History:

• Awake craniotomy has historical roots in ancient trepanation for various purposes, including epilepsy treatment.
• Modern AC began with Sir Victor Horsley in 1886 and was further developed by Wilder Penfield in the 20th century.

Indications:

1. Brain Tumor Resection: Awake craniotomy is commonly used for removing brain tumors located near eloquent areas, such as language or motor centers, to minimize neurological deficits.
2. Epilepsy Surgery: It is employed for resection of epileptic foci to precisely map the seizure focus and surrounding functional areas.
3. Vascular Malformation Treatment: Awake craniotomy aids in the removal or treatment of vascular malformations in the brain while preserving critical functions.
4. Functional Brain Mapping: It allows surgeons to map and identify crucial brain functions, such as language, sensory, and motor areas, to avoid damage during surgery.
5. Resection of Lesions in Deep Brain Structures: AC can be used for lesions deep within the brain, where precise mapping is vital for preserving function.

Advantages:

1. Preservation of Brain Function: AC enables real-time assessment and preservation of critical brain functions, reducing the risk of permanent deficits.
2. Maximized Tumor Resection: Surgeons can maximize the extent of tumor removal while minimizing damage to essential brain regions.
3. Improved Patient Outcomes: Patients undergoing awake craniotomy often experience better postoperative quality of life due to reduced neurological deficits.
4. Tailored Surgical Approach: Surgical plans can be adjusted during the procedure based on functional mapping, increasing surgical precision.
5. Patient Cooperation: Patients can provide feedback during the procedure, allowing surgeons to assess their cognitive functions and responses.

Complications:

1. Seizures: Intraoperative seizures may occur during brain mapping or manipulation.
2. Patient Anxiety: Patients may experience anxiety or distress during awake surgery.
3. Hemodynamic Instability: Fluctuations in blood pressure and heart rate can occur, requiring careful monitoring.
4. Neurological Deficits: Despite meticulous mapping, unintended neurological deficits can still occur.
5. Infection: As with any surgery, there is a risk of infection at the surgical site.
6. Pain and Discomfort: Even with local anesthesia, patients may experience pain or discomfort.
7. Bleeding: Intraoperative bleeding can pose challenges during the procedure.
8. Cerebral Edema: Swelling of the brain tissue can occur postoperatively.
9. Respiratory Complications: Maintaining adequate oxygenation and ventilation can be challenging.
10. Conversion to General Anesthesia: In some cases, the procedure may need to be converted to general anesthesia due to patient discomfort or complications.

Preoperative Evaluation:

• Thorough assessment of the patient’s neurological and medical status.
• Evaluation of the patient’s ability to cooperate and follow commands during surgery.
• Identification of potential contraindications or risks.

Operating Room Preparation:

• Ensuring a sterile surgical field.
• Setting up equipment for neurological testing and monitoring.
• Preparing for potential conversion to general anesthesia if necessary.

Anesthesia Techniques:

• Asleep-Awake-Asleep Anesthesia: Initial induction of general anesthesia (asleep) followed by awakening the patient for mapping, and then returning to general anesthesia (asleep) for the remaining surgery.
• Scalp Block: Administering local anesthesia to numb the surgical area, reducing pain and discomfort.
• Sedation: Using light sedation (e.g., propofol) to maintain patient cooperation without full unconsciousness.

Medication Titration:

• Medications are titrated to maintain the patient’s comfort and cooperation.
• Anesthesia depth is adjusted to the surgical phase, with lighter sedation during mapping and potentially deeper sedation during the resection.
• Monitoring of vital signs, patient responses, and neurological function guides titration.

In summary, awake craniotomy is a specialized neurosurgical technique with historical significance. It’s indicated for cases where precise brain mapping and monitoring are essential. The procedure offers advantages in preserving brain function but requires careful preoperative evaluation, meticulous operating room preparation, and skilled anesthesia techniques, including titration of medications to maintain patient comfort and cooperation.

SECTION 2

“Asleep-Awake-Asleep” anesthesia technique

1. Induction Phase (Asleep):

• During the initial phase of awake craniotomy, the patient is placed under general anesthesia for comfort and to facilitate the securing of the airway.
• The anesthesia team administers medications such as propofol and opioids to induce deep sedation.
• An endotracheal tube (ETT) is carefully placed to secure the airway, and mechanical ventilation is initiated. This ensures the patient’s oxygenation and ventilation while deeply sedated.

