Awake Craniotomy

Anesthesia Implications

Position: Supine, Lateral, Bed turned 180 degrees
Time: 1-2 hours (average)
Blood Loss: Low (10-50 ml)
Post-op Pain: Moderate (3-6)
Maintenance Paralytic: No
Blocks: Scalp

Pre-op Verbal Preparation – Since the patient is awake and able to communicate with the OR team during the procedure, you should prepare them for the experience. Pre-operative scalp block, surgical pinning, OR noise, remaining still, and how to properly communicate discomfort/pain should all be discussed.

Pre-Induction Pharmaceutical Preparation – Just before induction, most patients will receive a loading dose of Keppra for seizure prophylaxis. A common loading dose is 500 mg IV.

Drips – The patient will be awake and able to speak (for neuro exams) all the way through the procedure. The propofol and remi drips are titrated basically just enough to manage pain and anxiety. Some suggest starting Remifentanil at .3-.5mcg/kg/min and Propofol at 100mcg/kg/min titrated to keeping the patient conscious.

Lines – Have two at least two large-bore IV’s. An arterial line will be placed either before the case in preop, or in the OR shortly after the patient arrives. It may be advisable/kind to have local anesthetic ready for that placement.

Airway Preparation – it is common to use a nasal cannula with ETCO2 monitor. However, have a nasal airway, supraglottic airway, and ETT ready in case of airway complications (eg. seizures).

5-ALA – this is a compound (swallowed by the patient before the surgery, in a liquid solution) that causes malignant glioma cells to fluoresce. If it’s used during the case, the OR lights will be turned off.

Organize Your Lines – Neurological assessments are conducted periodically during the case, so ensure that lines are positioned and secured in a manner that prevents them from malfunctioning or shifting due to patient movement.

Soft Bite Block – Make a soft bite block for the patient to absorb some of the vibration from the drill. A common method to create one: Roll up 4x4s and wrap with silk tape.

Scalp Block – use 0.0375% Bupivicaine, epinephrine, and sodium bicarbonate. The scalp block will be done in small (usually 10cc) doses around the areas that will be pinned or operated on. Watch carefully during pinning and incision to assess effectiveness of block or need for more local.

Intraoperative Drugs – Fosphenytoin is a drug that surgeons may ask for if they anticipate a lot of stimulation during the case. The use of this is highly variable and surgeon preference, so have it available. IV ondansetron and acetaminophen are also good to give before the end of case.

Sedation Cessation – Do not turn off sedation fully until the patient is out of the surgical pins.

180 degree turns (general considerations): Arrange lines and monitor cords in anticipation to turn. If turning right, keep cords and lines draped to the left. If turning left, keep cords and lines draped to the right. Have a circuit extension connected. Disconnect the circuit when turning and immediately reconnect.

Lateral position (general considerations): If an ETT has been placed, make sure ETT is secure with extra tape.  Unhook anesthesia circuit while turning lateral and be especially careful to keep patient’s head neutral and aligned with body to avoid neck injury. Once lateral, use pillows/blankets/foam headrest to keep the patient’s head in neutral position. The most common nerve injury for orthopedic lateral procedures are neurapraxias of the brachial plexus. These are motor and/or sensory loss for 6-8 weeks due to pressure on the contralateral (dependent) axilla. To prevent this, place an axillary roll under the patient (caudad to the axilla, on the rib cage, and NOT in the axilla). Check routinely to make sure the axillary roll does not migrate into the axilla. If the non-dependent arm is placed on a board, check padding and reposition regularly to avoid radial nerve compression. If a bean bag is employed, check the hard edges to ensure that unnecessary pressure isn’t being put on soft tissues. Pad all dependent bony prominences such as the fibular head (to prevent peroneal nerve injury), and place pillows between the knees and ankles (to prevent saphenous nerve injury). If anterior hip supports are in place, ensure they are properly padded or neuropraxias and/or occlusions of large blood vessels may result.

Mayfield Pins (general considerations): The Mayfield skull clamp is a 3-pin head immobilization device. Mayfield pins are usually applied after induction. Unless a scalp block has been administered, application of the pins is EXTREMELY stimulating/painful. Extra sedation (commonly propofol 50-100 mg) should be given prior to the pins being applied to avoid the hemodynamic response expected with extreme pain.

Arterial line (general considerations): Preoperatively check pulses to gauge the best side to attempt the A-line. Perform an Allen test to ensure adequate blood flow. Have the A-line equipment set up and ready in the room.