Neurosurgery Flashcards
Preop Considerations
Anticonvulsants - dose, frequency, last taken Continue DOS + supplementation NO sedation Antibiotics ordered/mixed Diuretics impact on electrolytes Stress dose steroids
Intraoperative Nerve Monitoring
Prevent brain, spinal cord, or nerve injury
MEP
SSEP
EMG
MEPs
Motor evoked potentials
Used in surgeries where motor track at risk
Direct & scalp electrodes
More sensitive to ischemia than SSEPs by 15min
Difficult to obtain d/t pre-existing or anesthetic conditions
NO paralytic
SSEPs
Somatosensory evoked potentials
Most commonly monitored
Stimulation peripheral sensory nerve
Mapping in spinal cord and sensory cortex
Ischemia detection in cortical tissue
Reduces risk of spinal cord/brainstem mechanical or ischemic insults
Paralytic okay sometimes
Motor monitoring less specific, does not measure motor deficits
EMGs
Electromyography
Reduces muscle electrical activity using needle pains
Continuous recording
Triggered responses
Used to detect nerve irritation, nerve mapping, assess nerve function, and monitor cranial nerves
Spinal surgeries to detect when screws are misplaced - passively monitors nerves
Stereotactic NSGY
Brain lab/mapping Fudicials affixed to patient scalp & forehead Interferes w/ Pox Smaller biopsies local or MAC Large resections require general
Craniotomy Medications
Induction - Fentanyl, Propofol, & Rocuronium Propofol 40-100mcg/kg/min Remifentanil 0.2mcg/kg/min Phenylephrine 0.2mcg/kg/min Decadron 10mg Mannitol 50-100g (0.25-0.5g/kg) Keppra 1g or Vimpat Vancomycin or Ancef Tylenol 30min prior wake-up Hydromorphone or Fentanyl Caffeine - adenosine receptor antagonist Physostigmine - anticholinesterase
Intracranial Mass Lesion
Clinical Presentation
Headache Seizures Focal neurological deficits Sensory loss Cognitive dysfunction
Supratentorial Mass Lesions
Seizures, hemiplegia, aphasia Frontal Parietal Temporal Occipital
Supratentorial Mass Lesion
Frontal
Personality changes, increased risk-taking, difficulty speaking (damage to Broca’s area)
Supratentorial Mass Lesion
Parietal
Sensory problems
Supratentorial Mass Lesion
Temporal
Problems w/ memory, speech, perception, & language skills
Supratentorial Mass Lesion
Occipital
Difficulty recognizing objects, an inability to identify colors, & trouble recognizing words
Infratentorial/Posterior Fossa Mass Lesions
Cerebellar dysfunction
Brainstem compression
Infratentorial/Posterior Fossa Mass Lesion
Cerebellar Dysfunction
Ataxia/poor balance, nystagmus, dysarthria, cannot perform rapid alternating movements, loss muscle coordination
Infratentorial/Posterior Fossa Mass Lesion
Brainstem Compression
Cranial nerve palsy, altered LOC, abnormal respiration
Primary Tumors
Glial cells - astrocytoma, oligodendroglioma, glioblastoma
Ependymal cells - ependymoma
Supporting tissues - meningioma, schwannoma, choroidal papilloma
Intracranial Mass Lesions
Anesthetic Considerations
Consider tumor location, growth rate, & size (slow growing tumors are often asymptomatic) EBL estimate
ICP elevation
Goals = control & maintain ICP
Anticipate sympathetic response w/ Mayfield head pins placement
Rapid emergence to allow neuro assessment
Intracranial Mass Lesions
Preop
Determine ICP
ICU patients w/ EVD
LOC & neuro deficits
Review PMH & general health status
Anticonvulsants & diuretics
Recent labs - glucose, drug levels, electrolytes, Hgb/Hct
Radiological studies - edema, midline shift, or ventricular size
Avoid benzodiazepines/narcotics
Continue corticosteroids & anticonvulsants
Intracranial Mass Lesions
Intraop
Hyperventilation maintain ETCO2 30mmHg Avoid excessive PEEP < 10 Glucose-free crystalloids or colloids Replace blood loss w/ blood or colloids EVD or lumbar drain to control ICP ↑CBF
Intracranial Mass Lesions
Monitors
A-line Foley IV access (central line?) PNS - do NOT monitor on hemiplegic side Ventriculostomy to monitor ICP (zero at auditory meatus) Consider IONM
Intracranial Mass Lesions
Positioning
Rotate HOB 90-180° Elevate 10-15° Supine, lateral, prone, or sitting Able to access all equipment IV tubing extension PNS on lower extremities
Intracranial Mass Lesions
Emergence
Slow & controlled
Prevent straining or bucking ↑ICP or worsen cerebral edema
Aggressive BP management systolic < 140-160
Hemorrhage or stroke risk - Clevidipine, Labetalol, and/or Esmolol
Neuro exam immediately after extubation
