Recommendations on the Use of Ultrasound Guidance for Adult Lumbar Puncture: A Position Statement of the Society of Hospital Medicine
1) When ultrasound equipment is available, along with providers who are appropriately trained to use it, we recommend that ultrasound guidance should be used for site selection of lumbar puncture to reduce the number of needle insertion attempts and needle redirections and increase the overall procedure success rates, especially in patients who are obese or have difficult-to-palpate landmarks.
2) We recommend that ultrasound should be used to more accurately identify the lumbar spine level than physical examination in both obese and nonobese patients.
3) We suggest using ultrasound for selecting and marking a needle insertion site just before performing lumbar puncture in either a lateral decubitus or sitting position. The patient should remain in the same position after marking the needle insertion site.
4) We recommend that a low-frequency transducer, preferably a curvilinear array transducer, should be used to evaluate the lumbar spine and mark a needle insertion site. A high-frequency linear array transducer may be used in nonobese patients.
5) We recommend that ultrasound should be used to map the lumbar spine, starting at the level of the sacrum and sliding the transducer cephalad, sequentially identifying the lumbar spine interspaces.
6) We recommend that ultrasound should be used in a transverse plane to mark the midline of the lumbar spine and in a longitudinal plane to mark the interspinous spaces. The intersection of these two lines marks the needle insertion site.
7) We recommend that ultrasound should be used during a preprocedural evaluation to measure the distance from the skin surface to the ligamentum flavum from a longitudinal paramedian view to estimate the needle insertion depth and ensure that a spinal needle of adequate length is used.
8) We recommend that novices should undergo simulation-based training, where available, before attempting ultrasound-guided lumbar puncture on actual patients.
9) We recommend that training in ultrasound-guided lumbar puncture should be adapted based on prior ultrasound experience, as learning curves will vary.
10) We recommend that novice providers should be supervised when performing ultrasound-guided lumbar puncture before performing the procedure independently on patients.
© 2019 Society of Hospital Medicine
Techniques
2) We recommend that ultrasound should be used to more accurately identify the lumbar spine level than physical examination in both obese and nonobese patients.
Rationale. Traditionally, an imaginary line connecting the iliac crests (intercristal line, Tuffier’s line, or Jacoby’s line) was considered to identify the L4 vertebra or the L4-L5 interspinous space in the midline; however, studies have revealed this traditional landmark to be much less accurate than previously thought. In general, palpating the iliac crests to mark the intercristal line identifies an interspinous space that is one space cephalad (ie, the L2-L3 interspinous space) but can range from L1-L2 to L4-L5.46,60-64 If an LP is inadvertently performed in the L1-L2 interspinous space, the risk of spinal cord injury is higher than that when performed in a more distal interspinous space.
A study by Margarido et al. with 45 patients with a mean BMI of 30 kg/m2 found that the intercristal line was located above the L4-L5 interspinous space in 100% of patients. More importantly, the intercristal line was above L2-L3 in 36% of patients and above L1-L2 in 4% of patients. It is important to note that patients with scoliosis or previous spine surgery were excluded from this study, and all examinations were performed by two experienced anesthesiologists with patients in a sitting position—all factors that would favor accurate palpation and marking of the iliac crests.60
In a study of nonobese patients (mean BMI 28 kg/m2) undergoing spinal anesthesia, Duniec et al. compared the lumbar level identified by palpation versus ultrasound and found discordance between the two techniques in 36% of patients; 18% were one space too cephalad, 16% were one space too caudal, and 2% were off by two interspinous spaces.61 Another study found discordance in 64% of patients (mean BMI 28 kg/m2) when comparing the interspinous level where spinal anesthesia had been performed by palpation versus a post-procedural ultrasound examination. This study revealed that the interspinous space was more cephalad in 50% of patients with 6% of punctures performed in the L1-L2 interspace.62 A similar study compared the accuracy of palpation vs ultrasound to identify the L3-L4 interspinous space in obese (mean BMI 34 kg/m2) versus nonobese (mean BMI 27 kg/m2) patients. This study found marking a space above L3-L4 in 51% of obese and 40% of nonobese patients and marking of the L1-L2 interspace in 7% of obese and 4% of nonobese patients.64
A study comparing palpation vs ultrasound found that 68% of obese patients with a BMI of >30 kg/m2 had difficult-to-palpate lumbar spine landmarks, but with the use of ultrasound, landmarks were identified in 76% of all patients, including obese and nonobese, with difficult-to-palpate landmarks.65
3) We suggest using ultrasound for selecting and marking a needle insertion site just before performing LPs in either a lateral decubitus or sitting position. The patient should remain in the same position after marking the needle insertion site.
Rationale. Ultrasound mapping of the lumbar spine can be performed in either a lateral decubitus or sitting position. Selecting and marking a needle insertion site should be performed at the bedside just before performing the procedure. The patient must remain in the same position in the interim between marking and inserting the needle, as a slight change in position can alter the needle trajectory, lowering the LP success rate. Although performing LPs in a lateral decubitus position has the advantage of accurately measuring the opening pressure, misalignment of the shoulder and pelvic girdles and bowing of the bed in a lateral decubitus position may lower LP success rates.
