Lumbar Punctures Flashcards
What are the indications for an LP?
- Evaluation for bacterial or viral meningitis
- Evaluation for subarachnoid bleed
- Diagnosis & therapeutic removal CSF in idiopathic intracranial hypertension (i.e. hydrocephalus)
- Infusion of chemotherapy or contrast media for spinal cord imaging
What are the contraindications for an LP?
1. Increased intracranial pressure (ICP) A. Can be cuased by suspected tumor or other mass lesion 2. Skin infection at site of puncture 3. Coagulopathy/Bleeding disorder 4. Spinal cord compression/deformity
What are the indications for a CT prior to an LP?
- Patients who are older than 60 years
- Patients with known CNS lesions
- Patients who have had a seizure within 1 week of presentation
- Patients with abnormal level of consciousness
- Patients with focal findings on neurological examination and or papilledema (ICP)
What are the potential complications to an LP?
- Post spinal tap headache (aka PDPH= postdural puncture headache)
- Nerve damage- back or leg pain and/or paresthesias
- Infection- local skin infections, spinal / epidural abscesses
4 Bleeding locally- Spinal Hematomas - Cerebral herniation into foramen magnum may occur in presence of inc ICP (that was not detected on PE)
What are the benefits of LP?
The benefits of the LP depend upon the exact situation but an LP can provide lifesaving information
What are the steps of an LP?
- Provide necessary analgesia and/or sedation
- Positioning the patient:
A. Lateral recumbent position (to measure opening pressure need this position)
B. Sitting position - Sterile technique/tray
- Finding Landmarks
- Site preparation
- Local anesthesia and needle insertion
- Collection of CSF and removal of the needle
- Post procedural care
- Interpretation of results
What is the lateral recumbent position?
- Position the patient in the lateral recumbent position with hips, knees, and chin flexed toward the chest in order to open the interspinous spaces.
- A pillow can be used to support the head.
What is the appropriate sitting position?
- The sitting position may be a helpful alternative position, especially in obese patients.
- In order to open the inter-laminar spaces, the patient should lean forward and be supported by a stand with a pillow on it
What are the pre-procedural considerations?
- Obtain informed consent
- Explain to the patient the risks and benefits of doing the procedure
- Explain the major steps of the procedure, positioning, and post-procedure care
- Is the patient stable?
- To CT or not to CT?
What equipment is needed for an LP?
- Personal protective equipment
- Antiseptic solution
- Sterile gauze & drape
- 1% - 2% lidocaine without epi
- 3 ml syringe with 25 gauge needles
- 3 way stopcock
- 4 plastic tubes (1-4)
- 22 gauge spinal needle (regardless of age)
How does the needle length change for age? Obese pts?
- Age 12 yrs, 3.5 inch needle
4. Obese pts may require longer needle
How far does the spinal cord extend in adults?
In adults, spinal cord ends at L1
Where is the cauda equina in adults?
Cauda equina extends distally from L1
Where is the preferred site for LP in adults?
Preferred site is @ L4-L5 or L3-L4 interspace
Where is the L4 spinous processes?
L4 spinous process is at level of post sup iliac crest
What does the LP needle pass through?
Needle passes through suraspinal lig, interspinous lig, ligamentum flavum, dura mater, arachnoid mater
How can the space between the spinous processes be increased?
- Spinous processes are angled caudally
2. Space between spinous processes can be increased by flexing lower back & hips
What are the procedure steps for an LP?
- Explain procedure to patient
- Gather all equipment
- Position patient
A. Lateral recumbent : Patient on side with hips and back flexed so patient appears to be in fetal position
B. Sitting position: Patient sits on edge of bed with lower back & hips flexed as much as possible - Identify landmarks
A. Puncture may occur immediately above L4 process, in L3-L4 interspace, or below it in L4-L5 interspace
B. Palpate depression between spinous processes and mark entry site - Put on personal protective equipment
- Prepare & drape region
- Anesthetize area
- Assemble equipment, including collection tubes
- Be sure stylet is inserted into spinal needle
- Assemble manometer with stopcock open to patient and manometer column
- Hold needle in dominant hand
- Slowly advance needle into skin at exact anatomic midline, aim it slightly superior toward umbilicus
- Stop every 4-5 mm & withdraw to check for fluid return
- Stop & remove stylet after feeling pops to see if subarachnoid space has been entered
- Reinsert stylet each time before needle is advanced
- Measure opening pressure
- Open manometer and port and drain fluid into first tube
- Continue to collect fluid by opening stopcock & filling each tube with 1 ml fluid sequentially
- Replace stylet
- Remove needle & clean skin; apply bandaid
How is the needle directed into the the entry site?
Use thumb & index finger of nondominant hand to direct tip of needle into entry site
How do you find the L3-L4 interspace?
- Locate the L3-L4 inter-space by palpating the posterior superior iliac crests and moving the fingers medially toward the spine.
- Palpate that inter-space (L3-L4) as well as one above (L2-L3) and one below (L4-L5) and mark the entry site with a thumbnail or a marker.
How is the site prepped?
- The site should be prepped with iodinated solution.
- Application is usually in a circular fashion, starting from the planned needle insertion point and encompassing the inter-space above and below (3 times)
How is local anesthesia placed?
- After applying a sterile drape over the area. Use lidocaine 1% to anesthetize the skin and the deeper
- Using the 25 gauge needle, create a skin wheal with local anesthetic at the insertion site. Now change to the 22 gauge needle to infiltrate the subcutaneous and inter-spinous areas
How is the needle inserted?
- Insert the needle at the identified site with the bevel facing upward
- Advance the needle until a slight “pop” is felt as the dura is penetrated
- Remove the stylet and wait 2 seconds for CSF drainage. If no CSF return, advance the needle 1-2 mm. at a time, checking for CSF return with each advance
What is normal opening pressure?
Normal is 7-18 cm H20
How is CSF collected?
- Collect 1 - 1.5 cc of fluid in each of the 4 tubes
2. Replace the stylet fully into the spinal needle before withdrawing the needle.
What is tube 1 used for?
Cell count
What is tube 2 used for?
glucose and protein
What is tube 3 used for?
Stat gram stain and (C and S)
What is tube 4 used for?
Cell count or Hold
What is included in post procedural care?
- Lying flat (prone) for 1- 3 hours
- Hydration and mild analgesics if needed
- Caffeine for HA
- Blood patch
Where is a LP performed in an Child?
L4-L5
What are normal values for CSF fluid?
- Protein : 15-45 mg/dl
- Glucose: 50-80mg/dl
- WBC:
what is the general CSF analysis? What does cloudy CSF mean?
:CSF is usually clear and colorless and looks like water. Cloudy spinal fluid may indicate infection because of increased cells and proteins suspended in the fluid.
When is Xanthochromia present in CSF?
Present if bleeding up to 12 hours
How often is gram stain positive in untreated bact meningitis?
Positive in 60-80%
What is cell count?
This includes the number and type of white blood cells and the number of red blood cells present. CSF normally does not contain more than a fewof these types of cells. The presence of too many white cells indicates an infection.
What is the protein analysis of CSF?
Large amounts of protein in the spinal fluid also suggest an infection or other disease.
What is the glucose analysis of CSF?
In bacterial infections of the spinal fluid, the glucose level of the fluid is often low.
What is the gram stain and culture of CSF?
In a gram stain, dye is added to the CSF sample, which is then examined under the microscope for bacteria. To confirm an infection
