Lumbar puncture Flashcards
what are the indictions for lumbar puncture
To obtain CSF for the diagnosis of:
Meningitis
Meningoencephalitis
Subarachnoid haemorrhage
Malignancy – diagnosis and treatment
Idiopathic Intracranial Hypertension
Other neurologic syndromes
Infusion of Drugs or contrast
what are the contraindication for lumbar puncture
unstable patient
- cardiovascular or respiratory
localised skin/soft tissue infection over puncture site
evidence of unstable bleeding disorder
- low platelets or clotting factor deficient
increased ICP
high complete subarachnoid spinal block - if LP down below the level of block can cause neurological deterioration
chiari malformations - structural defects of the cerebellum
what investigations can be done to determine if there is raised ICP before LP
fundoscopy - papilloedema, retinal haemorrhage
CT head - rule out impending cerebral mass herniation that could increase ICP
**normal CT does not rule out ICP
what equipment is used for lumbar puncture
anaesthetics
- topical
- lidocaine with 25 1% gauge needle and syringe
povidone-iodine solution and sponge wand
drapes, gauzes, bandages
manometer, stopcock valv, tubing
spinal needle - usually 22 gauge
OR
atraumatic needle
what is the benefit of using atraumatic needles
cause less spinal headaches
what are the different lengths of needles used in LP
- 5 inch for <1 yr
- 5 inch for 1yr- middle childhood
- 5 inch for older children and adolescents
larger for adults and large adolescents
what are the pre procedural steps for LP
Apply topical anesthetic 30-45 min prior to procedure
Spinal cord usually ends at L1-L2(check!), so sites for puncture are located at L3-L4 or L4-L5
Restrain patient in lateral decubitus position
- Maximally flex spine without compromising airway
- Keep alignment of feet, knees and hips
- Position head to left if right handed or vice versa
what is the procedure for LP insertion
cleanse skin around puncture site and allow to dry
anaesthetise with lidocaine if topical not used
insert spinal needle with stylet with bevel up to
aim towards umbilicus - directing needle slightly towards the head
remove stylet and check for flow of spinal fluid
what should be done if there is no fluid after the removal of the stylet
rotate needle 90 degrees
reinsert stylet and advance needle slowly checking frequently for CSF
what can increase CSF pressure in low flow situations
jugular vein compression
what does bony resistance felt immediately indicate
you are not in the spinal interspace
what should you do is deep bony resistance felt
withdrawal of needle to skin surface and redirect more towards the head
increase patient flexion
what should you do if bloody fluid that does not clear or that clots results
withdraw needle and reattempt at a different interspace
what does a pop of sudden decrease in resistance indicate
ligamentum flavum and dura punctured
what should be done if normal CSF is flowing
attach manometer and read column when highest level achieved
how much CSF should be collected
1ml of CSG in each of 3 vials
tube 1 - culture and gram stain
tube 2 - glucose and protein
tube 3 - cell count and differential
**extra CSF if desired for other lab tests
what should be done on finishing the LP
check closing pressure
reinsert stylet and remove needle in one quick motion
cleanse and cover puncture site
why might a sitting position be used for LP
infants
how is a LP done in a sitting position
Restrain infant in the seated position with maximal spinal flexion
Hold infant’s hands between flexed legs with one hand and flex head with the other hand
Insert needle so bevel is parallel to spinal cord (Bevel left or right)
what cannot be measured accurately in the sitting position
pressure
when is a paramedian/lateral approach used in LP
patient who have calcifications from repeated LPs or anatomical abnormalities
needle passes through erector spinal and ligamentum flavum
what is there less incidence of in paramedian LP and why
spinal headache
- less because the holes through the dura and arachnoid tissues do not overlap
what are the complications of LP
headache - most common
apnea (central or opstructive)
back pain - sometimes disc herniation
bleeding or fluid leak around spinal cord
infection, pain, haematoma
subarachnoid epidermal cyst
ocualr nerve palsy
nerve trauma
brainstem herniation
what are risk factors for spinal headache
female
18-30
lower BMI
