Asleep-Awake Craniotomy

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Questions and Answers

What is the primary goal of an asleep-awake craniotomy?

To remove the eloquent cortex

To suppress seizure focus during general anesthesia

To identify the seizure focus (correct)

To minimize brain injury

What is defined as areas of the cortex that, if removed, will result in loss of sensory processing or linguistic ability, minor paralysis, or paralysis?

Asleep-awake craniotomy

General anesthesia

Seizure focus

Eloquent cortex (correct)

In which lobes of the brain is the eloquent cortex most commonly located for speech and language?

Bilateral occipital lobes

Bilateral parietal lobes

Right temporal and frontal lobes

Left temporal and frontal lobes (correct)

What is a critical factor in the success of an asleep-awake craniotomy?

A highly motivated and well-informed patient Signup and view all the answers

What is a factor that can mitigate the success of an asleep-awake craniotomy?

Intraoperative confusion Signup and view all the answers

In what percentage of patients is an asleep-awake craniotomy necessary?

A small percentage Signup and view all the answers

What percentage of primary brain and central nervous system tumors are oligodendrogliomas?

10% Signup and view all the answers

What is the typical location of oligodendrogliomas in the brain?

Cerebral her Signup and view all the answers

What is the most common presenting symptom of oligodendrogliomas?

Seizures Signup and view all the answers

What is the significance of the slow growth of oligodendrogliomas?

It prolongs the time between initial symptoms and clinical diagnosis Signup and view all the answers

Why is total resection of the tumor the goal in oligodendroglioma treatment?

To reduce the risk of recurrence Signup and view all the answers

What is the importance of follow-up for patients who undergo total gross resection of oligodendrogliomas?

To detect recurrence or radiologic progression Signup and view all the answers

What is the primary purpose of Ojemann stimulation in an asleep-awake craniotomy?

To map areas of aphasia and anomia Signup and view all the answers

What is the purpose of placing cortical electrodes during an asleep-awake craniotomy?

To identify areas of seizure activity Signup and view all the answers

What is the significance of the boundaries identified by cortical mapping during an asleep-awake craniotomy?

They guide the surgical removal of the tumor Signup and view all the answers

What is the result of stimulating areas of aphasia during an asleep-awake craniotomy?

The patient is unable to speak Signup and view all the answers

What is depicted in Fig. 30.1 during an asleep-awake craniotomy?

The Ojemann stimulation of areas of aphasia and anomia Signup and view all the answers

Who should meet with the patient before the asleep-awake craniotomy?

Anesthetist Signup and view all the answers

What should the preoperative education focus on?

What to expect from a sensory standpoint Signup and view all the answers

Why is it essential to assess the patient's suitability for an asleep-awake craniotomy?

To ensure patient's cooperation during surgery Signup and view all the answers

What should be explained to the patient regarding the operating room environment?

The use of electrocautery and its odors Signup and view all the answers

What is a critical aspect of the preoperative education?

Emphasis on the sensations patients will experience Signup and view all the answers

What is the primary focus of preoperative education for awake craniotomy patients?

The required activities during the surgery and potential intraoperative issues Signup and view all the answers

Why is it essential for the anesthetist to have a clear understanding of the patient's seizure history?

To prepare for potential seizure activity during the surgery Signup and view all the answers

When do patients usually emerge from anesthesia during an asleep-awake craniotomy?

During the removal of the bone flap Signup and view all the answers

What should be explained to the patient regarding the sensation of feeling and touch?

The use of the Mayfield head holder Signup and view all the answers

What is a critical aspect of discussing potential intraoperative issues with the patient?

Discussing the potential need for emergent intubation and general anesthesia Signup and view all the answers

Why is it important to provide a written outline of details to the patient?

To ensure the patient understands the risks and benefits of the procedure Signup and view all the answers

Why is it essential for the anesthetist to meet with the patient before the asleep-awake craniotomy?

To assess the patient's suitability for the procedure Signup and view all the answers

What is the significance of addressing the patient's seizure history during preoperative education?

To prepare for potential seizure activity during the procedure Signup and view all the answers

Why is a well-informed patient crucial to the success of an awake craniotomy?

Because the patient's understanding of the procedure is essential for success Signup and view all the answers

What is the purpose of administering ondansetron before the induction of anesthesia?

To decrease the potential for nausea and vomiting Signup and view all the answers

What is the target end-tidal carbon dioxide (ETCO2) level during the induction of anesthesia?

Between 28 to 32 mm Hg Signup and view all the answers

What is the purpose of using a laryngeal mask airway (LMA) during the induction of anesthesia?

