Neuro Flashcards
What volatile anesthetic would you choose for a Neuro case and why?
Isoflurane because it causes the greatest drop in CMR
And it facilitates absorption of CSF
What are the dangers of using volatile anesthetic in a Neuro case with suspected ischemia?
Volatiles increase CBF by vasodilation, but not in ischemic areas so you could make this worse by circulatory steal
Would you use lidocaine infusion in a Neuro case? Why or why not?
I would because lidocaine decreases CBF and may also have neuroprotective effects
It also decreases MAC and opioid requirements –> reduces emergence delirium
What physical exam signs do you look for ICP?
Papilledema Focal signs CN deficits Lethargy Cognition Pupil size
How do you treat high ICP.
Head of bed up
Steroids if vasogenic edema (not in trauma)
Diuretics - goal of serum osmolality of 300-315 mOsm/L
Moderate hyperventilation (PaCO2 30-33 mmHg)
Anesthetics
Normothermia
Hypertonic saline
EVD
What are the contraindications for using mannitol?
Intracranial aneurysm AVM ICH Subdural hematoma (Until cranium is opened)
What are the potential dangers of using mannitol?
Rebound edema
Transient increase in intravascular volume –> pulmonary edema
Rupture of aneurysm/AVM/bridging veins due to abrupt change in transmural wall pressure and expansion of hematoma
Hypotension
What kind of preoperatively tests do you want for craniotomy surgery?
CT or MRI - looking for evidence of brain edema, size and location of tumors or aneurysm, midline shift or compression of the ventricles
Labs: glucose level, BMP for electrolytes (SIADH or diuretic therapy), Hct
How will you T this patient with a cranial mass up for surgery?
Make sure they get their anticonvulsant and steroid
Correct electrolytes
What other monitors do you want for a craniotomy case?
Arterial line - zeroed at external auditory meatus for measurement of CPP at circle of Willis
Central line for fluids, vasopressors and aspiration of catheter in case of VAE
Foley catheter
How will you induce a patient with high ICP?
Modest hyperventilation PaCO 30-33
Propofol + lidocaine + fentanyl + rocuronium - modified RSI
Fentanyl to blunt tachycardia response to DL versus esmolol
Propofol for deceased CMR and CBF
Lidocaine for decreased dosages of fentanyl/propofol and decreased CBF
Modified RSI to maintain normocarbia and prevent aspiration
Could you use succinylcholine in a patient with high ICP?
Yes, you could because the increase in ICP caused by succinylcholine is transient and failed airway, aspiration, hypoxemia and hypercarbia will be detrimental to this patient and also cause increased ICP
Patient with high ICP is tachycardic and hypertensive after intubation, what do you do?
Bolus of propofol (deepen anesthetic)
Beta blockade
How will you maintain a patient with high ICP for craniotomy?
TIVA
Or MAC < 0.5 volatile plus IV anesthetics: propofol, lidocaine, remifentanil
Continue hyperventilating (PaCO2 30-35)
IVF - no glucose! Causes increased ischemic brain injury
Why not hyperventilate below PaCO2 of 30?
Little to no benefit
Can cause cerebral ischemia and impair oxygen dissociation from hemoglobin
How will you emerge this patient?
Want to avoid coughing on tube - lidocaine down ETT
Resume spontaneous breathing
Reverse
What is your differential diagnosis for delayed wakening in a crani case?
Drugs: opioid, inhalational, NMB
Stroke
Metabolic derangement: glucose, hypoNa
Pneumocephalus
What monitors would you use for a posterior craniotomy?
TEE
Precordial Doppler
Central line with tip at junction of RA and SVC, syringe attached
Other monitors for VAE? Esophageal stethoscope PAC (increase in PAP) Mass spec of nitrogen on the monitor Drop on ETCO2 or oxygen
Where should CPP be kept in a crani case with increased ICP?
70-110
This correlates with a MAP 140-110 for ICP of 30
At the end of a longer spine case a patient wakes up and has visual loss, but no pain? What are you worried about? How did this happen?
Intraoperative optic nerve damage
Due to increase orbital venous pressure and decreased perfusion
What are the anesthetic considerations for prone positioning?
Airway and facial edema
POVL 2/2 impaired venous drainage
Cortical blindness due to decreased perfusion of the visual cortex
Abdominal compression–> impede venous return, contribute to blood loss thru engorgement of epidural veins!
Femoral artery occlusion –> a vascular necrosis
Genitals, knees, eyes, ENT
Brachial plexus injury
How will you reduce the risk of POVL?
Reverse Trendelenburg position
Avoid hypotension
Padding of pressured areas
Neutral head position for draining of head/neck
For an aneurysm case, what kind of monitors do you want?
Arterial line - tight BP control to avoid aneurysm rupture
Central line in femoral - cordis for volume resuscitation due to massive blood loss. Femoral to avoid imparing head/neck drainage with subclavian/jugular
How does mannitol work?
Osmotic diuresis
Must have intact bbb!
Why keep MAC < 0.5 in intracranial cases?
Because levels of volatiles above this cause cerebral vasodilation
Surgeon asks for hypotension during an aneurysm case, how will you do this?
I would start a nicardipine drip since it is titratable
Would also bolus propofol to decrease CMRO2
Keep Mac < 0.5
What is diabetes insipid us?
Brain is not releasing ADH
What is the treatment of diabetes insipidus?
Volume replacement
Vasopressin
Monitor sodium and fluid status
Tell me everything about motor evoked potentials?
Assess the lateral corticospinal tract
Minimally affected by IV anesthetics: ketamine, etomidate, opioid, dexmed