Neuromuscular Blocking Agents Flashcards
What is the triad of anesthesia with NMB agents?
Unconsciousness (hypnosis)
Analgesia
Muscle relaxation (loss of reflex)
What are NMB agents recommended for in vet med?
Intra-ocular surgeries
Intra-cranial surgeries
Thoracotomy
Mechanical ventilation
What are the 2 families of cholinergic receptors?
Muscarinic
Nicotinic
What is the neurotransmitter for cholinergic receptors?
Acetylcholine
True or False: somatic nicotonic receptors are different than autonomic nicotinic receptors
False, they are identical
What is required to stimulate a nicotinic receptor?
2 Ach (α subunits) molecules
What is an example of a non-competitive, depolarizing NMB?
Succinylcholine
What is the first phase of non-competitive, depolarizing NMBs? Second phase?
1: muscle depolarization (> [K])
2: muscle relaxation
When are non-competitive depolarizing NMBs unsafe?
With conditions predisposed to high serum K such as renal disease, HYPP horses, and burn victims
What can non-competitive depolarizing NMBs cause?
Acute increase in IOP and ICP
How do competitive, non-depolarizing NMBs work?
Takes one molecule to block somatic nicotinic receptors, interferes with Ach binding
What is the clinical effect of competitive, non-depolarizing NMBs?
At least 70% somatic nicotinic receptors blocked results in clinical loss of somatic muscle tone
What happens if NMB > Ach?
Paralysis
What happens if Ach > NMB?
Muscle tone
What are examples of benzylisoquinolones?
Curare
cis-Atracurium
What was the first known NMB alkaloid?
Curare
How is curare eliminated?
Hofmann elimination- temperature and pH dependent
What are examples of steroids that are NMB agents?
Pancuromium
Vencuronium
Rocuronium
What should be done once a patient is paralyzed?
Ventilate
Monitor the degree of block
What is NM block monitoring done via?
Peripheral nerve stimulator
What are the peripheral nerves stimulated with monitoring a NM block?
Common peroneal
Ulnar
Facial
What is muscle contraction/movement directly proportional to?
Number of active somatic nicotonic receptors
True or False: it is important to determine normal peripheral nerve stimulation prior to giving NMB agent
True
What are the modes of nerve stimulation?
Tetanic
Single twitch
What is the train of four?
4 single twitches 0.5 seconds apart (2 seconds)
2 Hz
Compare T4:T1 ratio; 1 = no block, smaller ratio, the greater the block
T4 fades first and recovers last
Used to determine/adjust dose regimen, recovery
What are examples of NMB reversal agents ?
Acetylcholinesterase inhibitors: neostigmine, edrophonium
Rocuronium specific reversal: Sugammadex
What do Ach-esterase inhibitors do?
Results in decrease in Ach metabolism thus increase in numbers of Ach molecule receptor interaction
Outcompetes with NMB agent
Return of muscular tone
What is required for Ach-esterase inhibitors?
Some muscular tone already present
True or False: Ach-esterase inhibitors are nicotinic cholinergic specific
False, the result is an increase in Ach interaction at both nicotinic and muscarinic receptors
What are side effects of Ach-esterase inhibitors?
Salivation
Bradycardia
How can the side effects associated with Ach-esterase inhibitors be prevented?
Anticholinergic administration prior to Ach-esterase administration
What must the patient be able to do prior to ending controlled ventilation?
They must be able to ventilate sufficiently
