6- Neuromuscular Blocking Agents Flashcards
Where do NA+ ion bind when an action potential is undergoing?
The presynaptic neuron axon terminal membrane
What ion voltage gates are open after NA+ channels are open?
Ca2+
What does Ca2+ do?
triggers the fusion of acetylcholine vesicles with the presynaptic membrane
The binding of acetylcholine to the postsynaptic membrane chemically opens what gates?
Na+ gate channels that depolarize the postsynaptic membrane
What happens to acetylcholine in the synaptic cleft after the action potential?
Broken down by acetylcholinesterase into Acetyl CoA + choline
What happens to the acetylcholine in the presynaptic cell after an action potential?
Synaptic transmission (acetylcholine and vesicles are recycled
What happens to acetylcholine once they enter the synaptic cleft?
Bind to receptors on the postsynaptic membrane
The action potential travels along what tubule
T-tubules
What happens after the action potential travels along the T-tubules?
It induces the Sarcoplasmic reticulum
What is released once the action potential induces the Sarcoplasmic reticulum?
More Calcium
What does Ca2+ bind to?
Troponin
What does Troponin relieve?
It relieves tropomyosin from the myosin binding site
How does myosin bind to actin?
Via ATP
What happens when ATP is hydrolyzed?
a power stroke occurs
During a power stroke, what is brought together?
Z lines
When Z lines are brought together what does it lead to?
Muscle contraction
During a normal action potential what neurotransmitter binds to the Nicotinic ACh-receptor?
ACh
During a (depolarizing muscle relaxant) action potential what neurotransmitter binds to the Nicotinic ACh-receptor?
Depolarizing muscle relaxant
What breaks down the depolarizing muscle relaxant and where is it returned?
broken down by pseudocholinesterase and returned to the BLOOD
What type of drug is Succinylcholine?
Depolarizing NMBA
What is the onset of IV Succinylcholine?
30 - 60 seconds
What are the routes of administration of Succinylcholine and what dose?
IV 1 mg/kg
IM 4 mg/kg
To what receptors does Succinylcholine bind?
Nicotinic postsynaptic receptors
What signs are seen upon the binding of Succinylcholine to the Nicotinic receptors?
1- Depolarization
2- Fasciculation
3- Flaccid paralysis
True or False:
Fasciculation ceases when all nicotinic receptors are bound to nicotinic receptors?
True
What age group is at increased risk of muscle pain with muscular builds after SCh?
Adolescents
What is the duration of Succinylcholine?
3-5 minutes
What are the clinical effects of Succinylcholine paralysis?
1- Adductor pollicis (10 minutes)
2- Diaphragm (5 min)
What is the first dose consideration seen with Succinylcholine?
Bradycardia
What is the second dose consideration seen with Succinylcholine?
Asystole
How do you attenuate to Succinylcholine induced Bradycardia and asystole? And what signs are sometimes seen?
Administer Atropine or glycopyrrolate
Increase in catecholamine release and tachycardia
What type of trigger is Succinylcholine?
Malignant hyperthermia
How does Succinylcholine lead to MH?
Increase in serum potassium by 0.5-1 mEq/L
Hyperkalemia
What type of patients needs extra care with Succinylcholine?
Pts that aren’t normokalemic rental faliure patients
What is a phase II block?
1- continuous activation of ACh receptors which leads to ongoing shifts of NA+ into the cell and K+ out of the cell
2- Receptors do not respond appropriately to ACh, neuromuscular blockade is prolonged
True or False:
Succinylcholine is incriminated as the trigger of allergic reactions more often than any other drug used in anesthesia?
True
approcimately 1:5,000 - 1:10,000
Abnormality of pseudocholinesterase activity leads to prolonged paralysis in two abnormal ways?
1- Hetrozygous -> 15 min more delay in paralysis
2- Homozygous -> 1-2 hours of delay
- Homozygous population is 1:3,000 - 1:10,000
How is pseudocholinesterase abnormality tested?
