Lumbar Punctures Flashcards
Indications for an LP?
To Diagnose:
Infection:
- Meningitis/Meningoencephalitis
Inflammation:
- Detect Oligoclonal bands to indicate CNS inflammation e.g. MS
Idiopathic:
- Idiopathic Intracranial Hypertension
Blood:
- Subarachnoid Haemorrhage
Malignancy:
- Tumour
To infuse drugs or contrast
Contraindications for a LP?
- Patient has CV or Resp Instability
- Infection in skin or soft tissue over puncture site
- Unstable bleeding disorder (Diagnosed, low platelets or low clotting factors)
- Raised ICP (CT first to spot a mass which may herniate)
What are the types of LP needle?
- Spinal needles usually 22 gauge
- Atraumatic needles (Cause less spinal headaches but cost more)
What is used to anaesthetize for an LP?
Topical anaesthetic to injection site such as EMLA
OR lidocaine inserted intradermally, then carried through on needle
In what position is an LP performed?
Lateral (Decubitus) position:
- Lying on left side with maximally flexed spine (particularly at hips)
Sitting (Infants):
- Infants hands held between its flexed legs using one hand and the other hand flexes its head
What vertebral level is an LP performed?
L3-4 in adults and L4-5 in infants
Procedure for an LP:
- ~Anaesthetize topically 30 mins before
- Adopt position
- Clean skin with Povidone Iodine to 10cm from puncture site and allow to dry
- Drape below patient and around site
- ~Anaesthetize with lidocaine
- Insert spinal needle + Stylet with bevel upwards (parallel to spinal cord)
- Aim Cephalad to get through slanted lamina
- Pop of sudden lack of resistance means your in, remove stylet and collect CSF
What do you do if theres no fluid?
- Rotate the needle 90 degrees
- Reinsert stylet and advance needle again
- Compress jugular
How is CSF pressure measured?
With a Manometer in the lateral position only, once CSF starts to flow
How much CSF do you collect on an LP?
3 vials as standard:
- Culture & gram stain
- Glucose & Protein
- Cell count & DDx
How is the LP ended?
Measure closing pressure with manometer if you want
- > Reinsert Stylet
- > Smoothly remove needle
- > Cleanse and cover puncture site
What is the Paramedian or Lateral Approach?
Approaching the spine at an angle not quite in the midline (10-15 degrees out)
This passes through the erector spinae & Ligamentum flavum rather than Supraspinal/interspinal ligaments
Helps in patient with calcifications, anatomical abnormalities or just to reduce Spinal Headaches (hole through dura&arachnoid wont overlap)
Complications of a LP?
- Headache
- Apnea
- Back Pain
- Bleeding or leaking
- Infection or Haematoma
- Subarachnoid Epidermal cyst (Carried Skin cells through to meninges)
- Nerve Trauma
- Ocular Muscle Palsy
- Brainstem Herniation
Describe spinal headache?
A common complication of LPs
More likely in women, young people, low BMIs and people with a history of headaches
Its bilateral and improves with lying down
How do we treat a spinal hedache?
It will last hours to weeks
We can help with:
- Hydration
- Caffeine (PO/IV)
- Epidural Blood Patch to stimulate healing
