Basic - Neuro Flashcards
When do you need to be careful administering Succinylcholine to patients who suffered burns?
Generally AFTER the first 24 hours - 2 years
- at that point, significant upregulation of nicotinic ACh receptors will occur
*same with pts with stroke and spinal cord injuries
Multiple sclerosis
- ACh receptors (up/downregulated)
- Depolarizing muscle relaxant
- Nondepolarizing muscle relaxant
ACh receptors: Upregulated
Depolarizing muscle relaxant:
Careful, especially if flaccidity or spasticity
Nondepolarizing muscle relaxant:
May be more resistant or sensitive
Conditions that cause an upregulation of ACh receptors
- MS
- Burns
- Stroke
- Spinal cord injury
- GBS
- Prolonged immobility
- Muscular dystrophies
- Prolonged use of NMB
*can cause an exaggerated increase in K+ after giving Sux
Lambert eaton syndrome
- disorder
- Depolarizing muscle relaxant
- Nondepolarizing muscle relaxant
prejunctional Ca2+ antibodies
Depolarizing muscle relaxant:
more sensitive
Nondepolarizing muscle relaxant:
more sensitive
Lambert eaton syndrome
- disorder
- Depolarizing muscle relaxant
- Nondepolarizing muscle relaxant
ACh receptor:
- downregulation
Depolarizing muscle relaxant (sux):
more resistant
Nondepolarizing muscle relaxant (roc):
more sensitive
Myasthenia gravis
- disorder
- Depolarizing muscle relaxant
- Nondepolarizing muscle relaxant
ACh receptor:
- downregulation
Depolarizing muscle relaxant (sux):
more resistant
Nondepolarizing muscle relaxant (roc):
more sensitive
How do barbiturates affect : ICP: Cerebral blood flow: Cerebral autoregulation: CMRO2:
ICP: Decrease
Cerebral blood flow: Decrease (dose dependent)
CMRO2: Decrease (dose dependent)
Cerebral autoregulation: Unaffected
Treatment for extrapyramidal symptoms or acute dystonic reactions?
- Anticholinergics
- diphenhydramine (both anticholinergic and antihistamine) - BDZ
- BB
*EPS: abnl movement when cholinergic-dopaminergic balance is off
________ on EEG is the goal target of reducing CMRO2 during an open cerebral aneurysm clipping
Burst suppression
What is the upregulation of postjunctional ACh receptors due to?
What risk does this pose?
Injury to nerves that cause decreased release of ACh or denervation or lack of ACh stimulus to the post-junctional receptor
hyperkalemia induced cardiac arrest
Cushing’s triad
- HTN
- Bradycardia
- Respiratory changes
= ominous sx of serious head injury -> urgent intubation
What is mannitol used for in neurosurgery?
osmotic diuretic -> quickly decrease ICP
- however, you NEED an intact BBB or else mannitol will raise brain osmolality, increase cerebral volume and risk herniation
Why is nitroglycerin not recommended in pts with head trauma if they are hypertensive?
Cerebral vasodilator -> may further raise ICP
What can cross the BBB
Small lipophilic molecules
- oxygen
- CO2
Treatment for elevated ICP intraop
hypertonic saline diuretics mannitol - draw fluid back across the BBB in hopes of decreasing the edema - however, you NEED an intact BBB
Effect of acute vs chronic use of phenytoin on nondepolarizing NMB
Acute:
- Potentiates blockade
(acute reduction in ACh release - less competitive inhibition)
Chronic:
- Increases resistance to blockade (ED95)
- Decreases duration of blockade
(increased postjunctional ACh receptor density - more receptors to block. and decreased sensitivity at the receptor)
What is the ED95 in neuromuscular blocking drugs?
dose required to achieve desired effect in 95% of population
Effect of phenytoin use on depolarizing NMB (succinylcholine)
Prolonged d/t upregulation in ACh receptors - higher risk of hyperK
Upregulation: denervation or lack of ACh stimulus to the post-junctional receptor
Post op vision loss secondary to ANTERIOR ischemic neuropathy (AION) is most likely to occur after which type of surgery?
