Spinal tap (umbar puncture or LP)

Due to the blood-brain barrier, systemic chemotherapy usually cannot destroy any
blasts in the central nervous system (brain and spinal cord). Chemotherapy drugs
must be directly injected into the cerebrospinal fluid to kill any blasts present and
prevent a possible central nervous system relapse. The drugs most commonly used
intrathecally are methotrexate, ARA-C, and hydrocortisone. The number of spinal
taps required varies depending on the child’s risk level, the clinical study involved,
and whether radiation is used.
Some hospitals routinely sedate children for spinal taps, and others do not. If the
child is not sedated, EMLA cream is usually prescribed. EMLA is an anesthetic cream
put on the spinal tap site one to two hours prior to the procedure. It anesthetizes
deep into the tissue, preventing some or all of the pain associated with the procedure.
To perform a spinal tap, the physician or nurse practitioner will ask the child to lie on
her side with her head tucked close to the chest and knees drawn up. A nurse usu-
ally helps hold the child in this position. The doctor will feel the designated spot in
the lower back, and will swab it with antiseptic several times. The antiseptic feels very
cold on the skin. A sterile sheet may drape the area, and the doctor will wear sterile
gloves. One or two shots of an anesthetic (usually xylocaine) may be injected into the
skin and deeper tissues. This causes a painful stinging or burning sensation that lasts
about a minute. If EMLA was used, the doctor may still inject anesthetic into the deep
tissues. A few minutes’ wait is necessary to ensure that the area is fully anesthetized.
My 4-year-old daughter had finished eighteen months of her treatment
for ALL when EMLA was first prescribed. She had been terrified of going
to the clinic. After using EMLA for her next LP, a dramatic change
occurred. She was no longer frightened to go for treatment, and her
behavior at home improved unbelievably. We use it for everything now:
finger pokes, accessing port, bone marrows, even flu shots.
It is essential that the child hold very still for the rest of the procedure. The doctor
will push a needle between two vertebrae into the space where cerebrospinal fluid
(CSF) is found. The CSF will begin to drip out of the hollow needle into a container.
After a small amount is collected, a syringe is attached to the needle in the back and
the medicine is slowly injected, causing a sensation of coldness or pressure down the
leg. The needle is then removed and the spot bandaged. The CSF is sent to the lab-
oratory to see if any cancer cells are present and to measure glucose and protein.
During spinals, Brent listens to rock and roll on his Walkman, but he
keeps the volume low enough so that he can still hear what is going on.
He likes me to lift up the earpiece and tell him when each part of the
procedure is finished and what’s coming next.
If your child or teen develops a persistent severe headache following the procedure
that lessens while he lies flat, but throbs when he sits up, notify your physician or
nurse. Keep your child lying flat, and offer high-caffeine beverages, such as Mountain
Dew. If these measures fail to give your child relief, an anesthesiologist sometimes
does a procedure called a “blood patch.” Your child lies in the same position as for
the spinal tap. The anesthesiologist will draw a small amount of blood from your
child’s arm or central line. She will then inject it at the site of the prior spinal tap
where CSF may be slowly leaking from the canal into the tissues. If this is the cause of
the headache, the relief is immediate. This procedure is generally performed in the
recovery room, emergency room, clinic, or inpatient unit. You can stay with your
child during the procedure.