Several investigators have described an interaction between muscle relaxants and corticosteroids which have showed different results. The exact mechanism of this action is not clear and there conflicting results have further confusion.
For the confirmation on how to interact these two drugs inpatients without influencing factors to the neuromuscular transmission, corticosteroids(hydrocortisone, methyl prednisolone) 0.5mg/kg and 5.0mg/kg mixed in 20ml of normal saline with
micro-dose
of various muscle relaxants(vecuronium 0.1mg/kg/30, d-Tubocurarine 0.4mg/kg/30, succinylcholine 1 mg/kg/30) were administered respectively into the vein at the distal pcrtion of a pneumatic tourniquet applied on the upper arm with higher pressure
than
arterial pressure. This was to study the dose response according to recovery time between the experimental group and the control group. Neuromuscular block was measured by recording the twitch response following ulnar nerve stimulation by
EMG(ABC,
Datex
Co., 2Hz 30mA supermaximal voltage). And at over 95% depression of the twitch height, following administration of muscle relaxants alone(control group) or muscle relaxants combined with corticosteroids(study group), the tourniquet was released,
and
recovery time from 25% to 75% recovery of twitch height was measured according to recovery index(RI).
@ES The results obtaind were as follows;
@EN 1) In the group which 0.5mg/kg of hydrocortisone was administered, the RI of vecuronium and d-tubocurarine was shorten to 3.47(1.43 and 9.30(1.48 minutes, and in hydrocortisone 5.0mg/kg, was prolonged to 12.30(2.18 and 17.96(0.62 minutes,
compared
with control group(8.08(1.48 in vecuronium and 13.43(2.32 in d-Tubocurarine).
2) Methyl prednisolone also tended to short the RI in 0.5mg/kg of corticosteroids and to prolong in 5.0mg/kg, but not significant.
3) Corticosteroids not to depend on dose prolonged the RI from succinylcholine induced neuromuscular blocks.
4) Plasma cholinesterase values following injection of hydrocortisone 0.5mg/kg and 7.0mg/kg were not changed significantly.
5) Hydrocortisone alone had significant effect on twitch tension, increased in dose of 0.5mg/kg and bepressed in dose of 5.0mg/kg.
Conclusively, in the interaction between corticosteroids and muscle relaxants, a combined effect of antagonism in small dose and enhancement in large dose of corticosteroids to non-depolarizing neuromuscular blocking action and a potenciated
effect
to
depolarizing neuromuscular blocking action, seems to be possible.
We recommend careful monitoring of neuromuscular transmission in patients receiving corticosteroids when neuromuscular blocking agents is used for muscle relaxation.
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