Page 35 - Radiology Book

myelogram / lumbar Puncture Protocol
I. Assess and consent the patient:
Assess the patient’s level of physical comfort or degree of pain. Evaluate the patient’s stress level. Perform an H&P and get informed consent. It is important to determine if the patient has sleep apnea. Remember that the patient may not know what this means, so you must speak in simple terms (e.g. have you been told you snore when you sleep? Do you wear a mask at night that helps you sleep better?) Consent the patient for potential complications of local pain, headache, infection, and bleeding. Allergies and medication history.
II. Obtain and USE prior MRI or CT studies of the lumbar spine
Look for areas of spinal stenosis and avoid puncturing at those levels. This alone may save you a lot of time. Also check to determine what level the conus is located. Choose a level to puncture, usually L2-3. Lower lumbar levels are generally more prone to focal degenerative canal stenosis than L2-3, so avoid making it hard on yourself and the patient. Use L1-2 cautiously (ONLY if you have an MRI showing the conus lies ABOVE this level and only under the direct supervision of an attending), since the conus medullaris may lie this low in some patients.
III. PREPARATION/TECHNIQUE
Put a pillow or bolster under the patient’s abdomen directly under the puncture site to reduce the lumbar lordosis and open up the interspinous distance. This is very important! In very obese people, consider saving time by beginning with a LONGER NEEDLE (15 cm, 20 gauge)
NEEDLE CHOICE: Beveled tip spinal needle 22 gauge is generally more useful, since it may be steered by rotating the bevel direction. Sprott side-hole needle has a statistically lower incidence of spinal headache complications, but cannot be steered other than by withdrawal and redirecting it.
MIDLINE APPROACH
1. Make sure the patient is prone on the table. If scoliotic, roll the patient until the spinous process at the intended puncture level is midway between the pedicles.
2. Fluoro to identify the desired disk level. Now remember your geometry with the spinous processes projecting LOWER than the disk level.
3. Clean and prep the puncture site. Lay sterile towels.
4. Anesthetize the skin generously with 1% lidocaine, and also the
top of the spinous process and interspinous ligament. Use the needle as an initial probe to con rm the location of the interspinous space and then NOTE the degree of cranial angulation. Your spinal needle will use the same angle.
5. Place the spinal needle though the skin 2-3 cm and check position
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LP ProtocoL