Awake

The Awake Craniotomy

Notes from Gupta/Gelb ch 20 “Perioperative Management of Awake Craniotomy” and Oxford Handbook of Anesthesia

 

Indications

-Tumor or lesion near eloquent areas of brain

-steroetactic and DBS for Parkinson’s

-epilepsy surgery

 

Background

-either local + sedation, or GA with i/o wake up, or combination of sedation + awake

 

Preop

-good rapport with patient essential

-determine if patient will tolerate, mentally, lying flat for long period (especially challenging in children)

-obesity, reflux and highly vascular tumors may also caution against

 

Cortical Mapping

-Cortical mapping = electrical stim to recognize sensitive areas, can ID motor, sensory, speech

-despite mapping, many surgeons prefer fully awake to ensure no neurodeficits post op

-intraop ECoG (electrocorticography) may be used to ID epileptogenic focus

 

I/O Management

-routine a-line, foley (if long)

-positioning in comfort is key, head best positioned with 3 pin fixator under local (minimize movement, max airway control)

-always have access to airway

-Multiple techniques: local, local + sedation, asleep awake asleep with GA and I/O wake up  (for more complex/extensive)

-Skin, scalp, pericranium and periosteum of skull –> extensive sensory innervation; use field block or scalp block (see prior post).  Dura has extensive innervation, so anesthestize nerve trunk near middle meningeal and edges of cranium (see scalp block post).

-Precedex and Remi, both good choices for short-acting pain control and sedation without profound respiratory depression (especially precedex).

-Anti-emetics important –> especially for temporal lobe epilepsy surgery –> highly emotogenic.

 

Airway Control

-many techniques, from spon vent without devices to ETT and LMA.

-Risk of coughing during removal of LMA or ETT when dura open!

-ETT/LMA allow more precise monitroing of ETCO2

-Can be difficult to reintubate, and ETT makes assessing verbal responses difficult/impossible

-Alternative: Soft nosopharyngeal airway (with 25% cocaine paste as per Gupta/Gelb), can remain in place throughout procedure and monitor ETCO2, oxygen through other nostril. Risky in obese patients.

 

I/O Problems

– Uncooperative patient, cardiovascular (htn, hypotension, tachy), excessive sedation–>increased PaCO2–>Edema, resp depression, loss of airway, brain swelling, seizures(tx with propofol 20-40mg, or iced saline spray to cortex), pain, Local toxicity

-Patients with mass effect tumors -> most at risk for PaCO2 related brain swelling