Lumbar Puncture Procedure

Lumbar Puncture (Spinal Tap)

• A procedure where a sample of cerebrospinal fluid (CSF) is taken for examination
• Also called a spinal tap
• Performed while lying on side in a curled up fetal position or sometimes in a sitting position
• Crucial to remain still during the procedure

Procedure

• Back is cleaned with an antiseptic and a local anesthetic is injected under the skin
• A special needle is inserted through the skin, between two vertebrae, and into the spinal canal
• Needle is gently advanced until it enters the subarachnoid space and CSF begins to flow
• An "opening" or initial pressure reading of the CSF is obtained
• A small amount of CSF is collected in multiple sterile vials
• A "closing" pressure is obtained, the needle is withdrawn, and a sterile dressing and pressure are applied to the puncture site

Post-Procedure

• Lie quietly in a flat position, without lifting head, for one or more hours to avoid a potential post-test spinal headache

CSF Analysis

• CSF cell count: measures the number of red and white blood cells in CSF
• Normal white blood cell count is between 0 and 5 per micro
• Normal red blood cell count is 0
• Increase in white blood cells indicates infection, inflammation, or bleeding into the CSF
• Finding red blood cells in CSF may be a sign of bleeding

Composition of Cerebrospinal Fluid

• CSF is produced at a rate of about 500 mL per day
• All of the CSF is replaced every few hours
• CSF is basically an ultrafiltrate of the blood
• Constituents of CSF such as protein and glucose are a percentage of blood levels

Clinical Significance of CSF Tests

• CSF tests can aid in the diagnosis of neurological diseases
• Can detect levels of protein and glucose in CSF
• Can detect the presence of microorganisms in CSF
• Can aid in the diagnosis of subarachnoid hemorrhage and central nervous system infections

Reference Ranges for Ions and Metals in CSF

• Sodium: 135-150 mmol/L
• Potassium: 2.6-3.0 mmol/L
• Chloride: 115-130 mmol/L
• Calcium: 1.00-1.40 mmol/L
• Magnesium: 1.2-1.50 mmol/L
• Iron: 0.2-0.4 µmol/L
• Glucose: 50-80 mg/dL
• Protein: 15-40-45 mg/dL
• Albumin: 7.8-40 mg/dL
• Lactate: 1.1-2.4 mmol/L
• Creatinine: 50-110 µmol/L
• Phosphorus: 0.4-0.6 µmol/L
• Urea: 3.0-6.5 mmol/L
• Carbon dioxide: 20-25 mmol/L

This quiz covers the steps involved in a lumbar puncture procedure, including obtaining CSF pressure readings and collecting cerebrospinal fluid samples. Learn about the importance of remaining still and the post-procedure care.