The LSUHSC New Orleans
Emergency Medicine Interest Group
The Student Procedure Manual
by Brian DeHart
- Diagnostic: meningitis(bacterial, viral, cryptococcal, TB, etc), multiple
sclerosis, neurosyphilis, subarachnoid hemorrhage
- Therapeutic: administration of antibiotics, analgesics, anti-tumor agents.
Treatment of pseudotumor cerebri
- Various neurosurgical procedures, myelography
- Infection at puncture site
- Suspected CNS mass lesion
- Increased intracranial pressure (relative)
- Coagulation disorders (relative)
- Sterile gloves
- Eye protection
- Cap and gown
- Spinal needle (20,22 gauge, smaller for peds)
- Manometer for opening pressures
- Three-way stopcock
- Collection tubes
- Lidocaine 1% with 5ml syringe
- 22 or 25 gauge needles for anesthesia
- Sterile drapes
- Materials for skin sterilization (Betadine)
- Adhesive dressing
Helpful hints before beginning
- Set up materials beforehand (i.e. culture tubes, opening pressure meter)
- Positioning the patient is the most important step
- Take your time, it often takes multiple attempts at redirecting the needle
- Fluid is obtained from subarachnoid space in the lumbar cistern located between
where the spinal cord terminates (conus medullaris, LI-2 for adults and L2-3
for infants) and where the dura terminates at the coccygeal ligament.
- Optimal interspace for obtaining fluid is the L4-5 located where the line connecting
the iliac crests is perpendicular to the midline of the back.
- Needle pierces through skin, supraspinous ligament, interspinous ligament, ligamentum
flavum, epidural space, dura mater, and subarachnoid membrane
- Perform fundoscopic and neurologic exam to rule out papiledema and focal neurological
deficit. View CT of head (if done) to assess evidence of increased intracranial
- Positioning and alignment: Lateral decubitus vs.
sitting: Sitting position is less difficult to obtain fluid but the opening
pressure will be inaccurate secondary to gravity. The lateral decubitus position
is the preferred method consequently, but it is more difficult because it requires
an alignment of the vertebral bodies.
- Have the patient flex hips and head into fetal position to obtain maximal vertebral
flexion in order to widen the interspace between the spinous processes. If patient
is uncooperative, have an assistant try to maintain this position. If the sitting
method is to be done, have patient lean forward over a table at the edge of
the bedside for vertebral flexion.
- Place a pillow under patient's head, neck and shoulder area to ensure spinal
cord is parallel to bed.
- Maintain proper lighting and raise bed to a level where you can comfortably
perform this procedure while seated.
- Palpate iliac crest with middle and ring fingers while using thumb to palpate
vertebrae to estimate puncture site.
- Open the LP tray and don sterile gloves.
- Set up the collection tubes in the space provided in the tray.
- Piece together the manometer and stopcock in order to be ready once fluid access
- Draw up the lidocaine with a syringe.
- Sterilize the skin with Betadine or equivalent type solution three times, each
time moving from center outward in a circular fashion.
- Place one sterile drape at base of patient on the bed, and place the drape with
the window over the desired area.
- Palpate landmarks again over sterile drape (iliac crest and spinous processes).
- Palpate spinous processes above and below desired site to make sure you have
the correct line.
- Inject lidocaine subcutaneously to make a wheal under the skin at the puncture
site. Then inject deeper aspirating each time before you inject. Withdraw needle
and exchange it for a longer one to get deeper anesthesia and repeat above.
As you withdraw the longer needle, inject to get adequate anesthesia.
- Insert spinal needle with stylet between spinous processes in midline, parallel
to the bed aiming 30 degrees cephalad towards umbilicus. Hold the needle between
thumb and middle finger or use two hands for stabilization. Do not bend or force
needle against too much resistance. When you feel you are in (supposedly a "pop"
is felt), withdraw stylet to see if fluid is returning. Sometime it helps to
rotate spinal needle. If no fluid returns, reinsert stylet and redirect needle
or go deeper. Do not redirect without first withdrawing the needle somewhat.
Often you may have the wrong angle or you are on bone or you're just not deep
enough; just keep repositioning and checking. This will take time and experience
so remain patient and stick with it.
Once fluid is obtained, allow a few drops to fall and then attach manometer
to get the opening pressure.
- Once pressure is obtained, attach collection tubes
below manometer or remove manometer and allow CSF to drip into tubes from manometer.
- Once fluid is collected, replace the stylet and carefully withdraw the spinal
- Achieve hemostasis with sterile gauze and place adhesive dressing over puncture
- Instruct patient to remain supine for the next 6-12 hours to minimize the chance
What do I send the tubes for?
Tube 1: Gram stain, culture and sensitivity, (AFB, fungal cultures when applicable)
Tube 2: Glucose and protein
Tube 3: Cell count (rbc, wbc with differential)
Tube 4: Hold in lab for further tests (VDRL, India ink, electrophoresis, antigen
*If suspecting subarachnoid hemorrhage, it is better to get cell counts in
first and last tubes for comparison. (If the first tube had many more cells
than the last, the cells came from a traumatic tap)-
- Spinal headache- have patient remain supine, use a smaller spinal needle
- Trauma to nerve root with complaints of parasthesias stop procedure
- Herniation - check before procedure for signs of increased ICP. If obtaining
CSF is a must, withdraw only what is needed and repeat pressure measurement
post-collection to ensure you do not go below one half of the initial pressure
- Infection - maintain sterility at all times
- Hemorrhage - rule out coagulopathy before procedure when applicable
- Bloody tap - repeat procedure at the next higher interspace normal ratio of
serum RBC:WBC is 500:1.
|wbc/rbc ratio = blood
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