To help with manual ventilation Signup and view all the answers

Why is it important to minimize CO2 levels during the asleep phase of the awake craniotomy?

To prevent increases in cerebral blood flow and intracranial pressure Signup and view all the answers

What is the purpose of infiltrating the surgical field with local anesthesia?

To reduce surgical pain during the procedure Signup and view all the answers

Why is the patient placed in a Mayfield headrest and secured to the operating table?

To prevent patient movement during the procedure Signup and view all the answers

What is the primary purpose of positioning the patient's head during an awake craniotomy?

To ensure access to the airway is always maintained Signup and view all the answers

What is the primary method used to reduce intracranial pressure during an awake craniotomy?

Use of osmotic diuretics and hypertonic saline Signup and view all the answers

What is the most common treatment for intraoperative nausea during an awake craniotomy?

Administration of ondansetron Signup and view all the answers

What is the primary anesthetic used during the awake phases of an asleep-awake craniotomy?

Local anesthesia with epinephrine Signup and view all the answers

What is the purpose of administering dexamethasone during an awake craniotomy?

To treat cerebral edema Signup and view all the answers

What is the primary focus of preoperative education for awake craniotomy patients?

The importance of patient cooperation during the procedure Signup and view all the answers

Why is it essential to avoid medications that increase intracranial pressure during an awake craniotomy?

To minimize the risk of cerebral edema Signup and view all the answers

What is the primary purpose of placing a light under the drapes during an awake craniotomy?

To provide light to the patient at all times Signup and view all the answers

What is the significance of maintaining a stable blood pressure during an awake craniotomy?

To maintain adequate cerebral perfusion Signup and view all the answers

Why is it essential to assess the patient's seizure history before an awake craniotomy?

To develop a plan for seizure management Signup and view all the answers

What should be avoided when sedating a patient before dural closure during an asleep-awake craniotomy?

Using medications that can cause respiratory depression Signup and view all the answers

Why is a nasal cannula with ETCO2 monitoring sufficient during the awake and sedation phases of an asleep-awake craniotomy?

Airway obstruction is usually associated with medication overdose Signup and view all the answers

What is the primary reason for using an LMA instead of an endotracheal tube during the asleep phase of an asleep-awake craniotomy?

Coughing and bucking are minimized Signup and view all the answers

What is the indication for reinserting the LMA during an asleep-awake craniotomy?

An unforeseen surgical event has occurred Signup and view all the answers

What is the purpose of talking to the patient and requesting that they take a breath during an asleep-awake craniotomy?

To relieve airway obstruction Signup and view all the answers

When should an endotracheal tube be placed using a fiber-optic approach during an asleep-awake craniotomy?

When the surgical events permit Signup and view all the answers

Why is an induction agent and muscle relaxant indicated during intubation in an asleep-awake craniotomy?

To rapidly facilitate airway management and avoid increases in ICP Signup and view all the answers

What should be done if the LMA cannot be reinserted during an asleep-awake craniotomy?

Remove the patient from the Mayfield headrest and establish bag-mask ventilation Signup and view all the answers

What is the primary concern if a grand mal seizure occurs during awake craniotomy?

Cervical trauma or laceration of the scalp Signup and view all the answers

What is the purpose of drawing blood immediately after the induction of anesthesia?

To determine the phenytoin and Depakote concentrations Signup and view all the answers

What is the technique used to inhibit seizure activity?

Cold irrigating fluid placed on the brain by the surgeon Signup and view all the answers

What is the significance of determining the presence of any 'aura' during preoperative seizure history?

To instruct the patient to report to the anesthetist if they occur Signup and view all the answers

What is the result of stimulating areas of expressive aphasia during Ojemann stimulation?

The patient is unable to speak Signup and view all the answers

What is the significance of explaining the noise from surgical interventions to the patient?

To minimize discomfort during emergence Signup and view all the answers

What is the consequence of continuing propofol and remifentanil infusions until the bone flap is removed?

Hypoventilation and hypercarbia Signup and view all the answers

What is the purpose of discontinuing the propofol infusion and decreasing the remifentanil drip during the creation of burr holes?

To enable the patient to emerge from general anesthesia Signup and view all the answers

Why is it essential to stop brain stimulation during Ojemann stimulation?

To prevent seizures Signup and view all the answers

What is the consequence of a sustained grand mal seizure during awake craniotomy?

Swelling of the brain and increased ICP Signup and view all the answers

What is a potential cause of nausea, confusion, and lethargy during the immediate postoperative period following an asleep-awake craniotomy?

