NMB agents Flashcards
(49 cards)
Drugs that affect skeletal muscle function are grouped as
- Those used during surgery and in ICU for paralysis
- Those used to reduce spasticity in a variety of painful conditions
NMB interfere with
transmission at the neuromuscular and plate= less CNS activity
Adjuncts are used during general anesthesia to
optimize surgical conditions, facilitate ET intubation, and ensure adequate ventilation
Neuromuscular blocking drugs structurally resemble these agents
- Depolarizing: succiylcholine
- Non-depolarizing isoquinolones: Tubocurarine
- Non-depolarizing steroid derivatives: pancuronium
Each subunit of nicotinic Ach receptor contains
4 helical domains; M1-M4
-M2 lines the channel pore
the N termini of two subunits of a full nACh receptor cooperate to form
two distinct binding pockets for ACh, at the a-B and B-a subunit interfaces
How do non-depolarizing agents work
Prevent opening of the channel when bound to the receptor
How do depolarizing agents work
Occupy the receptor AND block the channel
How are NMB agents administered
parenterally!
Rapid initial distribution followed by slow elimination
What happens to drugs excreted by the kidneys
They have a longer half life= longer duration of action
What happens to drugs excreted by the liver
They have a shorter half life= shorter duration of action
What is the MOA of Succinylcholine (depolarizing NMB)
- nACh receptor agonist= depolarizes and may stimulate receptor
- 2 molecules must bind to open the ion channels causing depolarization and generation of muscle fasciculations
- b/c it is not hydrolyzed well, succ. stays at receptor causing sustained local muscle end plate depolarization
- Na channels remain inactive for a long time
- Refractory to further release of ACh= flaccid paralysis
Toxicities of succinylcholine include
Hyperkalemia
increased intra-abdominal and intra-ocular pressure
post-op muscular pain
Arrhythmias
Succinylcholine is a great drug for
ET intubation!
What are non-depolarizing NMB agents used for
facilitating intubation
maintaining skeletal muscle relaxation during surgery
What is the MOA of non-depolarizing NMB agents
1+ molecule binds to the receptor to competitively inhibit normal channel activation and muscular depolarization
This results in flaccid paralysis
Which muscles are affected first with non-depolarizing agents
Small rapidly moving muscles first (face and eyes)
Then fingers, toes, extremities, trunk, intercostals
Last: diaphragm
Reverse sequence as paralysis resolves
(same for succinyl choline)
How can you shorten duration of NMB drugs
Administer cholinesterase inhibitors
This increases the amount of ACh in the synaptic cleft
How can you counteract the arrhythmias associated with cardiac muscarinic agonists (non-depolarizing drugs)
Give Atropine or Glycopyrolate WITH cholinesterase inhibitors
What would reduce the ability of cholinesterase inhibitors to reverse the NMB agents
high doses of non-depolarizing agents causing blocked ion channels at the end plate
Non-depolarizing agents interact with these drugs
- Aminoglycosides (genta, tobra): inhibit ACh release from nerves by competing w/ calcium AKA they enhance the NMB
- CCB (verap, dihydro): enhance effects of NMB
What is inhalation anesthesia
anesthesia induced by inhalation of a drug
What is minimum alveolar anesthetic concentration
alveolar concentration of an inhaled anesthetic required to prevent a response to standard painful stimulus in 50% of patients
What is analgesia
State of decreased awareness of pain, sometimes with amnesia
