Neuromuscular Blockers - Quiz 7 Flashcards by Donny Le

How does Acetylcholine bind to the Nicotinic Receptor?

The positively charged Nitrogen binds to both alpha subunits of the nicotinic receptor, allowing Sodium to enter.

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Which enzyme is responsible for the synthesis of Acetylcholine?

Choline Acetyltransferase

Choline + Acetyl CoA –> Acetylcholine

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Which Autonomic System does Acetylcholine Activate?

Both

Primarily Rest & Digest, but also Kick starts the Sympathethic Nervous System

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What deactivates Acetylcholine?

Acetylcholinesterase break down ACh into choline & acetate

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Why are Neuromuscular Blockades used?

Cause paralysis to reduce complications d/t movement & help with intubation

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What percentage of Suppression of Single Twitch Response is adequate for Surgery?

90%

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What is the difference b/t Depolarizing & Non-Depolarizing Agents?

Depolarizing: constantly stimulates muscle fiber and cant respond to ACh

Non-Depolarizing: Competetively blocks ACh from receptor

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What is ED₉₅

NMB dose with non volatile anesthetic needed for 95% supression of single twitch during

ED₉₅ is much less when used w/ gas

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How much NMB is needed for Tracheal Intubation in terms of ED₉₅?

2x ED₉₅

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What is the Order of Effect of NMBs?

Small quick moving muscles first (Eyes, Fingers)

then

Abdomen (Diaphragm) last

Reverses in reverse order d/t blood flow

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What is the effect of NMBs at the Laryngeal Muscles vs Peripheral Muscles?

More Rapid & Less Intense @ Laryngeal Muscles

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What are indicators of Laryngeal Relaxation when using NMBs?

Orbicularis Oculi - good indicator

Adductor Pollicis - poor indicator

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What do the Non-Depolarizing NMBs break down into?

Benzylisoquinolinium - Histamine Release

Aminosteroid

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What does the Quarternary Ammonium part of the NMB do?

Makes NMB highly ionized & water soluble - stays in blood

Does not cross into CNS or Placenta

Cant Give Orally

Binds to Alpha Subunits

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What does it mean for NMBs to be non selective?

They will effects at both Autonomic Nicotinic & Cardiac Muscarinic receptors

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Which Non-Depolarizing NMBs are Benzylisoquinoliniums?

NMBs that end with -curium

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Which Non-Depolarizing NMBs are Aminosteroids?

NMBs that end with -curonium

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Which Non-Depolarizing NMBs are Long Acting?

Pancuronium

Pipercuronium

Doxacurium

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Which Non-Depolarizing NMBs are Intermediate Acting?

Vecuronium

Rocuronium

Atracurium

Cisatracurium

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Which Non-Depolarizing NMBs are Short Acting?

Mivacurium

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What is the only Depolarizing NMB used?

Succinylcholine

Intense Rapid Paralysis

Onset: 30-60 seconds

Duration: 3-5 minutes

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What is the Mechansim of Action of Succinylcholine?

Binds to one or both alpha subunits @ Nicotinic receptor

Mimics ACh

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What is the Mechansim of Action of Succinylcholine?

Binds to one or both alpha subunits @ Nicotinic receptor
Mimics ACh, but longer duration d/t slower hyrdrolysis
Hyperpolarizes Receptor & no more ACh can activate the receptor
Big Na⁺ influx causes Efflux of K⁺

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What happens in Phase I of Block w/ Succinylcholine?

Depolarizing receptor stimulation
↓Contraction to single twich
↓Ampltidude of continuous stimulation
TOF > 0.7
Muscle twitches @ onset

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What happens in Phase II of Block w/ Succinylcholine?

Acts like Non-Depolarizer ACh can no longer act

How do Plasma Cholinesterase affect Succinylcholine?

Break SCh down to weak metabolite Give Neostigmine to reverse for pts w/ liver disease

How does High Estrogen & Reglan affect Succinylcholine?

High Estrogen reduces Cholinesterase levels Reglan Inhibits Cholinsterase Build up of Succinylcholine

How does Obesity affect Succinylcholine?

Obese pt's have more Cholinesterase and may reduce effects of SCh

How does Atypical Cholinesterase affect Succinylcholine?

May increase Duration of SCh from 10 minutes to 3+ hours Test w/ Dibucaine

How can side effects of Succinylcholine be reduced?

Pretreat with small dose of Non-Depolarizing NMB Non effective for Hyperkalemia

What kind of Arrythmias might Succinylcholine cause?

Bradycardia, Junctional Rhythm, Sinus Arrest d/t muscarinic receptors Worsens w/ 2nd dose in 5 min Give Atropine (May also see increased HR & BP)

Who is most at risk for Succinylcholine-induced Hyperkalemia?

Boys w/ muscular dystrophy or can't create muscle movement so nicotinic receptor upregulation happens Hyperkalemia can last from 96 hrs to 2 years

What is a side effect of Succinylcholine r/t muscles?

Myalgias in Neck, Back, and Abdomen

Where in the body might you see Increased Pressures from Succinylcholine?

Intragastric - Aspiration Intraocular Intracranial All Transient and Uncommon

What is the Mechanism of Action for Non-Depolarizing NMBs?

Competes with ACh for Nicotinic Receptors ↓Single Twitch TOF \< 0.7 Posttetanic Poteniation Antagonism by Anticholinesterase

What are the CV effects of Non-Depolarizing NMBs?

