Craniotomy

Anesthesia Implications

Position: Fowler’s, Semi-Fowler’s, Bed turned 90 degrees, Bed turned 180 degrees
Time: 2-4 hours (long)
Blood Loss: Moderate (50 – 200 ml)
Post-op Pain: Moderate (3-6)
Maintenance Paralytic: If full MAC approach

Neuro Assessment – Depending on the type of injury or disease (tumor, aneurysm, hematoma, skull fracture, etc), patient may have an acute or chronic neurological condition. A neuro assessment should be completed pre-operatively (e.g. Mental status, all extremities move equally, assess any extremity weakness, and facial expressions are equal/symmetric).

Surgeon Preferences – There are several surgeon preferences. General positioning (the location of the tumor or injury will determine this) and bed position (90-180 degrees after the Mayfield Pins). Some medications may need to be given pre or intraoperatively (e.g. mannitol, Dilantin, lasix, steroids, etc). Blood pressure range will also likely be a preference. Asking the surgeon his/her preference on each of these items will help form your plan.

Patient Drug Regimen – Find out if patient is already on steroids or anticonvulsants. This could change the patient’s dosage requirements intra-operatively.

Neuro Monitoring – Ask neuro-monitoring tech the plan for neuro monitoring (SSEP, MEP, EMG). This will help to determine if anesthetic gas can be added.

Setup – Have an A-line set up and ready. Two Large-bore IVs are required, or a central line. Have a nipride or nitroglycerin gtt available for HYPERtension. Have phenylephrine or levophed gtt available for HYPOtension. It is also prudent to have IV push phenylephrine, ephedrine, metoprolol, labetalol, and esmolol available for transient hemodynamic control.

Approach – Much depends on the neuro monitoring plan and the condition of the patient. If no neuro monitoring, many providers run a full MAC of anesthetic gas with IV narcotic gtt (e.g. remifentanyl, sufentanyl). If neuro-monitoring intra-operatively, consider a TIVA and reverse paralytic after induction.

Common IV Narcotic – A common IV narcotic drip to use with a full MAC of anesthetic gas is Remifentanyl (0.05-0.25 mcg/kg/min). Typical preparation is 5mg of Remi added to a 100 mL bag of NS.

Common TIVA combination – Propofol (50-200 mcg/kg/min) and Remifentanyl (0.05-0.25 mcg/kg/min)

Induction – If not already intubated, try to keep BP and HR as stable as possible during induction to prevent possible rupture of aneurysm or increase in BP and ICP. For this, consider using an LTA kit, esmolol, and/or fentanyl 1-2 minutes prior to induction. Low pressures should be avoided as well. Avoid hypotension in order to maintain Cerebral Perfusion Pressure (CPP).

Mayfield Pins – If mayfield pins are used for head stability, infuse propofol 50-100 mg 1-2 min prior to avoid a severe increase in BP.

Repositioning – after the Mayfield pins, the HOB is typically increased to 30 degrees and bed is usually turned 90-180 degrees (surgeon preference). It’s never a bad idea to make a quick disconnect/reconnect of the circuit when turning the bed.

ETCO2 – keep ETCO2 30-35 throughout case to keep a reduced ICP.

Fluids – Avoid large infusions of crystalloids. It’s best to keep patient the patient normovolemic. It is recommended to use isotonic crystalloids (eg. 0.9% NS and LR). Avoid dextrose-containing and hypotonic IV fluids.

Keep Normothermic – hyperthermia can cause increases in cerebral metabolism, cerebral blood flow, and ICP – which can lead to brain damage. Hypothermia reduces cerebral metabolism and cerebral blood flow, subsequently decreasing intracranial pressure (ICP). The goal will depend upon the case, but it’s generally best to aim for normothermia.

Stable Emergence – It is important to continue to avoid any large increase or decrease in BP during emergence, as well as any bucking or coughing that could increase ICP. Consider giving lidocaine 1-2 mg/kg and/or labetalol as needed a few minutes prior to extubation. A Precedex drip (0.2-1 mcg/kg/hr) or small bolus doses (5-20 mcg every 5-10 minutes) can also be very beneficial. Also recommended is to have a Cardene drip on standby to treat hypertension during emergence.

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.

Long procedure (general considerations): Procedures anticipated to last longer than 2 hours generally require a urinary catheter. Also consider checking lines and positioning regularly as the risks of infiltration and nerve damage are increased with procedure time. Consider an IV fluid warmer and a forced air warmer to keep the patient euthermic.

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.

MEPs (general considerations): Most commonly, anything above the cauda equina (T1/T2) will be MEP and SSEP monitored in spinal cases. Long-term paralytics are normally contraindicated. Short term paralytics (eg succinylcholine) may be used for intubation. Some surgeons will prefer complete TIVA (eg. a common combination is propofol 25-150 mcg/kg/min, remifentanil 0.125-1.0 mcg/kg/min), while others are fine with 1/2 MAC of gas and a propofol drip. Ask the surgeon. Additional equipment needed: bite block, BIS monitor (if using TIVA).

A craniotomy is necessary when an injury (e.g. skull fracture, hematoma, foreign object, cerebral swelling, infection) or disease (e.g. tumor, AVM, aneurysm) results in loss of brain function or risk of death.

An opening is cut into the skull to access the affected site and a piece of bone is removed, the size of which depends on the cerebral injury. The bone is then replaced after surgery with plates and screws to allow for bone regrowth.