XXIV. Seizure Surgery
A. Depth Electrodes
B. Surface Electrode Placement
1. Another technique for determining the location of the
focus of seizure activity involves placing electrodes
on the surface of the brain, discontinuing seizure
medications, and allowing the patient to seize while
recording from the grid of electrodes. Vector analysis
is then used to determine the exact location of the
seizure.
C. Pentothal Test
1. The EEG response is recorded from
previously placed depth electrodes as the
patient is progressively sedated with
pentothal. The end point is either apnea,
hemodynamic instability, loss of corneal
reflexes or the administration of one gram
of Pentothal.
2. Preparations
a. Anesthesia equipment (a cart can be
be prepared for this purpose) is taken
to the Epilepsy Center. Check the
laryngoscope.
b. Supplies to be taken include thiopental
(40cc), IV fluids and administration
set, pulse oximeter, Dynamap,
precordial stethoscope, and the
anesthesia record.
c. EKG is read off the EEG electrodes.
3. Procedure
a. People standing at the foot of the
patient's bed cause interference with
the EEG tracing.
b. Interview the patient, apply the B/P cuff
and pulse oximeter, start the IV and place
the precordial steth. over the patient's
trachea at the suprasternal notch.
c. Apply O2 via mask and check the suction
apparatus to be sure its ready.
d. Attach both syringes of pentothal to
the IV. Insure free flow of the IV.
e. Sit to the patient's right. The
neurologist will be standing at the
patient's left. Prepare to record B/P's
every 60 seconds on the anesthesia
record.
f. Push 25 mg increments of pentothal every
30 seconds. Start this when the second
hand hits twelve on the clock. Call
out in a loud voice "25 mg" with each
dose so that the RN can keep track of
the doses.
g. The patient will start having brief
apneic episodes that resolve
spontaneously as CO2 builds up. If
they don't resolve, administer chin
lift. If apnea persists despite chin
lift, stop giving pentothal.
h. Document the time the neurologist
calls the procedure. Document the time
the patient begins responding to
stimulation. Remove the oxygen after
an appropriate amount of time and
document that saturations are stable
on room air.
Head Trauma