Intermittent whole-body perfusion with "somatoplegia' versus blood perfusate to extend duration of circulatory arrest.

BACKGROUND

Continuous whole-body perfusion for > 3 hours with a cold asanguineous blood substitute, hypothermosol (HTS) solution, has been reported to preserve organ function. We used this solution in a survival animal model to evaluate its possible application in extending the safe duration of deep hypothermic circulatory arrest (DHCA).

METHODS AND RESULTS

Fifteen piglets were placed on cardiopulmonary bypass (CPB), were cooled to a nasopharyngeal temperature of 15 degrees C, and underwent 100 minutes of DHCA. Control animals (group C, n = 5) had uninterrupted DHCA, group HTS animals were perfused with maintenance HTS for 5 minutes every 25 minutes during DHCA (n = 5), and group B animals were intermittently perfused as for group HTS with the blood in the bypass circuit (n = 5). Cerebral oxygenation was assessed with near-infrared spectroscopy throughout CPB and DHCA. Animals were allowed to recover after CPB and underwent daily neurobehavioral evaluation by the neurological deficit score (NDS: 0, normal; 500, brain death) and overall performance categories (OPC: 1, normal; 5, brain death). Blood samples were drawn on postoperative day (POD) 1 for selected biochemistry analysis. On POD 4, the brain of each animal was perfusion-fixed for histological evaluation, and a neurohistological score (NHS: 0, normal; 5+, necrosis) was assigned for the degree of neuronal injury. All animals except one from group HTS survived surgery. Mean perfusion pressures were significantly elevated in group B compared with group C and group HTS during the rewarming phase (P < .05). The HbO2 signal increased in all groups during the cooling phase of CPB and remained significantly above baseline only in group B during DHCA (P < .05). SGOT, LDH, ALP, and CPK levels on POD 1 were elevated above baseline in all groups. The increase in SGOT and ALP was significantly greater in group HTS than in the other groups (P < .02). The NDS was lower in group B on each postoperative evaluation, being significant relative to group C and group HTS on POD 1 (P < .05) and significantly lower than group C on POD 2 (P < .05). The OPC score was significantly lower in group B than in group C and group HTS on POD 2 (P < .05) and significantly lower than in group C on PODs 3 and 4 (P < .05). The NHS was lower in group B than in the other 2 groups, being significant relative to group C in the neocortex (P < .007).

CONCLUSIONS

Intermittent whole-body asanguineous perfusion with hypothermosol solution does not extend cerebral protection in a porcine survivor model of DHCA. Neurobehavioral and histological outcomes are improved in animals receiving intermittent blood perfusion during prolonged DHCA.