Asgeirsson B, Grände P O
Department of Physiology and Biophysics, University of Lund, Sweden.
Intensive Care Med. 1994 Nov;20(8):567-72. doi: 10.1007/BF01705723.
To assess local haemodynamic effects of raised tissue pressure per se and of arterial and venous pressure variations during raised tissue pressure, and to evaluate the vascular waterfall phenomenon.
An isolated pump-perfused sympathectomised cat skeletal muscle enclosed in a plethysmograph.
Hydrostatic capillary pressure (Pc), tissue volume alterations and blood flow were recorded at various arterial (PA) or venous (PV) pressure levels at a raised tissue pressure (Ptissue). Total vascular resistance (Rtot) and its three consecutive sections, arterial resistance (Rart), venular resistance (Rvenule), and venous outflow orifice resistance (Rorifice), were recorded.
Increase in Ptissue increased Pc due to a marked increase in Rorifice and unchanged Rart and, when Ptissue > PV, by about 90% of the Ptissue increase. During the raised Ptissue, a PA increase (95 to 115 mmHg) increased Pc (by 3.1 +/- 1.1 mmHg) causing fluid filtration, and a PA decrease (95 to 75 mmHg) decreased Pc (by 2.4 +/- 0.5 mmHg) causing fluid absorption. Rart was unchanged, indicating impaired autoregulation. Increased PV had no haemodynamic effects when PV < Ptissue due to a gradual decrease in Rorifice towards zero when PV reached Ptissue. At PV > Ptissue blood flow and Pc increased gradually, causing fluid filtration.
Tissue volume is increased by raised and decreased by lowered PA, the latter may be of use to decrease ICP in the injured brain. The results indicate that PEEP or head elevation will not influence ICP from the venous side if CVP < ICP. Finally, the "vascular waterfall phenomenon" was rejected as Rorifice is a normal variable fluid resistance.
评估组织压力升高本身以及组织压力升高期间动脉和静脉压力变化对局部血流动力学的影响，并评估血管瀑布现象。
将一只去交感神经的猫的骨骼肌置于体积描记器中，进行孤立的泵灌注实验。
在升高的组织压力（Ptissue）下，于不同的动脉（PA）或静脉（PV）压力水平记录流体静力毛细血管压力（Pc）、组织体积变化和血流。记录总血管阻力（Rtot）及其三个连续部分，即动脉阻力（Rart）、小静脉阻力（Rvenule）和静脉流出孔阻力（Rorifice）。
Ptissue升高会使Pc升高，这是由于Rorifice显著增加且Rart不变，并且当Ptissue > PV时，Pc升高约为Ptissue升高幅度的90%。在Ptissue升高期间，PA升高（从95至115 mmHg）会使Pc升高（3.1±1.1 mmHg），导致液体滤过，而PA降低（从95至75 mmHg）会使Pc降低（2.4±0.5 mmHg），导致液体吸收。Rart不变，表明自动调节受损。当PV < Ptissue时，PV升高没有血流动力学影响，因为当PV达到Ptissue时，Rorifice会逐渐降至零。当PV > Ptissue时，血流和Pc逐渐增加，导致液体滤过。
PA升高会使组织体积增加，PA降低会使组织体积减小，后者可能有助于降低受伤大脑的颅内压。结果表明，如果中心静脉压（CVP）<颅内压（ICP），呼气末正压通气（PEEP）或抬高头部不会从静脉侧影响ICP。最后，由于Rorifice是一个正常的可变液体阻力，因此否定了“血管瀑布现象”。