Shearing of cerebral venous complexes leading to subdural hematoma Signup and view all the answers

Why is it important to exclude iatrogenic intracranial pathology during the postoperative evaluation of an asleep-awake craniotomy?

To rule out subdural hematoma Signup and view all the answers

What is the primary concern with Valsalva maneuvers and jerking movements during the postoperative period of an asleep-awake craniotomy?

Increased risk of intracerebral bleeding and cerebral edema Signup and view all the answers

What should be observed, noted, and reported to the surgeon during the postoperative period of an asleep-awake craniotomy?

Auras and small focal seizures Signup and view all the answers

What is the primary purpose of administering an induction dose of propofol during the postoperative period of an asleep-awake craniotomy?

To manage seizures Signup and view all the answers

Why is it important to caution the patient against exaggerated head movement during the postoperative period of an asleep-awake craniotomy?

To prevent subdural hematoma Signup and view all the answers

Study Notes

Asleep-Awake Craniotomy

Asleep-awake craniotomies are necessary for a small percentage of patients with suppressed seizure focus during general anesthesia or seizure focus adjacent to the "eloquent" cortex.

Eloquent Cortex

The eloquent cortex is defined as areas of the cortex that, if removed, will result in loss of sensory processing, linguistic ability, minor paralysis, or paralysis.
The most common areas of the eloquent cortex include:
- Left temporal and frontal lobes for speech and language.
- Bilateral occipital lobes for vision.
- Bilateral parietal lobes for sensation.
- Bilateral motor cortex for movement.

Importance of Awake Craniotomy

An awake craniotomy may be the best/only option to identify the seizure focus and minimize brain injury when the eloquent cortex is involved.
A highly motivated and well-informed patient is crucial for a successful asleep-awake craniotomy.

Factors Affecting Success

Intraoperative confusion, nausea, and seizures can mitigate the successful conduct of an asleep-awake craniotomy.

Oligodendroglioma

Oligodendroglioma is a well-differentiated, diffusely infiltrating tumor that accounts for approximately 10% of all primary brain and central nervous system tumors.
This tumor typically occurs in adults and is located in the cerebral hemisphere.
Oligodendrogliomas are composed of cells that morphologically resemble oligodendroglia.

Clinical Presentation

50% to 80% of patients with oligodendrogliomas present with seizures due to increased intracranial pressure.
The time between initial symptoms and clinical diagnosis can vary from 1 week to 12 years due to the slow growth of oligodendrogliomas.

Treatment and Prognosis

Surgery has historically been the primary treatment for oligodendrogliomas.
The extent of resection depends on the tumor's location and proximity to the eloquent cortex.
The goal of surgery is total resection of the tumor, and if achieved, no further treatment may be necessary.
However, patients must be followed up for clinical or radiologic recurrence due to the high rate of recurrence associated with oligodendrogliomas.

Asleep-Awake Craniotomy Procedure

The procedure involves removal of an oligodendroglioma recurrence using a left frontotemporal craniotomy.
The surgical approach involves adequate exposure of the cortical surface.
Mapping of areas that produce aphasia is done using an Ojemann stimulator.

Cortical Mapping and Electrocorticography

Ojemann stimulation identifies areas that produce aphasia, which are marked with numbered plastic indicators and recorded.
Further stimulation helps identify areas where naming of playing cards is affected (areas of aphasia and anomia).
Cortical electrodes are used to electrocortigraphically identify areas of seizure activity.
The boundaries identified through cortical mapping and electrocorticography guide the surgical removal of the tumor.

Preoperative Period for Asleep-Awake Craniotomy

Preoperative education is crucial for patients undergoing asleep-awake craniotomy, aiming to ensure the patient's understanding of the procedure and cooperation during surgery.
The anesthetist should meet with the patient before surgery to assess their suitability for the procedure and provide thorough education.
Patients must be able to clearly understand risks and benefits and cooperate during surgery to be considered candidates for an asleep-awake craniotomy.

Preoperative Education

Focuses on what the patient can expect from a sensory standpoint, including: • Visual expectations in the operating room • Odors, especially the use of electrocautery • Tastes regarding airway devices and medications • Sensations of feeling and touch, including positioning and the use of the Mayfield head holder • Sounds, including the drilling sound during bone flap removal

Patient Responsibilities During Surgery

Mapping of aphasia and anomia is explained to the patient, including the potential for temporary aphasia and anomia due to Ojemann stimulation.
Patients are informed about their role during surgery and how to respond to stimuli.

Intraoperative Issues

The patient's seizure history is thoroughly addressed, including: • Presence of "aura" • Time of day when most seizures occur • Medications
The anesthetist must understand the patient's seizure type and presentation.
Patients are informed about plans for dealing with seizures during the procedure.
Emergency plans, including emergent intubation and general anesthesia, are discussed.

