Neuro Flashcards
Describe the relationship between CBF and PaCO2
Low CO2 means decreased CBF (In fact, they are directly proportional!) So 1 mmHg less of CO2 means a 1-2 decrease in CBF
What is the structure in the carotid artery that contains baroreceptors? What happens when it is stretched? what surgery might you see this in? What contains chemoreceptors?
- Carotid sinus
- hypotension, bradycardia
- CEA
- Carotid body
Describe Charcot Marie Tooth disease
- demyelinating disease of the peripheral nerves
- leads to sensory and motor loss of the distal extremities
- autosomal dominant
What part of the brain controls inspiration and expiration?
Medulla
1. ventral: expiration
2. dorsal: inspiration
The lower pontine apneustic center stimulates the dorsal respiratory group while the upper pontine pneumotaxic center inhibits it.
What are the afferent and efferent limbs of the corneal reflex?
- trigeminal
2. facial
What defect is most commonly associated with a Myelomeningocele?
Chiari II malformation
What fibers run through the grey rami communicates?
post ganglionic sympathetic nerve fibers. The pre- ganglionic fibers run through the white rami communicates
What can you give as a pre-med to help with succinylcholine myalgias?
- lidocaine
- calcium gluconate
- vitamin C
When is a vasospasm following SAH most likely to occur? When is re-bleeding most likely to occur?
- 48-72 hrs
2. Within the first 48 hours
What are the most accurate sites to measure core temperature?
- TM
- distal esophagus
- pulmonary artery
- nasopharynx
What artery does trans cranial doppler (TCD) use to detect flow velocities during a CEA?
MCA
When is it common for women to develop a relapse from MS?
Post-partum
What electrolyte abnormality is associated with GBS? And why?
SIADH –> hyponatremia
Name two ways that you can decrease CPP
- directly drain CSF from drain
2. Increase MAP
Which nerves have PS pre- gangiolinc neurons? Where do they reside?
- III, VII, IX, X
- III: edinger westfall nucleus
- VII, IX, X: medulla oblongata
What drug interferes with microelectrode recordings?
Midazolam, most other IV agents are OK to use
True or False: Hyperthermia is brain protective after a neurologic insult
FALSE: HYPOthermia is neuroprotective
What tool can be used to help ensure no limb nerve injury occurs during spinal surgery?
SSEPs. These can alert of spinal cord damage or peripheral nerve damage
Which position puts you most at risk for post operative vision loss
Horseshoe head rest
Explain hyperkalemic periodic paralysis
What receptor is involved in hypokalemic periodic paralysis?
There is a mutation in the Na voltage gated channel that leads to prolonged depolarization, myotonia, and paralysis. Therefore, the patients are dependent on K efflux to start depolarization. If K is HIGH, then K efflux is slowed and the patient remains paralyzed. Can affect the tongue and eyelids
Factors that worsen this are 1) rest after exercise, 2) metabolic ACIDOSIS, 3) hypoglycemia, 4) extremes of temperature 5) depolarizing muscle blockers
Calcium receptor
What is a common complication of AVM embolization procedures? How do you treat it?
- cerebral edema
2. hypotension, hypocapnia, hypothermia, and propofol
Describe Autonomic hyperreflexia
- Happens when damage above T12 occurs
- Any sort of stimulation to the skin, bladder, uterus, viscera leads to activation of the the sympathetic pre-ganglionic fibers, which then affects the splanchnic outflow tract. However, the inhibitory fibers are damaged: SO below the injury you get uninhibited sympathetic stimuli (vasospasm), while vasodilation and sweating occur ABOVE the lesion
Describe some anesthetic considerations in kids with muscular dystrophy. What is an appropriate anesthetic plan?
- Cardiac defects: many of these kids can get CHF and dysrhythmia
- Respiratory issues: weak respiratory muscles and poor clearance of mucus leads to increased risk for pulmonary infections and therefore possible prolonged intubation following surgery
- GI dysmotility and gastroparesis: increased risk for aspiration
- Avoidance of succinylcholine due to up-regulated Ach receptors
- Avoidance of volatile anesthetics due to increased risk for rhabdomyolysis
- Induction with IV propofol and rocuronium
Which site on the NMJ post junctional nAchR does the Ach bind?
Alpha 1 subunit
Describe what a MEP is? When is it most commonly used? What is the pathway that the neurons follow?
- MEP: motor evoked potential, this is when electrodes are placed transcrianially (over the scalp) or directly on the brain to stimulate the descending motor pathway
- This is used in surgeries where the artery of adamkiewicz is at risk (the anterior blood supply to the spinal cord)
- Lower limb cortex –> inter capsule –> brainstem –> corticospinal tract –> peripheral nerve
Describe the role of the carotid body vs. the carotid sinus. What CN do each of these utilize to send messages to the brain to increase ventilation? What surgery puts the carotid body at risk?
- Carotid body is at the branch of the common carotid artery. It is a group of cells that transmits signals to the brain when PaO2 decreases below 100 and then below 50.
- The carotid sinus is in the proximal internal carotid artery and it detects PaCO2 levels
- Both use CN IX (glossopharyngeal) to send signals to the brain
- CEA: if this nerve gets knocked out, the the body is only relying on hypercarbic drive to increase ventilation and this is often times attenuated (or decreased) by narcotics and anesthetic gas
What vertebrae differentiates Quad vs. paraplegic?
