traumatic tap from a valid finding of bloody
CSF, centrifuge the first and last specimen tubes
collected. If the fractional volume of blood in
the last tube collected is much less than that in
the first, the blood probably comes from a
traumatic tap. A xanthochromic supernatant
following CSF centrifugation indicates that
blood was present in the CSF prior to puncture.
3. Adequate fluid should be withdrawn to perform
the requisite laboratory studies. It is not the
volume of fluid removed at the time of puncture
but the subsequent leakage of CSF through the
dural defect that is usually responsible for the
complications of the procedure related to CSF
volume depletion.
Medical Considerations
1. There are three settings in which the performance
of a lumbar puncture entails a significant risk of
a life-threatening complication. These are: a)
the patient with increased intracranial pressure;
b) the patient who has a hemorrhagic diathesis;
and c) the patient with an infection at the
proposed site of the lumbar puncture. Each of
these settings is a relative contraindication for a
lumbar puncture. The need for a CSF specimen
must outweigh the risk involved if a lumbar
puncture is performed in such cases.
2. Respiratory compromise, which can mimic venti-
lation failure from brain herniation, can develop
in weak patients or patients with pulmonary
disease who are held in a highly flexed position.
Be certain that the patient can breathe comforta-
bly while positioned for the procedure.
3. The most common complication of lumbar
puncture is postural headache, which is often
accompanied by backache. The incidence of
headache depends upon the technique and can be
as high as 20 percent. Headache is uncommon
when small-bore spinal needles are used and
when the number of punctures is minimized.
4. Radicular symptoms following a lumbar puncture
suggest spinal nerve root trauma. Incorrect
technique is the most frequent explanation for
this complication. Spinal nerves are displaced
and stretched when the CSF specimen is
obtained using plunger action or when the spinal
needle stylet is not replaced prior to withdrawal
of the needle.
Specimen Collection Procedures A-9
