Local vascular response during organ elevation : A model for cerebral effects of upright position and dural puncture

Dural puncture can be followed by postural headache and, in patients with cerebral infections, by brain stem herniation. The present study evaluates whether these complications may be related to the changes in hydrostatic pressure generated by the spinal fluid column when the dural sac surrounding the cerebrospinal tissue has been punctured. An isolated cat skeletal muscle enclosed in a plethysmograph connected to a tube served as a model imitating the brain, the cranium and the spinal canal. We investigated effects of organ elevation on tissue pressure, venous collapse (venous outflow resistance) and tissue volume with closed "spinal" tube (intact dural sac) and open "spinal" tube (dural puncture), and effects of compliance of the draining veins. Organ elevation with closed "spinal" tube induced a decreased tissue pressure, whereas tissue pressure remained unchanged if arterial inflow pressure to the muscle was kept constant. Organ elevation with the "spinal" tube opened distally caused a significantly larger decrease in tissue pressure, venous dilation and disappearance of venous outflow resistance. Transcapillary filtration increased, and the filtration rate was higher with high than with low venous compliance. If our results are applicable to the brain, changing to an upright position following a lumbar dural puncture may generate a negative hydrostatic force and a negative interstitial cerebral pressure, causing an increased transvascular pressure and dilation of the cerebral outflow veins. The corresponding increase in cerebral blood volume may induce post-spinal headache, and the increased transcapillary pressure may cause increased fluid filtration and brain oedema if the blood-brain barrier is disrupted.