Awake craniotomy is becoming more popular as a neurosurgical
technique that allows for increased tumor
resection and decreased postoperative neurologic morbidity.
This technique, however, presents many challenges
to both the neurosurgeon and anesthetist. An
ASA class II, 37-year-old man with recurrent oligodendroglioma
presented for repeated craniotomy. Prior
craniotomy under general anesthesia resulted in residual
neurologic deficits. An awake craniotomy was
planned to allow for intraoperative testing for maximum
tumor resection and avoidance of neurologic morbidity.
The patient was sedated with propofol, and bupivacaine
was infiltrated for placement of Mayfield tongs and
skin incision. Following exposure of brain tissue, propofol
infusion was discontinued to allow for patient cooperation
during the procedure. Speech, motor, and sensory
testing occurred during tumor resection until resection
stopped after onset of weakness in the right arm.
The propofol infusion was resumed while the cranium
was closed and Mayfield tongs removed. The patient was
awake, alert, oriented, and able to move all extremities
but had residual weakness in the right forearm.
Awake craniotomy requires appropriate patient
selection, knowledge of the surgeon's skill, and a thorough
anesthesia plan. This case report discusses the
clinical and anesthetic management for awake craniotomy
and reviews the literature.
Keywords: Anesthesia, awake craniotomy, opioid,
propofol.
Nonopioid Anesthesia for Awake Craniotomy:
A Case Report
Diane L Wolff, CRNA, MS
Robert Naruse, MD
Michele Gold, CRNA, PhD
Awake craniotomy for tumor resection presents
many challenges for the neurosurgeon
and anesthetist. Surgery performed on brain
tissue poses an inherent risk of permanent
neurological deficit, especially for tumor
resection involving the eloquent cortex. Awake craniotomy
allows for intraoperative speech, motor, and sensory
testing, with the goal of maximum tumor resection
while avoiding postoperative neurological morbidity.1-4
The anesthetic management for this surgery must provide
sedation, analgesia, respiratory and hemodynamic control,
and a responsive, cooperative patient for neurologic
testing intraoperatively.1
Case Report
A 37-year-old, 69-kg male was scheduled for a left frontal
awake craniotomy for resection of recurrent grade 2 oligodendroglioma.
The patient was diagnosed 5 months earlier
after sudden onset of seizures, and the initial resection of
tumor was done under general anesthesia 4 months earlier.
Postoperatively the patient suffered weakness of the right
hand and right-sided facial numbness. Current preoperative
assessment revealed residual facial numbness, but the
patient was otherwise neurologically intact. Medications included
levetiracetam, 5 mg twice a day, for seizure prophylaxis.
The patient reported a minor seizure 16 days earlier.
Laboratory results were reviewed and were within normal
limits. Preoperative vital signs were a pulse rate of 78/min
and blood pressure of 110/58 mm Hg. An 18-g intravenous
(IV) catheter was inserted in the right hand. Premedication
included glycopyrrolate, 0.2 mg IV; metoclopramide, 10 mg
IV; and ranitidine, 50 mg IV. The right naris was prepared
with phenylephrine drops, and a 7.5-mm nasal airway with
5% topical lidocaine was placed in case tracheal intubation
would be needed during the operation.
The patient was transported to the operating room
(OR). Standard monitors were placed, including electrocardiography
(ECG), noninvasive blood pressure monitoring,
pulse oximetry, and capnography. A simple
oxygen face mask was placed, with 6 L/min of oxygen.
Propofol, 100 mg IV, was administered, followed by continuous
infusion at 150 μg/kg per minute titrated to a respiratory
rate of 12 to 14/min. A 20-gauge right radial arterial
line was placed for continuous intraoperative
monitoring of blood pressure. An indwelling urinary
catheter was inserted for patient comfort during the
lengthy operation and for diuretic administration.
Cefazolin, 1 g IV, was given for infection prophylaxis.
Somatosensory and motor evoked potential monitoring
was instituted. Ten minutes before pinning of the
patient’s head in Mayfield tongs, 0.25% bupivacaine with
epinephrine was infiltrated by the neurosurgeon at the pin
sites. The patient was positioned with a right tilt and sniff
position was achieved to help facilitate a patent airway. A
tent was created under the drapes to allow visualization
and communication with the patient. The surgeon infiltrated
0.25% bupivacaine with epinephrine into the scalp
surrounding the entire surgical site before incision.
Dexamethasone, 10 mg IV, and mannitol, 1 g/kg IV, were
administered to help facilitate surgical exposure of the
brain. Vital signs before incision were a pulse rate of
73/min and blood pressure of 95/57 mm Hg. Blood pressure
after skin incision and during craniectomy remained
stable, with a systolic range of 95 to 108 mm Hg over a diastolic
range of 50 to 60 mm Hg; pulse rates were 70 to
80/min. The propofol infusion was stopped after craniectomy
and the brain tissue was exposed. Stereotactic monitoring
was employed to help identify tumor margins.
