In vivo release of a heparin-like factor in dogs during profound hypothermia.

Experimentally induced hypothermia (20 degrees C) for 60 minutes in dogs provokes a significant decrease in the platelet count, which reverses during subsequent rewarming, and the constant release of a heparin-like factor, which reacts as a specific inhibitor of factor Xa. This phenomenon is also rapidly reversible, and heparin values are not significantly different from control levels after 90 minutes of rewarming. The mean maximal concentration of heparin-like material is 0.