Biomedical subjects
Publications and source records attributed to M J Stewart.
A method has been developed for the emergency estimation of paracetamol using high performance liquid chromatography. The sample required is 100 microliters of plasma; the use of a micro-centrifuge reduces the total time for the estimation to 5 min from the receipt of the blood specimen. The method has been compared with a standard UV method.
One hundred cases of severe paracetamol poisoning were treated with intravenous N-acetylcysteine (acetyl-cysteine). There was virtually complete protection against liver damage in 40 patients treated within eight hours after ingestion (mean maximum serum alanine transaminase activity 27 IU/1). Only one out of 62 patients treated within 10 hours developed severe liver damage compared with 33 out of 57 patients (58%) studied retrospectively who received supportive treatment alone. Early treatment and acetylcysteine also prevented renal impairment and death. The critical ingestion-treatment interval for complete protection against severe liver damage was eight hours. Efficacy diminished progressively thereafter, and treatment after 15 hours was completely ineffective. Intravenous acetylcysteine was more effective than cysteamine and methionine and noticeably free of adverse effects. It is the treatment of choice for paracetamol poisoning.
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A method for the quantitative extraction of paraquat from plasma is described. The method relies on the use of an organic-soluble ion pair of paraquat with dodecyl sulphate. The use of the extraction procedure in conjunction with the dithionite colour reaction gives a method which is suitable for emergency estimations with a sensitivity limit of 50 micrograms/l. The extraction procedure alone offers a new first step in the clean up of paraquat for analysis by other methods.
A comparison was made between the RIA method for paraquat in plasma, and a modified colorimetric method involving ion-pair extraction of paraquat. The comparison was carried out on plasma from patients admitted with paraquat poisoning. The correlation between the methods was good and both were found to be sufficiently rapid for emergency use.
Methods for the estimation of plasma paracetamol which depend on acid hydrolysis to p-aminophenol without a prior extraction step also measure inactive metabolites which are present in high concentrations. The extent of the overestimate obtained with such methods was determined using 24 samples from patents after paracetamol overdosage. There was a positive error of between 40 and 700% compared with a high-performance liquid chromatography reference method which measured only unchanged paracetamol. These non-specific methods should not be used to determine the need for specific therapy in patients with paracetamol poisoning.
A 23-year-old woman ingested 2g. amylobarbitone, 10.4g. aminophylline and 2g. ephedrine. She was deeply unconscious, hypothermic, and went on to have supraventricular and ventricular dysrhythmias, convulsions and haematemesis. During the last convulsion she aspirated vomitus and died. The peak plasma concentration of amylobarbitone was 19mg. per l. and those of ephedrine and theophylline were 13 times higher than accepted therapeutic levels. During the course of the poisoning marked hypokalaemia (1.8mmol./l.) and hyperinsulinaemia (greater than 240mU./l.) were found in conjunction with mild hyperglycaemia (9.6mmol./l.) and elevation of free fatty acid levels (1860mumol./l.). The mechanism of these changes is discussed.
A rapid method was developed for the estimation of colchicine in plasma. The method was used to determine colchicine levels in a fatal case of colchicine self-poisoning.
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A brief review of the literature has been accomplished. A report is given on 32 ankles in 31 patients who had reconstruction of their lateral ligaments. The operative technique is described. A criteria for selection of patients is given.