A neuropsychologist performed speech testing after
the patient awakened. The patient was asked to squeeze
the anesthetist’s hand intermittently and move his feet.
The patient remained alert and oriented throughout the
awake portion without speech impairment. Blood pressure
remained 98 to 110/51 to 62 mm Hg, and pulse rate
ranged from 71 to 79/min. Seventy minutes into resection
the patient complained of persistent weakness of the
right hand and arm, prompting the neurosurgeon to stop
tumor resection. The propofol infusion was resumed and
continued until the cranium was closed and the Mayfield
tongs removed. Ondansetron, 4 mg IV, was administered
for prophylaxis of postoperative nausea. The patient was
awake by the time the head dressing was complete.
Immediate neurologic assessment was completed in the
OR and was repeated on arrival to the recovery room.
The patient was alert and oriented to person, place, time,
and situation, and he was able to move all extremities but
had residual weakness in the right hand and forearm. The
patient had no pain, and vital signs remained stable, with
blood pressure 114/56 mm Hg and pulse rate 81/min.
Oxygen saturations throughout the entire case were 100%.
No airway obstruction or complications occurred. The
patient remembered portions of the intraoperative testing
but stated he was comfortable throughout the operation.
The patient’s postoperative course was uncomplicated,
with the exception of residual right hand and forearm
weakness. Vital signs remained stable and the patient
complained of minor head pain on postoperative day 1
that was treated with hydrocodone initially and then
acetaminophen until discharge. The patient was discharged
home on postoperative day 4.
Discussion
Resection of tumor in the eloquent cortex of the brain has
an inherently high risk of postoperative neurologic morbidity.
Modern technological advances in magnetic resonance
imaging (MRI) and the use of intraoperative motor
strip testing, ultrasound, and stereotactic monitoring
have helped to decrease postoperative neurologic
deficits.2-4 Intraoperative wake-up testing or awake craniotomy
is becoming increasingly more popular to aid in
resection of tumors within the eloquent cortex.
Historically, awake craniotomy was used for epilepsy
surgery, which often involves resection of the temporal
region of the brain where the eloquent cortex is located,
but additional surgical procedures have shown benefit
from this technique1 (Table 1).
Awake craniotomy poses unique challenges, especially
for the anesthetist, who is faced with an unprotected
airway and limited access to the patient due to positioning
and pinning of the head. Therefore, appropriate
patient selection is of utmost importance for this method.
Patients must be cooperative, have a thorough understanding
of the procedure, able to lie still for an extended
time, and not have profound existing neurologic
deficit. Patients who are obese, have esophageal reflux,
sleep apnea, and difficult airways are not good candidates
for this type of craniotomy procedure (Table 2). Lastly,
patients must desire to proceed with this plan.1
Patients require sedation or general anesthesia until the
brain is exposed and again at the end of surgery while the
cranium is closed. Multiple anesthetic techniques have
been described in the literature without identification of a
superior technique.1-4 The anesthetic technique used
must provide adequate sedation and analgesia, maintenance
and control of respiratory and hemodynamic parameters,
and an awake and cooperative patient during
neurologic testing.1 Early techniques employed local
anesthetic at the incision site or scalp nerve blocks with
the addition of IV fentanyl or midazolam. Variations of
this technique use droperidol or a propofol infusion.
Patients were given oxygen via nasal cannula or face
mask. This combined local anesthetic and IV sedation
technique has a high potential for complications related to
an unprotected airway, including obstruction and desaturation
as reported in the literature.1-4 This technique is
Table 1. Operative Considerations
Awake craniotomy indications
Supratentorial tumors, eloquent cortex (motor strip cortex,
Broca and/or Wernicke area; sensory cortex)
Intractable epilepsy
Deep brain nerve stimulator
Arteriovenous malformation
Aneurysms
Benefits
Optimal tumor resection
Improved tumor diagnosis
Resection of tumor that is otherwise inoperable
still used by some, with increasing use of propofol infusion
and opioids together.1,3 Propofol decreases the cerebral
metabolic rate, reduces cerebral blood flow, and also
has anticonvulsant and antiemetic effects. All of these
factors benefit patients undergoing craniotomy surgery.
Dexmedetomidine, a selective α2 adrenoreceptor
agonist, is being increasingly used to provide sedation and
analgesia for awake craniotomy. Benefits of dexmedetomidine
are that it does not cause respiratory depression, as is
possible with other anesthetic agents, and it reduces intraoperative
and postoperative anesthesia requirements;
however, hypotension and bradycardia have been noted.
Case studies report that patients are easily aroused by
verbal stimuli, whereas some report concerns of impaired
neurocognitive testing, even after stopping the dexmed -
etomidine infusion for extended periods, delaying tumor
resection or resulting in cancellation of the case. These
reports also use a wide dose range of dexmedetomidine
infusion and various combinations of other drugs, including
opioids and midazolam. A case report by Moore and
colleagues discussed the successful use of dexmedetomidine
as a rescue drug during awake craniotomy that
avoided conversion to general anesthesia in a restless
patient. The literature reveals no consistent use pattern for
dexmedetomidine, which may explain the wide variability
of clinical outcomes.