Cardiac surgery
*cardiac sx is done on the anterior = AION
posterior spine sx are done on the posterior = PION
Post op vision loss secondary to POSTERIOR ischemic neuropathy (PION) is most likely to occur after which type of surgery?
posterior spine surgery
anterior ischemic optic neuropathy more common periop cause of vision blindness than posterior
Decreasing a pts PaCO2 by 1mmHg will decrease CBF by ____
1mL/100g/min
Pathway for eccrine sweat gland innervation (located all over the body except lips, and tip of penis and clit)
SYMPathetic preganglionic -> nicotinic receptor -> SYMPathetic postganglionic -> muscarinic receptor
Pathway for apocrine sweat gland innervation (located in armpit and perianal areas)
PARAsympathetic preganglionic -> nicotinic receptor -> PARAsympathetic postganglionic -> muscarinic receptor
_____ agents interfere with the sweating mechanism, which may lead to temp increases (esp child with fever)
Anticholinergic agents
- include in differential
In pts with methemoglobinemia (toxic side effect of benzocaine admin), the only value that significantly changes on ABG is ____
PaO2
- partial pressure of arterial oxygen
-
What is methemoglobinemia?
*occurs after exposure to substances that oxidize hgb faster than methemoglobin reductase can reduce it
Altered state of hgb where the FERROUS (Fe2+) form of heme is oxidized to the FERRIC form (Fe3+)
- cannot bind oxygen
What can cause methemoglobinemia?
- occurs after exposure to substances that oxidize hgb faster than methemoglobin reductase can reduce it
- prilocaine
- benzocaine
- abx: dapsone, sulfonamides, trimetoprim
- metoclopramide
- nitrates / nitrites
on ABG, which value is NOT directly measured, but calculated based on the assumption that ALL hgb is normal?
SaO2
- Can be falsely elevated in methemoglobinemia
How many days of immobility leads pts to have increased risk of hyperkalemia with depolarizing muscle relaxants?
> 16 days
The TOF of a nerve in a paralyzed extremity is ______
exaggerated
- production of extrajunctional ACh receptors in affected muscles -> increase response w/ stim
CMRO2 and CBF decrease ___% for every 1C decrease in temperature
6%
Increasing PaCO2 from 40-60 mmHg will cause an (increase/decrease) in CBF approximately __%
increase
60%
CBF remains unchanged within the autoregulatory range of MAP ____ and PaO2 ____
MAP 50-150mmHg
PaO2 >50mmHg
How do you calculate the diff in blood pressure in 2 different sites?
Height (cm) x 0.74
Subtract this value from the systolic and diastolic value at the heart
- mneumonic:
- pH = Pressure height
- pH 15 20 = pressure 15 = height 20 cm
Tetanus prevents neurotransmitter release (glycine and GABA) from ____ in the ____
inhibitory neurons
- inhibition of inhibitory neurons -> increased muscle contractions
Spinal cord
Botulism prevents neurotransmitter release (ACh) from ____ at the ____
nerves
neuromuscular junction
What illicit drug is a risk factor for tetanus contraction?
Heroin
Neurogenic shock following acute high spinal cord injuries is associated with severe bradycardia and hypotension from _______
unopposed vagal or parasympathetic activity and loss of cardiac accelerator fibers (if injury is above T1-T4)
Why would Pts with acute spinal cord injury become bradycardic during intubation?
Stimulation usually occurs above the level of spinal cord injury. Nerve transmission is unable ot descend and activate the thoracic sympathetic chain at T1-T4
Why would Pts with acute spinal cord injury present with paradoxical shallow respirations?
implies level of injury is between C4-C7
- C3, C4, C5 keeps the diaphragm alive
Autonomic hyperreflexia beings ___ weeks following acute spinal injury
2-3 weeks
Etomidate and ketamine (Increases/decreases) amplitude of Somatosensory evoked potential stimulus (SSEP)
increases
