DR
UNNIKRISHNAN P
MD,DA,PDCC,MBA
ASSISTANT
PROFESSOR
DEPT OF
ANESTHESIA
SCTIMST,
TRIVANDRUM
ANESTHETIC CHALLENGES
IN AWAKE CRANIOTOMY

Is the population becoming more
sensitive?
• Not sure; but the BRAIN IS STILL REMAINING
INSENSITIVE !!!

What’s the fun if everyone tells the
same?
Awake Craniotomy
Craniotomy with
Intraoperative
awakening

Why Awake Craniotomy ?
• Is a technique used for brain tumour excision
from eloquent cortex, epilepsy surgery, and
deep brain stimulation surgery
• Why a tumour in the eloquent area needs the
patient to be awake during surgery?
• fMRI, DTI
• MEP, SSEP
? Spinal;
I want GA

How it goes?

As an anesthesiologist, what you
are going to do preoperatively?
• Patients selected, on the basis of history and
characteristics, the likely extent and duration of brain
mapping required, and the likely ease of excision of the
tumour
• Significant burden of anxiety for the patient
• Prepare the patient psychologically; explain the
procedure
• Simulate their positioning on the operating table,
mapping tests, and honestly discuss possible negative
feelings (dry mouth, pain during manipulations), as well
as suggested ways to correct them

Premedication
• Patients must take their usual steroid, anti-epileptic*,
or anti-hypertensive medication, or anti aspiration
prophylaxis (if indicated)
• Seizures (2.9 to 54%) mostly during cortical mapping
• Risk factors: h/o preoperative seizures and the mastery
of the mapping technique
• Antibiotics, pre-incision
• Nausea & vomiting will increase ICP; give antiemetics
• Paracetamol intraoperatively

There should not be any
communication gap between the
two:
• Position / Table*
• Patient cooperation
• Comorbidities
• MAC or AAA
• Local anesthesia
• Timings of drug administration
• Closure

First impression is the best
impression
• The sedation and analgesia profile during the first phase
of awake craniotomy (i.e., scalp incision, bone flap
removal, dura opening) plays the crucial role in the
quality of intraoperative emergence

The position
• The patient position is dictated by the location of the
lesion.
• This is usually a lateral or supine position, but with
occipital lesions and testing the visual cortex, a sitting
position may be used

Actively involve in the
positioning of the patient
• The ability to communicate with the patient
and access to the patient should be
maintained at all times. Sterile drapes
shouldn’t encroach on patients face

Monitors
• Arterial line*
• Capnography*
• Depth of anesthesia monitors*
• Urinary catheterization*

Scalp
Block
and it should not hurt the
patient…
is your first
step

Stuff for Junior Residents
• What % of lignocaine solution do you use to infiltrate
brain parenchyma?

Scalp Block: The Do’s
• Bilateral scalp block before pinning of the head in
Mayfield Pins
• Communicate it with the neurosurgeon
(Temporalis fascia, dura mater infiltration)
• Analgesia even up to 6-8 hours
• Bupivacaine, levobupivacaine or ropivacaine
• Chlorhexidine or betadine, sterile gloves and a 23 G
needle, the local anaesthetic is infiltrated into the
following sites:

Our technique should ensure #
• Patient is awake, co-operative and comfortable during
the mapping phase
• Acquisition of reliable neurophysiological monitoring
signals
• A soft and slack brain during resection.
• Hemodynamic stability especially during painful phases
(skull pin placement, the craniotomy itself and dural
opening).

