Basi di NeuroAnestesia
Gestione delle emergenze per il
NeuroAnestesista
- Sanguinamento massivo da rottura
di aneurisma
- La rottura di
un aneurisma cerebrale durante induzione può manifestarsi
con un aumento improvviso della pressione
sanguigna e concomitante bradicardia. L'ipertensione
è una delle cause di rottura di aneurisma. Si può
formare un ematoma sufficientemente grande da
causare effetto massa, necessitando un
trattamento chirurgico addizionale.
- Rottura
intraoperatoria
- Discutere
in anticipo con il chirurgo del piano di
azione in caso di rottura intraoperatoria
di aneurisma.Per tutti gli interventi per
aneurisma bisogna avere
disponibilità di sangue in sala
operatoria. Il nitroprussiato (Nipride) o
il trimetofano camesilato (Arfonad), a
seconda delle preferenze dell'anestesista
di sala, dovrebbero essere diluiti e
pronti per l'infusione o per un bolo. L'anestesista
dovrebbe essere chiamato in sala prima
dell'applicazione della clip temporanea.
- L'entità
del sanguinamento guida il piano
di azione. La pressione sanguigna
può cadere acutamente senza che
l'anestesista abbia alcuna
possibilità di provvedere
efficacemente.
- Punto 1:
cominciare l'infusione di sangue e
chiamare aiuto
- Punto 2:
Aiutare il chirurgo a controllare il
sanguinamento. Il chirurgo cercherà di
posizionare una clip temporanea su un
vaso prossimale rispetto al punto di
sanguinamento. In rapporto all'entità
del sanguinamento il chirurgo può
richiedere che la pressione arteriosa sia
mantenuta normale o sia ridotta
acutamente per permettergli una migliore
visualizzazione del campo operatorio.
- Un
bolo di Nitroprussiato di 40-50
mcg è una buona dose d'innesco
per indurre una breve ipotensione.
Questa dose si ottiene con 0.2ml
di una diluizione di 50mg di
Nipride in 250ml in Glucosio al 5%.
- L'obiettivo
iniziale per ottenere questa
ipotensione controllata è una
pressione arteriosa media di
circa 40mmHg. La determinante
ultima della pressione arteriosa
è costituita dal fatto se il
chiurgo può o meno controllare
il sanguinamento.
- Un
sanguinamento massivo determinerà
ipotensione prima che il sia
somministrato il Nitroprussiato.
- Punto 3: La
compressione carotidea ipsilaterale può
essere utile per gli aneurismi del
circolo anteriore.
- Punto 4: Protezione
cerebrale: può essere
somministrato Tiopentone dopo che il
sanguinamento è stato arrestato e dopo
avere ottenuto una stabilità
emodinamicaaaaaaaaaa
- I
barbiturici devono essere usati
con grande cautela nella gestione
di un sanguinamento aneurismatico
attivo. Il loro uso deve essere
rgolato sulla risposta pressoria
ed elettrocardiografica.
- Mantenere
la pressione arteriosa con
fenilefrina (neosinefrina) mentre
si somministra tiopentone porta
al rischio di ischemia se il
riempimento non è stato ben
adeguato.
- Teoricamente,
si usa un bolo di tiopentone
sufficiente a causare la burst
suppression, seguito da un'infusione
sufficiente a mantenerla. Le dosi
sono dell'ordine di 300-500mg per
il bolo e una infusione di 6-12mg/Kg/h.
Vedi sezione su protezione
cerebrale.
- Edema cerebrale
- Un imrpovviso
inizio di edema cerebrale può essere causato da:
- sanguinamento
all'interno del cervello
- paziente
sveglio e stressato per un'anestesia o un
blocco neuromuscolare inadeguati.
- aaaaaaaaaaaaaaaa
- aaaaaaaaaaaa
- aaaaaaaaaaaaaaaaaaa
a. Bleeding inside the brain
b. Patient awake and straining due to
inadequate anesthesia or neuromuscular
blockade.
c. Blood pressure changes (both up and
down). Hypotension can cause a reflex
vasodilation.
d. Decreased venous return and/or
increased airway pressures. Small
amounts of PEEP (5-10 cm) will not
cause this problem.
