Neuro Flashcards
What is the cardiovascular response to ECT?
Transient bradycardia (occasional asystole)
leads to hypertension and tachycardia
Do you want patients undergoing ECT to be hypo or hypercapneic?
Hypo
Improves the quality and duration of the seizure
What artery supplies 70% of the brain’s blood supply?
the two internal carotid arteries
The rest comes from the vertebral arteries
What percent of oxygen consumption does the brain use?
20%
What percent of the body’s glucose is used up by the brain?
25%
What percentage of the CO goes to the brain?
15%
Cerebral autoregulation of blood flow remains intact for MAP between _____ and ______
60-160
What is the Monroe-Kellie doctrine?
an increase in the volume of one compartment in the brain will increase ICP unless another compartment decreases its volume by the same amount
What is normal ICP?
7-15
Poor neurologic outcomes are associated with ICP above _____
20-25
What most commonly causes an increase in ICP?
cerebral edema
There are three types of cerebral edema:
Cytotoxic (increased intracellular water from membrane breakdown)
Vasogenic (usually around tumors, abscesses, or contusions)
Interstitial (increased extracellular water from hydrocephalus or osmotic gradients)
How do acute and chronic spinal cord injuries differ in manifestation?
Acute: flaccid paralysis and hypotension
Chronic: spastic paralysis, pain, autonomic hyperreflexia
What constitutes a significant change to the SSEP waveform?
amplitude decreases by 50%
Latency increases by 10%
MEPS are useful for monitoring:
motor cortex and anterolateral spinal cord
What constitutes a significant change in MEPs?
decreased amplitude of 50%
Need to increase the stimulation intensity to get a signal
changes in latency aren’t as worrisome
What is EMG used for?
To measure the integrity of distinct peripheral or cranial nerves/nerve roots
EMGs measure _______
SSEPs and MEPs measure ______
EMGs measure thermal and mechanical injury but NOT ischemia
SSEPs/MEPs measure monitor all three
Is EMG effected by NMBAs?
Very much so
What are BAEPs used for?
assess integrity of hearing in an unconscious patient
What are VEPs used for?
Monitor the integrity of the visual tract during anesthesia
Are VEPs sensitive to NMBAs?
yes! in fact they’re sensitive to all anesthetics so it’s very difficult to get and interpret signals, so they’re not used very often
If MEPs are being monitored, what’s the most common anesthetic technique?
TIVA
Can use 0.5 MAC inhaled volatile anesthetic
If a Transcranial doppler detects increased flow velocity, what does that indicate?
Stenosis, emboli, or vasospasm
Can Transcranial doppler be used to determined cerebral blood flow?
No. It’s measuring velocity (speed of flow), not amount of flow
Which ICP Lundberg waves are pathologic?
A waves
occur due to intense vasodilation and are always pathologic
Which is more effective at lowering CMRO2: anesthesia or hypothermia?
Hypothermia!
How does hyperthermia impact cerebral ischemia?
It’s really, really bad
For every 1 degree Celsius rise, infarct size triples
What degree of midline shift indicates severe pathology?
Obviously any shift is bad, but over 5mm is advanced
The induction of patients with elevated ICP should be _____ and _____
slow and controlled
What’s worse in patients with elevated ICP: hypertension or hypotension?
Hypotension
YOU CANNOT decrease CPP or it won’t be sufficient to overcome ICP
For patients with elevated ICP, how much volatile anesthetic should they receive?
A maximum of 0.5 MAC if at all
What is the optimal anesthesia technique for neurosurgery?
TIVA with propofol and remifenanil
If you can’t give muscle relaxants or volatile anesthetics, what can you give in a neuro case to ensure immobility?
A remifentanil infusion of 0.2 mcg/kg/min can achieve immobility
Describe ventilatory management of a patient during neurosurgery.
Vt 6-8 ml/kg
Peak pressures < 40
No PEEP since it impedes cerebral vascular drainage
Why is PPV preferred in neurosurgery?
