Preventing hypothermia during continuous veno-venous hemodiafiltration (CVVHDF). A randomized controlled trial

Background. Continuous veno-venous haemodiafiltration is a common form of dialysis used in intensive care units. Unfortunately, patients often experience hypothermia as a side-effect of the therapy because of the necessity for extracorporeal blood flow. Intensive care nurses aim to prevent hypothermia developing. Intravenous fluid warmers are sometimes added to the dialysis circuit in an attempt to maintain patient temperature. However, the efficacy of this method has not been previously studied. Aim. This paper reports a study to investigate whether intravenous fluid warmers prevent hypothermia during continuous veno-venous haemodiafiltration. Method. A prospective randomized controlled trial was carried out in the intensive care unit of a metropolitan, tertiary-referral, teaching hospital. After Ethics Committee approval, 60 circuits in continuous veno-venous haemodiafiltration mode (200 mL/minute blood flow, 1 L/hour countercurrent dialysate, 3 L/hour pump-controlled ultrafiltration and prefilter fluid replacement of 1.7-2.0 L/hour) were studied. Circuits were randomized to have either an intravenous fluid warmer set at 38.5°C on the dialysate and 1 L/hour of replacement fluid lines or no fluid warmer. Patient core temperature was recorded at baseline and then hourly. Hypothermia was defined as a core temperature < 36.0°C. Results. Mean core temperature loss did not vary between circuits with or without a fluid warmer (0.92°C vs. 1.11°C, P = 0.339). Survival analysis found no difference in hypothermia incidence between groups (log rank = 0.47, d.f. = 1, P = 0.491). Lower baseline temperature (RR 0.142, 95% CI 0.044, 0.459, P = 0.001) and female gender (RR 0.185, 95% CI 0.060, 0.573, P = 0.003) were significant risks for hypothermia. Conclusions. Intravenous fluid warmers used as described do not prevent hypothermia during continuous veno-venous haemodiafiltration. Female patients and those with a low-normal baseline temperature are most likely to become hypothermic during this form of dialysis. Further research is needed to address effective ways of preventing hypothermia in critically ill patients receiving continuous renal replacement therapies.