Importance of Preoperative Education

A well-informed patient is crucial for a successful awake craniotomy.
A written outline of all details should be provided to the patient for further review.

Asleep-Awake Craniotomy

The purpose of the "asleep" portion of the awake craniotomy is to minimize patient discomfort and facilitate various procedures, including placement of invasive monitoring, patient positioning, local anesthetic injection, removal of the cranium, and placement of Mayfield pins.

Induction of Anesthesia

The patient is given prophylactic antibiotics before arrival in the operating room.
Ondansetron is administered before the induction of anesthesia to decrease the potential for nausea and vomiting.
Induction is accomplished using propofol followed by a remifentanil-and-propofol infusion.
A laryngeal mask airway (LMA) is placed and secured.
The patient is manually ventilated to achieve a rate and tidal volume that produces an end-tidal carbon dioxide (ETCO2) representative of low normocapnia (ETCO2, 28 to 32 mm Hg).

Invasive Monitoring and Patient Positioning

The patient is placed in a Mayfield headrest after local infiltration and secured to the operating table with straps across the chest, hips, and legs.
Careful attention is paid to head positioning to ensure:
- Access to the airway is always maintained
- The LMA is secured and positioned for rapid reinsertion if needed
- The patient can see the anesthetist and visual stimuli for anomia mapping
- Patient comfort is maximized
- The patient's joints are flexed, and the body is secured to avoid movement when turning the table

Controlling Intracranial Pressure

Controlling ICP is vitally important during an awake craniotomy.
The primary method used to reduce ICP is the administration of osmotic diuretics and hypertonic saline.
Mannitol (1 to 1.25 gm/kg) is administered immediately after the central line is secured and the urinary catheter has been placed.
Additionally, 150 mL of 7.5% normal saline are administered over a 2-hour period.
These medications facilitate the movement of fluid from the extravascular space into the intravascular space, decreasing the total brain fluid volume and ICP.

Managing Intraoperative Nausea, Confusion, and Seizures

Nausea: Treatment focuses on avoiding factors that contribute to nausea, such as hypotension, pain, and emetogenic medications.
Confusion: Treatment focuses on avoiding anesthetic agents that contribute to amnesia and can cause confusion.
Seizures: Treatment is predicated on the assumption that the potential for seizures has been adequately treated preoperatively.
Intraoperative seizure activity is treated by stopping the stimulation, and frequently, no further treatment is necessary.

Awakening the Patient

When the patient emerges from general anesthesia, they are in a confined, draped, and dark environment.
The propofol infusion is discontinued, and the remifentanil drip is decreased and then stopped during the creation of burr holes.
The patient emerges from general anesthesia, and the LMA is removed just before the bone flap removal.

Sedation Techniques

Sedation may be established when the neurosurgeon determines that patient participation is no longer essential.
The use of medications that can contribute to confusion and dysphoria should be avoided.
Dexmedetomidine may be useful for producing sedation without causing significant respiratory depression.

Airway Management

Any plan for managing the airway during an asleep-awake craniotomy must take into account the three distinct times of the surgery: the asleep phase, the awake phase, and the sedation phase.
The asleep phase must account for the physiologic stimulation that occurs during fixation of the head in the Mayfield headrest.
The awake and sedation phases do not frequently require airway manipulation.
Airway obstruction is usually associated with a medication overdose, and this situation is easily relieved by pulling the chin forward.

Postoperative Period of Asleep-Awake Craniotomy

After surgery, the patient's head is removed from the Mayfield headrest and drapes are removed.
Patients should be cautioned against excessive head movement to prevent complications.
Decreased intracranial volume due to tumor removal can lead to shearing of cerebral venous complexes, resulting in subdural hematoma.
Symptoms of subdural hematoma include nausea, confusion, and lethargy.
Any postoperative seizures should be evaluated and managed as in the intraoperative period.
Auras and small focal seizures consistent with preoperative history and intraoperative experience should be reported to the surgeon.
The surgeon decides whether to administer supplemental antiseizure medication during the postoperative period.
Focal seizures progressing to grand mal seizures may require administration of an induction dose of propofol and airway management initiation.
Valsalva maneuvers and jerking movements can lead to intracerebral bleeding, cerebral edema, and increased ICP.

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Description

Asleep-awake craniotomies are necessary in a small percentage of patients, typically those with seizure focus near eloquent cortex areas. Eloquent cortex areas include regions that control sensory processing, linguistic ability, and motor function.