GuidelinesEML (Adult Hospital STG)
Muscle Relaxants
Standard Treatment Guidelines and Essential Medicines List for South Africa, Hospital Level, Adults 2019 Edition
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Non-depolarising Muscle Relaxants (NDMR)
Muscle Relaxation for Rapid Sequence Intubation
Medicines to Reverse Muscle Relaxation
- Used to facilitate intubation and to provide intraoperative muscle relaxation for surgery.
- It must not be used if difficult intubation anticipated.
DEPOLARISING MUSCLE RELAXANTS
- Suxamethonium, IV, 1–1.5 mg/kg.
- Onset 30–60 seconds.
- Duration 5 minutes.
- Repeated doses associated with bradycardia and prolonged neuromuscular block.
- Contraindicated in patients at risk for developing suxamthonium-induced hyperkalaemia, e.g. upper or lower motor neuron defect, prolonged chemical denervation (ICU >3 days), direct muscle trauma, tumour or inflammation, burns, disuse atrophy, severe infection, pre-existing hyperkalaemia.
NON-DEPOLARISING MUSCLE RELAXANTS (NDMR)
- Use a nerve stimulator to monitor effect and determine when subsequent doses (about a fifth of the intubating dose) are required.
- Higher doses result in shorter onset times but longer duration of action.
- Intermediate-acting neuromuscular blocking agents, e.g.:
- Cisatracurium (shorter-acting)
- Intubation dose 0.1–0.15 mg/kg.
- Onset 3–5 minutes.
- Duration of action 45–55 minutes.
- Eliminated by Hoffman degradation, therefore can be used in renal or liver impairment.
- Vecuronium
- Intubation dose 0.08–0.1 mg/kg.
- Intubate after 2 minutes.
- Duration 20–30 minutes.
- Eliminated by liver and kidney: avoid in renal and liver impairment.
MUSCLE RELAXATION FOR RAPID SEQUENCE INTUBATION
- Patients at risk of aspiration (e.g. emergency surgery, incomplete gastric emptying) require a rapid sequence intubation.
- An IV induction agent is given through an IV line with fast running fluids, immediately followed by a rapidly acting muscle relaxant.
- Cricoid pressure is applied and then intubation proceeds.
- The rapid onset of action enables the time to intubation to be short enough to avoid mask ventilation, as this can result in gastric insufflation and aspiration of gastric contents.
- Suxamethonium, 1–1.5 mg/kg, IV. (See Depolarising muscle relaxants).
- Preferred agent as, in the event of a failed intubation, it wears off quickly enabling spontaneous respiration to resume.
- Contraindications to suxamethonium
- Congenital and acquired medical conditions associated with severe, potentially lethal suxamethonium-induced hyperkalaemia.
- Malignant hyperthermia.
- If suxamethonium is contra-indicated, consider:
- Rocuronium, 0.9 mg/kg, IV.
- Duration +/- 60 minutes.
- Sub-optimal conditions for intubating and prolonged effect can be problematic in the event of a difficult or failed intubation and if the procedure is short.
MEDICINES TO REVERSE MUSCLE RELAXATION
- Only administer when the clinical signs of NDMR are wearing off or at least 2 twitches occur using train-of-four on nerve stimulator.
- Neostigmine has profound cholinergic effects and, to counteract resultant profound bradycardia, is administered mixed with an anticholinergic agent, atropine or glycopyrrolate.
- Whilst atropine is effective and can be used for this purpose in otherwise healthy patients, the onset of neostigmine and duration of action more closely matches that of glycopyrrolate, so this is the preferred combination agent for patients who poorly tolerate tachycardia or bradycardia.
- Neostigmine, IV, 50 mcg/kg.
WITH EITHER:
- Atropine, IV, 20 mcg/kg (maximum 1.2 mg).
OR
- Glycopyrrolate, IV, 10 mcg/kg.
Standard Treatment Guidelines and Essential Medicines List for South Africa, Hospital Level, Adults 2024 Edition