Do not administer any opioids until cleared by surgical team to prevent any neuro assessment impairment
Intracranial Mass Lesions
Postop
Admit to ICU for observation - seizures, neuro deficits, or ↑ICP
Transport w/ HOB elevated 30°
Manage HTN
Transport on O2
Minimal pain post-craniotomy (headache most common)
Awake vs. Asleep Craniotomy
Awake-awake
Asleep-awake
Asleep TIVA w/ IONM or GETA
Considerations for awake craniotomy patients:
Used for epilepsy surgery & tumor resection in frontal & temporal lobes where speech & motor need to be assessed intraop
Airway
Cooperation
Secure A-line & PIVs
Awake-Awake Craniotomy
No infusions until closing
Propofol bolus for pins
Hand-holding
Asleep-Awake Craniotomy
Start under GA w/ LMA or ETT
Wake patient up once tumor exposed
Propofol 40mcg/kg/min
Remifentanil 0.2-0.4mcg/kg/min
Posterior Fossa Lesions
Cerebellum
Brainstem
Cranial nerves I-XII
Venous sinuses
Cushing’s Triad
↑ICP
Hypertension
Bradycardia
Irregular respirations
Trigeminal nerve stimulation
Bradycardia & Hypotension
Glossopharyngeal or Vagus nerve stimulation
Brainstem Injuries
Cushing’s triad
Bradycardia & hypotension
Damage to respiratory center → mechanical ventilation postop
Tumors around glossopharyngeal & Vagus nerves impair gag reflex & ↑aspiration risk
Cranial nerves IX, X, & XI control pharynx & larynx
Posterior Fossa Lesions
Anesthetic Considerations
Same periop considerations as intracranial lesions
Modified lateral or prone most common
Sitting Position
Advantages
Back elevated 60° & legs elevated w/ knees flexed
Head fixed in 3-point holder w/ neck flexed
Arms remain at sides w/ hands resting on lap
Improved surgical exposure & more anatomically correct
Less retraction & tissue damage
↓bleeding
Less cranial nerve damage
Improves lesion resection
Access to airway, chest, & extremities
Enhanced CSF & venous drainage
Sitting Position
Disadvantages
Postural hypotension, arrhythmias, & venous pooling
Pneumocephalus
Nerve injuries - ulnar compression, sciatic nerve stretch, lateral peroneal compression, brachial plexus stretch, cervical spine compression
Pneumocephalus
Open dura → CSF leak → air enters
After dural closure, air acts as mass lesion as CSF reaccumulates
Usually resolves spontaneously
Burr holes to relieve tension pneumocephalus
S/S include delayed awakening, headache, lethargy, confusion
Discontinue N2O before dural closure
VAE
Venous air embolism ↓ETCO2 ↑PaCO2 ↓SpO2 Spontaneous ventilation Mill-wheel murmur* (late sign) ET nitrogen detection Hypotension Dysrhythmias
VAE Monitoring
TEE detects 0.25mL air (most sensitive) Precordial doppler ↓ETCO2 w/ 15-25mL air ↑PAP w/ 20-25mL air CVP PaCO2 MAP
VAE Treatment
100% FiO2 Discontinue N2O Notify surgeon to flood field or pack wound Call for help! Aspirate CVP line 30-60mL Volume load - fluids wide open Inotropes/vasopressin Jugular vein compression PEEP Position L lateral decubitus w/ head down (Tredelenburg) CPR/EMCO
Chiari Malformation
Cerebellum protrudes through foramen magnum - compresses brainstem & cervical spinal cord
Types I-IV
Syringomyelia (fluid-filled cyst present in spinal cord)
Chiari Malformation
Anesthetic Considerations
Prone or sitting position
↑EBL d/t large venous sinuses
Vital sign instability d/t brainstem manipulation
Postop pain management
1° Head Injury
Contusion
Concussion
Laceration
Hematoma
2° Head Injury
Hematoma ↑ICP Seizures Edema Vasopressin
Skull Fractures Ypes
Linear - subdural or epidural hematomas
Basilar - CSF rhinorrhea, raccoon eyes, battle’s sign, pneumocephalus, & cranial nerve palsies
Depressed - brain contusion
Head Injury
Airway Management
C-spine precautions until cleared Manual inline stabilization Early intubation Awake fiberoptic intubation Full stomach precautions Blind nasal intubation contraindicated when basilar skull fracture present
Head Injury
Anesthetic Considerations
Seizure prophylaxis
Maintain Hct > 30%
Treat DIC w/ platelets, FFP, & cryo
Pituitary dysfunction
Pituitary Tumors
Non-Functioning
Non-secretory
- Arise from growth of transformed anterior pituitary cells
- Generally well tolerated until 90% gland non-functional
Pituitary Tumors
Functioning
Secretory
- Cushing’s disease ACTH
- Acromegaly (growth hormone)
- Prolactinomas (Prolactin)
- TSH adenomas
Pituitary Tumors
Preop
Visual field evaluation
↑ICP
Endocrine & electrolyte labs
Steroids
Pituitary Tumors
Intraop
