XV. Emergence
A. No one game plan can apply to all situations.
Factors such as initial difficult intubation,
full stomach, clipped aneurysm vs. unclipped
aneurysm, post-op airway edema from neck
surgery, or diminished gag reflex from tumor
effects can all impact on how the emergence is
planned.
B. Valsalva Maneuvers
1. The surgeon may test the integrity of the
dura with a valsalva maneuver to 35 cm
H2O. If the patient is not deep or
completely paralyzed, bucking may occur.
Gradually increasing the strength of
contractions on the breathing bag can help
determine the likelyhood of bucking.
C. Emergence Sequence #1 (extubate deep)
1. An extubation technique described in
Newfield and Cottrell is to extubate the
patient in a very deep plane of anesthesia
while breathing spontaneously and support
the airway while the Forane comes off.
This can be complicated by high CO2 levels
that can result in high blood pressures
and the necesssity for prolonged airway
support.
a. An advantage to this technique is that
it not necessary to use N2O. For
patients with poor lung function,
nitrous may cause hypoxemia.
b. The extubation is usually accomplished
with no bucking or hypertension at
least initially
c. The infusion for blood pressure
control should be completely connected
to the IV and ready to go when the ET
tube is taken out.
D. Emergence Sequence #2 (titrate slowly to wakefulness)
1. Maintain the twitch monitor TOF at 1/4
till the pins are out. The patient is left
on the ventilator till the very end. As
the Forane comes off at the end of the
case, rapid changes can occur in the train
of four. The removal of the volatile
anesthetic usually results in the TOF
going from 1/4 toward 4/4. Frequent
checking of the TOF is required.
2. When closing commences, start normalizing
the patient's temp and PaCO2.
a. A temp significantly below 35 degrees
makes for a chancy extubation.
(1) Remember that the main determinant
of body temp is room temp. Do not
be afraid to ask that the
thermostat be turned up.
b. If the last ABG was remote from the
times of extubation, order another
one. The ETCO2 may not have the same
realtionship to the PaCO2 as it did
earlier. A goal of PaCO2 around 40 or
perhaps a little higher is set. Failure
to normalize the CO2 can yield a
patient at the end of the case who is
thrashing around but apneic.
3. The thiopental infusion, if used, is turned
off as soon as closure is started. Several
hours may be necessary for its
elimination.
4. Discontinuation of the fentanyl infusion
and isoflurane is individualized to the
patient and the surgeon.
a. As a guide, the fentanyl is turned off
sometime during dural closure. This is
modified by your best estimate of how
much fentanyl is on board and how fast
the closure will be. For most patients,
try to discontinue the infusion about
45 minutes before extubation.
b. As a guide, the isoflurane is slowly
turned off in time for the end-tidal
concentration to be below .1 at the time
of extubation. Increasing the fresh
gas flow will speed removal of the
isoflurane.
5. When the isoflurane is turned off, the blood
pressure will generally start to rise. It
is important to treat this pre-emptively.
Do not wait till the BP is very high.
a. The first line drug is labetalol.
(1) Contraindications to this are
bronchospasm and conduction
blockade of the heart.
b. If the heart rate gets too slow or the
response to labetalol is inadequate,
go to hydralazine. It is permissable
to give the hydralazine in intervals
less than the classically taught 20
minutes, but be careful. The accumulated
dose may catch up on you unexpectedly if
the dosing interval is too short.
(1) The blood pressure just before
extubation should be below what
you want it to be at the time of
extubation.
(2) Failure of hydralazine leaves
Trimethophan (Arfonad) or Nitroprus-
side (Nipride). The amount of
hydralazine you give before giving
up on it is usually determined by
how rapidly the BP is rising and
how much time you have prior to
the end of the case. The Arfonad
or nipride should have been prepared
prior to this time and ready to
rapidly connect to a dedicated IV
with its own carrier fluid.
(3) The best indicator of depth of
anesthesia is the capnograph. Judicious
use of narcotic can be used to
appropriately adjust anesthetic
depth. 100 mg of I.V. lidocaine (in
the 70 Kg adult) can be used to reduce
sympathetic response to being intubated,
and should help prevent bucking for about
5-15 minutes. Having inadequate
narcotic on board at the time of
extubation will probably result in
bucking. A mixture of propofol and
alfentanil can be used in boluses
to deepen anesthetic. About a half cc
of each is a good choice.
6. If the capnograph is completely quiet, with
no curare clefts despite an end-tidal
isoflurane of less than .1 with an adequate
PaCO2, then anticipate high relative
levels of fentanyl. About the only thing
to do at this point is to increase the
ventilation and try to get more isoflurane
off.
