HUMORAL-FACTORS IN SHOCK CAUSING BRADYCARDIA AND MYOCARDIAL DEPRESSION

  • 1 January 1977
    • journal article
    • research article
    • Vol. 4  (2) , 153-161
Abstract
Hypovolemic shock was maintained for 6 h in dogs in which the heart was hemodynamically protected by a biological model described earlier. Blood of these dogs was exchanged with that of healthy dogs in which myocardial tension and heart rate were continuously monitored. Rate and force decline in the recipient dog in a fashion similar to the drop in the animal in shock. If the pH of the infused blood was raised to normal, the bradycardia in the recipient dog was prevented but the myocardial depression was not abolished. Administration of aprotinin alone did not prevent the bradycardia or depression of contractility, whereas correction of the pH and treatment with aprotinin not only prevented the decline in both but led also to a transient increase in myocardial tension of the recipient animal. In shock myocardial depression and cardiac slowing are apparently induced by humoral factors transferable by blood to a normal animal. Acidity causes the bradycardia but not drop of tension. Aprotinin may prevent the depression of contractility only in a normal pH medium. Aprotinin may prevent the action of a preformed myocardial depressant factor rather than inhibit its formation.