Pre-Op Evaluation and Premedications
A. Communicating with the surgeon
B. In addition to all the other things that are
normally investigated during an anesthesia pre-
op, the neuroanesthesiologist is interested in
determining where on the intracranial
compliance curve the patient is residing.
1. The classic physical signs of increased
ICP and decreased "compliance" include
lethargy, disorientation, slurred speech,
vomiting and headaches.
a. However, patients may be wide awake
and yet be at a point on the
compliance curve that is close to the
steep section, giving the patient very
little reserve. Knowledge of the CT
scan can help identify these patients.
2. Evaluate the CT scan for cerebral edema,
midline shift, ventricular distortion and
hydrocephalus to asses the ICP. Induction
technique and premedications will depend
on the degree of intracranial reserve.
C. The general rule for premeds is "less is best".
The lower the intracranial compliance, the less
premed. The pt with an aneurysm is more heavly
sedated than the tumor patient, giving due
considertion to the ICP.
1. Don't give long acting sedatives such as
Ativan.
2. More sedation, usually with fentanyl, may
be given in the OR prior to plavcement of
the A-Line
3. Consider Benadryl or Vistaril at a dose of
25 to 50 mg. IM or PO as a pre-op med.
4. Patients receiving phenobarbital on call to the
O.R. as a continuation of their anticonvulsant
regimen may become sedated with this
alone, especially if given IV.
5. Consider anticholinergics as a
premedication in patients whose surgeries
are known to cause strong vagal reflexes.
These include glycerol rhizotomy and
sterotactic brain biopsy.
D. Continue anticonvulsants and note times
that subsequent doses are to be given.
E. Anticonvulsants, antibiotics, steroids,
nimodipine, antihypertensives, cardiac meds,
aminophyllin and thyroid supplements.
1. Give the patient his normal morning dose
of the above medications except for
diuretics.
2. Note the time of the last dose of
anticonvulsants and steroids. Additional
doses may need to be given later in the
course of the operation. Steroids are
usually ordered by the surgeon. Ask him
about it if not ordered. If you feel
steroids are necessary for adrenal
insufficiency, give them.
3. Nimodipine is generally given as already
scheduled. It may be given with a sip of
water on the AM of surgery if normally
taken at that time.
a. Give consideration to an NG tube
rather than an OG tube for the patient
who will receive Nimodipine post-op.
4. Antibiotics are often given in the OR at
the start of the case. They are too easy
to forget. If they were not ordered, ask
the surgeon if he wants them. They are best
given BEFORE the surgeon makes first incision.
F. Phenothiazines are avoided in neurosurgery
because of their ability to lower the seizure
threshold. Tigan IM is the preferred agent.
G. Be sure to write specific orders regarding which
maintenance meds are to be given on the morning
of surgery. Be careful writing the order "take
all meds with sip H2O". With this wording, only
medications that the patient is due to receive
prior to leaving for the OR will be given. For
example, an antihypertensive scheduled for 7AM
will not be given if the patient leaves for the
OR at 6AM. Specify each drug and the time the
drug is to be given.
H. If the patient has a beard that will interfere
with taping the ET tube, get his consent to
shave it in the OR. A verbal, documented
consent will do. Failing this, lots of tincture
of benzoin or Mastisol, with tape completely
around the head (assuming the surgeons aren't
using a porterior approach) will help. Try to
use the cheek bones, where there may be some
exposed shin.
I. Patients with a history of hypothyroidism
should have thyroid function documented by a
set of thyroid funnction lab tests. Consider
hypothyroidism in the differential of
an unexplained hypotension under anesthesia.
Monitor Selection