You’d think spontaneous breathing would be better because it wouldn’t increase intrathoracic pressure
BUT
PPV allows tight control of CO2 and helps prevent Venous Air Emboli by avoiding negative pressure in the thorax
Which neurosurgical procedures constitute a high risk of bleeding?
AVM resection
Aneurysm clippings
tumor craniotomies that invade the sinuses
Should a patient have a type and cross for spinal surgery?
They should be T&C and have units available in the room
High risk of hemorrhage
Controlling hypertension during emergence is CRITICAL in which neurosurgery?
AVM resection
Decadron is not a good PONV prevention tactic in which patients?
Those having pituitary axis surgery
can suppress the HPA axis and create a false positive for postop hypopituitarism
The most common metastatic tumors to the brain are from:
melanoma
lung
breast
kidney
You should be vigilant while giving mannitol to patients with which comorbidities?
Any disease where a temporary massive increase in vascular volume will be hard to handle:
CHF
pulmonary edema
renal failure
What kind of fluid status is ideal during neurosurgery?
Euvolemia with dextrose free isotonic crystalloids or colloids
What surgical positions put patients at risk for VAE?
when the operative site is above the level of the RA in the presence of open, non-collapsible venous channels
Prevention measures for VAE include:
decreasing the heigh difference between the operative site and the heart as much as possible
maintaining euvolemia
using bone wax to occlude open sinuses
Treatment of VAE includes:
notifying the surgeon to flood the field
Administering 100% O2
Aspirating air through a CVC
What would you be aware of in developing an anesthetic plan for a patient with a GH secreting tumor?
Acromegaly of the mandible and hypertrophy of tissues → OSA and difficulty ventilating/intubating
They’ll need a smaller ETT
prone to cardiac rhythm issues and hypertrophic cardiomyopathy (avoid cardiac depressants)
What should you be aware of in the patient with an ACTH secreting tumor?
glucose intolerance
fragile skin
impaired wound healing
hypertension
SIADH is common with ______ tumors
Sellar
What are risk factors of cerebral aneurysm rupture?
Over 40
Female
Smoker
Hypertension
Connective tissue disorder
What is the most common cause of SAH?
Ruptured aneurysm
When is a cerebral vasospasm most likely to occur with an aneurysm?
greater than 72 hours
There are two drugs proven to reduce the risk of vasospasm:
nimodipine and statins
What is the greatest risk from AVM surgery?
Bleeding!
Why is hypotension so dangerous with AVM resections?
Many of these patients have seizures or focal neurologic deficits due to ischemic steal
hypotension makes these worse and can trigger a seizure
What is Normal Perfusion Pressure Breakthrough?
AVMs inhibit the autoregulation of the arterioles in the healthy tissue surrounding them, and they eventually lose the ability to vasoconstrict. The AVM sucks all the blood from them.
But when the AVM has been resected, these vessels are filled with blood (the AVM is no longer stealing it) but can’t constrict back down, and so they lead to hyperemia, edema, headache and postop bleeding
What percent of patient who undergo AVM resection have seizures postop?
50%!
They have to be on anticonvulsants postop
If a patient becomes agitated, confused, or unresponsive following carotid occlusion during CEA, what should the anesthesiologist do?
Assume cerebral ischemia is the culprit and increase BP to 20% over baseline SBP
What is stump pressure?
The pressure in the internal carotid artery measured distal to the cross clamp
supposed to reflex collateral blood flow through the circle of Willis
should be greater than 50
Usually if there is a discrete epileptic focus, it is located in which lobe?
temporal
Temporal lobectomy with amygdalohippocampectomy is the most common surgery to treat epilepsy
If a patient has a seizure during an awake craniotomy, what should be done?
Poor cold saline over the brain surface
Give 20mg propofol
In spinal surgeries, MAP should be kept greater than:
85
