Intracranial Neurosurgery ppt 2 Flashcards
Intracranial aneurysms are defined as:
focal protrusions arising from weakened arterial walls usually at major bifurcations of the arteries at the base of the brain
Intracranial aneurysms are most commonly treated by:
endovascular coiling (>50%) or microsurgical clip ligation.
Most important surgical considerations for intracranial aneurysms:
clinical presentation, aneurysm size and location, patient age, neurologic status, and medical comorbidities
Most common intracranial aneurysm clinical presentation:
Aneurysm rupture
System used for prognostic clinical outcome
Hunt Hess grading system (1 asymptomatic, 5 deep coma)
anterior intracranial aneurysms position:
supine, mayfield headrest, turned 30-45* to side away from aneurysm
posterior intracranial aneurysms position:
supine or lateral with mayfield headrest
EBL intracranial aneurysm:
250-1000 ml
Intracranial aneurysms considerations:
arterial clipping, mild hypothermia, intro angiography with access to femoral artery, electrophysiologic monitoring, brain relaxation, lumbar subarachnoid CSF drainage, decadron IV
intracranial aneurysm prep anesthesia considerations:
- 23% have neurogenic pulmonary edema
- PVCs, T wave inversion and ST depression are common
- Decreased Magnesium
- May present with increased ICP or cerebral vasospasm
- Digital subtraction angiography is gold standard for detection
- Pt should be Euvolemic
- hyponatremia from SIADH
- aline for tight BP control
increase in BP in intracranial aneurysm pt preop
rebleed, permanent neurologic deficits, or death
substantial decrease in BP in intracranial aneurysm prep:
cerebral ischemia or infarction
intracranial aneurysms induction:
- Smooth induction
- Decrease cerebral blood volume by inducing cerebral vasoconstriction
- Pts on nimodine may require pressors ie phenylephrine during and after induction
- Patients may benefit from moderate hyperventilation during induction
intracranial aneurysms maintenance:
- Iso or Sevo ½ Mac if EP monitoring
- Avoid N2O
- Propofol gtt: ↓ cerebral blood volume, ↓ cerebral metabolism, and ↓ CMRO2
↓ PaCO2 leads to:
↓ cerebral vascular volume (better surgical access) + ↑ CBF to ischemic areas (“Robin Hood” effect) + ↓ anesthetic requirements + ↑ lactic acid buffering.
Mannitol/furosemide leads to:
↓ K+; monitor level and replace as necessary.
If mannitol is administered too rapidly, what could occur?
↓ BP may occur, 2° peripheral vasodilation.
Mild hypothermia (33–34°C) is used to:
to ↓ CMRO2and to ↓ susceptibility to ischemic injury during temporary clip application.
At 30*C, CMRO2 decreases
~ 30%
BP control: During aneurysm exposure
decrease MAP to ~80% baseline
BP control: During temporary clipping
increase MAP to ~120% of baseline
BP control: postclipping
MAP typically 70-90 mmHg
BP control: if aneurysm ruptures
decrease MAP to 40–50 mm Hg
consider carotid compression
Deep hypothermia and CPBP is used only with what aneurysms?
> 2.5 cm in diameter
intracranial hemorrhage emergence:
Hunt Hess 4 and 5- remain intubated and sedated post-op
Hunt Hess 1-3- titrate BB and vasodilators as needed
smooth emergence, no cough
HOB elevated 30* on transport
Intra-op Concerns for AVM
Fiberoptic awake intubation if patient arrives with stereotactic frame.
Stereotactic frame is placed in pre-op awake with local anesthesia then patient goes to CT or MRI.
VAE Central line
Aline
Mild hypothermia
Brain Relaxation (decrease PaCO2, mannitol/furosemide)
Emergence for AVM
Increases in BP treat with B-Blockers or vasodilators
Close regulation of BP is key
Suppress cough with lidocaine IV
HOB elevated 20-30 degrees
BP should be maintained 10% below baseline
Craniotomy for Tumor Pre-Op Considerations
Neurogenic pulmonary edema
Increase ICP leading to Cushings Triad (HTN, Resp Depression & Bradycardia)
Anesthesia for Craniotomy
Stereotactic frame are placed on the patient’s head
The patient is taken to CT/MR for determination of the exact tumor site.
Surgeons may visualize certain tumors by utilizing iv fluorescent dyes (e.g., fluorescein)
When used in conjunction with a specialized operating microscope, these compounds allow greater definition of the tumor and its boundaries with normal brain tissue.
Anaphylactic reactions can occur with the use of these agents.
Stereotactic Surgery Considerations
Risk of air embolus
Brain stem manipulation causes BP and pulse instability
Dural patch is used to expand dura at foramen magnum
Craniotomy Intraoperative concerns
Awake Fiberoptic Intubation if stereotactic frame present Minimize Increases in ICP and MAP Pre-cordial doppler BAER, SSEP, MEP CVP
Emergence Craniotomy
Increases in BP treat with B-Blockers or vasodilators
Close regulation of BP is key
Suppress cough with lidocaine IV
HOB elevated 20-30 degrees
Surgeon may request transient increase in MAP 90-100mmHg to test hemostasis after the tumor is resected
Awake Craniotomy
May be used for epilepsy
Tumors involving motor or speech
Done under MAC or (asleep- awake- asleep) technique
LMA or ET
Awake Craniotomy- Premapping
Mannitol slow IV infusion Midazolam & Dexmedetomidine Propofol gtt Scalp block Aline Foley Mayfield headrest under Local anesthesia
ventricular shunt- diagnosis:
hydrocephalus
2 approaches to ventricular shunt:
Ventriculoperitoneal or Ventriculoatrial
Ventricular shunt pre-op:
Cushings triad
Headache with ICP > 15mmHg
No pre-op med required
Ventricular shunt induction:
minimize ICP
maintain normovolemia
Ventricular shunt maintenance:
PeCO2 35-40 mmHg
Hyperventilation and hypocarbia make cannulation of vessel difficult
Maintain normotension: Catheter tunneling is stimulating
