Part 2 of a Three-Part Mini-Series on Lumbar Puncture
This month we are back (no pun intended) with the second part of our mini-series focused on perfect patient positioning and lumbar puncture (LP). Part one can be found at http://bit.ly/ProceduralPause.
Now that you have the proper skills to position your patient for an LP, the procedure should be pretty simple, right? The answer is yes! We want you all to be experts. We know that you can and will master an LP after reading these short and sweet LP guidelines and clinical pearls.
Lumbar puncture in the emergency department.
Manual of Clinical Anesthesiology; Lippincott Williams & Wilkins, 2011.
You have already decided you will complete an LP. A few common reasons an LP may be indicated in the emergency department include:
n Headache with a fever (rule out meningitis or a central nervous system infection)
n Sudden “thunderclap” headache (rule out subarachnoid hemorrhage)
n Altered mental status
n Idiopathic intracranial hypertension
Always remember to consider the risks and benefits for any procedure and refer to the contraindications. Obtain informed consent before you perfectly position your patient and get sterile! Make sure you review the risks and benefits with each patient.
n Infection at the puncture site
n Thrombocytopenia (platelets <50,000)
n Prior surgery at the puncture site (i.e., discectomy or fusion)
n Presence of increased ICP related to a space-occupying lesion (i.e., tumor, Aspergillus abscess, etc.)
List adapted with permission from Roberts JR, Hedges JR. Clinical Procedures in Emergency Medicine, 6th edition, Philadelphia: Saunders/Elsevier, 2014, pg. 1218.
n Gather appropriate equipment, LP kit
n Patient positioning
n Identify appropriate landmarks
n Obtain opening pressure using a manometer (lateral decubitus position only)
n Lumbar puncture obtaining cerebral spinal fluid (CSF)
n Patient recovery
It is never a bad idea to buffer any lidocaine injection with bicarb. Try it.
Lumbar spinal puncture for CSF draw and spinal anesthesia illustrating location of CSF draw for LP specimen.
Grant's Dissector; Lippincott Williams & Wilkins, 2012.
n Obtain an LP kit and an extra Quincke spinal needle. Obtain a Sprotte needle if preferred. (NOTE: Most LP kits contain Quincke needle.)
n Grab an extra 1% lidocaine, a 10 mL syringe, antiseptic, and two pairs of sterile gloves.
n Position patient properly (read how to do that here: http://bit.ly/1zRSOdC)
The lateral recumbent positioning for lumbar puncture, top, compared with upright positioning, bottom.
Atlas of Primary Care Procedures; Lippincott Williams & Wilkins, 1994
n Give appropriate dosage of IV sedation such as midazolam (0.1-2.5 mg for patients 18-60) or fentanyl (0.5-1.5 mcg/kg for adults 18-20), if indicated. Sedation is recommended for all procedures because of test anxiety.
n Wash your hands, and identify your landmarks. Palpate the posterior superior iliac crests bilaterally and find the L4 spinous process, midline. Consider using ultrasonography. Mark with a pen.
n Don a sterile cap, a gown, gloves, and a mask.
n Open your LP kit and loosen the tops of all four of your sample tubes, but do not leave them open to air. Ask a partner/RN/tech to drop a sterile 10 mL syringe into the sterile field. LP kits usually only come with 3-5 mL syringes and not nearly enough lidocaine for appropriate anesthesia.
n Draw up your lidocaine into a syringe, and have it ready on the sidelines.
n Clean the patient’s back with antiseptic. Use extra if necessary. Clean using a circular motion from center extending outward in a large circle.
n Slide a sterile drape between the patient’s hip and the stretcher. This is the point at which many people tend to break the sterile field. If you do, simply put on a new set of sterile gloves.
n Use an additional drape with a hole over the site where you plan to insert the spinal needle.
n Warn patients of the needle stick.
n Infiltrate the skin over your landmark (between L4-L5 spinous process) with lidocaine injection. Start with a wheel under the skin using a 1.5-inch, 25-gauge needle and advance to subcutaneous tissue. A total of 5-10 mLs can be inserted. This is usually a painless procedure if you use enough lidocaine. It’s painful if you don’t.
n Wait one to two minutes. A common error is to fail to measure the opening pressure. Set up a stopcock and a manometer for opening pressure. (Note: Remember, this can only be obtained in lateral decubitus position, NOT sitting.) Ensure that the valve is working.
n Hold the selected spinal needle (3.5-inch, 20-gauge needle preferred) between your thumb and index finger of your non-dominant hand and insert perpendicularly into skin over the landmark by pressing the hub of the needle with your dominant thumb. (Pediatric LP to be covered later.)
n Slowly advance the needle below the L4 spinous process. Once you have infiltrated the subcutaneous tissue, aim the needle toward the umbilicus.
n Note: When you pass through the intra- and supra-spinal ligaments, you may feel a slight pop. If you feel bone (articular process), slowly remove the needle and ensure you are entering the midline of the spine. Re-angle your needle slightly to the left or right.
n Your goal is to reach the subarachnoid space.
n Attach the manometer, and obtain a pressure. The stopcock allows you to obtain the pressure and obtain CSF. Normal pressure is 7-20 cm/H20.
n Remove and replace the stylet at various stations (every few millimeters of advancements), entering the spinal column to check for CSF.
n Obtain desired CSF and replace the stylet before withdrawing the needle.
n Place bandage over infiltrated area and have patient lie supine for 30-60 minutes before sitting, standing, or walking to help avoid post-procedure spinal headache.
Find your landmarks by creating an imaginary line using this photo as a reference.
n Do not do this procedure without sedation, especially on those with altered mental status.
n Be generous with lidocaine administration.
n Be sure your needle is in midline and angled properly.
n Have an assistant help hold your manometer.
n Frequently check for spinal fluid once you are in the area by removing the stylet.
n Do not move the needle tip once you obtain CSF.
Tip of the Week
We all love to tape the lidocaine bottle to the stretcher post so we can draw up our own lidocaine without an assistant. We urge you, however, to grab a partner for this procedure. Your partner can provide an extra set of hands and patient comfort. It is vital to ensure that a nurse is close by to administer needed medications prior to the procedure. A difficult or altered patient is just too tricky to handle one-on-one, no matter how good you may be at LPs!
Evidence-Based Practice Pearl
A study in the New England Journal of Medicine discusses the use of head CTs in suspected meningitis patients. Clinical characteristics were identified in patients prior to receiving head CTs. If certain neurological characteristics were not present, the patients were unlikely to have an abnormal CT scan. The study concluded by stating that patients without specific neurologic abnormality characteristics at baseline (based on the Modified National Institutes of Health Stroke Scale) had a negative predictive value of 97%. The head CT was normal for 93 of 96 patients. Was it really necessary in absence of clinical abnormalities? Maybe not, but no one really wants to be that three percent. (N Engl J Med 2001;345:1727.)
Stay tuned for our third and final edition of this mini-series next month, “How to Handle Lumbar Puncture Results.”
Do you have any tips that help make LPs easier? Share them in the comments section below.