2. Awake Phase:

• After the initial surgical steps are completed, the anesthesia team reduces sedation to awaken the patient.
• Medications used for this phase may include lighter sedatives like remifentanil and dexmedetomidine, allowing the patient to be conscious and cooperative without interfering with cognitive function.
• The ETT remains in place to maintain airway patency, but mechanical ventilation is paused.
• Local anesthesia is administered to the scalp and skull to minimize pain during the procedure.

3. Return to Sedation (Asleep):

• Once necessary functional mapping or monitoring is completed, the patient is returned to a deeper state of sedation.
• Medications such as propofol or midazolam may be used for this purpose, titrated to achieve the desired level of unconsciousness.
• Mechanical ventilation may be resumed to ensure adequate oxygenation and ventilation.

4. Surgical Resection (Asleep):

• With the patient under general anesthesia once again, the surgeon proceeds with the resection of brain tumors or the treatment of other lesions.
• The ETT remains in place to maintain the airway, and mechanical ventilation continues to support the patient’s respiratory needs.
• Muscle relaxants may be used to ensure immobility during surgery.

5. Emergence and Extubation (Awake):

• Following completion of the surgical procedure, the patient is awakened.
• Medications are adjusted to facilitate a smooth transition from deep sedation to full consciousness.
• The ETT is carefully removed, and the patient is extubated.
• Postoperative monitoring and assessment are performed while ensuring the patient maintains an open and unobstructed airway.

The use of airway equipment, such as the endotracheal tube, ensures that the patient’s airway remains secure and adequately ventilated throughout the procedure. Medications play a crucial role in maintaining the desired level of consciousness and managing pain and discomfort during the awake phase. Careful titration of medications is essential to achieve the right level of consciousness at each stage of the procedure, and it requires close coordination between the anesthesia team and the surgical team to optimize patient outcomes in awake craniotomy.

SECTION 3

Medications:

1. Sedatives:
   • Propofol: Often used for induction and maintenance of sedation during the asleep phases of the procedure.
   • Dexmedetomidine: Useful for maintaining light sedation during the awake phase, allowing the patient to remain calm and cooperative.
   • Midazolam: May be used to supplement sedation as needed.
2. Analgesics:
   • Remifentanil: A short-acting opioid used to provide analgesia during the awake phase while minimizing respiratory depression.
   • Fentanyl: Another opioid that can be used to manage pain and discomfort.
3. Local Anesthetics:
   • Lidocaine: Administered as a scalp block to numb the surgical area and minimize pain during the procedure.
   • Bupivacaine: Another local anesthetic used for scalp blocks.
4. Muscle Relaxants (if needed):
   • Vecuronium or Rocuronium: Used for muscle relaxation during the asleep phases of the procedure when necessary to prevent patient movement.

Airway Equipment:

1. Endotracheal Tube (ETT):
   • An ETT is used to secure the patient’s airway during the initial asleep phase. It allows for mechanical ventilation to maintain oxygenation and ventilation.
   • During the awake phase, the ETT remains in place to ensure airway patency but is typically not connected to a ventilator, allowing the patient to breathe spontaneously.
2. Laryngeal Mask Airway (LMA):
   • In some cases, an LMA may be used instead of an ETT to secure the airway. It is less invasive and may be better tolerated during the awake phase when the patient is conscious.
3. Supplemental Oxygen Delivery:
   • Nasal cannulas or oxygen masks may be used to provide supplemental oxygen during the awake phase if needed.
4. Capnography:
   • Capnography is used to monitor end-tidal carbon dioxide levels to ensure proper ventilation and assess the patient’s respiratory status.
5. Suction Equipment:
   • Suction devices are readily available to clear the airway and manage secretions if necessary.

The choice of medications and airway equipment may vary depending on the patient’s condition, the surgeon’s preferences, and the specific requirements of the procedure. An experienced anesthesia team is crucial to safely manage the patient’s sedation, analgesia, and airway throughout the various phases of awake craniotomy.