Which is the best approach?
• There is no recognized consensus on the best
anaesthetic approach
• It depends on the surgeon, pathology, length
of surgery, and patient factors
• Most neuroanaesthetists have usually
developed a preferred technique and believe
their own approach to be the safest and the
best
MAC
AAA

Monitored Anesthesia Care
(MAC)
• Anesthesia Technique

Fine titration…
↓sedative load,
spontaneous
ventilation
Avoid sharp
asleep to awake
transition
↓hypo/hyper
active delirium ,
↑ mapping
reliability
Sedation
deepened during
painful events
Stopped during
mapping &
resection
Restarted for
closure

Problems
• If the level of sedation is not titrated correctly:
• Risks of airway obstruction which can lead to
hypercapnia, hypoxia, and increased intracranial
pressure with a ‘tight’ brain, or
• A patient who is not adequately sedated will be
uncomfortable and anxious

Dexmedetomidine is it the Most
Suitable Drug (MSD) in awake
surgeries ??!!
• Calm, cool patient!
• Anxiolysis-Analgesic-Opioid sparing*
• No effect on ICP
• Less respiratory depression less hypercapnia
• Easily arousable despite sedation
• Less nausea & vomiting
• Loading dose of 0.5–1.0 ug/kg over 20 min f/b an
infusion rate of 0.2–0.7 ug/kg/h + P’mol ± fentanyl
• Can start start scalp block, towards the end of the
LD

Dexmedetomidine : Issues
• ?lack of suppression of preoperative epileptic activity by
dexmedetomidine  ?seizure incidence more
• Significant variability in dose requirement among
patients
• Effects may not exactly get reflected in the BIS
• It does accumulate to some extent: longer durations of
infusion will result in a slower return to normal function
• Bradycardia
• Hypotension
• Hypertension

Propofol + Opioid Moderate
Sedation
• Propofol infusion & Fentanyl increments (India)
• TCI with Propofol & Remifentanil an excellent choice
• Precise dosing very important: hypercapnia
• Titrate according to BIS
• TCI: Use Propofol Schnider model @ 2-4 ug/mL target
concentration. Remifentanil @ 0.8-1 ng/mL

Volatile situation
• Inhalational anesthetics are not optimal due to higher
chances of a potential elevation of ICP, a higher risk of
nausea and vomiting and emergence delirium
• May not give an ideal situation for mapping
• It seems rational to REDUCE RELIANCE ON OPIOIDS
at preawake and awake phases due to potential
somnolence on emergence and decreased quality of
cooperation on the part of the patient

Asleep-Awake-Asleep (AAA)
• Anesthesia Technique

AAA Advantages
• Better comfort for the patient and surgical team during
the preawake phase
• Reliable protection of the patient from painful
sensations
• Protection from hypoventilation and opportunity to
control brain swelling via hyperventilation
• Protection from postoperative recollections about the
awake phase
• Prevents intraoperative movements by the patient
GA/airway
Drugs
stopped
NC
Testing
GA
restarted

Drugs for GA
• Propofol infusion (TCI/MCI) & Fentanyl increments
• TCI with Propofol & Remifentanil an excellent choice
• Volatile agent + Remifentanil
• Titrate according to BIS
• LMA/ ProSeal LMA/iGel/ Endotracheal tube
• Controlled ventilation, ±NMBA.

A great teaching tool; cuts down the
work load

We overcame all the hardships for
this!
• Currently, the gold standard technique for mapping
involves direct cortical electrical stimulation while the
patient is awake and able to attempt to perform a
relevant task, to determine if the stimulus disrupts
execution of the task.
• A calm, quiet environment is required during this
• Pain from the pins or discomfort from the prolonged
immobility, agitation or nausea, and vomiting.
• It is important to pick it and address it effectively as it
can lead to poor surgical conditions

Mapping
• The Broca’s area (for speech production and language
processing) and the Wernicke’s area (for language
comprehension),the motor and sensory cortex.
• Any alteration of speech, language, and motor function
by stimulation is communicated to the surgeon.
• Resection takes place once the cortex has been
functionally mapped by this process.