Atracurium & Mivacurium - Histamine Release Pancuronium - Blocks Muscuranic Receptor - ↑HR Blocks Nicotinic - Possible ↓HR & ↓BP Mostly CV Stable

What is a consideration after using Non-Depolarizing NMBs?

Critical Myopathy Long term paralysis on vent More common w/ Aminosteroids (especially w/ steroids) Can last for an unknown time

What is the main causes of Allergic reactions in the OR?

Neuromuscular Blocker Higher risk for Females More Nitrogen in the molecule = higher risk for allergic rxn

Which dementia meds inhibit Cholinesterase?

Razadyne Aricept (Donepezil) Exelon (Rivastigmine)

What Drugs Enhance NMBs?

* Anesthetic Gas * Local Anesthetics * Antiarrythmics - Lidocain, Quinidine * Aminoglycosides - Gentamicin * Diuretics * Mag & Lithium

How does Phenytoin effect the use of Vecuronium?

Reduce Duration

How do Cyclosporines affect NMBs?

Prolongs Block

How does Hypothermia affect NMBs?

Prolongs Duration For every degree change from 36C, prolongs block by 10-15 min

How does Hypokalemia affect Succinylcholine & Non-Depolarizing NMBs?

Sux: Resistance NDNMB: ↑Sensitivity

How does Hyperkalemia affect Succinylcholine & Non-Depolarizing NMBs?

Sux: ↑Effect NDNMB: Opposes

How do Burn Injuries affect Non-Depolarizing NMBs?

Resistance to NDNMBs

Would a patient who is already has Hemiplagia need more or less of a NMB dose?

More d/t upregulation of receptors

How are Infants & Elderly affected by NMBs?

Infants: Reduce Dose, Shorter Onset, Longer Recovery Elderly: Longer Duration

How many Nitrogens does Pancuronium have?

Two - Bisquartenary

What is the ED₉₅, Onset, and Duration of Pancuronium?

ED₉₅: 70 mcg/kg Onset: 3-5 min Duration: 60-90 min

How is Pancuronium Eliminated from the Body?

80% in urine - renal failure reduces to 50% Half Potent Metabolite Liver Disease prolongs duration

What are the CV effects of Pancuronium?

Most CV effects out of all Long Acting NMBs ↑HR, ↑BP, ↑MAP d/t vagal block Big risk for Dysrhythmias when given with Digoxin

How many Nitrogens does Doxacurium have?

Two - Bisquaternary

What is the ED₉₅, Onset, and Duration of Doxacurium?

ED₉₅: 30mcg/kg Onset: 4-6 min Duration: 60-90 min

What is the difference b/t Doxacurium & Pancuronium?

Less CV effects More Metabolites

Why are Intermediate NMBs preferred?

Better Clearance Shorter Duration Faster Recovery Predictable

What is the Priming Principle for NDNMBs?

Give baby dose of NMB to bind spare receptors Next dose will have rapid effect

What is the ED₉₅, Onset, and Duration for Atracurium?

ED₉₅: 0.2mg/kg Onset: 3-5 min Duration: 20-35 min

How is Atracurium Eliminated?

80% Protein Bound Rapid Clearance

What is Hoffman Elimination?

Relates to Atracurium & Cisatracurium Does not Rely on Kidneys or Liver 3 Steps: Hoffman --\> Hydrolysis --\> Hoffman **Laudanosine** Metabolite

What is Laudanosine and what does it do?

Inactive Metabolite of Atracurium & Cisatracurium from Hoffman Elimination CNS Stimulant Peripheral Vasodilation Increase MAC of Gas

Whare are the CV effects of Atracurium?

**Generally Safe** but @ 3x ED95 ↑HR & ↓MAP Histamine Release - use H1/H2 Blocker

What are some dosing considerations when giving Atracurium to Infants & Elderly?

Infants: Half Dose - More Sensitive & More Rapid Clearance Elderly: No dose adjustments

How does Cisatracurium compare with Atracurium?

Pretty much the same Less CV Effect No Histamines Prolong Duration in Obese

How many Nitrogen groups does Vecuronium have?

One - Monoquaternary

How is the elmination of Vecuronium different from Atracurium & Cisatracurium)

Relies on Liver & Kidneys More Lipid Soluble Half Potent Metabolite then Very Weak 2nd Metabolite

What are the CV effects of Vecuronium?

No Histamine More Stable than Cis & Atracurium

How man Nitrogen groups does Rocuronium have?

One - Monoquaternary

What is the ED₉₅, Onset, and Duration for Rocuronium?

ED₉₅: 0.3 mg/kg **Onset: 1-2 min** Duration: 20-35 min

How does giving 3-4x ED₉₅ dose affect Rocuronium?

Speeds up Onset & Increase Duration

How is Rocuronium eliminated?

Relies on Liver and Kidneys

What are the CV effects of Rocuronium?

Same as Vecuronium CV Safe No Histamines

What is the ED₉₅, Onset, and Duration for Mivacurium?

ED₉₅: 80 mcg/kg Onset: 2-3 min **Duration: 12-20 min**

How is Mivacurium Eliminated?

Cholinesterase Effected by Liver & Kidneys Rapid Spontaneous Recovery

What are the CV effects of Mivacurium?

Generally Safe but at 3x ED₉₅: Histamine Release, ↓MAP & Bronchospasm