Effect of profound hypothermia on leukocytes and platelets

Seventeen patients who underwent aortic arch replacement were subjected to profound hypothermia and circulatory arrest. At maximum cooling, platelet count dropped from 184 +/- 122 to 37 +/- 30 thousand per microliter, and the total leukocytic count fell from 6.27 +/- 4.0 to 1.47 +/- 0.6 thousand per microliter. The thrombocytopenia was partially reversed with rewarming. The total white cell count consistently returned to precooling values or higher (10.5 +/- 4.0). The mechanism for this cold induced phenomenon is not well understood.