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

Central and Peripheral Nervous Systems Flashcards by Lauren Buhl

Which hypothalamic nucleus regulates circadian rhythm?

suprachiasmatic nucleus

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Which hypothalamic nucleus regulates body temperature?

pre-optic anterior hypothalamus (also regulates thirst and non-REM sleep)

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Where is vasopressin synthesized?

supraoptic and paraventricular hypothalamic nuclei, connected to the posterior pituitary

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Which post-ganglionic sympathetic nerves use ACh as their neurotransmitter?

sweat glands and skeletal blood vessels

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Which spinal levels provide sympathetics to the upper extremity?

T1-T4/5

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Which anti-emetics should be avoided in patients with Parkinson’s disease?

metoclopramide, haloperidol, droperidol

(all are dopamine antagonists)

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Why are patient’s with Parkinson’s disease poorly responsive to ephedrine?

catecholamine depletion

*direct-acting agents are preferable*

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What makes a seizure “complex?”

impaired consciousness

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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*

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Which induction agent can cause extrapyramidal myoclonus prior to giving muscle relaxant?

etomidate

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What is the most common cause of stroke during CEA?

embolism

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Patients with which spinal cord lesions are at risk of autonomic hyperreflexia?

T6 and above

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What are the common triggers for autonomic hyperreflexia?

distention of a hollow viscous

trauma

thermal stimulation

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How do TCAs alter the effects of ephedrine?

can potentiate due to increased norepinephrine

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How soon after the last alcoholic drink does delerium tremens become a concern?

2 days

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At what point does hypoxia begin to affect cerebral blood flow?

Once PaO₂ drops to 50, cerebral blood flow starts to rise exponentially

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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

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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)