Active internal re-warming using a centrifugal pump and heat exchanger following haemorrhagic shock, surgical trauma and hypothermia in a porcine model.

BACKGROUND: The centrifugal vortex blood pump (CVBP) using heparin-bonded circuitry allows re-warming of hypothermic trauma patients without anticoagulation. Study objectives were to confirm efficacy, and to characterise the physiology of CVBP re-warming in a porcine model.
METHODS: Sixteen pigs were randomised to conventional or CVBP re-warming. They were bled to a mean arterial pressure of 30 mmHg and cooled to 29 degrees C. A physiological analysis was recorded during resuscitation to normo-tension and re-warming back to 37 degrees C.
RESULTS: CVBP animals re-warmed significantly faster: 85.0+16.4 min versus 217.4+49.3 min (p<0.0001). Activated clotting time was significantly elevated in both groups at 29 degrees C with a marked trend to normalise faster in CVBP pigs. The peak cardiac index (CI) was significantly lower (1.14+0.68 versus 4.83+1.50 L/(min m2), while the systemic vascular resistance (SVR) was significantly higher (4239.9+1173.0 versus 1472.6+451.2 dyn x S x m2/cm5) with CVBP (p<0.001).
CONCLUSION: CVBP is simple and very effective at re-warming hypothermic animals and may also reverse coagulopathy more quickly. Physiological derangements of elevated SVR and diminished CI require further study to elaborate underlying aetiology, and define optimal re-warming strategies.