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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of suxamethonium and tubocurarine on the refractoriness of neuromuscular transmission were studied in 21 anaesthetized adult subjects under various levels of neuromuscular block. The ulnar nerve was stimulated every 12 s with twin supramaximal stimuli 4 ms apart. At any level of block, the refractory fraction (the fractional decrement of the compound electromyographic response of the adductor pollicis to the second twin stimulus, relative to the response to the first) was used to quantify neuromuscular refractoriness. The magnitude of block was determined by the response to the first stimulus. Correlation between refractoriness and the degree of block was sought. Without block, neuromuscular transmission averaged 23% (SEM 4) refractory with this twin interval. The refractory fraction was increased markedly by suxamethonium, reaching 0.69 (SEM 0.1) at 50% block. Complete refractoriness occurred during 25--75% block in eight of 11 instances. Tubocurarine did not significantly alter refractoriness, paired responses to the twin stimuli decreasing proportionately during block.
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PMID:Neuromuscular refractoriness during blockage of transmission. A quantitative study. 21 92

The effect of tubocurarine and gallamine pretreatments on suxamethonium relaxation was measured in 81 patients. The blocking effect of a constant infusion of suxamethonium (0.58 mg/sec) on the recorded thumb adduction in response to supramaximal ulnar nerve stimulation was reproducible in 18 control subjects: infusion time for 50% block was 37.7 (+/- SEM 1.02) sec. Tubocurarine 3 mg and 6 mg increased the infusion time required to produce 50% block by 33.4 and 54.8% respectively. Gallamine had a similar effect. Clinical conditions for endotracheal intubation were evaluated on a blind basis. Both drugs produced impairment of clinical conditions for intubation after suxamethonium 60 mg infusion. However, when pretreatment by tubocurarine 3 mg was followed by suxamethonium infusion at 1 mg/sec the time course of neuromuscular blockade was identical to that of the controls. There were no fasciculations with this dosage and conditions for endotracheal intubation were excellent.
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PMID:Inhibition of suxamethonium relaxation by tubocurarine and gallamine pretreatment during induction of anaesthesia in man. 110 38

We have studied the effect of prior administration of non-depolarizing neuromuscular blocking drugs on suxamethonium-induced increases in masseter muscle tension in 21 children aged 3-10 yr, anaesthetized with nitrous oxide and halothane using supramaximal stimulation of the ulnar nerve and the nerve to masseter. Resting tension and isometric force of contraction were measured in the adductor pollicis and masseter muscles. A sub-paralysing dose of tubocurarine 0.05 mg kg-1, a paralysing dose of atracurium 0.5 mg kg-1 or saline was given, followed 3 min later by suxamethonium 1 mg kg-1. Onset times of suxamethonium and atracurium block were shorter in the masseter than in the adductor pollicis muscle. When preceded by a sub-paralysing dose of tubocurarine, suxamethonium produced an increase in masseter tension (47 (SEM 15) g) similar to that produced by suxamethonium alone (59 (13) g). Prior administration of a paralysing dose of atracurium almost abolished this increase in tension (2.5 (2.5) g) (P less than 0.05 vs saline). The tension increase in adductor pollicis was 0, 3.2 (2.2) and 5.9 (1.1) g in the atracurium, tubocurarine and saline groups, respectively. Tubocurarine and atracurium prevented muscle fasciculations in all patients. It was concluded that increased muscle tone is a normal response to suxamethonium and is greater in the masseter than adductor pollicis. Sub-paralysing doses of non-depolarizing neuromuscular blockers have little effect, in contrast with paralysing doses. This suggests that the effect is mediated via postsynaptic receptors.
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PMID:Pretreatment with non-depolarizing neuromuscular blocking agents and suxamethonium-induced increases in resting jaw tension in children. 235 96

The effects of atracurium and tubocurarine on heart rate and arterial pressure were studied in anaesthetized patients. A bolus of 0.6 mg kg-1 of either atracurium or tubocurarine was administered. Following atracurium, the change in heart rate was minimal (mean +/- SEM: -1.6 +/- 1.3 beat min-1) whereas after tubocurarine heart rate was increased (mean +/- SEM: +9.9 +/- 1.9 beat min-1). Atracurium produced a transient decrease in arterial pressure in 28% of subjects; by the 4th min after its injection the change was minimal (mean +/- SEM: -1.5 +/- 1.1 mm Hg). Tubocurarine produced an initial decrease in mean arterial pressure in all patients, of up to 50% of control values. In the 4th min following its injection arterial pressure was still significantly different from control (mean +/- SEM: -10 +/- 1.5 mm Hg). Endotracheal intubation caused an increase in arterial pressure in all subjects. It is concluded that atracurium has minimal effects on heart rate and arterial pressure when compared with tubocurarine. It does not appear to have a vagal blocking action.
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PMID:Comparison of the effects of atracurium and tubocurarine on heart rate and arterial pressure in anaesthetized man. 668 26