Transmural pressure of epidural veins in the thoracic and lumbar spine of pigs.
BACKGROUND
The aim of this study was to determine the transmural pressure gradient of epidural veins located within the spinal column and to investigate the effects of increased intra-abdominal and intrathoracic pressure on this gradient.


METHODS
Fourteen pigs were sedated with ketamine and anesthetized with halothane. Ventilation was controlled after tracheotomy. Needles were inserted into the epidural and subarachnoid space, and a catheter was threaded into an epidural vein. Pressures in these structures were measured during controlled and spontaneous ventilation, increased abdominal pressure, and thoracic compression. Measurements were made in both the thoracic and lumbar regions.


RESULTS
The pressure gradient between the epidural vein and the surrounding epidural space was low-11 or 2 mmHg--in both the lumbar and thoracic areas. This gradient was not affected by the mode of ventilation or increased abdominal or thoracic pressure (or both), even though the absolute intramural pressure increased.


CONCLUSIONS
The pressure gradient between the epidural vein and the surrounding space is low and does not change when abdominal or thoracic pressures are increased.
Nystrom
E U
EU
Department of Anesthesiology, University of Pittsburgh, Pennsylvania, USA.
Blomberg
S G
SG
Buffington
C W
CW
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000502:physiology; D004824:Epidural Space / Q000098:blood supply*; D006339:Heart Rate / Q000502:physiology; D008161:Lumbosacral Region / Q000502:physiology; D008297:Male; D013131:Spine / Q000098:blood supply*; D013552:Swine; D013909:Thorax / Q000502:physiology; D014680:Veins / Q000502:physiology