Biomedical subjects
Publications and source records attributed to W J Kerr.
Analysis of 20 cases of Class III malocclusion treated with the FR.III showed that correction of the anterior crossbite was effected by adjustment of incisor inclinations and backward rotation or repositioning the mandible accompanied by an increase in face height. Subjects which responded most favourably to the FR.III were those with severe Class III malocclusion and a deep incisor overbite.
A survey of appliance breakages over a 12-month period revealed that the acrylic baseplate and bite planes (57 per cent) fractured more frequently than wire elements (43 per cent). The number of appliances broken represented about one in five of new appliances fitted during the period. More than half of the breakages were perpetrated by persistent offenders and 31 per cent of appliances broke while they were removed from the mouth, but in the care of the patient. Inadequate properties of the acrylic resin and carelessness on the part of the patient are suggested as the most important causative factors.
Two cases of profound bradycardia (one progressing to asystole) during orbital surgery where the relevant eye had been removed years earlier are reported. Cessation of stimulation was followed by recovery of heart rate. Intravenous atropine prevented further bradycardia.
The antagonistic action of a bolus dose of edrophonium 0.75 mg kg-1 on the neuromuscular blockade induced by atracurium was studied in 10 patients anaesthetized with nitrous oxide and narcotic supplements. The reversal agent was administered when the twitch height had recovered spontaneously to approximately 20% of control. Twitch response was restored to 100% of control after 4.7 +/- 2.2 min. Clinically adequate reversal (train-of-four ratio of 75% or better) was achieved 6.6 +/- 1.5 min following injection of the edrophonium and there was no evidence of subsequent muscle weakness. The possible advantages of the clinical use of edrophonium in producing a rapid reversal of atracurium blockade are discussed.
Some actions of Org NC 45 have been compared with those of pancuronium in a study on 50 patients anesthetized with nitrous oxide and narcotic supplements. The train-of-four technique was used to assess the recovery of neuromuscular blockade and its antagonism. Org NC 45 was shown to have a duration of action from injection of the intubating dose (0.1 mg kg-1) to the reappearance of the first twitch response of 23.5 +/- 1.1 min; the corresponding time for pancuronium 0.1 mg kg-1 was 50.5 +/- 3.6 min. Recovery time from the initial incremental dose to the reappearance of the first train-of-four response was 11.6 +/- 0.8 min with Org NC 45 and 31 +/- 4.7 min with pancuronium. No evidence of cumulation was seen following several incremental doses of Org NC 45. The rate of onset of paralysis of adductor pollicis was faster with Org NC 45 than with pancuronium, but the difference did not reach statistical significance. Satisfactory spontaneous recovery from Org NC 45 blockade could be achieved without undue delay. Org NC 45 was shown to produce significantly less tachycardia.
Some actions of the muscle relaxant drug Org NC 45 on the tibialis anterior muscle of cats under barbiturate-chloralose anaesthesia have been studied. Its effects were characteristic of a neuromuscular blocking agent that acts predominantly, although not necessarily exclusively, by blocking postjunctional cholinoceptors. It was confirmed that one of the important features of the action of Org NC 45 is that, despite its high potency, its offset of action is unusually rapid. The pronounced antagonism of the block following an interposed tetanus suggested that Org NC 45 is more easily displaced from the endplate cholinoceptors than are tubocurarine or pancuronium, and this led to the idea, confirmed by experiment, that edrophonium would be a more effective antagonist of Org NC 45 than of most other neuromuscular blocking drugs. Edrophonium was about 12 times less potent than neostigmine in antagonizing Org NC 45. However, with equipotent antagonistic doses, edrophonium restored transmission to control (as measured by the train-of-four test) at least twice as rapidly as neostigmine and, more importantly, edrophonium had a much weaker effect than neostigmine on the cardiac vagus. The results obtained in cats with edrophonium were essentially confirmed in preliminary studies on nine anaesthesized patients. In these studies, a dose of edrophonium 0.5 mg kg-1 i.v. was found to produce adequate and rapid antagonism of Org NC 45, and because of the relatively weak side-effects of edrophonium, it was necessary, about 30 s before edrophonium, to administer only 0.6 mg of atropine (about 9 micrograms kg-1), which is half the dose commonly used when neostigmine is the reversal agent. These preliminary observations in man suggest that edrophonium may be the reversal agent of choice for Org NC 45.
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A skeletal class II malocclusion can be dealt with in a number of ways. The preferred option is to use orthodontic treatment and growth modification if at all possible, but in cases where this is not possible the problem might be camouflaged or treated by surgery. In the case reported here the options are fully discussed and the opinions of the orthodontists expressed in the CASES project made clear. The actual treatment undertaken is also described.