Guidelines for Performing a Guarded Lumbar Puncture (LP)
Lumbar puncture should be performed in patients with suspected encephalitis or meningitis as soon as possible after hospital admission, unless there are specific clinical contraindications. 1
Contraindications to Immediate LP
Absolute Contraindications:
- Evidence of elevated intracranial pressure with space-occupying lesion 2, 3
- Local skin infection at the LP site 1
- Uncorrected coagulopathy 2
- Clinically unstable patient (circulatory shock or respiratory insufficiency) 1
- Clinical suspicion of spinal cord compression 1
Relative Contraindications Requiring CT Before LP:
- Moderate to severe impairment of consciousness (GCS < 13) 1, 2
- Focal neurological signs (including unequal, dilated or poorly responsive pupils) 1
- Abnormal posture or posturing 1
- Papilledema 1
- Recent seizures until patient is stabilized 1
- Relative bradycardia with hypertension 1
- Abnormal 'doll's eye' movements 1
Management of Anticoagulation Before LP
- For patients on heparin: Adequate reversal with protamine is mandatory 1
- For patients on warfarin: Reversal with vitamin K, prothrombin complex concentrate, or fresh frozen plasma is required 1
- For patients with bleeding disorders: Appropriate replacement therapy is indicated 1
- Platelet count should be ≥100 × 10^9/L before performing LP 1
- Consult a hematologist if unclear how to proceed 1
Pre-LP Imaging Considerations
- Clinical assessment, not cranial CT, should be the primary determinant of whether it's safe to perform an LP 2
- If clinical contraindications suggest possible raised intracranial pressure, perform CT scan first 1
- After a normal CT in patients with suspected raised ICP, LP should be considered on a case-by-case basis 1
- If immediate CT is not indicated, imaging (preferably MRI) should be performed as soon as possible after LP 1
LP Procedure Best Practices
- Position patient in lateral decubitus (fetal) position 2
- Use atraumatic needles to reduce post-puncture headache risk 2
- Insert needle with bevel parallel to dural fibers 2
- Extract CSF by gravity (avoid active aspiration) 2
- Limit CSF extraction to no more than 30 ml 2
- Make no more than 4 attempts at puncture 2
- Ensure needles meet National Patient Safety Agency standards 1
Post-LP Care
- Prolonged bed rest is not necessary and does not reduce post-puncture headache risk 2
- Immediate mobilization does not increase headache risk 2
Risk Factors for Post-LP Headache
- Young age 2
- Female sex 2
- History of previous headache 2
- Low BMI (≤25 kg/m²) 2
- Fear of the procedure 2
- Use of cutting-edge needles 2
- Multiple puncture attempts 2
When LP is Initially Contraindicated
- Review the situation every 24 hours 1
- Perform LP when it becomes safe to do so 1
- If initial LP is non-diagnostic, consider a second LP 24-48 hours later 1
CSF Collection and Analysis
- Document opening pressure (unless LP is performed in sitting position) 1
- Collect CSF for cell count, protein, and glucose (with concurrent plasma glucose) 1
- Consider CSF lactate measurement (values <2 mmol/l help rule out bacterial disease) 1
By following these guidelines, clinicians can safely perform lumbar punctures while minimizing risks and maximizing diagnostic yield in patients with suspected CNS infections or other neurological conditions requiring CSF analysis.