Hypothermic cardiopulmonary bypass: A comparison between alpha and pH stat regulation in the dog

Abstract

The accepted normal pH of 7.40 may not be optimal at lower temperatures. This study evaluated the effect of maintaining pH in the accepted normal range at hypothermia (group 1, pH stat) or at normothermia (group 2, alpha stat) on organ blood flow and hemodynamics in dogs. The desired pH was achieved at all temperatures by adjusting pCO2. Hypothermia to 20[deg]C was induced by high flow bypass in both groups followed by 45 min of reduced flow before rewarming. In group 1 (n = 10), pH was 7.45 +/- 0.02 at 20[deg]C and in group 2 (n = 11) it was 7.64 +/- 0.01. A greater base excess developed by the end of the low flow period in pH stat animals (-9.4 +/- 1.1 vs -2.8 +/- 0.8, P P P P P P P P pCO2 control between alpha and pH stat regulation assume lesser importance for regional blood flow when normal systemic flow is maintained during cooling and rewarming.