Methods for warming intravenous fluid in small volumes

Purpose: Laboratory experiments were performed to determine warming rates o f albumin 5% at room temperature and human packed red blood cells (PRBCs) a t 4 degrees C in small volumes, Four methods used in clinical practice to w arm volumes appropriate for neonates were studied. Methods: The fluids were warmed either by infusion through a fluid warmer w ith temperature-controlled coaxial tubing (Group I), immersion in a water b ath at 37 degrees C (Group II), placing pre-filed syringes (IO and 20 mi) b etween a circulating water mattress and a forced-air warming blanket (Group III), or placing the same syringes between the water mattress and cotton t owels (Group IV). The temperature of each fluid was recorded for the next 6 0 sec after the bolus injection in group I and every five minutes for a tot al of 30 min for the other groups, The time constant of warming for each gr oup was calculated. The time constant and the temperature reached after the warming period were compared among groups. Results: In group I 20 mi room temperature albumin 5% or 4 degrees C blood reached temperatures of 36.9 +/- 1.5 degrees C and 34.5 +/- 2.3 degrees C w ithin 60 sec, respectively. This was faster than all other techniques used (P < 0.001). The time constants measured for the albumin and the PRBCs were 0.23 +/- 0.1 and 0.20 +/- 0.05 minutes respectively. After 15 min albumin and PRBCs in group II reached 35.5 +/- 0.4 degrees C and 33.4 +/- 0.3 degre es C, in group III reached 33.7 +/- 1.0C and 32.8 +/- 1.7C, and in group IV reached 29.5 +/- 0.1 degrees C and 23.3 +/- 0.8 degrees C after 15 min res pectively. Conclusion: Warming of intravenous fluids in small volumes is accomplished most rapidly using a fluid warmer with temperature-controlled coaxial tubin g and occurs more slowly in syringes, bottles, or bags exposed to various e nvironmental conditions.