Epidural space as a starling resistor and elevation of inflow resistance in a diseased epidural space

摘要: Background and Objectives The origin the presence of negative pressure in epidural space as well relationship extent anesthesia to has long been a subject controversy. To further elucidate its time course, at needle tip was continuously measured it traversed interspinous ligament ligamentum flavum. Methods In group 22 patients, fluid infused under gravity, second 25 boluses were administered controlled infusion rates gravity. volume-pressure-flow thus one two ways, either with manual syringe transducer or pressure-monitoring-computer-controlled volumetric pump. Results Natural pressure, (i.e., before instrumentation is applied) could be approached when first entered (initial pressure); after had (residual pressure). Epidural extrapolated from upsweep by projecting back just injection. lay between initial residual pressures. Medicinal solution placed barrel did not infuse gravity until lifted certain height, which flow began continued perceptible rate, very little no increase height required maintain flow. critical opening characteristic Starling resistor. Furthermore, resistance inflow related absence natural surgical disease space. Resistance significantly higher diseased than group, 114 (range, 22-226) mm Hg/L/h versus 46 8-86) Hg/L/h. Three phases seen pressure-time recordings. Conclusions Volume-pressure-flow relationships can explained model subarachnoid pressures are inextricably dependent on pressure. This suggests reasons why spread anesthetics might difficult predict.