Download Muscle Relaxation

Paediatric Critical Care
Muscle Relaxation
Important points:
1. Ensure adequate depth of anaesthesia before administering muscle
relaxation and for duration of its action.
2. High risk intubations: e.g. potentially difficult intubation, upper
airway obstruction or mediastinal mass, always plan for a “can’t
intubate, can’t ventilate scenario” post administration of muscle
relaxation.
Indications for muscle relaxation
1. Safe transfer of patient (inter / intra hospital)
2. Facilitate/ manipulate ventilation (e.g. bronchiolitis/ ARDS, CO2
control)
3. Prevent muscle shivering during active cooling
4. Post operative stability (e.g. LTR patients or high risk cardiac
surgery)
Pancuronium
Rocuronium
Atracurium
Suxamethonium
Indication
Intubation and intermittent
paralysis
Intubation and intermittent
paralysis
Rapid sequence induction or acute
intubation following loss of airway
Dose (IV)
0.1 mg/kg
1 mg/kg
Intubation and intermittent
paralysis
0.5mg/kg
25% of dose
Use standard dose
Agent
Myasthenia gravis dose
Onset of action
25% of dose
25% of dose
3-5 minutes
4-5minutes
30 -45 seconds
Duration of action
45-60 min
30 min
Metabolism
Hepatic to active metabolites
Hepatic
Excretion
50% urine, 10% bile
50% unchanged in bile and 20%
urine
Prolonged action
Renal failure (use same dose).
See drug list below*
Hepatic dysfunction (use same
dose)
See drug list below*
(intubation)
30 seconds
30-45mins
3-5 min
Ester hydrolysis and Hofmann
elimination
10% excreted unchanged in
urine
Not confirmed even in hepatic or
renal disease
Isoflurane, aminoglycosides,
lithium, magnesium salts
prolong action
Carbamazepine & phenytoin
reduce efficacy
Drug interactions
Histamine release causing
flushing, bronchospasm and
transient drop in blood pressure.
Side effect
Vagolytic (tachycardia does not
contraindicate but avoid in
tachyarrhythmia)
Anaphylaxis rare but possible
Malignant hyperthermia
risk
Safe in malignant hyperthermia
Safe in malignant hyperthermia
Safe in malignant hyperthermia
Known anaphylaxis. Caution in
asthma or cardiovascular
instability due to potential for
histamine release
Contraindications
Tachyarrhythmia’s
Known anaphylaxis
Storage
Fridge drug 2-8 oC . Light
sensitive.
Fridge drug. Keep at 2-8 oC
Unopened vial stable at 25 oC for
1 month
2 mg/kg IV (always use with atropine)
Fridge drug. Keep at 2-8 oC.
Unopened vial stable at 25 oC
for 14 days
Hydrolysed by plasma cholinesterase
10% excreted unchanged in urine
Plasma cholinesterase deficiency
(genetic or acquired). Propofol
(competes with enzyme)
Cholinesterase inhibitors –
organophosp. Digoxin potentiates
arrhythmias. Precipitates thiopentone
Bradycardia (muscarinic effect.) always
use with atropine. Histamine release
(avoid in asthma) Increases K (0.5
mmol/L). Anaphylaxis.
Contraindicated. Malignant
hyperthermia trigger
Muscle injury (burns, rhabdomyolysis,
trauma, denervation injury/cord
transection)
undiagnosed or central/minicore
myopathy
Fridge drug 2-8 oC
Unopened vial stable at 25 oC for 24
hrs
To reverse non depolarising muscle relaxants (rocuronium, pancuronium) use Neostigmine 50mcg/kg AND Glycopyrolate 10mcg/kg.
To reverse Rocuronium in children > 2 years: sugammadex 2mg/kg may be used. This will reverse neuromuscular blockade from rocuronium within 5-15 minutes. You must wait 24
hours before re-administering rocuronium.
The action of Rocuronium/Pancuronium prolonged by ↓K, ↓Ca, ↑Mg, ↑Na, hypothermia, antibiotics (gent, vanc, clindamycin), antiarhythmics (lignocaine, verapamil).
Monitoring neuromuscular blockade
1.
2.
3.
4.
Avoid continuous infusions and use intermittent bolus if regular muscle relaxation required. This reduces the risk of critical care polyneuropathy.
To asses the degree of neuromuscular block use Train of Four test (TOF) using a nerve stimulator.
With ECG clips attached over the ulnar nerve at the wrist, press the TOF button (A). This sends 4 equal strength nerve stimuli in rapid succession and
produces a repetitive full strength twitch of the stimulated muscle if no muscle relaxant is present.
Absent twitch after TOF = full neuromuscular blockade. <4 equal and sustained twitches = partial neuromuscular blockade. 4 full equal intensity twitches =
recovery from neuromuscular blockade
TOF TWITCHES
TOF
Butto
1 twitch
Therapeutic
paralysis
Press
TOF
3 unequal
twitches
TOF
RS6 nerve
stimulator
Ulnar
nerve
4 unequal
twitches
Partial
paralysis
4 equal
twitches
No
paralysis
Strength of TOF twitch
1. Sasada & Smith. Drugs in Anaesthesia & Intensive Care. 3rd Edition. 2. Caudia et al. Paed Anes. 2002 12:140-146. 3.Fisher D. BJA1999. 83: 58-64. 3. Rex et al. Current opinion in
anaesthesiology 2010 23:461-465.
August 2015