(1) Pneumothorax
(2) Obstruction to flow from abnormal
head position is one of the most
common causes of brain swelling.
This is especially true for the
patient whose head is supported
with a doughnut rather than pins.
The head is often moved gradually
so as to occlude venous return.
(3) Pericardial Tamponade
(4) Bronchospasm secondary to mainstem
intubation, asthma or aspiration.
(5) Inadvertent venous occlusion
intracranially by the surgeon.
(6) Bronchospasm - especially with
aspiration from a TE fistula.
e. Hyperemic response to head trauma.
f. Flushing an ICP transducer
2. Gradual Onset of brain swelling
a. If a specific cause is identified,
correct that first.
b. Steps to rectify swelling assuming
that the amount of isoflurane being used
has already been limited to an
endtidal of 0.4% to 0.5% with 50% N2O.
(1) Check head poition and possibily
tilt the table to bring the head
up. Take into consideration the
increased risk of air embolism.
(2) Consider increasing the minute ventil-
lation to hyperventilate and decrease
cerebral vascular volume through
vasoconstriction. This may not
be an early option for the aneurysm
patient in whom vasospasm is a
problem.
(3) Check the serum osmolality to make
sure it has risen by 10 mOsm since
the mannitol was given. Subsequent
fluid administration may have
diluted out the osmotic gradient.
(4) Suggest CSF drainage to the
surgeon. The CSF drain may be
plugged up, requiring irrigation
with a TB syringe. This is done
very carefully with a TB syringe
and strict aspetic technique using
non-bacteriostatic saline. Discuss
this with the surgeon.
(5) Administer a bolus of thiopental or
etomidate. The pentothal bolus can
be followed by an infusion at 2 to
? mg/kg/hr. This will allow
further reduction in the volatile
agent concentration.
C. Brain Protection
after Insult
1. Dose recommendations in Newfield and
Cottrell for thiopental.
D. Air Embolism
1. Points in the surgery most likely to be
associated with air embolism.
Relationship of AE to CVP and BP.*(AK's
experience)
2. Discontinue N2O - Not so much to
decrease expansion as to treat hypoxia
3. Treat hypotension with fluids or a vasoactive
drug such as ephedrine or phenylephrine.
4. Recover air through central venous catheter.
[Special multiport
catheters especially for
this purpose exist, and should be put in at
the begining of any
case where the head is
elevated, as these
patients are at greater
risk of air embolism.]
5. Compress Neck vein
6. Remember, you don't see bleeding with air
entrainment
7. Peep is not effective
8. Should you cancel case if you can't get a
central line or should you use IJ if you
can't get antecubital?
E. Arrhythmias from
Surgical Manipulation
1. Types of arrhythmias likely to occur:
a. bradycardia
b.
2. When is it likely to occur
a. Decompression of cystic intracranial
structures
3. When to treat
4. Tell surgeon
5. Have atropine ready
F. Iatrogenesis
Imperfecta Magna - System Faults
to
be Avoided
1. Ventricular catheter flushing
a. These catheters are sometimes placed
for the purpose of controling ICP by
allowing CSF to escape when a set
pressure is exceeded.
b. The catheter can be connected to a
reservoir for the purpose of draining
CSF or it may be connected to a
transducer. This transducer is usually
constructed with no flush system.
However, if the catheter is connected
to a transducer with a flush system,
it is imperative that it never be
flushed. Never, ever, flush a ventricular catheter
via a transducer flush valve. To do so is
catastrophic.
c. When doing a pre-op, note
how many
centimeters above the head the EVD
drip chamber is maintained. This is
the ICP.
2. Nitroprusside (nipride): aways have running
a. Nipride is probably the most
potentially lethal of all the
medications that an anesthesiologist
employs.
b. It has a sneaky way of running rampant
and causing incredible hypotension.
Take every precaution to keep this
from happening. If it can, it will.
