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586 PART 8 ■ Fundamentals of Hematological Analysis
tube 3 is or gross examination, cell count, and morphol-
Reasons for Performance of a
TABLE 29.2 Lumbar Puncture and Removal ogy. Because cells disintegrate rapidly, they must be counted
within 1 hour o specimen collection.
of an Aliquot of CSF
Caution: All CSF specimens should be handled with
Therapeutic Relief of increased intracranial pressure extreme care. T ese specimens could potentially harbor
viruses or other in ectious organisms.
Diagnostic Identi cation of conditions such as sub-
arachnoid hemorrhage, meningeal infec- Gross Physical Exam ination
tion (meningitis), multiple sclerosis, and T e spinal f uid is examined visually or turbidity (cloudi-
neoplasms
ness), color, and viscosity. Normal CSF is clear and colorless.
Its appearance and viscosity are comparable to those o water.
Specimen Collection: Lumbar Puncture Turbidity
CSF is ound inside all the ventricles, in the central canal o the I any turbidity exists, it should be graded using a scale o 0 to 4+.
spinal cord, and in the subarachnoid space around both the In the absence o a set o known standards or comparison, the
brain and the spinal cord. T e subarachnoid space is the area rating scale is subjective. T is scale ranges rom 1+, slight cloudi-
between the arachnoid mater, the middle meningeal mem- ness, to 4+, in which newsprint cannot be seen through the tube.
brane covering the brain and spinal cord, and the pia mater, Cloudiness or turbidity may be caused by pleocytosis
the innermost meningeal membrane. T e total maximum (increased concentrations o leukocytes, erythrocytes, or
volume o CSF in adults is about 150 mL. T e maximum vol- microorganisms) or, less commonly, radiographic contrast
ume in neonates is approximately 60 mL. T e rate o orma- media or the presence o at globules.
tion in adults is approximately 500 mL/d or 20 mL/h and is Grossly bloody specimens can result rom a traumatic tap or
reabsorbed at the same rate, so the volume remains constant. rom conditions such as a bleeding subarachnoid hemorrhage
In a lumbar puncture, introducing a needle into the subarach- or intracerebral hemorrhage. raumatic taps more commonly
noid space makes it possible to measure CSF pressure and to occur in children because o movement during the procedure.
obtain f uid or analysis ( able 29.2). T is procedure is contra- It is important to di erentiate between specimens rom a
indicated when there is a skin in ection at the puncture site or traumatic tap and those that are related to the patient’s clini-
when the patient has septicemia or a general systemic in ection, cal condition. A reshly collected specimen should be exam-
because o the risk o spreading the in ection into the meninges. ined immediately. I the reddish color diminishes between
Te patient is placed in a horizontal position, and the site is the rst and the last tube, the blood in the specimen is due to
thoroughly cleansed to reduce the possibility o contamination a traumatic tap. In addition, clots may be observed in trau-
with normal skin microbial f ora. A stylet needle is introduced matically collected specimens because o the presence o an
by a physician into the intervertebral space between the L4 and increased concentration o protein or blood or in a specimen
L5 (lumbar) vertebrae. Up to 20 mL o f uid can be removed rom a patient with a subarachnoid block or meningitis.
i the patient has a normal opening pressure. T e specimen
should be placed into sterile tubes. A er CSF collection, the Color
closing pressure is measured, the stylet replaced, and the needle Any presence o color should be noted. A yellow coloring
removed. Specimens must be promptly delivered to the labora- o a specimen or the supernatant o a centri uged specimen
tory or analysis. T e patient should be given appropriate a er- is re erred to as xanthochromia. T e release o hemoglobin
care because the procedure is not without risk. rom hemolyzed erythrocytes (red blood cells [RBCs]) in
Indications or spinal f uid examination are changing as the CSF is a potential cause o xanthochromia. T e lysis o
other diagnostic methods are improved. Only in a ew condi- RBCs in CSF begins about 2 hours a er the occurrence o
tions, such as meningitis, is the lumbar puncture essential and a subarachnoid hemorrhage ( able 29.3). Other conditions
o en diagnostic. It may be o di erential value in other cases.
Laboratory Analysis Changes in CSF Follow ing
TABLE 29.3
General Principle Hemorrhage
A specimen o CSF is examined visually and microscopically. Gross Examination
T e total number o cells can be enumerated, and the types o
cells can be morphologically distinguished. 2–12 h Xanthochromia (pink to orange)
12–24 h Xanthochromia (yellow color, disappears in 2–4 wk)
Specim en
Microscopic Examination
From three to ve samples o 2 to 4 mL each are collected in 2–24 h Erythrocytes, neutrophilic granulocytes (PMNs),
sterile tubes by a physician. T e number o tubes and speci- monocytes, and a few lymphocytes
ed examination related to each tube depends on institutional
protocol. ypically, tube 1 is or chemical and serological ≥48 h Monocytes and PMNs, erythrophagocytosis,
examination; tube 2 is or microbiological examination; and siderophages (may persist for 2–8 wk)
