Lumbar Puncture Notes

Lumbar Puncture (LP)

  • Definition: Obtaining cerebrospinal fluid (CSF) to detect microorganisms, RBCs, or WBCs; measure CSF pressure.

Site of Puncture

  • Spinal needle inserted between L3-L4 vertebrae.
  • CSF collected from thecal sac around spinal cord.

Indications

  • Suspicion of meningitis, encephalitis, brain abscess.
  • Suspicion of subarachnoid hemorrhage.
  • Suspicion of CNS diseases like Guillain-Barré, carcinomatous meningitis, multiple sclerosis.

Contraindications

  • Increased intracranial pressure (ICP); CT scan needed to rule out mass effect.
  • Abnormal respiratory pattern, hypertension with bradycardia, deteriorating consciousness.
  • Platelet count less than 50x109/L50 x 10^9/L.
  • Vertebral deformities (scoliosis or kyphosis) in inexperienced hands.

Equipment

  • Diagnostic tray, spinal needle (18G/20G for adults, 22G for children), sterile collection bottles, sterile gloves.
  • Xylocaine injection or EMLA cream, examination light, clean gloves, linen protector.
  • 3-way stop cock with manometer (if needed), elastoplast/transparent dressing, povidone-iodine/alcohol spirit.

Procedure

  • Verify client identity and explain LP purpose for diagnosing tumors, hemorrhage, infection, autoimmune CNS diseases.
  • Explain needle insertion into subarachnoid space at L3-4 or L4-5 to measure CSF pressure and obtain fluid.
  • Obtain history of allergies and current medications; obtain consent.
  • Instruct client to empty bowel and bladder; perform hand hygiene.

Positioning

  • Lateral recumbent: C-shaped, back at edge of table, chin to chest, knees to abdomen.
  • Sitting position: For obese patients, straddling a chair with head resting on arms.

During Procedure

  • Assess and document vital signs; continuous monitoring as needed.
  • Expose only client’s back; open sterile tray.
  • Assist client in relaxation exercises, instruct in deep breathing.
  • Monitor vital signs during procedure.

Sample Collection

  • 2-3 mL of spinal fluid in each test tube.
  • Spinal fluid should be clear and colorless; bloody fluid may indicate subarachnoid hemorrhage or traumatic tap.

Post-Procedure Care

  • Label CSF samples and send to lab ASAP.
  • Apply dressing to puncture site; remove gloves and perform hand hygiene.
  • Monitor vital signs, neurological status, intake & output, puncture site.
  • Instruct client to lie flat for 4-24 hours; encourage fluids (3L in 24 hours if not contraindicated).
  • Observe for spinal fluid leak, hematoma, headache, or neurological changes.

Complications

  • Headache, anesthetic reaction, meningitis, epidural or subdural abscess.
  • Bleeding into spinal canal, CSF leak, local pain, oedema or hematoma.
  • Difficulty voiding, fever, spinal cord herniation, and medullary compression.

Normal CSF Results

  • Appearance: Clear & colorless.
  • Volume: 135-150 mL.
  • White Cells: 0 neutrophils, 0-10 lymphocytes.
  • Red Blood Cells: 0.
  • Protein: 5-25 mg/dL.
  • Glucose: 3.3-4.4 mmol/L (or ≥≥60% of plasma glucose).
  • pH: 7.35-7.45.
  • Pressure: 70-180 mmH2O (LP), 3-15 mmHg (ventricular).
  • SG: 1.007.

Abnormal Results

  • Raised ICP > 180 mmH2O tumor, hemorrhage, or oedema.
  • Decreased ICP < 50 mmH2O spinal subarachnoid obstruction.
  • Cloudy: Infection.
  • Yellow or blood-stained: Intracranial hemorrhage or spinal cord obstruction.