How to operate lumbar puncture in the practicing physician skills exam

Usually take the bent back position, from the lumbar 2 to the sacral 1 (mainly lumbar 3-4) intervertebral space puncture. After routine local disinfection and anesthesia, wear rubber gloves, and use a 20-gauge puncture needle (21-22 for children) to slowly pierce in the direction of the spinous process. After correcting the angle, perform puncture. When the needle is inserted about 4-6cm for adults (about 3-4cm for children), the dura can be penetrated to reach the subarachnoid space, and the core of the needle can be drawn out to flow out the cerebrospinal fluid. After measuring the pressure and slowly discharging the fluid (no more than 2-3ml) , and then insert the needle core and pull out the puncture needle. Slight pressure on the puncture point to stop bleeding, apply sterile gauze and fix it with tape. Lie down for 4-6 hours after surgery. If the initial pressure exceeds 2.94kPa (300mm water column), it is not suitable to discharge the liquid, and only the cerebrospinal fluid in the manometry tube is sent for cell counting and protein quantification.

1.

Instruct the patient to lie on the side on the hard board bed, with the back perpendicular to the bed surface, bend the head forward to the chest, hold the knees with both hands close to the abdomen, and make the torso arched; Hold the popliteal fossa of both lower extremities and hold them tightly, so that the spine is kyphotic as much as possible to widen the intervertebral space and facilitate needle insertion.

2. Determine the puncture point, take the intersection of the line connecting the iliac crest and the posterior midline as the puncture point, usually the 3rd-4th lumbar spinous process space, and sometimes in the upper or lower lumbar intervertebral space.

3. After routine disinfection of the skin, wear sterile gloves and a hole-covering patch, and use 2% lidocaine for local infiltration anesthesia layer by layer from the skin to the intervertebral ligament.

4.

The surgeon fixes the skin of the puncture point with the left hand, and holds the puncture needle with the right hand to puncture slowly in the direction perpendicular to the back. The needle insertion depth is about 4-6cm for adults and 2-4cm for children. When the needle passes through the ligament and dura, you can feel the sudden loss of resistance and a sense of loss. At this time, the needle core can be slowly withdrawn (to prevent the rapid outflow of cerebrospinal fluid, resulting in brain herniation), and the outflow of cerebrospinal fluid can be seen.

5.

Connect the pressure measuring tube to measure the pressure before discharging the liquid. CSF pressure in normal lateral position is 0.69-1.764kPa or 40-50 drops/min. If you know whether the subarachnoid space is blocked, you can do the Queckenstedt test. That is, after measuring the initial pressure, the assistant first compresses one side of the neck

The vein is pressed for about 10s, then the other side is pressed, and finally the bilateral jugular veins are pressed at the same time; after normal compression of the jugular vein, the pressure of the cerebrospinal fluid immediately doubles rapidly, and 10-20s after the compression is released, it quickly drops to the original level. The obstruction test was negative, showing patency of the subarachnoid space. If the pressure of the cerebrospinal fluid cannot be increased after the jugular vein is compressed, the obstruction test is positive, indicating that the subarachnoid space is completely obstructed; if the pressure rises slowly after the pressure is applied, and then decreases slowly after relaxation, it indicates incomplete obstruction. All patients with increased intracranial pressure should not perform this test.

6. Remove the pressure measuring tube and collect 2-5ml of cerebrospinal fluid for inspection; if culture is required, use aseptic operation to retain the specimen.

7. After the operation, insert the needle core and pull out the puncture needle together, cover it with sterile gauze, and fix it with tape.

8. After the operation, the patient should go to the prone position (if difficult, lie down) for 4-6 hours, so as to avoid postoperative hypotension headache.

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