T1
Describe neurogenic pulmonary edema
Following TBI and increased ICP, there is a massive discharge of sympathetic activity that causes pulmonary vasoconstriction. This can happen w/in a few hours
Compare tetanus and botulism
- Tetanus inhibits GABA and Glycine release from at the pre-synaptic channels in the brain, which inhibits the inhibitory neurons –> tetany
- Botulism inhibits Ach release in the spinal cord, so the alpha motor neurons are not activated –> flaccid paralysis
Why should mannitol be given over 10-15 minutes?
It causes brain engorgement and has a vasoDILATORY effect, leading to increased ICP
Describe the effect that propofol has on the brain
Decreased CMRO2, cerebral 02 consumption, and decreases ICP. The concern is that a decrease in MAP will lead to a decrease in CPP
Describe HYPOkalemic periodic paralysis
- Defect in the Ca channel
2. Leads to weakness of the trunk and limbs, but sparing of the diaphragm
What are the ICP and CPP goals in a patient with TBI?
ICP < 20-25, CPP > = 60
Describe the difference between phase 1 and phase 2 blockade of Succinylcholine?
- Phase 1: Sux is bound to the POSTsynaptic ach receptors, TOF with NO fade
- Phase 2: Sux is bound to the PREsynaptic ach receptors, TOF WITH fade
What are the goals of fluid management in a neurosurgical patient? Why?
- Want them euvolemic or slightly hypervolemic to maintain CPP
What will you see on ICP waveform when there is a sudden increase in ICP?
A plateau wave (AKA Lundberg’s wave): increase in P2 > P1
What is another word for myasthenia syndrome?
LE syndrome
Describe the effects of anesthetic gas on CMRO2 and CBF at 0.5-1 MAC and 1.5 MAC and above
- 0.5-1.0 MAC: Leads to decreased CMR02 and CBF
2. 1.5 and above leads to decreased CMRO2, but vasodilation leads to increased CBF
What are the only two agents to not decrease CMRO2?
- Ketamine: minor effect, increase in CBF, Increases ICP
2. N20: increases CMR02, CBF, and ICP
What criteria are used to determine if a patient with MG needs post operative ventilation?
- NIF < 20
- VC < 2.9
- other compounding lung disease
- Disease > 6 years
- Daily pyridostigmine dose > 750
What receptors and neurotransmitters to pre and post ganglionic neurons of the 1. Sympathetic and 2. PS systems use?
- sympathetic: PRE: Ach/nAchR, POST: NE,E, Alpha/beta
2. PS: PRE: Ach/nAchR, POST: Ach/mAchR
How does Mg cause muscle weakness?
Blocks Ca influx into the presynaptic terminal, leading to decreased Ach release
What is the path that CSF drainage takes?
Lateral ventricles –> third ventricle –> 4th ventricle –> cisterna magna via the foramen magendie (median aperture)
Sacral spinal nerves affect which types of nerves?
parasympathetics!
How would you describe the TOF ratio between the upper limb and the lower limb in a paraplegic patient? Why is this the case?
- The TOF ratio will INCREASE
2. This is due to up regulation of Ach receptors in the injured limb
What is important to ensure following deep hypothermic cardiac arrest in attempts at neuro protection?
CPB is maintained for 20-30 minutes once the blood has reached a temp of 15-22 C. This is because there is no way to directly correlate blood temp to brain temp.
What is a paradoxical reaction that is associated with succinylcholine?
Laryngospasm
Describe the neurologic changes seen with aging
- Increased BBB permeability
- Preserved cerebral auto regulation of blood flow
- Increased sensitivity to LA
- uneven distribution of neuronal cell loss
What is a normal serum osmolality?
Hypo-osmolar: < 280
Hyper osmolar: > 285
What is the effect of barbiturates on cerebral auto-regulation?
It is maintained!
Describe SSEPs
Somatosensory Evoked Potential:
Stimulation of a peripheral sensory nerve leads to activation of the sensory cortex (supplied by the MCA, which is important in CEA surgery when the carotid is clamped)
What hormones are released from the pituitary?
Anterior: ADH, oxytocin
Posterior: ACTH, LH, FSH, GH, prolactin, TSH
Describe the defect in mitochondrial disorders. How can we mitigate this in the perioperative period?
- inability to make ATP
2. limit stressors, such as hypoglycemia, emotional stress, hypothermia, or hyperthermia, acidosis
Describe the blood flow in the spinal cord
There are two posterior and one anterior artery. The ASA supplies 75% of blood flow to the spinal cord (supplies motor tracts), whereas the posterior two supply blood to the sensory tracts
Why is it safe to use succinylcholine in MG and LE syndrome?
there is NO up regulation of the the nAchR
Compare persistent vegetative state to a coma
PVS is when a person in a coma has made a small improvement. They can open their eyes, cry, laugh, make NON-purposeful movements, but cannot think, communicate, or move in a purposeful way
Coma: GCS < = 8 for > = 6 hours
What drug can be used to treat paralysis in both hypo and hyperkalemic periodic paralysis?
acetazolamide, for reasons unknown
True or false: Ketamine can induce seizures
TRUE, esp in those patients with a lower seizure threshold
What agents should be used in ECT? What are some reasons to not use one of them?
- Methohexital “gold standard”
2. Etomidate: does not blunt the sympathetic response to seizures, so should be avoided in those with HTN and CAD
