Lumbar puncture

Contraindications

1. Infection at LP site
2. Platelet count <20K
   1. Platelet counts >50K are safe for LP
3. INR >1.5
4. Heparin administration in past 24hr
5. Hemophilia, von Willebrand disease, other coagulopathies
6. Trauma to lumbar vertebrae

See also CT Before Lumbar Puncture

Procedure

1. Sterile prep L3-L4 and L4-L5 interspaces; prepare and confirm correct tubes in numerical order
2. Positioning
   1. Pt on side: able to measure opening pressure
   2. Pt sitting: helpful for difficult habitus, but must move pt to measure opening pressure
3. Needle selection
   1. 3.5 in atraumatic 22ga needle is ideal
   2. Needle >20ga almost doubles incidence of post-LP headache
4. Anesthetize both superficial skin as well as along intended path of LP needle
5. Insert needle with bevel facing the ceiling (if pt is on side)
6. Opening pressure should be measured with pt on side with legs extended
7. Collect 1mL in each tube

CSF Studies

Standard

• Tube 1: Gram Stain and culture
• Tube 2: Protein and glucose
• Tube 3: Cell count w diff
• Tube 4: Hold

Additional

1. Cryptoccal ag
2. India ink
3. AFB PCR
4. RPR, VRDL
5. Fungal cx
6. viral cx
7. Herpes PCR
8. LDH
   1. >40 suggests bacterial meningitis
   2. <40 suggests viral

Diagnosis

Measure	Normal	Bacterial	Aseptic (Viral)	Fungal	Tuberculosis	Subarachnoid hemorrhage	Neoplastic
Appearance	Clear	Clear, cloudy, or purulent	Clear	Clear or opaque	Clear or opaque	Xanthochromia, bloody, or clear	Clear or opaque
Opening Pressure (cm H2O)	10-20	>25	Normal or elevated	>25	>25	>25	Normal or elevated
WBC Count^ (cells/µL)	0-5^	>100^	5-1000	<500	50-500	0-5 (see correction section)	<500
% PMNs		>80-90%	1-50%^^	1-50%	Early PMN then lymph		1-50%
Glucose	>60% of serum glucose	Low	Normal	Low	Low	Normal	Normal
Protein^^^ (mg/dL)	< 45	Elevated	Elevated	Elevated	Elevated	Elevated	>200
Gram Stain	Neg	Pos	Neg	India ink	Tb stain	Blood

• ^Normal or lower WBC results may be found in immunocompromised, early, or partially treated (e.g. with oral antibiotics) bacterial menintigis, and those with tuberculosis meningitis
• ^^Lymph predominance may be found in patients with early bacterial meningitis or those that have been partially treated (e.g. with oral antibiotics)
• ^^^For unexplained elevations of protein, consider encephalitis, MS, Guillian Barre

Corrections

• WBC correction (for bloody tap)
  • Simplified version (if peripheral WBC and RBC counts are within normal limits):
    • Subtract 1 WBC for every 750 RBC in CSF
  • Complex version (WBC and/or RBC not within normal limits):
    • "WBCs added" = WBC(blood) x [RBC(CSF) / RBC(blood)]
    • WBC counted/resulted - "WBCs added" = actual WBC
• Protein correction (for bloody tap)
  • For each 1000 RBC decrease protein value by 1mg/dl

Complications

1. Post-Lumbar Puncture Headache
2. Spinal Epidural Hematoma

See Also

• Meningitis
• CT Before Lumbar Puncture

Source

• Tintinalli
• Hasbun, R. et al, (Yale), NEJM, Dec 13, 2001.