Lumbar Puncture - 3
Important Good patient positioning and an experienced assistant are the most important factors for success.
Procedure
-Wash hands, put on gloves, gown, mask per hospital policy
-Open CSF tubes and have ready - ensure correct labelling 1,2,3
-Cleanse skin with chlorhexidine or betadine
-Place sterile drapes around site
Local anaesthetic
-Infiltrate site with local anaesthetic :
Raise skin bleb, then infiltrate more deeply
Aspirate before injecting to avoid accidental intravascular or spinal injection of local anaesthetic
[some people prefer to put the local in before putting the skin prep on, which gives it plenty of time to work.]
Inserting the spinal needle
-Recheck patient position - check the patient's back is vertical.
-Grasp spinal needle with bevel facing upwards.
-Insert needle into skin at selected site, ensuring the aim of the needle is perpendicular to the back.
-As the needle is inserted, there is the distinctive 'pop' as the sharp tip of the spinal needle punctures first the ligamentum flavum, and then the dura mater.
-withdraw the sylet, and wait for CSF to appear in the hub. [this can take a little while with the thinner needles e.g. 25G and below]
If no CSF appears
-Advance the needle slowly until CSF appears
-Try rotating the needle through 90-180 degrees
-If this does not work, withdraw needle and try again
The presence of blood rather than CSF in the hub signifies :
a) Traumatic tap ; should clear with time, collect fluid and will need to account for this when interpreting results
b) Entry into epidural or spinal veins ; does not clear over time - withdraw needle and try again to collect CSF
When CSF appears from the needle hub
- Ensure patient remains still.
- Some operators prefer to discard the first couple of drops if they are grossly bloodstained.
- Place labelled tubes in order under hub of needle and allow CSF to drip into tubes - collect 8-10 drops per tube
Be patient... do not rush this stage
NEVER ATTEMPT TO ASPIRATE FLUID FROM NEEDLE
-Note the color of the fluid - turbid fluid indicate bacterial meningitis
-Once fluid is collected, remove needle, apply pressure at the site for 30-60 seconds and cover site with a light, sterile dressing.
-Send tubes to Pathology requesting (as appropriate)
1) CSF glucose and protein
2) CSF microscopy
3) Cell counts
4) CSF gram stain
5) Antigen testing
6) Presence of xanthochromia
7) Culture and sensitivities
Ensure you notify the lab and request the results be processed urgently, and have results phoned to you directly.
If the CSF is turbid, and the patient is unwell.
Treat with appropriate 'blind' antibiotics, if you have not done so already.
Local protocols vary, but a common regime is
i.v. benzyl penicillin 50mg/kg up to 4g
AND
i.v. ceftriaxone 50mg/kg up to 2g
