Supratentorial Anesthesia

Anesthesia for Supratentorial Surgery, from Gupta et al, Essentials of neuroanesthesia and neurointensive care, ch 16

Overall Goals
-maintain cpp
-smooth induction and emergence
-immobility and relaxed brain

Background
Tumors:
-60% primary tumors, gliomas most
-benign to GBM
-Glial tumors disrupt BBB
-autoregulation impaired
-htn can worsen blood flow and cause bleeding
-edema responds to steroids
-meningiomas grow slow and vascular, often require multiple operations and embolization
-secondary neoplasms (35%), from lung (50%) adn breast (10%)
Abscesses:
local spread from sinus/ear, commin in DM, right-to-left shunts, and IVDA

Patient presentation
-most slow, large, adaptable: patient present with ICP increase, seizures, focal deficits

Surgical Notes
-stereotactic or mini-craniotomy
-debulking usually pterional (through temporal and parietal lobes) or frontral (biftornal crani for bifrontral and midline lesions)
-bone flap held if swollen brain

Pre-op
-note potential for changes in icp, location and access to lesion
-assume raised ICP
-document neurological signs and preop GCS
-c/w anticonvulsants and steroids
-benzo ok for anxiety

I/O
-smooth induction/emergence
-hemodynamic stability (hemorrhage vs. ischaemia)
-relaxed brain
-rapid emergence

Induction
-smooth IV
-normotension
-blunt response to DL with bolus induction, short acting opiod or beta blocker, IV lidocaine
-think about set up for doppler, ssep, emg, bis, a line, central line etc.
-Pins, stimulating: blunt response as per DL, consider scalp blocks

Positioning
-neutral head, elevated 15-30 degree ead good to decrease ICP
-PEEP can increase ICP, but less than 10 is ok and maintains CPP and ICP

Maintenance
-dealers choice if neuromonitoring not an issue, but opiods should be short acting (remi, alfentanil) essential for rapid emergence
-keep muscle relaxed unless cannot d/t monitoring
-normocapnia, normothermia

Fluid management
-glucose free iso-osmolar crystalloid and colloid to prevent hypoosmolality leading to edema
-no glucose (unless needed for metabolic disorder) as gluocse–>ischamia and edema
-no need for “tight” glycemic control

I/O complications
-hemorrhage, edema, air embolism
-goal hct 30, give blood
-thromboplastin release –> DIC, give factors early
-aggressive management of cerebral edema

Cerebral edema management
-oxygenate
-check venous head drainage
-reduce CMRO2: deepen, bolu IV induction agents or lidocaine
-Reduce fluid volume: mannitol, hypertonic saline, lasix
-drain CSF
-consider hypocapnia (short acting for only 6 hrs)
-consider anticonvulsants
-?hypothermia
P/O
-icu usually
-preop GCS >12 = extubate
-tx htn, but no vasodilators as they can increase ICP (think bb esmolol, labetolol)
-tx pain p/o, think long acting and adjuncts (apap)

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