Lumbar Puncture (Spinal Tap) - Nursing Responsibilities

A lumbar puncture (spinal tap) is an invasive procedure: a hollow needle goes into the space surrounding the subarachnoid space in the lower back to pull cerebrospinal fluid (CSF) for analysis. Most central nervous system disorders are diagnosed off changes in CSF composition and dynamics, so the sample matters. The same access is also used to measure CSF pressure, instill medications, or introduce contrast into the spinal canal. The procedure runs about 30 to 45 minutes and is often done outpatient at a hospital or clinic.

Your job around it is information and positioning. A patient who knows what is coming holds still, stays calm, and has fewer complications afterward. Teach before, support during, monitor after.

Indications

• Measure cerebrospinal fluid (CSF) pressure.
• Help diagnose suspected CNS infections (bacterial or viral meningitis, meningoencephalitis), intracranial or subarachnoid hemorrhage, and some malignancies.
• Evaluate demyelinating or inflammatory CNS processes such as multiple sclerosis, Guillain-Barré syndrome (GBS), and acute disseminated encephalomyelitis (ADEM).
• Infuse medications: spinal anesthesia before surgery, contrast for imaging such as CT-myelography, and chemotherapy directly into the spinal canal.
• Treat normal pressure hydrocephalus, cerebrospinal fistulas, and idiopathic intracranial hypertension (IIH).
• Place a lumbar CSF drainage catheter.

Contraindications

Absolute contraindications:

• Increased intracranial pressure from a brain tumor. Withdrawing CSF can trigger cerebral or cerebellar herniation with severe neurological deterioration.
• Skin infection near the puncture site. You risk seeding infected material into the CSF.
• Severe degenerative vertebral joint disease. The needle cannot pass cleanly through a degenerated, arthritic interspinal space.
• Severe coagulopathy. High risk of epidural hematoma.

Equipment

The lumbar puncture kit contains:

• Sterile gloves
• Sterile drapes and procedure tray
• Sterile gauze pads
• Aseptic solution: povidone-iodine (Betadine)
• Local anesthetic: lidocaine 1% solution
• 25G needle
• 10ml syringe (1)
• Spinal needle with stylet (22G or 25G)
• CSF tubes (2 to 4)
• Stopcock
• Manometer tubing

Procedure

1. Position the patient in a fetal position. Side-lying at the edge of the bed, knees drawn to the abdomen, chin tucked to the chest. Sitting and leaning over a bedside table also works. If supine, support the spine on a horizontal plane with pillows.
2. Sterilize and drape the insertion site, then inject the local anesthetic.
3. Insert the spinal needle in the midline between the spinous processes, usually between the third and fourth or the fourth and fifth lumbar vertebrae.
4. Remove the stylet. Properly placed, CSF drips from the needle. Attach a stopcock and manometer to read the opening (initial) CSF pressure.
5. Collect the specimens into the appropriate containers.
6. Remove the needle and apply a small sterile dressing.

Nursing Responsibilities

Before the procedure

• Explain the procedure. Purpose, how and where it is done, and who is performing it.
• Obtain informed consent. Confirm the consent form is signed if the institution requires it.
• Reinforce diet. Fasting is not required.
• Promote comfort. Have the patient empty bladder and bowel first.
• Establish baseline data. Vital signs plus neurologic assessment of the legs: movement, strength, sensation.
• Position in lateral decubitus. Fetal position near the side of the bed, neck, hips, and knees drawn to the chest. Sitting and leaning over a bedside table is the alternative.
• Instruct the patient to stay still. Any unnecessary movement during the procedure can cause traumatic injury.

After the procedure

• Apply brief pressure to the puncture site to prevent bleeding, then cover with a small occlusive dressing or band-aid.
• Keep the patient flat for 4 to 6 hours per physician order. Side-to-side turning is fine as long as the head stays down.
• Monitor vital signs, neurologic status, and intake and output at least every 4 hours for 24 hours.
• Watch the puncture site for CSF leakage and bleeding. Signs of leakage: positional headache, nausea and vomiting, neck stiffness, photophobia, sense of imbalance, tinnitus, phonophobia.
• Encourage fluids (up to 3,000 ml in 24 hours) to replace removed CSF.
• Label and number the specimen tubes correctly and send to the lab immediately.
• Give analgesia as ordered. Post-procedure headaches can last hours to days and are treated with analgesics.

Normal Results

• Pressure: 70 to 180 mm H20
• Appearance: clear and colorless
• CSF total protein: 15-45 mg/dL
• Gamma globulin: 3 to 12% of total protein
• CSF glucose: 50 to 80 mg/dl
• CSF cell count: no RBCs; WBC count 0-5 WBCs per microliter (all mononuclear)
• CSF chloride: 118 to 130 mEq/L
• Gram stain: no organisms present

Abnormal Results

• Pressure: increased ICP from tumor, hemorrhage, or trauma-induced edema; decreased ICP may signal a spinal subarachnoid obstruction.
• Appearance: cloudy suggests infection; yellow to reddish suggests spinal cord obstruction or intracranial hemorrhage; brown to orange suggests increased protein or RBC breakdown.
• CSF protein: increased with tumor, trauma, diabetes mellitus, or blood in the CSF; decreased with rapid CSF production.
• Gamma globulin: increased in demyelinating disease (multiple sclerosis, neurosyphilis, Guillain-Barré syndrome).
• CSF glucose: increased with hyperglycemia; decreased with hypoglycemia, bacterial or fungal infection, tuberculosis, or meningitis.
• CSF cell count: increased WBCs suggest meningitis, tumor, abscess, acute infection, stroke, or demyelinating disease; RBCs indicate bleeding into the spinal fluid or a traumatic tap.
• CSF chloride: decreased with infected meninges.
• Gram stain: gram-positive or gram-negative organisms indicate bacterial meningitis.

Complications

• Post-lumbar puncture headache. The most common complication, from CSF leaking out of the puncture site or into surrounding tissue. Worse sitting, standing, or coughing; resolves lying down.
• Back pain from trauma to local soft tissue.
• Pain or numbness, a temporary tingling in the lower back and legs.
• Bleeding, usually at the puncture site, rarely into the subarachnoid, subdural, or epidural space.
• Brainstem herniation. Removing CSF can shift brain tissue suddenly and compress or herniate the brainstem.