▶Sialanar(Proveca Ltd)
Glycopyrronium bromide 400 microgram per 1 mlSialanar
320 micrograms/ml oral solution sugar-free| 250 mlP£ 320. 00
DT = £ 320. 001.1 Neuromuscular blockade
Neuromuscular blockade
Neuromuscular blocking drugs
Neuromuscular blocking drugs used in anaesthesia are also
known asmuscle relaxants. By specific blockade of the
neuromuscular junction they enable light anaesthesia to be
used with adequate relaxation of the muscles of the
abdomen and diaphragm. They also relax the vocal cords and
allow the passage of a tracheal tube. Their action differs from
the muscle relaxants used in musculoskeletal disorders that
act on the spinal cord or brain.
Children who have received a neuromuscular blocking
drug shouldalwayshave their respiration assisted or
controlled until the drug has been inactivated or
antagonised. They should also receive sufficient
concomitant inhalational or intravenous anaesthetic or
sedative drugs to prevent awareness.Non-depolarising neuromuscular blocking drugs
Non-depolarising neuromuscular blocking drugs (also
known as competitive muscle relaxants) compete with
acetylcholine for receptor sites at the neuromuscular
junction and their action can be reversed with
anticholinesterases such as neostigmine p. 648. Non-
depolarising neuromuscular blocking drugs can be divided
into theaminosteroidgroup, comprising pancuronium
bromide p. 815 , rocuronium bromide p. 815 , and vecuronium
bromide p. 816 , and thebenzylisoquinoliniumgroup,
comprising atracurium besilate p. 813 , cisatracurium p. 814 ,
and mivacurium p. 814.
Non-depolarising neuromuscular blocking drugs have a
slower onset of action than suxamethonium chloride p. 813.
These drugs can be classified by their duration of action as
short-acting ( 15 – 30 minutes), intermediate-acting
( 30 – 40 minutes), and long-acting ( 60 – 120 minutes),
although duration of action is dose-dependent. Drugs with a
shorter or intermediate duration of action, such as
atracurium besilate and vecuronium bromide, are more
widely used than those with a longer duration of action, such
as pancuronium bromide.
Non-depolarising neuromuscular blocking drugs have no
sedative or analgesic effects and are not considered to trigger
malignant hyperthermia.
For patients receiving intensive care and who require
tracheal intubation and mechanical ventilation, a non-
depolarising neuromuscular blocking drug is chosen
according to its onset of effect, duration of action, and side-
effects. Rocuronium bromide, with a rapid onset of effect,
may facilitate intubation. Atracurium besilate or
cisatracurium may be suitable for long-term neuromuscular
blockade since their duration of action is not dependent on
elimination by the liver or the kidneys.
Atracurium besilate, a mixture of 10 isomers, is a
benzylisoquinolinium neuromuscular blocking drug with an
intermediate duration of action. It undergoes non-enzymatic
metabolism which is independent of liver and kidney
function, thus allowing its use in children with hepatic or
renal impairment. Cardiovascular effects are associated with
significant histamine release; histamine release can be
minimised by administering slowly or in divided doses over
at least 1 minute. Neonates may be more sensitive to the
effects of atracurium besilate and lower doses may be
required.Cisatracurium is a single isomer of atracurium besilate. It is
more potent and has a slightly longer duration of action than
atracurium besilate and provides greater cardiovascular
stability because cisatracurium lacks histamine-releasing
effects. In children aged 1 month to 12 years, cisatracurium
has a shorter duration of action and produces faster
spontaneous recovery.
Mivacurium, a benzylisoquinolinium neuromuscular
blocking drug, has a short duration of action. It is
metabolised by plasma cholinesterase and muscle paralysis
is prolonged in individuals deficient in this enzyme. It is not
associated with vagolytic activity or ganglionic blockade
although histamine release can occur, particularly with rapid
injection. In children under 12 years mivacurium has a faster
onset, shorter duration of action, and produces more rapid
spontaneous recovery.
Pancuronium bromide, an aminosteroid neuromuscular
blocking drug, has a long duration of action and is often used
in children receiving long-term mechanical ventilation in
intensive care units. It lacks a histamine-releasing effect, but
vagolytic and sympathomimetic effects can cause
tachycardia and hypertension. The half-life of pancuronium
bromide is prolonged in neonates; neonates should receive
postoperative intermittent positive pressure ventilation.
Rocuronium bromide exerts an effect within 2 minutes and
has the most rapid onset of any of the non-depolarising
neuromuscular blocking drugs. It is an aminosteroid
neuromuscular blocking drug with an intermediate duration
of action. It is reported to have minimal cardiovascular
effects; high doses produce mild vagolytic activity. In most
children, the duration of action of rocuronium bromide may
be shorter than in adults; however, in neonates and children
under 2 years, usual doses may produce a more prolonged
action.
Vecuronium bromide, an aminosteroid neuromuscular
blocking drug, has an intermediate duration of action. It
does not generally produce histamine release and lacks
cardiovascular effects. In most children, the duration of
action of vecuronium bromide may be shorter than in adults;
however, in neonates and children under 2 years, usual doses
may produce a more prolonged action.
Depolarising neuromuscular blocking drugs
Suxamethonium chloride has the most rapid onset of action
of any of the neuromuscular blocking drugs and is ideal if
fast onset and brief duration of action are required e.g. with
tracheal intubation. Neonates and young children are less
sensitive to suxamethonium chloride and a higher dose may
be required. Unlike the non-depolarising neuromuscular
blocking drugs, its action cannot be reversed and recovery is
spontaneous; anticholinesterases such as neostigmine
potentiate the neuromuscular block.
Suxamethonium chloride should be given after anaesthetic
induction because paralysis is usually preceded by painful
muscle fasciculations. Bradycardia may occur; premedication
with atropine sulfate p. 810 reduces bradycardia as well as
the excessive salivation associated with suxamethonium
chloride use.
Prolonged paralysis may occur in dual block, which occurs
with high or repeated doses of suxamethonium chloride and
is caused by the development of a non-depolarising block
following the initial depolarising block. Children with
myasthenia gravis are resistant to suxamethonium chloride
but can develop dual block resulting in delayed recovery.
Prolonged paralysis may also occur in those with low or
atypical plasma cholinesterase. Assisted ventilation should
be continued until muscle function is restored.812 Anaesthesia adjuvants BNFC 2018 – 2019
Anaesthesia15