Neuromuscular Blocking Drugs Flashcards
What is the definition of NMBDs?
Interrupts transmission of nerve impulses at the neuromuscular junction
What is the result of using NMBDs?
Complete paralysis of striated muscles while consciousness is retained, there is no analgesia, and spontaneous respiration ceases
What is the major indication for use of NMBDs?
Aid for intraocular or corneal surgeries; most common indication in vet med
What are minimum requirements when using NMBDs?
Use mechanical ventilation; monitor CV, respiratory systems, oxygenation, and neuromuscular function
When using NMBDs, what are the only possible responses of the patient to noxious stimuli?
Tachycardia and high blood pressure
What is the MOA of NMBDs (depolarizing vs non-depolarizing)?
Depolarizing: act as an agonist on the nicotinic ACh receptors, causing muscle membrane depolarization
Non-depolarizing: act as a competitive antagonist on the nicotinic ACh receptors, stabilizing muscle membranes
What is the proper order in which muscle relaxation occurs with NMBDs?
Ocular muscles > all other muscles > diaphragm
What type of drugs can potentiate NMBD effect?
Inhalation anesthetics; aminoglycoside antibiotics; local anesthetics; cardiac anti-arrhythmic drugs; diuretics; Mg
What other factors can influence the depth of NMBD effect?
Hypothermia; electrolyte abnormalities; acid-base disorders; age; thermal burn
True/False: atracurium and succinylcholine are more like to cause histamine release.
True
Which of the following NMBDs is a depolarizing NMBD?
Atracurium Cisatracurium Succinylcholine Rocuronium Vecuronium
Succinylcholine
What type of NMBD are atracurium, cisatracurium, rocuronium, and vecuronium?
Intermediate-acting (10-30 min) non-depolarizing NMBDs
What is the Phase-1 block of succinylcholine?
Sustained muscle membrane depolarization initially leads to muscle fasciculation, then the post junctional Na channels close and remain closed until SCh is present, preventing neuromuscular transmission
What is the Phase-2 block of SCh?
Similar to the non-depolarizing blockade; occurs after prolonged or high dose of SCh administration
What are adverse effects of SCh?
Cardiac arrhythmias; hyperkalemia; fasciculation, myalgia, myoglobinuria; elevated intra-ocular and intra-gastric pressures; may trigger malignant hyperthermia
What is the major metabolite of atracurium, and what does it cause?
Laudanosine; may cause seizures
True/False: atracurium may cause histamine release at high doses.
True
What is used to antagonize rocuronium?
Sugammadex
True/False: rocuronium recovery is relatively slow.
False. Recovery is fast.
How do you monitor neuromuscular function when using NMBDs?
Monitoring with peripheral nerve stimulators is necessary
What is an acceptable neuromuscular recovery from NMBDs?
TOF ratio >/= 0.9
True/False: peripheral nerve stimulators are commonly combined with an accelerometer.
True. Accelerometer quantifies the extent of movement.
What sites are used for stimulation with a peripheral nerve stimulator?
Dogs and cats: peroneal and ulnar nerves
Horses: facial and peroneal nerves
What are the two stimulation patterns used?
Single twitch and Train of four (TOF)
What is the single twitch stimulation pattern?
Used at 1 Hz before injecting NMBD to determine the minimum necessary current to evoke maximal movement response; called supra maximal stimulus
What is the TOF stimulation pattern?
Four stimuli following each other; with complete blockade, no response at all; with partial blockade, first twitch is largest and the last is smallest; ratio between first and last twitch is the TOF ratio
True/False: it is generally safe to antagonize a depolarizing NMBD.
False. Antagonizing a depolarizing NMBD is unpredictable and not recommended.
What is used to antagonize a non-depolarizing NMBD?
Acetylcholinesterase inhibitors (edrophonium, neostigmine)
Which AChE inhibitor is preferred, and why?
Edrophonium is preferred over neostigmine because there are less side effects
What is Sugammadex?
Chelating agent used for reversal of rocuronium.
