ZAHID AZIZ

1. I/V MUSCLE RELAXANTS
DR.ZAHID AZIZ
DEPARTMENT OF
ANAESTHESIOLOGY SICU AND
PAIN MANAGEMENT CIVIL
HOSPITAL KARACHI

2. INTRODUCTION
Muscle relaxants are the agents that
act peripherally at neuromuscular
junction/muscle fibre itself to block
neuromuscular transmission.
In order to facilitate muscle relaxation
for surgery & for mechanical
ventilation during surgery or in ICU.

3. SITE OF ACTION OF MUSCLE
RELAXANTS
 Muscle relaxants blocks nicotinic receptor
of Acetylcholine peripherally at the
neuromuscular junction.
 Mainly at postjunctional receptors.
 Either acting as agonist(depolarizing) or
antagonist(non-depolarizing).

4. TYPES OF MUSCLE RELAXANTS
 NON-COMPETITIVE(DEPOLARIZING)
SUCCINYLCHOLINE
DECAMETHONIUM (No longer available)
 COMPETITIVE(NON-DEPOLARIZING)
ATRACURIUM
CISATRACURIUM
ROCURONIUM
PANCURONIUM
VECURONIUM
MIVACURIUM

5. 5 12/11/16
SUCCINYLCHOLINE
 STRUCTURE: Consists of two joined acetylcholine
molecules
 MECHANISM OF ACTION: Succinylcholine act like
acetylcholine but persist at the synapse at high concentration
and for longer duration and constantly stimulate the receptor.
 First, opening of the Na+ channel occurs resulting in
depolarization, this leads to transient twitching of the muscle,
continued binding of drugs make the receptor incapable to
transmit the impulses, paralysis occurs.
 The continued depolarization makes the receptor incapable of
transmitting further impulses.

6. SUCCINYLCHOLINE
 INDICATIONS: Patient with full stomach.
Obstetric patient.
Anticipated difficult intubation.
 DOSE: Intubating 1.0-1.5mg/kg.
 ONSET OF ACTION: 30-60 seconds
 DURATION OF ACTION: Less than 10 mins.
 METABOLISM: By Plasmacholinestrase or
Butrylcholinestrase or Pseudocholinestrase.
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7. SUCCINYLCHOLINE
 Succinylcholine on breakdown by
butrycholinesterase produces
succinylmonocholine.
 The duration of action is prolonged by high dose
or by abnormal metabolism.
 Abnormal metabolism may result from
hypothermia, low enzyme levels or genetically
aberrant enzyme.
 Hypothermia decreases rate of hydrolysis.

8. SUCCINYLCHOLINE
 Low levels of pseudocholinesterase accompany
liver disease,carcinomatosis and
starvation,pregnancy,anticholinestrases,hypothyr
oidism,renal disease.
 Prolonged paralysis caused by atypical
cholinesterase should be treated with cont
mechanical ventilation until muscle function
returns to normal.

9. 9 12/11/16
SIDE EFFECTS OF
SUCCINYLCHOLINE
 Bradycardia preventable by atropine.
 Hyperkalemia in patients with massive
trauma,burns,stroke,tetanus,closed head injury.
 Muscle pain.
 Fasciculations.
 Intragastric pressure elevation.
 Intraocular pressure elevation.
 Malignant hyperthermia.
 Prolonged paralysis (Succinylcholine apnea).
 Intracranial pressure elevation.

