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KMID : 0350519920450030955
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Journal of Catholic Medical College
1992 Volume.45 No. 3 p.955 ~ p.964
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Changes of the Anterior Horn Cells of the Spinal Cord by Induced Spinal Epidural Hematoma in Rabbit
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Abstract
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Literally the most common complication following epidural analgesia is puncture of a blood vessel. The use of epidural analgesia is contraindicated in patients who are already receiving anticoagulant therapy or are about to undergo
anticoagulation
intraoperatively, since they may bleed into the epidural space if a needle or catheter traumatizes one of the blood vessels.
However, there are reports in which epidural analgesia has been safely performed in anticoagulated patients. The true incidence of epidural hematoma following epidural anesthesia is unknown because most of the literature consists only of isolated
case
reports. This complication is rare, but further data is clearly needed to identify the safe application of regional techiques.
The present study was undertaken in an attempt to evaluate the effects of raised epidural pressure by epidural hematoma on anterior horn cells of the spinal cord.
We studied two group of rabbits weighing 2.05 to 2.25kg : a control group and an induced epidural hematoma group. The animals were anesthetized with 7ml/kg body weight 25% urethane intraperitoneally. In the epidural hematoma group(N=6) an
indwelling
catheter was placed in the left femoral artery and an epidural catheter inserted into the sacral canal. After 5000 units of heparin were injected through a venous catheter of the ear vein by means of a vinyl tubing, arterial blood was perfused
from
the
femoral artery into the sacral canal through an epidural catheter for 65 minutes. Mean arterial pressure and epidural pressure were measured at 5 minute intervals during perfusion of the arterial blood. Additionally, cerebrospinal fluid pressure
was
continuously monitored by a catheter placed in the cisterna magna. At the end of experiment the 6th-7th lumbar vertebral region was removed and through the histological process, specimens were sectioned transversely or longitudinally to evaluate
the
histological changes to the spinal cord and the peridural structures.
To compare the ischemic changes of anterior horn cells in the spinal cord, a control group was subdivided into a normal control group(N=3), 60 minutes cross-clamping of the abdominal aorta group(N=5) and a 90 minutes cross-clamping of the
abdominal
aorta group(N=3).
In the normal control group after anesthetization the 6th-7th lumbar vertebral region was removed. In the cros-clamping o fthe abdominal aorta groups an abdominal incision was made and the lower abdominal aorta was ligated just distal to both
sides
of
the renal arteries and the animals were then allowed to rest. At the end of experiment the 6th-7th lumbar vertebral region was obtained and histological study was performed on all control group.
@ES The results were as follows:
@EN 1. During the perfusion of arterial blood into the sacral canal cerebrospinal fluid pressure was slightly raised form a mean control pressure of 9.1mmHg to 11mmHg.
2. The arterial pressure was relatively stable during the experiment of the epidural hematoma.
3. Measured epidural pressure during perfusion of arterial blood into the sacral canal was abruptly raised from mean control of 11.4mmHg to 59.4mmHg in the 10 minutes from the start of the perfusion, thereafter, about 66mmHg of epidural pressure
was
maintained throughout the experiment.
4. At the time when the specimen was obtained from the lumbar region of the all epidural hematoma groups, an extensive ecchymosis was discovered in the lumbodorsal fascia.
5. Epidural hematoma was seen in the sectioned specimens of the epidural hematoma group.
The hematoma was diverged from the epidural space through the intervertebral foramen and along the spinal nerves. It was found that the perimysial lymphatics of the posterior spinal muscles, the psoas muscle and also the collecting lymphatics and
common
iliac lymph nodes, were filled up with many red blood cells of hematoma.
6. In the epidural hematoma group, morphological features of the ventrolateral motor neurons appeared similar to those of the normal control group. The ventrolateral motor neurons in the crossclamping of the abdominal aorta groups showed that
the
cells
were subjected to ischemia or infarction due to the duration of the clamping.
Our observations demonstrate that raised epidural pressure exerted by an epidural hematoma in this model may be of insufficient duration for the development of ischemic changes in motor neurons. In this tudy we disclosed the existence of a
pathway
from
the epidural space to the lymphatic system. Further investigation is necessary to identify the factors which induce the neurologic complications of an epidural hematoma.
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KEYWORD
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