The climax…
• The last phase of an awake craniotomy (haemostasis,
dural, skull and skin closure) can be uncomfortable
• Particularly during skin closure
• Patient might have been lying immobile for some time,
with resultant musculoskeletal discomfort
• Scalp block start to wean

Challenging act!
• Induction of GA at this stage requires experience and
expertize
• LMA insertion is often preferred - as tracheal intubation
is challenging in these patients who are usually in a
right lateral position, with the head clamped, and in an
unfavourable position for laryngoscopy.
• If MAC, can restart dexmedetomidine/ propofol
• When surgery finishes, the pins removed and the
patient woken up.
• If remifentanil has been used, it can be run at low
infusion rates to aid a ‘smooth’ wake-up and avoidance
of coughing

How the literature compares both?
• Eseonu CI et al, World Neurosurg 2017 :Similar;
reduced duration in the MAC group
• Sz Dilmen et al, J Clin Neurosci 2017 : seizures,
agitation, PaCO2, non-critical desaturation, brain
edema and c/o pain were more in MAC group
• Elbakry et al, Minerva Anes 2017 : Dexmedetomidine
MAC vs Propofol MAC, similar
• Seuro et al, JNSA 2018 : MAC vs AAA Similar; lower
incidence of respiratory and hemodynamics
complications in the dexmedetomidine groups.

Goettel et al, BJA 2016
• Dexmedetomidine vs propofol remifentanil conscious
sedation
• fentanyl bolus the assigned drug regimen started
Scalp Block Before and after mapping, sedation was
titrated to MOAA/S score of 2–4
• In the propofol-remifentanil group, propofol was
stopped, and remifentanil infusion rate decreased, 10
min before mapping.
• In the dexmedetomidine group, the infusion rate was
decreased to 0.1–0.4 mcg/kg/h 10 min before mapping.
• Similar; DEX- lesser HR, more seizures. P-R: more
adverse respiratory events

So which one is better?
• If the overall procedure >4 hours AAA. MAC if <4
hours.
• Once we get remifentanil….more options
• TCI MAC and TCI AAA
• For MAC, Dexmedetomidine Vs Propofol-Remifentanil
TCI….

COMPLICATIONS
How will you manage the..

Painful Facts
• Despite the scalp block, complaints of pain during
surgery are common.
• Are sensations associated with manipulations of the
skull-base structures or perivascular tractions. Local
analgesics cannot resolve this
• opioids can reduce the reliability of brain mapping.
• The main solution to this problem may be a change in
surgical approach: transcortical access to underlying
tissues, avoiding traction of vessels, and skull-base
structures

Seizures
• treated by irrigating the brain tissue with ice-cold
saline.
• low doses of propofol
• no benefits of prophylaxis with phenytoin or valproate
• ? levetiracetam superior
• If these fails: benzodiazepines, anti-epileptic drugs, or
re-sedation with airway control
• An emergency plan for airway control: LMA
• Others: patient intolerance of the procedure, often
because of the urinary catheter or prolonged positioning
and intra-operative seizures.
• Conversion rate to GA is less

Post Operative Care
• Usually returns to ICU; in some centres to
NS ward
• Analgesia; scalp block may ↓ requirements
• Close neurological monitoring especially in
the first 6 h after operating; haematomas 
may require an urgent repeat craniotomy &
evacuation
• Most patients are in hospital for 1–2 days
after operation
• DAYCARE : Selection based on stringent
inclusion and exclusion criteria, routine
postoperative imaging for haematomas and
access to advice after discharge

Claimed Advantages
• Increased lesion removal
• Minimize the damage to eloquent cortex
• Shorter hospitalization time
• Reduced cost of care
• Decreased incidence of postoperative
complications such as nausea and vomiting

Outcome
• ? the frequency of new-onset postoperative neurological
deficits after awake craniotomy is no less than that for
surgery ↓GA
• The cause is ischemic injury of the subcortical structures
(internal capsule, etc.) or anatomical damage of the
subcortical pathways.
• Are often due to mistakes in mapping methodology,
excessive sedation, or fatigue of the patient at the awake
stage.

How to fix?
• It seems that the most effective way to avoid these
complications is to use a transcortical approach to deep
structures, which prevents vascular traction and
reduces risk of ischemic injury.
• Such an approach can prevent fatigue and pain because
sensitive tissues around the vessels and leptomeninges
remain intact

THANK