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

During hemorrhage fluid is absorbed from the extravascular space of skeletal muscle into the intravascular compartment in order to compensate for the blood loss. In a previous report (Lundvall & Hillman 1978) this process was found causally linked to reflex, beta-adrenergic control of the capillary hydrostatic pressure (via adjustment of pre-/postcapillary resistance) and of the capillary exchange area (via adjustment of "precapillary sphincter' tone). The present study extends the experimental evidence for such beta-adrenergic control of plasma volume in bleeding, showing that it operates for prolonged periods of time and in a graded manner over a wide range of hemorrhagic hypovolemia. The investigation also provides information about the quantitative importance of the fluid gain from muscle to blood for plasma volume restoration in hemorrhage. Thus, during moderate bleeding (10 ml x kg b.wt.-1) the cumulative (45 min) fluid gain from muscle to blood averaged 1.4 ml x 100 g muscle. -1 This implies, when calculated for the total muscle mass, that about 2/3 of the shed blood volume will be replaced by interstitial fluid within less than one hour.