[AUTOLINE. Effectiveness of an infusion warmer concept]

Coaxial fluid warmers directly heat the tubing surrounding the infusate right up to the intravenous cannula of the patient. This study examined whether the heating capability of one such fluid warmer, the Autoline, could be further increased by using pre-heated infusions as well as using a specifically designed warm-plated infusion holder, the Autotherm, which surrounds the bottled infusions.

The final temperatures of crystalloid infusates were measured at the end of the Autoline tubing. With the initial infusion temperatures being kept at either 20 degrees C or 36 degrees C, the subsequent measurements took place at 7 different flow rates between 50 and 1000 ml/h. Using the 36 degrees C pre-heated crystalloid group, further separate measurements were also undertaken by additionally installing the Autotherm. All measurements took place at a constant room temperature of 20 degrees C. The final temperatures were analysed for significant differences between the groups using the one-way ANOVA and post-hoc tests (Bonferroni).

Using pre-heated infusions at low flow rates of 50 and 100 ml/h, the heating capability of the Autoline could be increased by 0.8 and 1.6% (p<0.01), respectively. However, the additional use of the Autotherm device reduced its heating capability by 3.2 and 6.1% (p<0.001), respectively. Using flow rates above 200 ml/h, the heating capability of the Autoline could be increased between 9.2 and 28.6% by pre-heating infusions to 36 degrees C (p<0.01). The additional use of the Autotherm device at these higher flow rates resulted in an increase of the final infusate temperature of 12.7% up to 40.5% (p<0.01).

The Autoline demonstrated sufficient heating capabilities at flow rates between 50 and 200 ml/h, which can be further increased by pre-heating the infusions to 36 degrees C. At flow rates above 200 ml/h, however, it becomes necessary to use pre-heated infusions, whereas at flow rates above 600 ml/h it becomes further necessary to also use the Autotherm device if final infusates of at least 34 degrees C are to be achieved.