10. MECHANISM OF ACTON:MECHANISM OF ACTON:
• These have an affinity for the Nicotinic (NM)
receptors at the muscle end plates but have no
intrinsic activity.
• The antagonism is surmountable by increasing
the conc. of Ach.
NON-DEPOLARIZING AGENTS

11. Non depolarising neuromuscular blocking
drugs classification (on basis of chemical
strucure)
Benzylisoquinolinium
(Release histamine)
D-tubocurarine
Metocurine
Doxacurium
Atracurium
Cisatracurium
Mivacurium
Aminosteroids
(Not release histamine)
Pancuronium
Vecuronium
Rocuronium
Rapacuronium

12. ATRACURIUM
 Benzylisoquinoline derivative
 Intubating dose 0.5mg/kg.
 Onset of action 2.5-3.0 mins.
 Duration of intubating dose 30-45 mins.
 Maintenance by boluses 0.1mg/kg.
 May release histamine and may therefore can cause
hypotension,tachycardia,bronchospasm.
 Non-organ dependent elimination
 Non specific estererase: 60% of elimination
 Hofmann elimination : spontaneous nonenzymatic
chemical breakdown occurs at physiologic pH and
temperature.

13. ATRACURIUM
 Laudanosine toxicity
-breakdown product from Hofmann elimination, assoc.
with central nervous system excitation resulting in
elevation of MAC and precipitation of seizures.
 Temperature and pH sensitivity-action markedly
prolonged in hypo- thermic or acidotic patients.
 Available as a solution of 10mg/ml.It must be stored at 2-
8 centigrade.At room temperature,it should be used
within 14 days to preserve potency.

14. CIS-ATRACURIUM
 Benzoisoquinoline derivative
 Intubating dose 0.2mg/kg
 Onset 2-3 mins.
 Duration of intubating dose 40-75 mins.
 3x more potent than atracurium.
 No ester hydrolysis.
 More hoffman degradation.
 Produces less laudanosine.
 Minimal histamine release
 Useful in critically ill patient requiring prolonged infusion
of neuromuscular blocking drugs.

15. MIVACURIUM
 Benzylisoquinoline derivative.
 Potency, 1/3 that of atracurium
 Metabolized by plasma cholinestrase at 88% of
the rate of succinylcholine.
 Intubating dose 0.1-0.15 mg/kg
 Onset of action 2.5-3.0 mins (similar to
atracurium).
 Duration of intubating dose 15-20 mins
(recovery faster than atracurium).
 Produces similar amount of histamine release to
atracurium.

16. MIVACURIUM
 Useful particularly for surgical procedures
requiring muscle relaxation in which even
atracurium and vecuronium seem too long-
acting and when it is desirable to avoid side
effects of succinylcholine e.g. for
bronchoscopy,esophagoscopy or tonsillectomy.
 Duration of action may be increased due to
reduced plasma cholinestrease activity because
of either inherited or acquired factors.

17. PANCURONIUM
 Bisquaternary aminosteroid muscle relaxant.
 Intubating dose 0.08-0.12mg/kg.
 Onset 2-3 mins.
 Duration of intubating dose 60-120 mins.
 The clinical duration of action is long,especially
in the presence of potent inhalational agents or
renal dysfunction as 60% of dose of drug
excreted unchanged through the kidneys.
 Does not stimulate release of histamine.
 Direct vagolytic and sympathomimetic effects
which may cause tachycardia and hypertension

18. VECURONIUM
 Monoquaternary aminosteroid.
 Developed in an attempt to reduce the
cardiovascular effects of pancuronium.
 Intubating dose 0.1mg/kg.
 Onset 2-3 mins.
 Duration of intubating dose 45-90 mins.
 Depends primarily on biliary excretion
secondarily on renal excretion.
 Does not have any direct cardiovascular effects
although potentiation of opioid induced
bradycardia may be seen.

19. ROCURONIUM
 Monoquaternary aminosteroid analogue of
vecuronium designed to provide rapid onset
of action.
 Intubating dose 0.45-0.9 mg/kg.
 Onset 60-90 seconds.
 Duration of intubating dose 35-75 mins.
 Suitable alternative for rapid sequence
inductions but at the cost of a much longer
duration of action.

20. ROCURONIUM
 Stimulates little histamine release or
cardiovascular disturbance.
 Mild vagolytic property in high doses which
sometimes causes tachycardia.
 Excreted unchanged in the urine and in the
bile and thus the duration of action may be
increased by severe renal or hepatic
dysfunction.
 Rocuronium has no metabolites with
significant neuromuscular blocking activity.