Dibucaine number (genetic testing)
Normal 80
Hetro 50
Homo 20
True or False:
Non-depolarizing and Depolarizing Neuromuscular blockers bind differently to the nicotinic receptors?
False
The only difference:
Depolarizing such as Succinylcholine is returned into the BLOOD
Non depolarizing such as Rocuronium is returned to the LYMPH
Non-depolarizing agents are classed based on chemical structure into?
1- Aminosteriods (Rocuronium, Vecuronium pancuronium)
2-Benzylisoquinolinium (mivacurium, atracurium, cisatracurium)
For pancuronium, what is the bolus dose, and where is metabolized?
0.05-0.1 mg/kg
(Nondepolarizing Aminosteriods)
renal
For vecuronium, what is the bolus dose, and where is metabolized?
0.08- 0.1 mg/kg
(Nondepolarizing Aminosteriods)
Hepatic
For Rocuronium, what is the bolus dose, and where is metabolized?
0.6 - 1 mg/kg
(Nondepolarizing Aminosteriods)
Hepatic
For Atracurim, what is the bolus dose, and where is metabolized?
0.4- 0.5 mg/kg
(Nondepolarizing Benzylisoquinolinium )
Hoffmann reaction
For Cisatracurium, what is the bolus dose, and where is metabolized?
0.1-0.2 mg/kg
(Nondepolarizing Benzylisoquinolinium )
Hoffmann reaction
For Succinylcholine, what is the bolus dose, and where is metabolized?
1 mg/kg
(depolarizing)
Plasma cholinesterase
How many stimuli are delivered and at what time/frequency for the Train of Four Monitoring?
4 stimuli
2HZ over 1.5 seconds
What is the percent of blocked receptors for the Train of Four Count?
TOFC of 1= >95% of receptors blocked
TOFC of 2= 85-90% of receptors blocked
TOFC of 3= 80-85% of receptors blocked
TOF of 4= 70-75% of receptors blocked
How is the estimated degree of the block calculated?
ratio of T4/T1
Majority of Surgeries require what percent of block?
80%
TOFC of 3
What are the clinical signs of the level of paralysis?
1- Sustained head lift = 50% blockade
2- Hand grasp= 50% blockade
3- TV > 5 ml/kg = 80% blockade or less
What areas precede the adductor pollicis by 1-2 min following an NMBD?
Larynx and orbicularis oculi
True or False:
Muscles with relatively high blood flows have faster onset and recovery?
TRUE
such as diaphragm, masseter, and laryngeal muscles
True or False:
the effectiveness of reversal agents depends directly of the degree of recovery present and should be given on when 4 twitches are visible “ preferably measured at the adductor pollicis”?
TRUE
Why isn’t the presence of spontaneous ventilation considered a sign of adequate neuromuscular recovery?
Because the diaphragm recovers earlier than the much more sensitive upper airway muscles
EX: Geniohyoid recovers on average at the same time as the adductor pollicis
Reversal agents are divided into two types?
Anticholinesterases
Sugammadex
What is the MOA of Anticholinesterases?
Impairs the breakdown and rate of ACh which in return allows the excess ACh to displace the non-depolarizing NMBA
What is the dose of Neostigmine?
0.05 mg/kg
max 5mg
When Neostigmine is given, Glycopyrrolate is given?
0.2 mg of Glyco for every 1 mg of neo
max 1mg
Preceding NEO, Atrpine/ Edrophonium given, what crisis could result?
Acute cholinergic crisis
How does Sugammadex work?
it encapsulates nondepolarizing steroidal NMBAs in a 1:1 ratio
What should you tell your female patients after giving Sugammadex?
Decreased effectiveness of hormonal birth control
what is the dose of Sugammadex?
Based on the depth of NMBA
TOF> 2 2mg/kg
TOF=1 4mg/kg
TOF=0 16mg/kg (in this case Roc can not be used for 24 hrs)
what is the emergency dose of Sugammadex?
16mg/ kg
