A method for estimating the delivery temperature of intravenous fluids.

Abstract

Despite rigorous efforts to monitor and control the fluid temperature within a warmer, the actual delivery temperatures of intravenous (i.v.) fluids at a patient infusion site are not assessed in current clinical practice. A method which correlates the warmer temperature with the delivery temperature will provide the appropriate quality assurance framework. For fluids administered through typical 0.260- and 0.300-cm-diameter polyvinyl chloride (PVC) i.v. tubing, we developed such a method by directly measuring the delivery temperatures for saline, 6% hydroxyethyl starch (HES), 5% albumin, plasma, and packed red cells (PRC) using intratubing thermocouple wire probes. A kinetic analysis of the data yielded the following relationship governing temperature equilibration for fluids in i.v. tubing: f = L/(24 Q + L), where f represents the equilibration fraction, L the tubing length (cm), and Q the flow rate (mL/min). The equilibration fraction f is defined as (Ti - Td)/(Ti - Ta), where Ti, Td, and Ta represent the initial fluid temperature, the delivery temperature, and the ambient air temperature in centigrade, respectively. Both the fluid type and the variability in tubing construction had negligible effects on the delivery temperature. Under given conditions of Q and L, the relationship enables the calculation of the temperature equilibration fraction f and, subsequently, the delivery temperature. Furthermore, the i.v. tubing length or the particular L/Q may be calculated for a desired target temperature and the corresponding f. We conclude that, despite many complicating variables, one can effectively assess and even control the delivery temperature of i.v. fluids administered through typical i.v. tubing.(ABSTRACT TRUNCATED AT 250 WORDS)