Dosing Heat: Expected Core Temperature Change with Warmed or Cooled Intravenous Fluids

Abstract

Emergent modification of a patient's body temperature is crucial in certain disease or injury states. Advanced targeted temperature management techniques such as central venous catheter devices are not universally available, however, virtually all medical centers have access to intravenous fluids. This study approximates the change in body temperature for a given volume of room temperature, chilled, or heated isotonic crystalloid bolus. Using thermodynamic principles, a mathematical model was created to approximate change in body core temperature in response to a given volume and temperature of intravenous fluid. The model assumes rapid fluid infusion and the previously published specific heat capacity of the human body of 3.47 J/kg $°C. Values were calculated under conditions of varying body temperatures from profound hypothermia to hyperthermia (18°C-45°C). Various crystalloid temperatures representing iced, room temperature, and warmed (4°C, 20°C, 42°C) were used in the calculations. Each 30 mL/kg dose of 20°C crystalloid is expected to cool a hyperthermic (38°C-45°C) patient by 0.6°C-0.9°C. Each 30 mL/kg dose of 4°C crystalloid is expected to cool a hyperthermic (38°C-45°C) patient by 1.2°C-1.4°C. Each dose of 42°C crystalloid is expected to warm a hypothermic patient by 0.2°C-0.8°C. Using the results in this study, clinicians may roughly estimate the effect of temperature management with varying doses of intravenous fluids and thus assess the benefits of this technique. Risk should be evaluated based on inevitable coadministered volume and electrolytes. Individuals with volume-sensitive conditions such as heart, liver, or kidney failure deserve particular attention. Based on a mathematical model, typical expected core temperature change is about 0.2°C-1.4°C per 30 mL/kg crystalloid bolus, depending on patient and fluid temperature.

Verification of an intravenous fluid warmer: A prospective, two-center observational trial

“…Barthel and Blumenberg separately designed models that predict that the average adult core temperature is likely to decrease by approximately 0.3°C-0.4°C with every liter of room temperature IV fluid, whereas the rise in core temperature using the same volume of warmed infusate is calculated at 0.1°C. 33,34 Our results corroborated these predicted outcomes. Not only did the patients in this trial demonstrate a less significant decrease in core temperature after induction of anesthesia and throughout surgery compared with previously published data of non-warmed IV fluids, 14 but the degree to which temperature dropped in these patients mirrors data previously described with other active fluid warming devices 35 and in the proposed mathematical models.…”

Verification of an Intravenous Fluid Warmer: A Prospective, Two-Center Observational Trial

“…Barthel and Blumenberg separately designed models that predict that the average adult core temperature is likely to decrease by approximately 0.3-0.4°C with every liter of room temperature IV uid, whereas the rise in core temperature using the same volume of warmed infusate is calculated at 0.1°C. [30,31] Our results corroborated these predicted outcomes. Not only did the patients in this study demonstrate a less signi cant decrease in core temperature after induction of anesthesia and throughout surgery compared with historical data of non-warmed IV uids, but the degree to which temperature dropped in these patients mirrors data previously described with other active uid warming devices and in the proposed mathematical models.…”

Accidental Hypothermia: 2021 Update

“…When intravenous or intraosseous fluids are required, they should be warmed to 38–42 °C and should be given in boluses guided by vital signs [ 3 , 77 ]. Use of heated fluids helps to limit secondary cooling and may protect lines from freezing but has little direct effect on rewarming [ 77 , 82 ].…”