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Exam 2
Neuromuscular blocking drugs
27
Veterinary Medicine
Professional
04/01/2016

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Term
What are the general characteristics of neuromuscular blocking drugs?
Definition
-paralytic agents: msut ventilate the patient!
-provid skeletal muscle relaxation
-often used as adjuncts during anesthesia
-hypothermia
-do not cross BBB or placenta
Term
True or False: Neuromuscular Blocking Drugs produce analgesia and unconsciousness htus can be used on an awake patient.
Definition
-FALSE, do NOT produce analgesia or unconsiousness and CANNOT be used on consious patient
Term
What are the two mechanisms for skeletal muscle relaxation?
Definition
-interference with ACh transmission in somatic nervous sysstem
-enhanced activity of endogenous inhibitory mechanisms
Term
What are the two components of interference with ACh transmision in somatic nervous system?
Definition
-presynaptically
-postsynatpically
Term
What are the two presynaptic mechanisms of interference with ACh transmission for skeletal muscle relaation? Give an example of each.
Definition
-Inh of ACh synthesis: Hemicolinium
-Inh of ACh release: Botulinum toxin
Term
What are the two postsynaptic mechanisms of itnerference with ACh transmission for skeeltal muscle relaxation? Give an example of each.
Definition
-Persistent depolarization: succinuylcholine
-Competitive (non-depolarizing) blockade of ACh receptors: curare
Term
What are the two drug types that give enhanced activity of endogenous inhibitory mechanisms and how do they work specifically?
Definition
-Benzodiazepines: GABA-ergic
-Guaifenesin: depression transmission through polysynaptic (interneuron) pathways
Term
What are the indications for use of NMBs?
Definition
-facilitate intubation: more for humans
-control ventilation
-facilitate fracture reduction: traction would be more useful
-prevent eye rotation during eye surgery
-as a part of balanced anesthesia: especially in humans
Term
What are the 4 types of neuromuscular blockade and give an example of I and II?
Definition
-Phase I: depolarizing block (Ex: succinylcholine)
-PHase II: competetive (non-depolarizing) block (curare-like)
-mixed: any combo of Phase I and II
-Dual block: occurs with excessive amounts or times of exposure to depolarizing agents
Term
What is the sequene of muscle relaxation after neuromuscular blockade?
Definition
-oculomotor m => palpebral m => facial m => tongue and pharynx => jaw and tai => limbs => pelvis m => caudal abdominal m => cranial abdominal m => intercostal n => larynx => diaphragm
Term
What are the 4 main factors that inlfuence nneuromuscular blockade?
Definition
-temperature
-acid-base balance-fluid and electrolyte imbalance
-antibiotics
Term
How does temeprature affect neuromuscular blockade?
Definition
-hyperthermia antagonizes competitive (non-depolarizing) blockade but enhaces/prolongs depolarizing blockade
-hypothermia prolongs competitive (non-depolarizing) NMB
Term
How does acid/base balance influence neuromuscular blockade?
Definition
-respiratory acidosis augments competitive (non-depolarizing) NMB
-inadequate reversal of competitive block = resp acidosis enhances blockade = viscious cycle
Term
How does fluid and electrolyte imbalance influence neuromuscular blockade?
Definition
-hypokalemia and hypomcalcemia potentiate competitive NM
-dehydration inc plasma conc of normal dose of competitive NMB, augmenting effect
-high Mg blood levels enhance both depolarizing and competitive NMBs
-NMB that occurs with electrolyte imbalance is referred to as a non-acetylcholine block
Term
How do antibiotics influence neuromuscular blockade? Examples?
Definition
-may potentiate competitive NMB
-ex: Neomycin, streptomycin, gentamycin, kanamycin, paromycin, viomycin, polymyxin A and B, colistin, tetracycline, lincomycin, clindamycin
Term
What are the characteristics of a depolarizing neuromuscular blockade?
Definition
-paralysis is die to prolonged depolarization of motor endplate
Term
How is paralysis of a depolarizing neuromuscular blcoade terminated?
Definition
-termination of paralysis is due to metabolism of pseudocholinesterase => plasmachilinesterase
Term
IS a depolarizing neuromuscular blockade reversible? Give an example of a depolarizing NMB.
Definition
-NO
-ex: succinylcholine
Term
Compare Succinylcholine and Acetylcholine regarding the following:
a) duration of motor endplate depol
b) hydrolyzed by enzyme _______
c) split products
d) location of enzyme
Definition
a) S: 1-10 min & A: milliseconds b) S: plasmachilesterase & A: acetylcholinesterase
c) S: succinylmonocholine chloride and succinic acid & A: choline and acetate
d) S: plasma (pdc in liver) & A: nerve, muscle, RBCs
Term
What are the adverse effects of succinylcholine?
Definition
-hyperkalemia: use with caution in burn victims, patients receiving digitalis, massive m trauma victims
-muscle soreness
-histamine release
-potential bradycardia or tachycardia an d hypertension
-malignant hyperthermia (with halothane)
-deficiency/abnormal plasmacholinesterases (prolonged blockade)
Term
What are the contraindications for using a depolarizing NMB?
Definition
-liver disease, chronic anemia, or malnutirtion decrease plasmacholinesterases
-hyperkalemia
-organophosphates
--glaucoma, penetrating eye wound
Term
What are the characteristic so f a ceompetitive neuromuscular blockade?
Definition
-competitive with ACh for postysynaptic Rc (no muscle fasciculation)
Term
What are some exampless of a competitive NMB?
Definition
-Pancuronium, atracurium, cis-atracurium
Term
What type of drugs can be used to reverse a competitive blockade?
Definition
-Edrophonium
Term
Why should an anticholinegic be administered prior to reversal of a competitive blockade?
Definition
-to block muscarinic effects (bradycardia, salivation, bronchial secretions)
Term
The reversal drugs for competitive blockade cna also be used to diagnose and treat what disease?
Definition
-myasthenia gravis
Term
What does a respirometer measure?
Definition
-tidal volume
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