PHYSIOLOGICAL PRINCIPLES FOR VOLUME REGULATION OF A TISSUE ENCLOSED IN A RIGID SHELL WITH APPLICATION TO THE INJURED BRAIN

Background: Preservation of a high cerebral perfusion (mean arterial) pressure to prevent ischemia has become the primary focus during; trea tment of severe head trauma because ischemia is favored as a triggerin g mechanism behind intracellular brain edema development and poor outc ome. A high cerebral perfusion pressure, however, simultaneously may i ncrease the hydrostatic vasogenic edema. The present paper evaluates t he mechanisms behind the vasogenic edema by analyzing the physiologic hemodynamic mechanisms controlling the volume of a tissue that is encl osed in a rigid shell, possesses capillaries permeable for solutes, an d has depressed autoregulation. Results and Conclusions: We contend th at in the long run, the interstitial volume in such a tissue can be re duced only through reduction in arterial inflow pressure providing an otherwise optimal therapy to improve microcirculation. Therefore we ar gue, in contrast to the conventional view, that antihypertensive and a ntistress therapy may be of value by reducing the interstitial tissue volume during treatment of brain edema, and that the problem with isch emia during such therapy can be handled when considering an otherwise optimal intensive care. These physiologic principles of interstitial t issue volume regulation form the basic concept for the ''Lund therapy' ' of severe head injuries, which is a new and controversial therapy of posttraumatic brain edema.