Aim of the study: To demonstrate the effect of a new device for treating and supporting patients with moderate accidental hypothermia, tested in a porcine model. Validation of rewarming capabilities is done by comparing the experimental results with data from already known techniques, through a literature review. A target rewarming rate (°C/h) for HeatCath is furthermore to be settled under the criterion that it meets the lowest rewarming rate, defined as 25. percentile, of the best technique used for treating accidental moderate hypothermia.
Methods: Anesthetized pigs (n= 2 weighing 49 -53 kg) were cannulated for ECMO and cooled to 26 °C. Core temperature was measured by a catheter in the bladder and one in the abdomen. Pigs were randomly selected into one of two groups (i) Intervention-group (n=1) rewarmed for 3,5 hours through the insertion of a central warming catheter “HeatCath®”. (ii) No treatment was applied to the control group (n= 1). When the intervention pig was warmed for 3,5 hours, the rewarming technique was applied to the control animal for further analysis of practicality and rewarming rates at a given temperature.
Results: Through literature review, it was confirmed that pleural lavage is the best contemporary rewarming technique for moderate hypothermia, and the rewarming rate was equal to 2,8 °C/h, thereby defined as our target rewarming rate for HeatCath. Through the experimental rewarming phase of 195 min, the average rewarming rate was 1,3 °C/h for the intervention versus 0,4 °C/h for the control. During rewarming of the control animal, a mean MAP of 61 mmHg (±7 mmHg) with a heart rate of 57 bpm, and the intervention animal had a mean MAP of 71 mmHg (± 8 mmHg) with a heart rate of 57 bpm (± 13 bpm). Initiating the treatment with HeatCath on the control pig after 195min, showed a rewarming rate on 1,1 °C/h. during a 60 min. period.
Conclusion: HeatCath produced a rewarming rate of 1,3 °C/h in the intervention pig. 0,9 °C/h greater than the non-treated control pig, during the rewarming time of 195 min. Initiating treatment with HeatCath on the control animal after 195 min. at a temperature of 27,1 °C produced a rewarming rate of 1,1 °C/h over 60 min. The display of functionality and controlled rewarming fulfilled the expectations. The intervention animal presented more stable vital signs compared to the control animal, but the aim of a rewarming rate of 2,8 °C/h was not met, and further development of HeatCath could be beneficial.