Temperature Differentials and Metabolic Acidosis in Profound Hypothermia

METABOLIC ACIDOSIS following profound hypothermia has been attributed to hypoxia due to inadequate perfusion. This condition is most severe when complete circulatory arrest is effected. Evidence has been presented suggesting that temp differentials within the body may be a major contributor to this hypoxia.^1-3 Lactic acid concentrations have been observed to be higher in femoral vein blood than in mixed venous blood. Temp differentials could result in hypoxia of peripheral tissues, since with blood heat exchanger techniques their circulation would be curtailed early in accordance with the decreased "core" temp before the average body temp is reduced adequately. The major muscle mass lies within these peripheral areas. Under normothermic or moderately hypothermic conditions, it is possible to maintain a rate of perfusion which will minimize this effect. However, when central temp are below 20 C (68 F), it is difficult to have higher flow rates because of the