neuromuscular blocking agents in large animals
DESCRIPTION
Neuromuscular blocking agents(NMBA) used in animals and humans for muscle relaxation.This presentation is all about NMBA used in large animals viz. cattle and horse. Although use of NMBA alone is very limited, but this ppt can help in knowing NMBA along with doses,their mechanism of action, non neuromuscular effects and reversal of muscle relaxation. thank you Dr. Amandeep GADVASUTRANSCRIPT
Neuromuscular Blocking Agents
Submitted by – Amandeep
Department Of Veterinary Medicine
L2013V40M
INTRODUCTION
• Agents that interfere with transmission of
nerve impulse from somatic nerve ending to
skeletal muscle fibres
• Profound muscle relaxation & even paralysis
of skeletal muscles
Muscle Relaxants
Peripheral acting muscle
relaxant
Centrally acting muscle relaxant
Peripheral Acting Muscle Relaxant
Neuromuscular blocking agents
Directly acting drugs
Why?
• Inhalant anesthetics(IA) are complete anesthetics
• Fulfill triad-unconsciousness, analgesia & muscle
relaxation- of anesthesia
• Light planes- good loss of consciousness
• Deeper planes- analgesia & M. relaxation
• Cardiovascular compromise
Balanced Anesthesia
• Low concentration of IA to provide unconsciousness
• Analgesic to inhibit nociceptive processing
• NMBA to relax skeletal muscle
Physiology
At Microscopic Level
• Protruded circular area- binding site for Ach
• Pit- extracellular opening for ion channel
• Ach binds to one R• R composed of alpha,
beta, gamma & delta• 2 molecules of Ach bind
to 2 alpha subunits• Protein rotates into new
conformation
Uses of NMBA
• Adequate surgical muscle relaxation without compromising
recovery
Absolute relaxation, eg : intra-ocular procedures, microsurgery
Specific muscle relaxation, eg : laparotomy , Caesarean
section, some orthopaedic surgery (reduction of dislocations),
diaphragm surgery
Uses of NMBA
• Reduction of anaesthetic dose
• Preservation of cardiopulmonary function
• Reduced operating times in 'high risk' patients
• Where positive pressure ventilation (PPV) required
• Where spinal reflexes need to be suppressed, eg: ear canal
surgery
Non – Depolarizing Depolarizing
• Act by competitively
blocking the binding of ACh
to its receptors / directly
block the ionotropic activity
of the ACh receptors
• Bind to Ach receptors but no
activation occurs
• Act by depolarizing the
plasma membrane of the
skeletal muscle fibre similar
to Ach
• Bind to Ach receptors
causing activation
Muscle paralysis
Neuromuscular Blocking Agents
• Non depolarising-
1. Long acting e.g tubocurarine
2. Intermediate acting e.g vecuronium, atracurium
3. Short acting e.g mivacurium
• Depolarising eg suxamethonium & decamethonium
Dose rates
• Pancuronium –
• In cattle - 0.04mg/kg, slow I/V(initial dose),
followed by increments of 0.008mg/kg
• In horse – 0.06mg/kg, , slow I/V(initial dose),
followed by increments of 0.001mg/kg
Dose rates
Doxacurium- usually not used
Atracurium –
Horse@ 0.15mg/kg, slow I/V(initial dose), then
increments of 0.06 mg/kg
Vecuronium- Horses@ 0.1 mg/kg slow I/V initial dose,
then increment of 0.02mg/kg
Mivacurium- it does not need reversal
Drug ( Depolarizing NMB)
Horse(mg/kg)
Cattle(mg/kg)
Succinyl choline(Scoline ®)
0.12-0.15 0.01-0.02
Non Neuromuscular effect
• Cardiovascular effect
• Histamine release
• Placental transfer
• CNS effects
• Protein binding
Non Neuromuscular Effect Of Succinylcholine
• Hyperkalemia
• Intraocular pressure
• Intragastric pressure
• Intracranial pressure
• Muscle soreness
Reversal Of NM Blockade
Achieved by establishing high concentration of acetylcholine at the
binding site
Atropine (0.04 mg/kg S/C)
Glycopyrrolate (0.01 mg/kg I/M) administered intravenously atleast
one minute prior to the administration of reversal agent to block the
muscarinic effects of acetylcholine
Reversal Of NM Blockade
• Neostigmine 0.1 mg/kg I.V
• Edrophonium 1.0 mg/kg I.V
Cholinesterase Reversal
Cholinesterase reversal by increasing ACh and
displacing NMBA from receptors
Sugammadex MOA
• Modified cyclodextrin
• Cavity created by ring
is lipophilic, exterior is
hydrophilic
• Encapsulate lipophilic
drugs yet remain soluble
in water
Sugammadex MOA
• Resultant sugammadex bound NMBA (inclusion
complex) is then excreted by the kidneys
• Renal clearance of the NMBA has been found to be
enhanced by sugammadex encapsulation
Thanks