Anesthesia Adjuncts (Exam IV) Flashcards by Andrew Everett

β agonism results in activation of _____ which then produces _______.

Adenylyl Cyclase (AC)

cAMP

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What does cAMP enhance?

Calcium influx

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Does Ca⁺⁺ influx or efflux during β agonism?

Influx

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What type of receptors are β receptors?

GPCR

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What types of β receptors are there and where are they primarily located?

β1 - Heart
β2 - Lungs
β3 - Fat/Muscle

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Chronic administration of β blockers results in what effect on receptors?

Receptor upregulation (aka ↑ # of receptors)

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After β receptor desensitization from prolonged catecholamine exposure, what drug class can restore receptor responsiveness?

β-blockers

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How do β blockers protect myocytes from perioperative ischemia?

By ↓O₂ demand on the heart

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T/F. β blockers will potentiate renin release.

false. β blockers will inhibit renin release

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How will β blockers affect the cardiac foci action potential?

Prolong Phase 4

-↓ rate of spontaneous depolarization
-↓ dysrhythmias during ischemia and reperfusion.

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How will β blockers affect diastolic perfusion time?

β blockers will increase diastolic perfusion time.

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What type of HTN is a possible indication for β blocker therapy?

Essential Hypertension (HTN not a result of medical condition)

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What is SCIP?
Describe the protocol and its goals pertaining to betablockers

Surgical Care Improvement Protocol
β-blockers must be given within 24 hrs of surgery for patients at risk for cardiac ischemia and ones already on β-blocker therapy.

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What were the three β1 selective agents discussed in lecture?

Atenolol (tenormin)
Metoprolol (lopressor)
Esmolol (brevibloc)

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What percentage of β₁ receptors are in the myocardium?

75%

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Do cardio-selective β-blockers cause vasodilation?

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What non-selective β-blocker has active metabolites and is generally not used for anesthesia?

Propanolol

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Differentiate the clearance mechanisms of metoprolol, esmolol and atenolol.

Metoprolol: Hepatic
Esmolol: Plasma hydrolysis
Atenolol: Renal

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Differentiate the E½ of metoprolol, atenolol and esmolol.

Metoprolol E½ = 3-4 hours
Atenolol E½ = 6-7 hours
Esmolol E½ = 0.15hr (9min)

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When propanolol is given, what effect lasts longer, negative inotropy or negative chronotropy?

Negative chronotropy (bradycardia) lasts longer

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What is a possible reason why the heart rate slowing effects of propanolol last longer than the negative inotropic effects?

Possible β1 sub-receptor types (ex. β1_A, β1_B, etc.)

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Propanolol will decrease the clearance of which two important anesthetic drug classes?

Opioids
Amide LA’s

(due to lower CO and slower HR)

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What drug is the most selective β1 antagonist?

Atenolol (tenormin)

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What are the three benefits of Atenolol?

Good for non-cardiac sx CAD patients (↓ complications for 2 years)
No insulin-induced hypoglycemia
Does not cross the BBB (no fatigue)

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What is the dose for Atenolol?

5mg q10min IV

What is the dose of metoprolol?

1mg q5min (Given in 5mg "blocks")

What two PO formulations of metoprolol are there? What are their E½?

- Metoprolol Tartate = E½: 2-3 hr (bid-qid) - Metoprolol Succinate = E½: 5-7hr (qd)

What β blocker would be used to treat intubation stimuli?

Esmolol

What are the onset and offset of esmolol?

Onset: 5 min Offset: 10-30min

What is the initial dose for esmolol?

20-30mg IV

Caution should be taken when giving esmolol with which two conditions? Why?

- Cocaine and/or epinephrine - Can cause pulmonary edema and cardiac collapse

Are the effects of CCBs and β-blockers additive?

No, synergistic

What two scenarios were given in class for a β1 indication over a non-selective β blocker?

- DM: β2 can cause hypoglycemia by insulin potentiation - Airway: blocking β2 potentiates bronchospasm

What volatile anesthetic will cause the greatest additive depression when combined with a β blocker? The least? Why does this not matter?

- Enflurane = greatest additive depression - Isoflurane = least additive depression - Not significant between 1-2 MAC

What 2ⁿᵈ messengers are potentiated by ⍺₁ agonism? What are the effects?

IP₃ → Ca⁺⁺ release from SR affecting vascular smooth muscle

What occurs with ⍺₂ agonism?

↓ release of NE in the brainstem

Is phenylephrine primarily a venoconstrictor or an arterioconstrictor?

Venous constriction > arterial constriction

Phenylephrine clinically mimics norepinephrine but is....

less potent and longer lasting

What is the normal dosing of phenylephrine?

50-100mcg IV push

What cardiovascular adverse effect results from phenylephrine? How is it resolved?

- Reflex bradycardia - Stopping the drug

What is the ratio of β to ⍺ blockade for Labetalol?

