Neuromuscular Blockers - Quiz 7 Flashcards
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.
Which enzyme is responsible for the synthesis of Acetylcholine?
Choline Acetyltransferase
Choline + Acetyl CoA –> Acetylcholine
Which Autonomic System does Acetylcholine Activate?
Both
Primarily Rest & Digest, but also Kick starts the Sympathethic Nervous System
What deactivates Acetylcholine?
Acetylcholinesterase break down ACh into choline & acetate
Why are Neuromuscular Blockades used?
Cause paralysis to reduce complications d/t movement & help with intubation
What percentage of Suppression of Single Twitch Response is adequate for Surgery?
90%
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
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
How much NMB is needed for Tracheal Intubation in terms of ED95?
2x ED95
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
What is the effect of NMBs at the Laryngeal Muscles vs Peripheral Muscles?
More Rapid & Less Intense @ Laryngeal Muscles
What are indicators of Laryngeal Relaxation when using NMBs?
Orbicularis Oculi - good indicator
Adductor Pollicis - poor indicator
What do the Non-Depolarizing NMBs break down into?
Benzylisoquinolinium - Histamine Release
Aminosteroid
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
What does it mean for NMBs to be non selective?
They will effects at both Autonomic Nicotinic & Cardiac Muscarinic receptors
Which Non-Depolarizing NMBs are Benzylisoquinoliniums?
NMBs that end with -curium
Which Non-Depolarizing NMBs are Aminosteroids?
NMBs that end with -curonium
Which Non-Depolarizing NMBs are Long Acting?
Pancuronium
Pipercuronium
Doxacurium
Which Non-Depolarizing NMBs are Intermediate Acting?
Vecuronium
Rocuronium
Atracurium
Cisatracurium
Which Non-Depolarizing NMBs are Short Acting?
Mivacurium
What is the only Depolarizing NMB used?
Succinylcholine
Intense Rapid Paralysis
Onset: 30-60 seconds
Duration: 3-5 minutes
What is the Mechansim of Action of Succinylcholine?
Binds to one or both alpha subunits @ Nicotinic receptor
Mimics ACh
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+
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
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
