Cerebrospinal Fluid (CSF) Analysis
Cerebrospinal fluid is a clear substance that circulates in the subarachnoid space, protects the brain and spinal cord from injury and transports products of neurosecretion, cellular biosynthesis, and cellular metabolism through the Central Nervous System.
For qualitative analysis, CSF is obtained most commonly by lumbar puncture (usually between the third and fourth lumbar vertebrae) and, rarely by cisternal or ventricular puncture. A CSF specimen may also be obtained during other neurologic tests such as myelography.
Purpose of Cerebrospinal Fluid Analysis
- To measure cerebrospinal fluid (CSF) pressure as an aid in detecting an obstruction of CSF circulation.
- To aid in the diagnosis of viral or bacterial meningitis, subarachnoid or intracranial hemorrhage, tumors, and brain abscesses.
- To aid in the diagnosis of neurosyphilis and chronic central nervous system infections.
- To check for alzheimer’s disease.
Cerebrospinal Fluid Analysis Procedure
- Tell the patient that this test usually takes at least 15 minutes.
- Inform him that a headache is the most common adverse effect of lumbar puncture, but reassure him that his cooperation during the test helps minimize the reaction.
- Make sure that the patient or a responsible family member has signed an informed consent form.
- If the patient is unusually anxious, assess and report his vital signs.
- If the patient is positioned on his side, provide pillows to support the spine on a horizontal plane. This position allows full flexion of the spine and easy access to the lumbar subarachnoid space.
- Help him maintain his position by placing one arm around his knees and the other arm around his neck.
- If the sitting position is used, help the patient maintain this position throughout the procedure.
- After the skin is prepared for injection, the area is draped.
- The anesthetic is injected, and the spinal needle is inserted in the midline between the spinous vertebral process, usually between the third and fourth lumbar vertebrae.
- When the stylet is removed from the needle, CSF drips from it if the needle is properly positioned.
- A stopcock and manometer are attached to the needle to measure initial (opening) CSF pressure.
- After the specimen is collected, label the containers in the order in which they were filled and record the doctor’s specific instruction for the laboratory.
- A final pressure reading is taken, and the needle is removed.
- Clean the puncture site with local antiseptic, such as providone-iodine solution, and apply a small adhesive bandage.
- Send the form and labeled specimens to the laboratory immediately.
- Check whether the patient must lie flat or if the head of his bed may be slightly elevated.
- Encourage the patient to drink fluids. Provide a flexible straw.
- Check for the puncture site for redness, swelling, and drainage every hour for the first 4 hours, and then every 4 hours for the first 24 hours.
- If CSF pressure is elevated, assess the patient’s neurologic status every 15 minutes for 4 hours. If he’s stable, assess him every hour for 2 hours and then every 4 hours or according to the present schedule.
- Clear, colorless fluid.
- Cell count: No red blood cells (RBCs); 0 to 5 white blood cells (WBCs).
- Gram stain: No organism
- Pressure: 50 to 180 mm H2O
- Cloudy, bloody, brown, orange, or yellow fluid.
- Cell count: RBCs present; increased WBCs
- Gram stain: Gram positive or gram-negative organisms.
- Pressure: Increased or decreased.
- Infection at the puncture site contraindicates CSF removal.
- In the patient with increased intracranial pressure, CSF should be removed with extreme caution because fluid withdrawal can cause a rapid reduction in pressure and cerebellar tonsillar herniation and medullary compression.
- Patient position and activity may possibly increase or decrease in CSF pressure.
- Crying, coughing, or straining.
- Delay between collection time and laboratory testing that may possibly invalidation of test results, especially cell counts.
- Reaction to anesthetic, meningitis, bleeding into the spinal canal, cerebellar tonsillar herniation, and medullary compression.
- Signs of meningitis.
- Signs of herniation.