Transsphenoid approach HOB elevated 10-20° Oral RAE or reinforced ETT Avoid hyperventilation ↓ICP impedes surgical access Carotid arteries adjacent to suprasellar area Document throat pack in/out Place OG tube Avoid positive airway pressure
Pituitary Tumors
Postop
DI common after pituitary surgery & usually resolves w/in 7-10 days
Treatment: Vasopressin or Desmopressin (DDAVP)
SIADH
Cerebral Aneurysm
Leading cause non-traumatic intracranial hemorrhage
Commonly located in anterior Circle of Willis
→ permanent brain damage, disability, or DEATH
Cerebral Aneurysm S/S
Unruptured
Headache Unsteady gait Visual disturbances - loss, diplopia, photophobia Facial numbness Pupil dilation Droopy eyelid Pain above or behind eye
Cerebral Aneurysm S/S
Ruptured
Sudden, extremely severe headache N/V LOC Prolonged coma Focal neuro deficits Hydrocephalus Seizure ↑ICP
Hess & Hunt
Aneurysmal subarachnoid hemorrhage grading system
Grade 0-2 = low mortality rate
3-5 ↑mortality rates
Ruptured Cerebral Aneurysm
Vasospasm
Ischemia or infarction Exact mechanism unknown 14% morbidity & mortality Not detectable until 72hrs after subarachnoid hemorrhage Calcium channel blockers
Rupture Cerebral Aneurysm
Re-Bleeding
Peaks 7 days post incident
8% morbidity & mortality
Antifibrinolytic therapy
Vasospasm Treatment
Triple H
- HTN goal systolic 160-200 (MAP 80-100)
- Hemodilution ideal Hct 33% balance b/w O2 carrying capacity & viscosity
- Hypervolemia aggressive IV crystalloid and colloid infusion (CVP > 10mmHg or PCWP 12-20)
IR Endovascular Aneurysm Coiling
Anesthetic Considerations
GETA w/ complete muscle paralysis Control CPP (lower BP during surgery) Minimal narcotic needs - minimally invasive A-line preferred Minimal to no blood loss Heparin ACT 200-250
Coil inserted via femoral vessels into aneurysm
Standard angiogram to locate aneurysm
Coiling Complications
Aneurysm rupture Subarachnoid hemorrhage Vasospasm CVA Incomplete coiling
Cerebral Aneurysm
Surgical Treatment
Microsurgical clip ligation
Craniotomy approach
Large aneurysms > 2.5cm may require deep circulatory arrest
Cerebral Aneurysm
Pre-Induction
Limit sedation (hypercapnia) Monitors: - A-line - PIV x2 Type & cross 2-4 units PRBCs available
Cerebral Aneurysm
Induction
Smooth induction
Consider difficult airway or full stomach
Aggressive BP & HR control w/ narcotics, β blockers, deepen anesthetic
Cerebral Aneurysm
Intraop & Maintenance
Rotate HOB 90-180° TIVA or anesthetic gases Temporary cerebral artery occlusion Maintain BP 15-20% below baseline to prevent vasospasm, ↓EBL, & allows improved exposure & visualization Cerebral protection methods to ↓ICP Optimum CPP ↓CPP occurs rapidly during surgery when aneurysm ruptures Maintain transmural pressure MAP - ICP Decrease intracranial volume (blood & tissue) to provide "slack" Minimize CMRO2 (oxygen demand) Fluids < 10mL/kg + UOP Expand volume w/ colloids NO GLUCOSE CONTAINING SOLUTIONS
Cerebral Aneurysm
BP Management
↓BP to prevent aneurysm rupture risk
Temporarily ↑MAP per surgeon request to provide collateral flow to feeder vessel clamped to allow clipping
Post-clipping maintain MAP 80-100mmHg
When is an aneurysm most likely to rupture intraoperatively?
Dural incision
Excessive brain retraction
Aneurysm dissection
During clipping or releasing the clip
Aneurysm Rupture Treatment
Immediate, aggressive fluid resuscitation & replace blood loss
Propofol bolus to ↓MAP & blood loss
Surgeon may apply temporary clip on parent vessel to control bleeding
Restore BP after clipping to improve collateral flow
AVM
Arteriovenous malformation
Congenital abnormality that involves direct connection from an artery to vein “nidus” w/o pressure modulating capillaries
Most common presentation = intracranial hemorrhage
Same preop considerations as aneurysm
Significant blood loss potential up to 3L
AVM Treatment
Intravascular embolization
Surgical excision
Radiation
Cranial Nerve Decompression
Treat cranial nerve disorders - trigeminal neuralgia, hemifacial spasm, & glossopharyngeal neuralgia
Unilateral
Usually caused by vascular structure compression
Cranial Nerve Decompression
Anesthetic Considerations
Position lateral, prone, or supine TIVA or brain relaxation Facial nerve or EMG monitoring Brainstem auditory evoked response Multimodal PONV
Spinal Cord Surgeries
Spinal cord stimulators Intrathecal pumps Scoliosis Anterior/transforaminal lumbar interbody fusion Anterior cervical discectomy & fusion
