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KMID : 0378019660090100053
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New Medical Journal
1966 Volume.9 No. 10 p.53 ~ p.73
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Studies on the Effects of Hypercapnia in the Development of Ventricular Fibrillati on and Cardiopulmonary Function in the Hypothermic Dog
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Abstract
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The effects of inhalation of room air, 5.5 % CO2=20%02 and 8.5 % CO2+20 % 02 gas mixture on the development of. ventricular fibrillation and cardiopulmonary function were studied on 49 hypothermic dogs. Hypothermia was achieved by means of body surface cooling with ice water and rewarming with warm water. The range of esophageal temperature was 25+1°C.
Results were as follows:
1. Among 29 dogs of room air group, 6 dogs died because of ventricular fibrillation. In contrast to this, all 20 dogs, 10 in each of the 5.5% CO2 group and the 8.5% CO2 group survived.
2. The mean arterial CO2 tension was markedly elevated during cooling correspondingly to the C02 content in the inhaled gas mixture, and then returned to normal with rewarming. The arterial pH was decreased with cooling, especially in the 8.5% CO2 group, and returned to normal with rewarming.
3. The minute ventilation was decreased with cooling and increased with rewarming. The higher the CO2 content in the inhaled gas mixture, the more the minute ventilation. This change was brought about by changes of the respiration rate and tidal volume.
4. The 02 consumption was similarly decreased in the 3 groups with cooling and was gradually increased during rewarming. However, in the 8.5% CO2 group markedly increased value was noted. The CO2 elimination was of similar pattern to the 02 consumption, and it was noted that the higher the C02 content in the inhaled gas mixture, there was less tendency to the CO2 elimination. In the cases of shivering the 02 consumption and the CO2 elimination were temporarily increased significantly.
5. The heart rate and cardiac output were significantly decreased with cooling and increased during rewarming, without regard to any difference of C02 content in the inhaled gas mixture, but the stroke volume was not changed by alteration of esophageal temperature or difference of CO2 content of the inhaled gas mixture.
6. The femoral arterial pressure was progressively lowered during cooling in similar degree in the 3 groups and was slightly elevated during rewarming.Total peripheral resistance was markedly increased to almost the same degree in all 3 groups, but the femoral venous pressure was not changed by alteration of esophageal temperature or. difference of the CO, content of the inhaled gas mixture.
7. The pulmonary arterial mean pressure was similarly lowered with cooling in all 3 groups, but in the C02 gas groups it was returned to a lesser degree than precooling state with rewarming. Total pulmonary resistance was markedly increased as the result of cooling.
8. The systolic pressure of the right ventricle was lowered with cooling and was gradually recovered with rewarming, whereas the end diastolic pressure of the right ventricle was not influenced by any change of esophageal temperature or difference of the CO2 content in the inhaled gas mixture.
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