Awake Craniotomy Flashcards
(11 cards)
What is the sensory innervation of the scalp?
Posterior Scalp to the Auricle:
Branches of the cervical plexus (lesser occipital, greater auricular) and the greater occipital nerve
Anterior Scalp:
Branches of the ophthalmic division of the trigeminal nerve (CN V1)
Supraorbital and Supratrochlear
Lateral Scalp:
Zygomatiotemporal nerve, which is a branch of the maxillary division of the Trigeminal nerve (CN V2)
Auriculotemporal nerve, which is a branch of the Mandibular division of the Trigeminal nerve (CN V3)
What are the indications for an awake craniotomy
Tumour excision from an area within or close to a functionally important cortex
Epilepsy surgery
deep brain stimulation surgery
Resection of vascular lesions from vessels supplying functionally important areas of the brain
Typically, awake surgery is performed in order to maintain real-time neurological assessment of the impact on the surrounding brain
What are the general contraindications to awake craniotomy
Absolute:
Patient refusal
Inability to lie still/flat
Inability to co-operate due to confusion
Anxiety
Low GCS
Learning Disability
Relative:
Morbid Obesity
Severe Sleep Apnoea
Anticipated Difficult Intubation
Uncontrollable seizures
Chronic Cough
Young Age (presumably a child)
What are the surgical contraindications to awake craniotomy
Highly Vascular legions
Significant Dural involvement - as this will likely cause pain during the resection.
Low occipital lobe lesions - patients may be unable to tolerate positioning for surgical access
What anaesthetic techniques can be used for an awake craniotomy?
Local Anaesthesia with Sedation:
Scalp Blocks are performed
Conscious sedation is maintained with target-controlled infusions of propofol and/or remifentanil, and sedation is deepened for the stimulating parts of the operation, e.g., pinning for the Mayfield clamp, skin incision, removal of bone flap, and dura.
General anaesthesia (asleep/awake/asleep)
The patient is anaesthetisted and an airway (supraglottic or ET tube) is placed
Maintenance is established (most likely TIVA)
When cortical mapping needs to commence the patient is woken up and the airway removed
The patient can be anaesthetised again and an airway reinserted after mapping is complete
N.B. Awake craniotomy only means that the patient is awake during cortical mapping and lesion resection, while the rest of the operation can be performed with the patient asleep or sedated. Scalp blocks may be used for both of the above methods.
What are the advantages of using dexmedetomidine for sedation as part of an awake craniotomy technique?
It’s analgesic properties
Causes minimal respiratory depression
Has minimal effect on ICP
Has both sedative and anxiolytic properties
Minimal effect on interictal epileptiform activities (IEAs), the presence and location of these IEAs can be used to localise an epileptogenic focus and guide surgical resection
What are the disadvantages of using dexmedetomidine for sedation as part of an awake craniotomy technique?
Bradycardia
Hypotension
User Unfamiliarity
What is the immediate management of an intraoperative seizure during an awake craniotomy?
Irrigation of the brain with ice-cold saline (if this fails pharmacological management will be required)
Declare an emergency
Ask surgeons to stop and call for help
Rapid and succinct A to E assessment
Apply 100% O2
Airway management with a SAD (given the patient’s head most likely will be fixed in position with pins and the head may also be distant from the ventilator SAD insertion is probably a better option than intubation
N.B. Seizures may occur during cortical mapping the awake part of the procedure
Which drugs and their doses could be used to terminate an intraoperative seizure during an awake craniotomy
Propfol 10-30mg titrated to effect
Midazolam 2-5mg titrated to effect
Thiopentone 25-50mg titrated to effect
N.B. Irrigation of the brain with ice-cold saline is the first-line treatment, and then, if this fails, proceed to pharmacological management.
What are the possible effects/consequences of using pharmacological management to terminate seizures during an awake
May cause significant sedation with a need to secure the airway, delaying the awake phase of the surgery and potentially leading to delayed wake-up postoperatively
Interference with neurophysiological monitoring because:
Thiopentone activates interictal epileptiform activity (IEA)
Benzodiazepines suppress IEA
Propfol has a variable effect on IEA
Most IV anaesthetics and benzodiazepines also suppress ECoG activity
N.B. ECoG or Electrocorticography refers to the placement of EEG electrodes on the cortex to detect IEA to guide localisation of targets in epilepsy surgery
List Intraoperative complications that may occur during awake craniotomy
Airway and Respiratory:
Alveolar hypoventilation due to sedation/airway obstruction / aponea with the head immobilised
Hypoxia and hypercapnia (leading to poor surgical conditions with brain swelling)
Failure to resite airway device
Laryngospasm
Aspiration
Circulation
Difficult to manage hypotension due to sitting position and venous pooling
Disability
Patient intolerance of the procedure due to pain from semi-seated position with an immobilised head, catheter irritation, seizures, and need to convert to GA
Ineffective Local Anaesthetic leading to technique failure
Venous Air Embolus
Focal Neurological Deficit
