PROLONGATION OF TOTAL PERMISSIBLE CIRCULATORY ARREST DURATION BY DEEPHYPOTHERMIC INTERMITTENT CIRCULATORY ARREST

Objective: We determined whether the duration of permissible circulato ry arrest could be prolonged by deep hypothermic intermittent circulat ory arrest. Methods: Twenty-five beagles were cooled on bypass to 18 d egrees C to initiate deep hypothermia that was maintained for 3 hours. Five protocols were then studied: group 1, uninterrupted bypass durin g hypothermia; group 2, arrest for 40 minutes during hypothermia; grou p 3, arrest for 60 minutes during hypothermia; group 4, arrest for 80 minutes during hypothermia; and group 5, intermittent circulatory arre st, consisting of six cycles of 20 minutes of arrest followed by 10 mi nutes of systemic recirculation during hypothermia (total, 120 minutes of arrest). The oxyhemoglobin concentration in the brain was measured with near infrared spectrophotometry, Results: In groups 2, 3, and 4, the oxyhemoglobin concentration in the brain decreased continuously a fter arrest, finally reaching a plateau after 24.9 +/- 1.2 minutes. Th is finding suggested that the available cerebral oxyhemoglobin was dep leted. In contrast, the available cerebral oxyhemoglobin was not deple ted during hypothermic intermittent arrest in group 5, The mitochondri al respiratory control index was significantly lower in group 4 than i n the other groups (p < 0.05). However, there were no significant diff erences in the respiratory control index for groups 1, 2, 3, and 5, Mo reover, the formation of brain edema was significantly lower in group 5 than in the other groups (p < 0.05), Conclusions: These results indi cate that deep hypothermic intermittent arrest can increase the durati on of total permissible circulatory arrest and will be a useful modali ty when prolonged arrest is anticipated.