Keywords
awake craniotomy - airway anesthesia - brain mapping - electrocorticography - eloquent
area
Introduction
Awake craniotomy (AC) permits mapping of eloquent areas of the brain, thereby facilitating
optimal lesion resection without producing new neurological deficit. Success of this
procedure depends on active participation of the patient. Despite the widespread use
of this surgical technique, its optimal anesthetic management remains a challenge.[1] Most anesthesiologists practice asleep–awake–asleep (AAA) technique, without any
airway maintenance device. However, many practitioners provide general anesthesia
(GA) with airway maintenance devices like laryngeal mask airway (LMA) or nasopharyngeal
airway (NPA). The airway device is removed during the awake phase to avoid patient
straining on it during neurological testing and for verbalization of patient in case
of speech/language testing. Significantly, these devices do not ensure airway safety,
especially if surgery is conducted in an abnormal position.
Unsecured airway is a potential source of ventilation complications.[2] Such serious issues may arise either due to unintended deep sedation during AAA
technique or from administration of sedatives/hypnotic for controlling generalized
seizures. The occurrence of seizures is always a possibility in these cases. In such
circumstances, the patient requires emergent tracheal intubation.[3] Securing the lost airway or reinsertion of airway device after completion of brain
mapping/lesion resection is extremely difficult because of immobility of head and
neck in a pinion head holder. This may jeopardize the patient’s safety apart from
compromising the sterility of the surgical field.
We present a case report of a patient scheduled to undergo AC for intraoperative brain
mapping and resection of a recurrent lesion close to motor strip. This patient refused
AC and demanded GA because of his past unpleasant experience of AC.
Case Report
A 27-year-old, otherwise healthy, male weighing 85 kg, known case of recurrent right
frontal oligoastrocytoma abutting the motor strip, presented with the history of tonic
clonic seizures. He had undergone AC for the resection of the same lesion 4 years
ago and remained seizure free for 3 years. However, from the past 1 year the patient
was experiencing frequent seizures daily which were refractory to three antiepileptic
drugs.
To preserve motor strip, neurosurgical plan was neuronavigation and magnetic resonance
image (MRI) guided AC. However, the patient refused AC citing his past nightmarish
experience. Therefore, it was decided to administer general endotracheal anesthesia
and awaken him for neurologic examination during brain mapping, without removing the
endotracheal tube. He was counseled for the same during the preanesthesia period and
advised to remain calm and cooperative during the awake phase.
Anesthesia was induced with fentanyl and propofol, and muscle relaxation was achieved
with rocuronium. However, before tracheal intubation, transtracheal 4% xylocaine 3
ml was injected. Following intubation, cuff was inflated with 6 ml of 2% plain xylocaine
instead of air. In addition, bilateral superior laryngeal nerve block was performed
with xylocaine 2% containing adrenaline. Anesthesia was maintained with oxygen in
air, sevoflurane, and infusions of rocuronium and fentanyl. Besides routine ASA monitoring,
invasive blood pressure monitoring was also done.
Approximately 10 minutes before the opening of dura, infusions as well as sevoflurane
were discontinued. Rocuronium was antagonized with sugammadex and the patient received
3 mg midazolam and 100 mg xylocaine intravenously (IV). When the patient became awake,
the neurosurgeon performed the brain mapping, while the patient’s motor power in the
left upper and lower limb was continuously tested with the patient’s cooperation.
The mapping was completed in 30 minutes and he tolerated the endotracheal tube during
this time without coughing or straining. GA was reintroduced after completion of brain
mapping. At the end of the surgery, residual effect of rocuronium was reversed with
sugammadex and trachea was extubated (after aspirating residual xylocaine from the
cuff). The whole procedure lasted for approximately 7.5 hours. The patient was interviewed
next day and he had no recall of the awake period.
Discussion
Awakening a patient with tracheal tube in situ in the presence of an open skull may
be hazardous because of coughing/straining by the patient, and that may result in
brain swelling. Furthermore, even minimal head movement would also be a risk, with
loss of neuronavigation. An MRI-compatible pinion head holder does not completely
prevent head movements, unlike the Mayfield head holder. The pins of latter hold the
head tightly at 60 lbs/in[2] of pressure on the skull in an adult. However, pins of an MRI-compatible head holder
exert a weaker pressure on the skull compared with the Mayfield head holder and an
uncooperative patient can still move his/her head. Therefore, as a rule, surgery of
lesions of eloquent areas of brain is performed in an awake state, with the patient
counseled preoperatively, to avoid onset of new postoperative neurologic deficit.
Despite the benefits of AC, sometimes the awake procedure has to be converted to GA
due to various reasons.[3]
[4]
The AC under sedation (AAA) technique results in higher incidences of hemodynamic
disturbances versus the GA techniques.[5] The technique of GA with LMA may be an acceptable choice but can cause delayed awakening,
dull response, or respiratory depression from residual anesthetic effects after extubation.[6] Additionally, LMA fails to prevent aspiration of gastric contents.[7] LMA also risks dislodgement in an abnormal position surgery and its reinsertion
after completion of brain mapping/lesion resection in a fixed head is not easy and
requires considerable expertise. Reinsertion of any airway device would necessitate
removal of the sterile drapes, thereby disrupting the sterility of the surgical field.
Anesthesia management with NPA for AC is associated with incidences of hypoxia and
hypercarbia.[8] Importantly, both of these airway devices are unsafe in presence of obesity or obstructive
sleep apnea.
Since an awake/unanesthetized patient cannot tolerate the ET, we anesthetized the
airway with transtracheal administration of 4% xylocaine and blocking the superior
laryngeal nerve, bilaterally. This technique of anesthetizing the airway is frequently
employed for awake fiberoptic tracheal intubation to suppress the cough reflex. To
further enhance tolerance to ET we inflated the cuff with xylocaine, and administered
xylocaine intravenously as well.[9]
[10] A small dose (3 mg) of midazolam was given IV to achieve amnesia during awake state.[11] Such a small dose of midazolam does not interfere with acquisition of electrocorticography
(ECoG) signals.[12] Our patient remained fully cooperative during the neurological testing, without
straining/coughing or making any undesirable movements. He had no obvious discomfort,
and had good surgical outcome without any new neurological deficit.
At least 6.4% awake craniotomies need conversion to GA.[13] Our technique of combining airway block and GA will be beneficial in apprehensive
patients requiring brain mapping procedures and do not need verbalization by the patient.
However, our technique cannot be used for resection of lesions adjacent to speech/language
areas which require patient to converse with the neurosurgeon.
Conclusion
General endotracheal anesthesia in combination with airway anesthesia to facilitate
ET tolerance during the awake state along with midazolam and preoperative counseling
is a suitable alternative to AC. This is especially beneficial in an apprehensive
patient who demands GA but whose pathology otherwise has a strong indication for AC
for brain mapping for optimal resection of lesion.