(1) Nitroprusside is best infused into
its own line with its own carrier
fluid. Tape over the injection
ports to prevent accidental use of
the carrier line. Nitroprusside is
hooked into the carrier as close
to the vein as possible. Nipride
is mixed in D5W but the carrier
can be crystalloid.
(2) If boluses of nitroprusside are used,
consider putting full-strength
nitroprusside into a tuberculin
syringe rather than diuluting the
infusion. Use a long needle on the
syringe. The usual dose is 0.2ml
or 40mics. Errors in dilution
calculation could be devastating.
c. Runaways can occur when the IVAC door
is opened up. Tape the door of the
IVAC shut so that you won't let this
happen to you. Syringe pumps can leak
if the carrier line into which they
feed has an upstream disconnect. Do
not flush the line after a disconnect.
d. Some authorities recommend no
treatment of the blood pressure in
nitroprusside runaways. They feel that the
brief period of hypotension is better
tolerated than hypertension from
overtreatment. Do not use epinephrine.
Cerebral hemorrhage has occured from
treating Nipride hypotension with epi.
I have used 2cc's of phenylephrine (200
mcg) without overshoot in these
circumstances.
3. Phenylepherine (Neosynephrine): aways have running
a. If using only a 60gtt/cc mini-dripper
to regulate an infusion, beware of
mistaking a steady fine stream of
fluid in the drip chamber for no fluid
running.
b. A better approach is to use a drip
controller.
4. Failure to zero the A-Line
a. If someone else sets up your A-line,
it may not have been zeroed.
b. Double check your zero and take a cuff
pressure at the start of the case. If
the systolic of the cuff is the same
as the systolic of the A-line, get
suspicious. The mean pressures should be
the same but the systolic of the A-line
is
almost always higher.
5. Losing the ET Tube
a. Neuro cases involve table turns and
loss of access to the ET tube.
b. Be thoughtful of what you anchor the
ET tube to. Taping the tube to an IV
pole has resulted in immediate
extubation when the pole was moved.
c. If the patient is prone, try whenever
possible to run the tape all the way
around the neck. This will not be
possible when the C-spine or the
occipital area is being operated on.
Discuss with the surgeon ahead of
time.
d. Pink tape on well cleaned skin is the
best tape if you can't go all the way
around the head. If you can go around,
the white cloth tape works well. White
cloth tape varies greatly in stickiness
from one roll to another. The tongue
blade trick is useful for handling
cloth tape. The use of mastisol or
tincture of benzoin will enhance the
adhesiveness of cloth tape. CLoth tape
is good because of its flexibility and
moulding to the shape of the face.
e. Anode tubes can be bitten so that the lumen
becomes permanently occluded, with
subsequent loss of the airway. Place
an oral airway at the end of the case
to prevent this from happening.
f. Anode tubes with a rim where the pilot
tube runs can be rendered undeflatable
when the tube is wired to the teeth.
Don't use this brand__________ of tube
when wiring to the teeth.
g. Use Tegaderm over the tape to keep the
tape waterproof. This is especially
useful for Transphenoidal surgery
where tape cannot be put over the lip
and abundant surgical prep is done on
the face rather than the top of the
skull.
6. Malposition of the patient
a. Avoid placing the patient on the wrong
type of table or placing the patient
on the OR table with the wrong end
pointing toward the anesthesia
machine. Different surgeons doing the
same case will want the patient at
different ends of the table. The pad
can also be going the wrong way.
Where does the surgeon want the patient
with regard to the crack in the bed?
7. Dilantin disasters
a. Load dilantin slowly lest the BP plummet.
Watch the ECG for
lengthening of the Q-T
interval. Try
putting appropriate loading
dose into about 250 cc
crystaloid and
running it through a 60
drop/ml minidrip set.
8. Coagulation Crisis
9. Loss of Neuromuscular Blockade
10. CSF Catheter runaways and plugups
a. When placing a lumbar epidural
catheter for withdrawing CSF, very
little CSF should be allowed to escape
initially.
b. Remember that a patient with a VP
shunt may have all of his CSF escape
into the abdomen when the head is
opened.
11. Intracranial injection of local anesthetic
12. Bumping the Scope and moving the patient
Pre-operative Evaluation