Exploration of a Method for Standardizing Hemorrhagic Shock

Abstract

The urgency in developing standardized laboratory procedures for production of shock which will enable us to evaluate the efficiency of remedial measures with greater certainty is generally recognized. While no claim to such achievement can be made, we desire to report results which point to certain trails that ought to be explored more thoroughly.

Since the bulk of experimental work 1 strongly suggests that the progressive decline in arterial pressures is associated with reduced circulating volume, it appeared probable that the greatest hope of developing a standard laboratory procedure for producing shock lay in reducing the blood volume by bleeding. However, our studies showed that the dangerous factor in shock, viz., its irreversibility, is not as definitely related to the percentile reduction in blood volume as it is to the degree and duration of hypotension which eventuates. As is well known, stray dogs differ greatly in regard to the percentile reduction in blood volume withstood before they develop a protracted low arterial pressure. Consequently, attempts to standardize procedures for creation of experimental hemorrhagic shock which are based on withdrawal of definite volume percent of the estimated blood are doomed to disappointment.

We have sought to determine the degree and duration of post-hemorrhagic hypotension which leads to a circulatory state that cannot be benefited more than temporarily by substantial infusions of the withdrawn blood (heparinized), and is generally accompanied by severe congestion, edema and hemorrhage of the upper intestinal mucosa.

Result Fig. 1 shows graphically representative results selected from 75 experiments.

The data plotted in section A are from experiments in which mean arterial pressures were maintained by regulated bleeding between 46-60 mm Hg (average 50) for 1 ¾-4 hours. Irreversible shock never resulted. This emphasizes (1) the importance of distinguishing between posthemorrhagic hypotension and hemorrhagic shock, (2) the remarkable ability of tissues of withstand reduced blood flow and (3) the impracticability of such a procedure for production of experimental shock.