Slide 1: How should I prepare the patient? After obtaining informed consent, position the patient in either the seated or lateral recumbent positions. TIP! Flexion of the hips up to the abdomen combined with tucking the chin down onto the chest, enlarges the intervertebral space, making LP easier to accomplish.

Slide 2: Step 1. Identify the midline. Place the transducer in a transverse orientation. Slide the probe superiorly until the spinous process is identified. Graphic showing identification of midline of spinous process. The bone is hyperechoic (white) with a shadow (black) behind it.

Use a marking pen to mark the center of the spinous process. Repeat at multiple levels to define the midline of the spine. Once the midline is identified, rotate the transducer into a longitudinal orientation aligned with the sagittal plane.

Slide 3: Step 2. Identify the interspace level. The superior and inferior spinous process are visible. The ligamentum flavum may also be visible as a hyperechoic horizontal line. Identify and mark the space directly between two spinous processes. Compare L3/4 and L4/5 to see if one space is larger than the other; you can mark both sites. Measure the distance to the ligamentum flavum to estimate how far the needle will have to pass.

Slide 4: Step 3. Perform the LP. By marking the skin in the transverse and longitudinal axes you should have formed an X at the Perfect site for needle entry. Now preform the LP as you normally would, with the needle inserted at the site identified and directed towards the umbilicus.

Summary. POCUS improves the patient experience, speed, and success rate of LP. POCUS is used to mark the spinous anatomy to facilitate LP. Two ultrasound views are obtained in perpendicular planes: transverse – identify the spinous processes to mark the midline; longitudinal – identify spinous processes to find the proper interspace. LP is performed using standard sterile technique.

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