Gesell has distinguished between the initiating and the sustaining factors in shock. The previous paper of this series 1 was concerned with evidence for a toxic agent developed in damaged tissue and acting as an initiating factor in the onset of shock. The present paper is concerned with a sustaining factor—low blood pressure.
The low blood pressure in both experimental and clinical shock is explained by a diminution of blood volume, an actual decrease in the amount of fluid which is kept circulating. In the early stages of secondary shock, however, the diminished volume may not be associated with a reduced arterial pressure. The only way in which the pressure can be maintained in the presence of a smaller amount of circulating fluid is by a lessening of the capacity of the circulatory system. This diminished capacity is the consequence of extra activity of the vasoconstrictor center causing greater contraction
W. B. CANNON, McKEEN CATTELL. STUDIES IN EXPERIMENTAL TRAUMATIC SHOCKV. THE CRITICAL LEVEL IN A FALLING BLOOD PRESSURE*. Arch Surg. 1922;4(2):300–323. doi:10.1001/archsurg.1922.01110110046003