Evaluation of a new fluid warmer effective at low to moderate flow rates.

BACKGROUND: The tendency of intravenous fluid exiting the heat exchanger of a fluid warmer to cool to room temperature increases as the rate of infusion slows and the length of tubing between the heat exchanger and the patient increases. Thus, slow to moderate flow rates result in the delivery of fluid near room temperature despite the use of a fluid warmer. The volumes infused even at low flow rates may be large relative to the size of infants and children and may result in a significant decrease in patient temperature. METHODS: A new warmer (Hotline, Level 1 Technologies) that actively heats the fluid in the delivery tubing was evaluated and compared to two different conventional dry-wall warmers: the model DW1000A (Baxter Health Care) and the FloTem IIe (DataChem). Cold blood (4-10 degrees C) and room temperature saline (22 degrees C) were pumped through the warmers and the delivered temperature was measured as the flow rate was varied from 50 to 12,000 ml/h. RESULTS: The Hotline was more effective than the Baxter or the FloTem IIe at flow rates between 50 and 6,000 ml/h for saline and at flow rates between 50 and 3,000 ml/h for blood. Insulating the tubing beyond the heat exchangers of the conventional warmers improved their performance, but the delivered temperatures were still less than those of the Hotline at low flow rates. CONCLUSIONS: The Hotline is more effective than conventional warmers at slow flow rates, and may be useful for preventing hypothermia when large volumes of fluid relative to patient size are infused at slow rates.

Evaluation of a new high-efficiency blood warmer for children.

Because currently available blood warmers are inadequate for infants and children requiring massive transfusion, the performance of a new high-efficiency pediatric blood warmer (System 250TM, LEVEL 1 Technologies Inc., Marshfield, Massachusetts) was evaluated and compared with a commonly used conventional blood warmer (Model DW1000A, American Pharmaseal, Valencia, California). Cold (5-6 degrees C), diluted red blood cells (RBC) (Hct = 30%) were infused through the warmers over a series of flow rates, and the resulting temperatures of the infusate were measured. The flow rates of diluted packed RBC were also measured over a series of infusion pressures. At a flow rate of 225 ml/min, the output temperature of the System 250TM was 33.6 degrees C compared with 24.6 degrees C (P less than 0.05) for the conventional warmer. Above a flow rate of 250 ml/min, however, the water bath of the System 250TM cooled significantly, resulting in a deterioration of performance and an output temperature of only 24.2 degrees C at a flow rate of 400 ml/min. With a 16-G catheter attached, the flow rate at a pressure of 300 mmHg was 223 ml/min through the System 250TM compared with 160 ml/min (P less than 0.05) for the conventional warmer. The System 250TM produced higher output temperatures and a lower resistance to flow compared with the conventional warmer, but flow rates of cold blood through the System 250TM should be restricted to 250 ml/min or less to ensure adequate warming.