Forty-seven patients demonstrating prolonged apnoea after suxamethonium have been investigated in a 3-year survey carried out in southeast Scotland. Clinical information, and serum cholinesterase studies using a new substrate, succinyldithiocholine, provide evidence on the aetiology of suxamethonium hypersensitivity. While 13 patients possessed only variant forms of the serum enzyme, the remaining 34 patients appeared to have a catalytically active form of cholinesterase. The causes of prolonged apnoea in the latter group are discussed. The value of screening the relatives of patients with cholinesterase variants is demonstrated by the finding of 26 relatives "at risk" out of 123 screened.

The rate of decrease in the plasma concentration of indocyanine green (ICG) following a bolus i.v. injection has been studied in two groups of patients before and during anaesthesia. In eight patients anaesthetized with nitrous oxide and oxygen, and who received a neuromuscular blocking drug, induction of anaesthesia was not associated with a significant change in ICG half-life (from 4.59 to 3.85 min) but the subsequent administration of cyclopropane was associated with a statistically significant increase to 5.61 min. In a second group of anaesthetized patients, breathing spontaneously a mixture of oxygen, nitrous oxide and halothane, the induction of arterial hypotension with either lumbar extradural block or sodium nitroprusside was not associated with significant changes in ICG half-life.

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