7:1 (more beta effect than alpha)

Is Labetalol a selective β antagonist?

No: non-selective β and selective α1 antagonist

Which of the following receptors does Labetalol antagonize? A. α1 B. α2 C. β1 D. β2

A, C, and D

What is the dose for labetalol? How long would it take to see max effect from IV dose?

2.5 - 5mg IV; 10mg max IV max effect 5-10 min

How does labetalol lower systemic BP?

lowers systemic BP by ↓SVR, reflex tachycardia attenuated by beta blockade

What is the single IV dose for vasopressin?

1-2 units IV

Which of the following drugs would you utilize for a post-carotid endarterectomy with a BP of 214/62 ? Labetalol Esmolol

Esmolol- quick on and off *Labetolol could drop the DBP further*.

Which drug is an indirect acting sympathomimetic?

Ephedrine *Releases NE*

What is the IV push dose of epinephrine? How long does it last?

- 2-8mcg IVpush - 1-5 min

What is the infusion dose of epinephrine for β2 effects?

1-2 mcg/min

What is the infusion dose of epinephrine for β1 effects?

4 mcg/min

What is the infusion dose of epinephrine for predominantly α effects?

10-20 mcg/min

What catecholamine will have the greatest effect on heart rate and cardiac output?

Epinephrine

What catecholamine will have the greatest effect on PVR?

Phenylephrine

What is the single IV push dose for ephedrine?

5-10mg IV

Which SNS agonist can be given IM? What dose? Why would this be done?

- Ephedrine IM 50mg - Long lasting increase in BP for OB patients.

Why does tachyphylaxis occur with ephedrine?

depleted NE stores

What is the preferred sympathomimetic for parturient patients? Why?

Ephedrine (It doesn't affect uterine blood flow)

How does phenylephrine compare to ephedrine in parturient patients?

Phenylephrine has similar effects but some data shows additional benefit of a higher umbilical pH in neonates.

What is the mechanism of action of vasopressin?

Stimulation of vascular V1 receptors → arterial vasoconstriction Also increases renal water reabsorption

What drug would be utilized for catecholamine-resistant hypotension?

Vasopressin

What drug would be used for ACE-Inhibitor induced resistant hypotension?

Vasopressin *Resistant hypotension can occur with both ACEi and ARBs*.

How does Nitric Oxide cause vasodilation? *In broad terms*.

NO → GC → cGMP → inhibits Ca⁺⁺ entry and increased uptake by ER.

How can vasodilators alleviate pulmonary congestion?

By decreasing venous return via venodilation

What does Nitroprusside dissociate on contact with? What is the result?

Dissociates on contact with oxyhemoglobin → methemoglobin, NO, and cyanide released.

What does Sodium nitroprusside vasodilate?

Arterial **and** venous vasculature (more arterial)

What vasodilator absolutely requires arterial line monitoring?

Nitroprusside.

What is the dose of Nitroprusside?

Initial: 0.3 mcg/kg/min Tritrate slowly to 2 mcg/kg/min

When is nitroprusside used?

- Controlled Hypotensive necessary surgeries (aortic, spine, etc.) - Hypertensive emergencies (post CEA's)

What signs would tip you off to possible cyanide toxicity secondary to nitroprusside administration?

- ↑ need for SNP - ↑ SvO₂ - Metabolic acidosis - LOC changes

Where does nitroglycerin work?

- large Coronary arteries - Venous capacitance vessels

Would nitroglycerin increase or decrease preload?

↓ preload

How is tachyphylaxis reversed for nitroglycerin?

drug free intervals (12-15 hr)

What is the nitroglycerin dose?

Initial: 5 - 10 mcg/min

What is the firstline treatment for sphincter of Oddi spasm? What is second?

- Glucagon - Nitroglycerin

What are the indications for nitroglycerin?

- Acute MI - Controlled Hypotension - Sphincter of Oddi spasm - Retained placenta

How does hydralazine work?

↓ Ca⁺⁺ release and systemic arterial vasodilation

When does hydralazine peak? What is it's half-life?

- Peak: 1 hour - ½-life: 3-7 hours

What is the initial dose of hydralazine?

2.5mg IV

What are the three categories of CCBs? Where do each interact?

-Phenylalkylamines & Benzothiazepines: AV node -Dihydropyridines: arteriolar beds

How do CCBs generally work?

Bind and block L-type VG-Ca⁺⁺ channels thus ↓ Ca⁺⁺ influx.

CCBs will ______ blood pressure and ________ coronary blood flow.

decrease; increase

Which CCB has the greatest coronary artery dilation and least myocardial depression?

Nicardipine

What is the dose of nicardipine?

5mg/hr (↑2.5mg x4hr) max 15mg/hr

What is the formula for MAP?

[DBP + 1/3(SBP-DBP)] or [(2DBP+SBP)/3]

Anesthesia Adjuncts (Exam IV) Flashcards

(85 cards)