Lumbar Puncture

Published on 22/03/2015 by admin

Filed under Critical Care Medicine

Last modified 22/04/2025

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W18 Lumbar Puncture

Sarice L. Bassin, Thomas P. Bleck

Before Procedure

Indications

• Suspicion of central nervous system (CNS) infection

• Suspicion of subarachnoid hemorrhage

• The need to obtain cerebrospinal fluid to diagnose other inflammatory or degenerative CNS diseases

• Reduction of cerebrospinal fluid (CSF) pressure in pseudotumor cerebri

Contraindications

• Intracranial or spinous (especially intramedullary) mass (e.g., tumor, abscess). If there is concern, an imaging study should be performed before the procedure. A rapid decrease in intracranial pressure from withdrawal of CSF could precipitate herniation or worsening of spinal cord function if a mass lesion is present.

• Overlying skin infection

• Lumbar spine disease

• Coagulopathy and/or thrombocytopenia, because an epidural hematoma can develop at the puncture site. Fresh frozen plasma and platelets should be infused to correct hematologic abnormalities before the procedure. If a coagulopathy is discovered after the procedure, therapy should still be given, because bleeding can occur for many hours.

• If a lumbar puncture is being performed to evaluate a patient for aneurysmal subarachnoid hemorrhage, withdraw the smallest possible amount of CSF to obtain the necessary laboratory tests. Reducing the CSF pressure could precipitate rebleeding.

• Uncooperative patient

Equipment

• Lumbar puncture tray or individual components (see later)

• Chlorhexidine or povidone-iodine prepping solution

• Sterile drape with central opening

• 1% Lidocaine and a syringe with 25- and 22-gauge needles for local anesthesia

• 20- or 22-gauge spinal needle

• Tubes for CSF collection

Anatomy

The site of intended puncture is generally either the L4-L5 or L5-S1 interspace. These can be determined as follows. The L3-L4 interspace can be located by drawing an imaginary line between the posterior iliac crests. This is usually the most rostral space employed, because the adult spinal cord ends at L2. Walk the fingers down the spinous processes to identify the L4-L5 and L5-S1 interspaces, and mark them on the skin. Note that when lumbar spine disease, the question of a spinal mass, or an overlying skin infection prevent the lumbar approach, a lateral cervical approach can be performed by a physician trained in this technique. In cases of difficult lumbar puncture in obese patients, bedside ultrasound can be helpful.

Procedure

• Place the patient in the lateral decubitus position with knees flexed to the abdomen and head flexed with the chin toward the chest.

• Position the patient’s back as close as possible to the edge of the bed nearest the examiner.

• Before preparing the skin, locate the L4-L5 and L5-S1 interspaces and mark them.

• The skin should then be prepared with chlorhexidine or povidone-iodine. The preparation should proceed outward in a spiral and cover several interspaces in case multiple attempts are necessary.

• Drape the patient’s back with a sterile sheet with an opening for the prepared area so that it covers the posterior iliac crest.

• Anesthetize the skin with 1% lidocaine using a 25-gauge needle, which may be exchanged for a longer 22-gauge needle to reach deeper tissues.

• Using a 20- or 22-gauge spinal needle, advance it with the stylet in place to avoid introduction of epidermal cells into the subarachnoid space.

• Direct the bevel of the needle upward to separate the fibers of the ligamentum flavum. Angle the needle 15 degrees cephalad and slightly downward toward the bed.

• When the dura is punctured and a slight “pop” is felt, the stylet should be withdrawn.

• If free flow of CSF does not occur, the needle can be rotated or may have to be advanced (after replacing the stylet).

• Once free flow of CSF is obtained, attach a manometer to the spinal needle, usually by way of a stopcock. CSF should rise steadily in the manometer until the opening pressure is reached and respiratory fluctuation can be visualized in the fluid column.

• The patient’s legs should be carefully extended and relaxed for an accurate pressure reading.

• Collect 4 tubes of CSF (3 mL of fluid in each) and send them for appropriate studies.

• In cases of pseudotumor cerebri where lumbar puncture has been chosen as a therapeutic modality to reduce raised intracranial pressure, after quantifying opening pressure, removal of 20 mL of CSF is generally recommended and closing pressure documented.

• Replace the stylet to minimize the possibility of pulling a nerve root through the dura as the needle is removed.

• Withdraw the needle and apply pressure to the puncture site.

• If the subarachnoid space cannot be entered with this technique or the patient cannot lie in the lateral decubitus position, lumbar puncture can be performed with the patient sitting on the side of the bed leaning forward over a bedside table. However, once free CSF flow occurs, the patient should be returned to the recumbent position for accurate pressure measurements.

• If a patient is unable to bend one leg (e.g., after an angiographic procedure), lumbar puncture can be attempted in the lateral position with the bottom leg held straight and the top leg bent into the abdomen and supported with a pillow.

Outcomes and Evidence

• To ensure an optimal diagnostic outcome when performing a lumbar puncture, it is wise to check with the laboratory before the procedure if any unusual tests are being performed, because an additional tube or larger volumes or special handling of CSF may be required. Regarding optimal patient outcomes, if a diagnostic lumbar puncture is delayed for imaging in a suspected case of bacterial meningitis, blood cultures should be obtained and empirical antibiotics should be administered, as CSF cultures can be obtained up to 4 hours after starting treatment.

Suggested Reading

Bleck TP. The clinical use of neurologic diagnostic tests. In: Weiner WJ, Goetz CG, editors. Neurology for the non-neurologist. 4th ed. Philadelphia: Harper & Row; 1999:27-37.

Nathan BR. Cerebrospinal fluid and intracranial pressure. In: Goetz CG, editor. Textbook of Clinical Neurology. 2nd ed. Philadelphia: WB Saunders; 2003:511-529.

Roos KL. Lumbar puncture. Semin Neurol. 2003;23:105-114.

Nomura JT, Leech SJ, Shenbagamurthi S, et al. A randomized controlled trial of ultrasound-assisted lumbar puncture. J Ultrasound Med. 2007;26:1341-1348.

Peterson MA, Abele J. Bedside ultrasound for difficult lumbar puncture. J Emerg Med. 2005;28:197-200.

De Simone R, Ranieri A, Bonavita V. Advancement in idiopathic intracranial hypertension pathogenesis: focus on sinus venous stenosis. Neurol Sci. 2010;Suppl. 1:S33-S39.

Spennato P, Ruggiero C, Parlato RS, et al. Pseudotumor cerebri. Childs Nerv Syst. 2011;27:215-235.

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