Changes in Forelimb Weight and Segmental Vascular Resistances Following Severe Hemorrhage

Abstract

The forelimb was used to study capillary fluid fluxes following hemorrhage in dogs anesthetized with sodium pentobarbital. Arterial hemorrhage (48 ml/kg) and 4 hours of hypovolemia produced decreases in forelimb weight, arterial and venous pressures, and skin and skeletal muscle blood flows. Segmental resistances (large artery, small vessel, large vein) in both skin and skeletal muscle increased markedly, and the increase was either completely or largely maintained throughout the hypovolemic period. The large arteries and large veins constricted proportionately more than the small vessels following hemorrhage. In animals that survived the hypovolemic period, the large arteries and large veins constricted almost proportionately, whereas in the animals that died, the large veins constricted proportionately more than the large arteries. The weight loss exceeded forelimb vascular volume, indicating that net extravascular fluid reabsorption occurred. In fact, the weight loss from 60-240 minutes after hemorrhage began appears to be largely attributable to extravascular fluid reabsorption, since resistance and, inferentially, blood volume were relatively constant in the forelimb capacitance vessels. These data fail to support the hypothesis that fluid filtration is a determinant of irreversibility but rather suggest that the compensatory responses to blood loss in the forelimb, i.e., vasoconstriction and net extravascular fluid reabsorption, persist during severe prolonged hemorrhagic hypotension.

Further studies on beta‐adrenergic control of transcapillary fluid absorption from skeletal muscle to blood during hemorrhage

“…The latter aspect will first be commented upon. Grega, Schwinghamer & Haddy 1971, Jarhult 1973, Hall, Schwinghamer & Lalone 1976). In most of these studies a fixed hypotension level achieved with the aid of a pressure bottle (Werle, Cosby & Wiggers 1942) has been gsed.…”

Blood volume, hemodynamic, and metabolic changes in hemorrhagic shock in normal and splenectomized dogs

“…These fluid shifts were associated with higher values of hematocrit and blood viscosity in the SpI-D dogs in late oligemia and after retransfusion. The transcapillary fluid loss seen in the SpI-D dogs probably reflects a rise in the postcapillary to precapillary resistance ratio in the limb vessels (8, 26,32,42), and a portion of this fluid loss may occur in the intestine (14, 48). It is interesting to note that, of the four groups studied, pathologic changes in the intestine were most pronounced in the SpI-D dogs ( Table 2).…”

Transcapillary Fluid Movements in Sympathectomized Intestine and Skin during Hemorrhagic Hypotension

“…In the intact cat paw (Oberg 1964) and dog foreleg (Schwinghamer et al 1970, Grega et al 1971, hemorrhage has been shown to cause a fluid absorption, which was attributed to adrenergic resetting of the pre-to postcapillary resistance ratio.…”