Technique of Lumbar Puncture Flashcards
Disadvantage of seated position
Opening pressure readings may not be accurate
PMNs in CSF
Usually absent
may be found in centrifuged specimen
Effective strategies for reducing post LP headache
Use of small-diameter needle (22-gauge or smaller)
Use of atraumatic needle (Sprotte and others)
Replacement of stylet prior to removal of needle
Insertion of needle with bevel oriented in a cephalad to caudad direction (when using standard needle)
How to differentiate bloody tap from SAH
centrifuged sample’s supernatant
clear- bloody tap
xanthochromia-SAH
Bloody tap clears spontaneously
Onset of post LP headache
48 hrs but may be delayed upto 12 days
Mechanism of action of epidural blood patch
sealing off a dural hole with blood clot
compression of the CSF space by the clot, increasing CSF pressure
Positioning for LP in seated attitude
foot resting on chair
curl forward trying to touch umbilicus with nose
When should one completely withdraw needle and reposition
second hit against bone
Ask the patient to straighten back before repositioning
Strategies not effective in reducing post LP headache
Bed rest (up to 4 h) following LP
Supplemental fluids
Minimizing the volume of spinal fluid removed
Immediate mobilization following LP
Normal total CSF protein
15–50 mg/dL
Associated symptoms with post LP headache
nausea
neck stiffness
blurred vision
photophobia
tinnitus
vertigo
Location of postLP headache
occipitofrontal
Aggravating and relieving factors for post LP headache
Aggravating: sitting,standing
relieving factors: reclining,abdominal compression
Normal CSF glucose
40–70 mg/dL
Normal CSF volume
150ml
INR and platelet counts at which bleeding complications rarely occur
platelet count>50,000
INR
LMWH should be stopped _______ hrs before LP
24
Complications of LP
Cerebral herniation
Injury to spinal cord,nerve roots
hemorrhage
infection
back ache
Post dural puncture headache
radicular pain or numbness
LP should be delayed for ________ min after injection of anesthetic
10-15min
Supportive care for post LP headache
trendelenberg position
analgesics
antiemetics
caffeine
How much of CSF can be safely removed
20-30 ml
Cells normally absent in CSF
No RBCs
No PMNs
Normal CSF ammonia
25–80 µg/dL
Normal CSF pressure
50–180 mmH2O
Vertebral level at which spinal cord ends
L1 in 94%
L2-L3 interspace in remaining 6%
Characteristic of Post LP headache
dull ache or throbbing
Upper limit of normal opening pressure in supine patients
180mm H2O
May be as high as 200-250 in obese adults
Normal CSF lactate
10–20 mg/dL
Platelet count less than _________ is a contraindication to LP
20,000
Increased risk of post LP headache
younger age
female gender
Anxiety alleviation before LP
Lorazepam 1-2mg PO 30 min prior to procedure
or IV 5min before
Normal CSF differential
Lymphocytes 60–70%
Monocytes 30–50%
Neutrophils None
Does lying recumbent for 1h after LP decrease headache
no
patients at risk of herniation following LP
altered level of consciousness
a focal neurologic deficit
new-onset seizure
papilledema
an immunocompromised state
Next step if no fluid is seen after apparently correct placement
rotate the needle 90-180 degrees
If still no fluid is seen,advance needle with stylet slightly
Tests to be performed if a bleeding disorder is suspected
platelet count
INR
aPTT
Local anesthesia in LP
1% lidocaine 3-5ml
Side effect of IV caffeine
atrial fibrillation
Removal of LP needle
Insert the stylet before removing
studies performed on CSF samples
(1) cell count with differential
(2) protein and glucose concentrations
(3) culture (bacterial, fungal, mycobacterial, viral)
(4) smears (e.g., Gram’s and acid-fast stained smears)
(5) antigen tests (e.g., latex agglutination)
(6) polymerase chain reaction (PCR) amplification of DNA or RNA of microorganisms (e.g., herpes simplex virus, enteroviruses)
(7) antibody levels against microorganisms
(8) immunoelectrophoresis for determination of -globulin level and oligoclonal banding
(9) cytology
In adults,needle is advanced _______ cm before SAS is reached
4-5cm
Normal CSF IgG
0.9–5.7 mg/dL
post LP headache occurs in _______ % of pts
10-30%
Quincke needle(traumatic)
When should one partially withdraw needle and reinsert at different angle
needle hits bone
sharp radiating pain down one leg
if no fluid appears (“dry tap”)
Rx of pts with persistent pain
IV caffeine 500 mg in 500 mL saline administered over 2 h
Epidural blood patch(15ml of autologous whole blood)
Normal CSF albumin
6.6–44.2 mg/dL
Normal WBC count
< five mononuclear cells (lymphocytes and monocytes) per µL
complications of LP in pts on anticoagulants or pts with coagulation defects
subdural or epidural hematomas
Topical anesthesia for LP
Lidocaine 4% cream applied 30 min before procedure
lidocaine/prilocaine must be applied 60-120min prior
causes of xanthochromia
SAH
liver disease
elevated CSF protein >150-200mg/dl
When should spinal imaging precede LP
symptoms suggestive of cord compression
back pain
leg weakness
urinary retention or incontinence
positioning for LP
edge of bed
roll up into ball
pelvis and shoulder should be vertically aligned without any tilt
OGB(oligoclonal bands)
duration of post LP headache
subsides within a week
minority can persist for weeks or months
The latency of subsidy of headache is __________ proportional to duration of standing
directly
sprotte needle( atraumatic)
