CIRCULATORY ASPECTS ON RAISED TISSUE PRESSURE-BASED ON ANIMAL-EXPERIMENTS WITH APPLICATION TO THE BRAIN

This paper describes circulatory effects of increase in tissue pressur e and of venous and arterial pressure alterations on a skeletal muscle preparation enclosed in a plethysmograph and effects of vertical elev ation of the muscle. The experimental set up allows registration of ar terial, hydrostatic capillary, large venous and venous otflow pressure as well as blood flow and tissue volume alterations. From a haemodyna mic point of view, the model may simulate the brain enclosed inside th e dura and surrounded by cerebrospinal fluid. We conclude that raised tissue pressure has important circulatory effects mainly through the d evelopment of a venous resistance just at the venous outlet which prot ects the organ haemodynamically from variations in venous pressure. As having a tissue pressure above the venous pressure, also the normal b rain may be protected via this mechanism. The results also show that a n increase in arterial pressure will increase capillary filtration and vice versa. Results supporting dihydroergotamine as being a precapill ary vasoconstrictor inducing transcapillary absorption are presented.