Abstract
In a previous study, 1 the effects of uncomplicated hemorrhage on cardiac output and blood pressure were determined. Repeated removal of blood was usually associated with a decline in the cardiac output from 30 to 50% below the normal level before a marked diminution in the blood pressure occurs. Johnson and Blalock 2 found that secondary shock as a result of trauma to muscles, trauma to the intestines or burns is associated with a definite decrease in the output of the heart before the blood pressure is altered appreciably. On the contrary, the introduction of histamine 2 causes an initial decline in the blood pressure followed by a decrease in the cardiac output. Following the removal of the adrenal glands, 3 the blood pressure usually declines before the cardiac output is altered. Trauma to the central nervous system 4 is usually associated with a simultaneous decline in both the cardiac output and blood pressure.
The alterations in the cardiac output and blood pressure in primary shock were determined in the present experiments in order to compare these changes with those observed in secondary shock.
Dogs were profoundly anesthetized by sodium barbital administered intravenously. The dosage was 0.3 gm. per kilo of body weight. The control determinations of the cardiac output and blood pressure were performed approximately 2 hours after injection of barbital. The anterior abdominal wall of the animal was then struck many blows in rapid succession with flat surface of a board. This procedure occupied approximately 2 minutes. Thirty to sixty seconds later, the cardiac output and blood pressure were again determined. If free hemorrhage into the peritoneal cavity resulted from the traumatization, the experiment was discarded.
A cannula that was placed in the femoral artery was used for the determination of the blood pressure. The cardiac output was computed by the Fick principle:
Oxygen consumption per minute No. cc. of blood
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