• 
  

  Knowledge of anatomical landmarks and proper sterile technique are important when performing a lumbar puncture (LP).

  
  
• 
  

  Absolute contraindications to LP are skin infection over puncture site and a brain mass causing increased intracranial pressure.

  
  
• 
  

  Herniation is the most serious complication of a LP, whereas post-LP headache is most common.

Lumbar puncture (LP) is performed in the emergency department (ED) primarily to diagnose central nervous system (CNS) infections (ie, meningitis) and subarachnoid hemorrhage (SAH). It may also be performed to relieve cerebrospinal fluid (CSF) pressure and to confirm the diagnosis of idiopathic intracranial hypertension (pseudotumor cerebri). Other indications include the diagnosis of demyelinating or inflammatory CNS processes and carcinomatous/metastatic disease.

Absolute contraindications for performing a LP include infected skin over the puncture site, increased intracranial pressure (ICP) from any space-occupying lesion (mass, abscess), and trauma or mass to lumbar vertebrae. A noncontrast head computed tomography (CT) scan should be performed to rule out an intracranial mass before performing an LP in the following clinical situations: altered mental status, focal neurologic deficits, signs of increased ICP (papilledema), immunocompromise, age >60 years, or recent seizure. Relative contraindications include patients who have bleeding diathesis or coagulopathy (Table 5-1).

Most EDs have a commercially available LP kit, which contains a 20-gauge spinal needle, 22- and 25-gauge needles for lidocaine administration, 4 collection tubes, stopcock and manometer with extension tubing, sterile drapes, skin-cleansing sponges, and lidocaine (Figure 5-1). Smaller spinal needles may be used (22, 25 gauge) and may decrease the incidence of post-LP headache; however, a 22 or larger gauge needle must be used to determine an accurate opening pressure. Other required supplies include additional 1% lidocaine without epinephrine, povidone-iodine (Betadine), and sterile gloves.