NMBDs Dr. Ambrisko Flashcards
Definition of Neuromuscular Blocking Drugs
Paralysis of striated muscles
Consciousness is retained
No analgesia
Spontaneous respiration ceases
Animal welfare issue
Indications for use of NMBDs
Position the eyeball centrally
most common indication in vet. med.
In balanced anesthesia what is a common difference between use in Veterinary medicine & Human
Human medicine uses NMDBs for immobility
whereas in Veterinary medicine we use 1 MAC inhalant anesthetic gas
When using NMBDs what is the minimum requirements needed during use
Use mechanical ventilation
Monitor CV, resp, oxygenation & neuromuscular functions
Tachycardia & high BP is the only sign they can show in response to noxious stim when NMBDs are used!
Contraindications for using NMBDs
If no possiblity to ventilate & monitor pt
If pt remains conscious - conscious experience of complete muscle paralysis is EXTERMELY DISTRESSING even without pain
MUST NOT be used as a sol agent for any kind of procedure (painful or not)!
MUST NOT be used as a sole agent for euthanasia!
What is function of NMJ (neuromuscular junction)
- Impulse arrives
- Release of acetylcholine
- Binds to nicotinic ACh receptors
- Ion flux triggers an action potential →muscle contraction
- ACh is rapidly metabolized
MoA of NMBDs
Depolarizing NMBDs - act as an agonist on nicotinic ACh receptors, causing muscle membrane depolarization (leaves receptor open so cant close)
Non-depolarizing NMBDs - act as competative antagonist on nicotinic ACh receptors, blocking signal (so no potential is reached)
Order of muscle relaxation with NMBDs
Ocular muscles most sensitive
Diaphragm most resistant (last to paralyze first to recover!)
Typical order of onset: Eyes>larynx>diaphragm
What can potentiate NMBD effect
Inhalation anesthetics
amionoglycoside antibiotics
local anesthetics
cardiac antiarrhythmic drugs
diuretics
mangesium
Other factors that influence the depth of NMBD effect
Hypothermia
Electrolyte abnormalities
Age
Acid-base disorders
thermal burn
Chemical properties of NMBDs
Water soluble (hydrophilic)
What is a rare complication of NMBDs
Which more likely to cause
What is consequence of the complication
How to tx
Histamine release
Atracurium
Bronchoconstriction, CV: vasodilation, (-) inotropy, tachycardia
low dose epinephrine
(Side-) effects at the ANS of NMBDs
Unlikely with modern NMBDs
Classification of NMBDs
The only ones used in Vet Med:
Non depolarizing, Intermediate acting (10-30 min):
Atracurium
Cisatracurium
Rocuronium
Vecuronium
Succinylcholine (SCh)
Only depolarizing NMBD used in clinic
has a Phase-1 block ⇒Phase-2 block
