Survival of hypothermic dogs after 2-h circulatory arrest.

Adult mongrel dogs were rapidly cooled to a body temperature of 4-5 degrees C with a combination of internal (core) cooling and external surface cooling. All dogs survived profound cooling and 2-h circulatory arrest when profound hemodilution and drainage of the left ventricle were used during cooling and when preferential microwave chest rewarming and hypervolemia were employed during rewarming. After recovery no permanent neurological damage was observed. The histology of the brain and heart of animals killed 6 mo after the cooling indicated normal tissue. When during rewarming the selective microwave chest heating was not used, fewer dogs survived the 2-h circulatory arrest.