the 25 gauge needle, create a skin wheal with local anesthetic at
the insertion site. Now change to the 22 gauge needle to infiltrate
the subcutaneous and interspinous areas. Before injecting anesthetic,
draw back the plunger to ensure that the needle has not reached
the subarchnoid space, and then gradually withdraw the needle while
injecting anesthetic along the path that your LP needle will follow.
A volume of 3 cc. of 1% lidocaine solution should be sufficient.
there is an allergy or contraindication to lidocaine,
this local anesthetic is most often used. Some authors
recommend a few c.c.'s of lidocaine be used. This
amount of medication may distort an easily felt spinous
process with a "lidocainoma". If the supraspinous
ligament is felt easily, you can use just a small
amount of lidocaine. Make all of your needle insertions
in the midline to avoid confusion.