It is an adjunct to analgesia and anaesthesia. It is used in acutely painful procedures of short duration especially dental procedures and childbirth. When mixed with 50% it is known as Equanox® (previously, Entonox®)
Mode of Action:
The molecular mode of action is unknown. Patients using nitrous oxide are sedated but remain responsive to commands and remain conscious. It has rapid onset and rapid recovery time. Nitrous oxide can cause transient bone marrow depression and peripheral neuropathy due to less availability of vitamin B12 however if when used for short procedures the recovery is usually uneventful.
Suxamethonium by Shamim Nassrally
Indication: muscle relaxation (rapid onset, short duration)
Suxamethonium chloride has the most rapid onset of action of any of the muscle relaxants with a brief duration of action. Its duration of action is about 2 to 6 minutes following intravenous doses.
Suxamethonium acts by mimicking acetylcholine at the neuromuscular junction but hydrolysis (breakdown) is much slower than for acetylcholine; depolarisation is therefore prolonged, resulting in neuromuscular blockade. Unlike the non-depolarising muscle relaxants, its action cannot be reversed and recovery is spontaneous; anticholinesterases such as neostigmine potentiate the neuromuscular block.
Suxamethonium should be given after anaesthetic induction because paralysis is usually preceded by painful muscle fasciculations. While tachycardia occurs with single use, bradycardia may occur with repeated doses in adults and with the first dose in children. Premedication with atropine reduces bradycardia as well as the excessive salivation associated with suxamethonium use.
Prolonged paralysis may occur in dual block, which occurs with high or repeated doses of suxamethonium and is caused by the development of a non-depolarising block following the initial depolarising block; edrophonium may be used to confirm the diagnosis of dual block.
Individuals with myasthenia gravis are resistant to suxamethonium 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.
postoperative muscle pain
tachycardia, arrhythmias, cardiac arrest
prolonged respiratory depression