Procedural Steps
Patient Positioning
Site Preparation
Local Anesthesia
Needle Insertion
Collection of CSF
Removal of Needle
Post-procedural Care
Interpretation of Results
CSF Pressure

LP Pressure Quick Guide

Under Development
© Faculty of Medicine, University of Ottawa,
Version January 2, 2003

Full guide www.med.uottawa.ca/procedures/lp

LP (or CT scan) should NOT delay antibiotics and fluid resuscitation in patients with probable meningitis.

Contra-indications to LP: symptoms or signs of raised intracranial pressure (these include a decreased level of consciousness, localizing (focal) neurologic signs and papilledema), a severe bleeding diathesis or coagulation disorder or the patient is on anticoagulation therapy, infection at the planned site of the puncture.

Consent: Obtain a signed informed consent from the patient or a substitute decision maker after explaining the risks and benefits of the procedure.

Preparation: Have an assistant available. Use an LP kit in the hospital setting. Use a 22 or 25 gauge-3 inch LP cutting needle or an atraumatic non-cutting needle.

Patient positioning: If the patient is too ill to sit upright, then position the patient in a left lateral or right lateral lying position. The patient, with a pillow under the head, should curl into a fetal position, placing the lumbar spine in maximal flexion. The patient's back should be at the edge of the bed.

Landmarking: A line drawn between the superior borders of the posterior iliac crests will intersect the L4 spinous process. Identify the L4-L5 interspinous process space midline as your needle insertion site. If insertion at this space is unsuccessful, try the L3-L4 space.

Site preparation: The site is cleansed with iodinated solution, applied in a circular fashion followed by a careful application of isopropyl alcohol or a chlorhexidene based solution to wash off the iodinated solution.

Local anaesthesia: Using a 25 gauge needle, create a skin wheal with 1% xylocaine at the insertion site. Now change to the 22 gauge needle to infiltrate the subcutaneous and interspinous areas with up to 3 cc. of 1% lidocaine solution.

Spinal needle insertion
If using the standard cutting needle, insert the needle at the identified site with the bevel facing upward (if the patient is in the left or right lateral position). The bevel should be parallel to the axis of the spine ensuring that the bevel is parallel to the dural fibres. Direct the needle at an angle of approximately 10 degrees cephalad. Advance the needle approximately 1.5 inches or until a slight "pop" is felt as the dura is penetrated. Remove the stylet and wait 2 seconds for CSF drainage. If there is no CSF return, advance the needle 1-2 mm. at a time, checking for CSF return with each advance. If the needle tip encounters bone, withdraw the needle tip to just below the skin, check your landmarks and patient positioning and advance the needle again.

Collection of CSF: Collect 1.5-2 cc. of fluid in each of 4 to 5 test tubes.

Removal of needle: Replace the stylet fully into the spinal needle before withdrawing the needle. Apply pressure on the site with a gauze and then apply a band-aid. Place the patient in a comfortable body position.

CSF analysis: In the emergency department send for these tests: Tube 1 - cell count, Tube 2 - stat gram stain and culture (C+S), Tube 3 - glucose and protein, Tube 4 - cell count (for comparison to Tube 1), Tube 5 (optional) - virology, mycology, cytology, etc.


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