Factors and methodology in achieving ideal delivery temperatures for intravenous and lavage fluid in hypothermia

Abstract

A study was undertaken to determine the relationship between temperature and delivery rate of warmed intravenous fluid using standard intravenous infusion equipment and tubing. One-liter bags of 0.9% NaCl were warmed to 60°C and run through standard microdrip tubing for 1 hour at rates of 1,000, 800, 600, and 400 mL/h. Thermistor probes were placed into the bag and into the tubing at 0, 100, 180, 230, and 280 cm from the intravenous bag. Separate fluid bags were also warmed to 39.3° and 75°C, and the fluid was run through the same apparatus at 1,000 mL/h and 200 mL/h, respectively. Temperatures were recorded at each site at the start of the infusion and every 10 minutes thereafter for 1 hour. Subsequently, 60-mL syringes of fluid warmed to 39.5°C were eluted through 50 cm tubing over 10 minutes at 300 mL/h and 360 mL/h. Mean delivery temperature over each 10-minute infusion was determined. Fluid preheated to 39.3°C approached room temperature at delivery even at a flow rate of 1,000 mL/h and tubing lengths as short as 100 cm. Fluid preheated to 60°C was delivered at near 37°C using tubing lengths as long as 280 cm when eluted at 1,000 mL/h. Fluid preheated to 39°C in 60-mL syringes and eluted through 50 cm of tubing over a period of 10 minutes at 300 mL/h or 360 mL/h was delivered near a mean temperature of 37°C. These results show that warmed fluid can be delivered through standard intravenous tubing at or near 37°C if the fluid is preheated to 60°C and eluted through long tubing (280 cm) at high flow rates (1,000 mL/h). Alternatively, fluid warmed to 37°C to 42°C can be delivered at or near 37°C via intermittent bolus through short tubing (50 cm) either by hand or syringe pump. The latter approach would be particularly beneficial in the pediatric population, in whom it is not advisable to administer fluid at flow rates as high as 1,000 mL/h.