Another technique known as asleep-awake-asleep uses
a laryngeal mask airway (LMA) or an endotracheal tube
(ETT).1 Recent retrospective case review shows an increased
use of LMAs for awake craniotomy surgery.
Anesthesia is initially induced with propofol and an
opioid infusion, such as remifentanil, and an LMA is
placed. This allows for spontaneous breathing and for
positive pressure ventilation should it be needed. At the
appropriate time during the surgery, anesthesia is
stopped, the LMA is removed, and intraoperative neurologic
testing is performed. After the awake portion is
completed, anesthesia is induced once again, and the
LMA is reinserted until the end of surgery.1 Patients not
appropriate for LMA may have a nasal ETT placed, which
is removed for the wake-up period and then reinserted
with the use of a fiberoptic bronchoscope. The advantage
of this technique is that it does provide airway protection
and an ability to provide a deeper level of anesthesia for
the patient during the most painful and stimulating parts
of the surgery. This is beneficial if the surgeon
Table 3. Anesthesia Considerations
OR indicates operating room; ETT, endotracheal tube; LMA, laryngeal mask airway; ETCO2, end-tidal carbon dioxide; CVP, central venous
pressure; ECG, electrocardiography; BP, blood pressure.
Goals = 4 As
Adequate sedation
Analgesia
Awake cooperative
Airway, respiratory, and hemodynamic control
Anesthesia options
SAS = sedate-awake-sedate
AAA = asleep-awake-asleep
With or without local anesthetic infiltration
Emergency preparedness/OR setup
Airway: available ETT, oral/nasal airways, LMA, fiberoptic scope
Breathing: ETCO2, O2 delivery, direct visualization of patient
Circulation: ± arterial line/CVP, hemodynamic support,
transfusion ready
Monitors: ECG, oximetry, BP, ETCO2, temperature, CVP, Foley
catheter
Additional OR setup
Patient comfort: pillows, padding, temperature control
Minimize noise/movement
Sign on door “Awake Patient”
Table 2. Patient Selection Criteria
BMI indicates body mass index; GERD, gastroesophageal reflux disease.
Inclusions
Normal airway examination
Able to lie still for extended period
Cooperative
Relative exclusions
Obesity, BMI > 40 kg/m2
Obstructive sleep apnea
Symptomatic GERD
Altered mental status
Communication barrier (language, profound dysphagia)
Extreme anxiety
Large vascular tumor or substantial dural involvement
does not provide adequate infiltration of local anesthetic
at the sites of the incision or Mayfield tongs.1
The use of opioids is controversial owing to the sedative
and respiratory depressant effects that occur with
their administration. This can interfere with providing an
awake, cooperative patient and lead to brain swelling due
to hypercarbia.1,5,9 In clinical practice, some anesthesia
professionals believe intraoperative opioids are unnecessary
in craniotomy surgery because manipulation of brain
tissue is painless.10 Pain associated with craniotomy is
superficial at the incision site and meninges, suggesting a
somatic versus visceral origin for this pain. Therefore, it
could be inferred that hemodynamic changes normally
attributed to pain, such as increased heart rate and blood
pressure, may in fact be caused by catecholamine release
from sympathetic fiber stimulation of the brain parenchyma.
10,11 Hence, during tumor resection patients can be
awake and performing various speech and motor tests
without pain. This physiology supports the use of an
awake craniotomy technique in which analgesia is administered
during scalp incision and craniectomy, the
time when pain fiber stimulation occurs.
Anesthetic management of this case followed a traditional
awake craniotomy by administering a propofol infusion
for sedation and administering oxygen through a
simple face mask. No sedative or opioid drugs were given
and the patient was pain free, which further supports that
brain parenchyma may lack pain receptors. The surgeon
did an extensive and thorough infiltration of local anesthetic
before head pinning and incision. This provided
anesthesia at the incision, where nerves are located.
Avoidance of opioids and sedatives decreased the risk of
airway complications from concomitant use with propofol.
The patient still received analgesia but without the
respiratory depressant effects of systemic opioids. The
technique used also provided for a very fast intraoperative
wake up and an alert and cooperative patient with no
anesthetic complications to facilitate the extensive intraoperative
neurologic testing during tumor resection.
Several factors influenced the decision to choose this
approach to awake craniotomy versus the asleep-awakeasleep
technique. Patient factors included a good airway
on examination, appropriate weight, no history of
esophageal reflux, and willingness to cooperate with directions
from the anesthesia care team. Additional important
factors included a surgeon known to be very
skilled at performing this surgery, good local anesthetic
infiltration at the incision site, and additional attention to
patient needs and OR setup (see Table 3). Lastly, the
surgeon, anesthesia team, and patient all had a thorough
understanding of the surgical and anesthesia plan and
agreed to proceed.