7. The reversal is given after the pins are
out.
a. Suction prior to reversal. Remove the
OG tube and the esophageal
stethoscope.
b. This timing is modified by how much
narcotic effect the patient has on
board. The heavily narcotized patient
can be reversed immediately after pin
removal. If the patient is light, give
more narcotic or lidocaine or propofol
prior to reversal. The capnogram is a
good source of information about the
narcotic level. This will not be true
if the CO2 has not been normalized. Be
sure to differentiate cardiogenic
oscillations from curare clefts.
(1) If the patient is to be turned to
supine prior to extubation, the
decision must be made as to
whether to wait for re-positioning
before reversal.
(2) The surgeon will be putting the
head through a great many
gyrations during dressing
placement after the pins are out.
Bucking and straining are highly
likely at this time.
8. When the reversal is given, the patient is
generally taken off the ventilator.
Remember to open the pop-off valve. In
most cases, the patient will shortly
commence spontaneous ventilations without
the need for excessively high PaCO2
levels.
a. Avoid giving big squeezes on the bag
after the patient is reversed. This
may precipitate bucking. Also refrain
from using the twitch monitor or
suctioning if there is any chance the
patient can move.
9. Before turning off the N2O, make sure the
patient is ready for extubation.
Secretions can make the tape very
difficult to remove from the face. Peel
the tape back so that the tube can be
quickly removed at the appropriate time.
a. If the patient is at high risk for
aspiration, allow full return of the
TOF prior to turning off the N2O. The
patient can sometimes wake up very
fast after turning off the N2O.
Consider this in the patient who is
obese or who had abundant fluid in the
stomach when the OG tube is placed.
10. Now is the time to sit back and do as
little as possible. If the patient is not
bucking, leave him alone. The more nitrous
that can be eliminated before waking the
patient, the smoother will be the
extubation. Encourge others in the
operating room to not touch the patient.
Do not suction the patient any further
unless absolutely necessary (vomiting).
a. Checking the train-of-four can be
problematic at this point. The
stimulation may induce bucking.
Failure to adequately reverse has its
own consequences.
11. A tidal volume of 300 is a good goal to
acheive prior to waking the patient. When
the moment of truth has arrived, have the
mask and syringe ready. Note the volume
and rate of the patient's respirations. If
respirations are adequate, softly say to
the patient "first name, open your eyes".
If all has gone well, the patient will
open his eyes. Deflate the cuff and pull
the tube. Remember that cuff deflation
will usually induce some bucking. It is
helpful to squeeze the bag gently as you
pull the tube, so the first respitory action
the patient takes is to exhale, not aspirate
and inadvertent airway secretions.
E. The Less than Smooth Emergence
1. You call the patient's name and nothing
happens:
a. If the patient was less than awake on
induction, he will probably not be
awake on emergence.
b. The agents responsible for keeping the
patient asleep are pentothal, fentanyl
and possibly lidocaine. A low body
temperature may also be keeping the
patient asleep.
(1) If the respirations are above 12,
it is probably not fentanyl that
is causing problems.
(a) Small doses of naloxone may be
indicated. Try 50 mcg boluses
about 2-3 min apart until you
start to see some respirations.
(2) The best thing to do is give the
patient more time.
c. Gradual escalation of the degree of
stimulation above calling out the name
may be indicated.
d. Deciding when to leave the patient
intubated is individualized. The key points
include: ability to maintain spontaneous
respirations, and the ability to safely
maintain the airway (depressed airway reflexs?
Paralysis not reversed enough to cough?)
2. The patient starts bucking before he is
awake.
a. This is often the result of
stimulating the patient before time
has been allowed for the N2O to
escape. If the patient is not taking
good breaths, do not attempt to
stimulate his breathing by suctioning
or even calling out his name.
b. Premature removal of the ET tube may
result in laryngospasm. Leaving the
tube in can cause intracranial
problems. Laryngospasm is a rare event
in an adult patient who has had a
predominantly narcotic-based anesthetic.
c. An individualized decision must be made
about whether to remove the tube or give
something to ablate the
bucking.
F. Extubating patients with possible airway edema.
1. Prolonged operations on the C-spine with
retraction of the trachea may cause edema
that could make respiration difficult post
extubation. Examples of such operations
include anterior corpectomy and any
prolonged case.
2. Shortly after intubation, establish that
an air leak exists when the cuff is
deflated. If, at the end of the operation,
this same leak can still be demonstrated,
then concerns about airway edema are not as
great. The concern is also lessened if the
patient can breath around an ET tube when
the cuff is let down.
a. Consider coming off on propofol
instead of N2O in those patients who
have poor lung function and are unable to
tolerate less than high levels of N2O.
Try PEEP before giving up on N2O. A
few centimeters of PEEP (eg. 10cm)
will usually not be enough to cause an
elevation in the ICP.
Transport and PACU Management