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LUMBAR PUNCTURE

 

 

Indications

 

1.                  Suspected CNS infection

2.                  Suspected subarachnoid hemorrhage

3.                  Therapeutic reduction of cerebrospinal fluid (CSF) pressure

4.                  Sampling of CSF for any other reason

 

Contraindications

 

1.                  Local skin infections over proposed puncture site (absolute contraindication)

2.                  Raised intracranial pressure (ICP); exception is pseudotumor cerebri

3.                  Suspected spinal cord mass or intracranial mass lesion (based on lateralizing neurological findings or papilledema)

4.                  Uncontrolled bleeding diathesis

5.                  Spinal column deformities (may require fluoroscopic assistance)

6.                  Lack of patient cooperation

 

Materials

 

1.                  Lumbar puncture tray (to include 20 or 22 gauge Quinke needle with stylet, prep solution, manometer, drapes, tubes, and local anesthetic)

2.                  Universal precautions materials

 

 

Preprocedure patient education

 

1.                  Obtain informed consent

2.                  Inform patient of possibility of complications (bleeding, persistent headache, infection) and their treatment

3.                  Explain the major steps of the procedure, positioning, and postpocedure care

 

 

Procedure

 

1.                  Assess indications for procedure and obtain informed consent as appropriate

2.                  Provide necessary analgesia and/or sedation as required

3.                  Position patient: lateral decubitus position with “fetal ball” curling up, or seated and leaning over a table top; both these positions will open up the interspinous spaces (see Figure 1)

 

 

Figure 1: Positioning patient for lumbar puncture

 

 

4.                  Locate landmarks: between spinous processes at L4-5, L3-4, or L2-3 levels (see Figure 2). On obese patients, find the sacral promontory; the end of this structure marks the  L5-S1 interspace.  Use this reference to locate L4-5 for the entry point. You will aim the needle towards the navel.

 

 

 

 

Figure 2. Anatomy of lumbar spine

 

5.                  Prep and drape the area after identifying landmarks. Use lidocaine 1% with or without epinephrine to anesthetize the skin and the deeper tissues under the insertion site

6.                  Assemble needle and manometer. Attach the 3-way stopcock to manometer

7.                  Insert Quinke needle bevel-up through the skin and advance through the deeper tissues. A slight pop or give is felt when the dura is punctured. Angle of insertion is on a slightly cephalad angle, between the vertebra (Figure 3). If you hit bone, partially withdraw the needle, reposition, and re-advance

 

Figure 3

8.                  When CSF flows, attach the 3-way stopcock and manometer. Measure ICP…this should be 20 cm or less. Note that the pressure reading is not reliable if the patient is in the sitting position

9.                  If CSF does not flow, or you hit bone, withdraw needle partially, recheck landmarks, and re-advance

10.              Once the ICP has been recorded, remove the 3-way stopcock, and begin filling collection tubes 1-4  with 1-2 ml of CSF each

 

Tube 1: glucose, protein, protein electrophoresis

Tube 2: Gram’s stain, bacterial and viral cultures

Tube 3: cell count and differential

Tube 4: reserve tube for any special tests

 

11.              After tap, remove needle, and place a bandage over the puncture site. Instruct patient to remain lying down for 1-2 hours before getting up

 

NOTES:

 

1.                  Insertion of the  needle bevel-up minimizes dural trauma

2.                  A traumatic “bloody tap” occurs when a spinal venous plexus is penetrated. Often the fluid will clear as succeeding tubes are filled. Spin down the first tube: if red blood cells have been in the spinal fluid for some time (for example, subarachnoid hemorrhage), xanthochromia will be present in the supernatant fluid. If the fluid is clear after it is spun down, the tap was only traumatic

3.                  In some cases, conscious sedation is helpful in reducing patient anxiety and allowing maximal spinal flexion

 

Complications, Prevention, and Management

 

Complication

 

Prevention

 

Management

 

 

Bleeding from puncture site post-tap

 

None

 

 

Local pressure

 

Bloody spinal fluid

 

 

None

 

 

Withdraw needle and perform tap at interspace either above or below

Infection

 

 

Do not perform tap through infected skin

Use sterile technique

Antibiotics

 

 

Post-tap persisting headache

 

 

Use pencil-tipped needle if possible; insert needle bevel-up

 

 

 

Post-procedure epidural blood patch by anesthesia consultant

 

 

 

 

 

 

Documentation in the medical record

 

            Include in your note a brief history and physical examination of the patient,,  the reasons for performing the lumbar puncture, and consent. Note in particular a brief examination of the cranial nerves, presence or absence of papilledema, or any other lateralizing neurological finding. Also include a brief note of examination of the patient’s spine with attention to any obvious spinal deformity.

            Document position of patient during the procedure, opening pressure, and clarity/color of the CSF. Once results of the CSF analysis are available, they can be appended to your note.

 

 

Parameter

Normal Values

 

 

Protein

15-45 mg/dl

Glucose

50-80 mg/dl

WBC

< 5 mm3

RBC

0-5

Opening pressure

5-20 cm

Clarity, color

Clear and colorless

 

 

NORMAL CSF VALUES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Items for evaluation of person learning this procedure

 

 

1.                  Anatomy of lumbar spine

2.                  Indications of procedure

3.                  Contraindications for procedure

4.                  Interaction between physician, staff, patient, and/or family

5.                  Sterile technique, universal precautions

6.                  Technical ability

7.                  Appropriate documentation

8.                  Understanding of potential complications and their correction