Central and Peripheral Nervous Systems Flashcards
Which hypothalamic nucleus regulates circadian rhythm?
suprachiasmatic nucleus
Which hypothalamic nucleus regulates body temperature?
pre-optic anterior hypothalamus (also regulates thirst and non-REM sleep)
Where is vasopressin synthesized?
supraoptic and paraventricular hypothalamic nuclei, connected to the posterior pituitary
Which post-ganglionic sympathetic nerves use ACh as their neurotransmitter?
sweat glands and skeletal blood vessels
Which spinal levels provide sympathetics to the upper extremity?
T1-T4/5
Which anti-emetics should be avoided in patients with Parkinson’s disease?
metoclopramide, haloperidol, droperidol
(all are dopamine antagonists)
Why are patient’s with Parkinson’s disease poorly responsive to ephedrine?
catecholamine depletion
*direct-acting agents are preferable*
What makes a seizure “complex?”
impaired consciousness
How long should anti-epileptic drugs be continued in patients with severe TBI?
7 days
*anti-epileptics are very effective in preventing “early seizures” in the first 7 days, but ineffective in preventing “late seizures” after 7 days*
Which induction agent can cause extrapyramidal myoclonus prior to giving muscle relaxant?
etomidate
What is the most common cause of stroke during CEA?
embolism
Patients with which spinal cord lesions are at risk of autonomic hyperreflexia?
T6 and above
What are the common triggers for autonomic hyperreflexia?
distention of a hollow viscous
trauma
thermal stimulation
How do TCAs alter the effects of ephedrine?
can potentiate due to increased norepinephrine
How soon after the last alcoholic drink does delerium tremens become a concern?
2 days
At what point does hypoxia begin to affect cerebral blood flow?
Once PaO2 drops to 50, cerebral blood flow starts to rise exponentially
How does PaCO2 affect cerebral blood flow?
cerebral blood flow increases linearly with rising PaCO2 until the curve begins to flatten around 80 and completely flatten around 120
What techniques can cause a coupled decrease in both cerebral blood flow and CMRO2
hypothermia to 34 oC
barbiturates
propofol (greater reduction in CBF than in CMRO2)
What are normal values for cerebral blood flow and CMRO2?
CBF: 50 mL / 100 g / min
CMRO2: 3.5 mL / 100 g / min
What can lead to disruption of the blood-brain barrier?
extreme hypercapnea or hypoxia
sustained seizure
tumor
stroke
trauma
infection
What is the normal volume of CSF and production rate of CSF in an adult?
normal volume: 150 mL
normal production: 500 mL / day
How does dexamethasone decrease ICP?
limiting brain swelling
decreasing CSF production (in animal models)
What is the transmural pressure of a cerebral aneurysm?
TMP = MAP - ICP (or - CVP, whichever is larger)
How do opiates affect cerebral blood flow and CMRO2?
minimal effects on both
What is the reverse steal effect (e.g., Robin Hood effect)?
brain vasculature to normal tissue vasocontricts in response to a stimulus (e.g., hypocarbia, propofol, barbiturates, benzodiazepines) while brain vasculature to damaged/ischemic areas can’t respond, thus redirecting blood flow to damaged/ischemic areas
How does succinylcholine affect ICP?
transient, mild increase
*can be blunted with a defasciculating dose of non-depolarizing muscle relaxant*
How much and how long does hypocarbia reduce cerebral blood flow?
2% reduction in CBF for every 1 mmHg reduction in PaCO2
effect lasts 6-24 h
What are the most sensitive monitors for venous air embolism?
TEE > prechordial doppler > PA pressure changes > etN2
Where should a CVL be placed to use for potential aspiration of a venous air embolism?
at the junction of the SVC and right atrium
When should brain relaxation techniques be used in surgery for aneurysm clipping?
after the dura is open to avoid increasing aneurysm TMP by dropping ICP
*Before the dura is open: TMP = MAP - ICP
*After the dura is open TMP = MAP
What are the two approaches to aneurysm clipping and how do they affect your BP management
Traditional: clips on either side of the aneurysm, better outcomes with induced hypotension or even circulatory arrest
Modern: temporary clip on feeding vessel(s), better outcomes with elevated MAPs to maintain collateral blood flow to the territory of the feeding vessel
What are the ECG changes associated with SAH?
increased sympathetic outflow causing PVCs, prolonged QT, ventricular tachyarrhythmias, and ischemic changes from left heart strain
U waves from increasing ICP
What is the Hunt and Hess scale for SAH?
What is the incidence and timing of vasospasm after SAH?
15%
Risk peaks at 1 week, occurs rarely after 2 weeks
What is the best monitor for cerebral vasospasm?
transcranial doppler and frequent neuro checks
What is the approach to preventing cerebral vasospasm after SAH?
Triple H therapy: hypertension, hypervolemia, hemodilution
Nimodipine
Intra-arterial catheters for direct delivery of Ca2+ channel blockers in refractory cases
What are the endocrinopathies of the pituitary gland?
anterior: GH, PRL, LH, FSH, ACTH, and TSH
posterior: oxytocin and vasopressin
What happens to autoregulation and CO2 responsiveness in TBI?
autoregulation is lost
CO2 responsiveness is maintained
At what ICP does herniation become an imminent risk?
30-40 mmHg
What causes “neurogenic” pulmonary edema in the setting of TBI?
LV dysfunction from increased catecholamines
capillary leak syndrome of unclear etiology
What are the causes of hyponatremia in the setting of TBI? How can they be distinguished?
SIADH: euvolemic, typically responsive to salt tabs and fluid restriction, can be treated with “vaptan” drugs (vasopressin receptor antagonists)
Cerebral salt wasting: hypovolemic, poorly responsive to fluid restriction and salt tabs
How is spinal shock from a high cervical injury managed acutely?
fluid resuscitation (hypovolemia due to increased venous capacitance with unopposed vagal tone)
vasopressors with a ß1 component (counteract unopposed vagal tone)
What kinds of injuries are associated with an unstable C-spine?
cervical burst fractures
ligamentous injury (esp. alar and tectorial)
dens fractures
What is the Glasgow Coma Scale?
Eye response (out of 4)
Verbal response (out of 5)
Motor response (out of 6)
