© 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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