Lithium: an anaesthetic risk.

A 64-year-old woman had suffered from recurrent depressive illnesses, although two attacks of manic behaviour had followed treatment for depression. She was first admitted to hospital in 1954 because of depression. Subsequently she had been admitted on fifteen occasions. As is common in the affective disorders, her attacks had become progressively more frequent and she had spent most of the previous 10 years, and all of the previous 3 years, in hospital. Each depressive illness lasted about 3 weeks, and was separated from the next illness by an interval of about 3 or 4 weeks when she was free from symptoms. At the beginning of each attack of depression she was suicidal but quickly passed into a state of depressive stupor. It was felt that an attempt should be made to relieve her recurrent and increasingly severe depressions with lithium carbonate. This was given in doses ranging from 750 to 1,000 mg daily over a period of 11 months. The dose was adjusted according to weekly estimations of the serum lithium concentration. Her serum lithium concentration reached 1.8 m.equiv/1. on one occasion, following which the dose was reduced from 1,000 to 750 mg dailv. At all other times, her serum lithium concentration had remained within the normal therapeutic range. For the 8 months prior to the episode to be described, she was given lithium carbonate 250 mg three times a day. Apart from lithium carbonate she was receiving no other drug therapy. During the year the patient received two courses of e.c.t. Lithium carbonate therapy was being given during the second but not the first course. The same drugs and techniques were used for all of her anaesthetics. The premedication was atropine sulphate 0.6 mg given intramuscularly 1 hour before anaesthesia which was induced with sodium methohexitone 60 mg followed by suxamethonium bromide 30 mg, both given i.v. IPPV with oxygen was given from a mask before and after each treatment. The problem occurred on one occasion during the second course of e.c.t. On examination before this anaesthetic she was depressed and withdrawn, which was characteristic of her psychotic state. She was physically normal and showed no signs of lithium toxicity, drowsiness, tremor or gastro-intestinal symptoms. She was given the usual anaesthetic and at no time was she cyanosed or hypotensive. Spontaneous respiration returned within the expected time but the patient could not be roused for over 2 hours, and she remained drowsy for the rest of the day. A venous blood sample was taken for estimation of urea and serum electrolytes (sodium, potassium, bicarbonate and chloride) and lithium concentration. Her blood urea and serum electrolyte concentrations were normal but the serum lithium concentration was 3.4 m.equiv/1. Lithium carbonate treatment was stopped and a week later the serum lithium concentration was 0.5 m.equiv/1. At this time, the patient received a further anaesthetic for e.c.t. using the same drugs and techniques and she recovered uneventfully.