and 2,100 ml/h). We also measured the temperature changes at room temperature (RT) and 5℃, 10℃, and 15℃ above RT.

Results

The time to maintain solution temperature as 40℃ was 165, 122, 37, 37, 21, and 19 s at flow rate 100, 200, 300, 700, 1,400, and 2,100 ml/h. The peak temperature was 43.58 ± 0.58, 44.43 ± 1.18, 44.37 ± 0.70, 43.79 ± 0.61, 42.82 ± 0.97, and 42.11 ± 0.92℃ according to increasing flow rate. The temperature at 100 cm apart from warmer was 23.96 ± 1.53, 25.46 ± 2.76, 29.32 ± 3.47, 31.40 ± 5.38, 31.39 ± 6.75, and 38.14 ± 0.96℃ according to increasing flow rate.

Conclusions

These results suggested that the decreasing rate of temperature was related inversely to the flow rate and directly to the catheter length. There may be needed a rapid infusion pump with adequate heating system at a high flow rate and to locate the warmer close to patient for reserving a heating effect.