Wed10November0747AM 1

A 55-year-old male presented six hours after taking an overdose of lithium tablets which had been prescribed for a bipolar affective disorder.

On examination he was tremulous, had suffered a convulsion and had a Glasgow coma scale of 12/15. His serum lithium concentration was 5.0 mmol/L (0.5-1.0)

Which of the following options is the most appropriate management of this patient?

(Please select 1 option)

Haemodialysis Correct

Activated charcoal

Forced alkaline diuresis

Furosemide 100 mg intravenously twice daily

Measure lithium concentration in two hours

Explanation

The patient has a severe lithium overdose as reflected by markedly elevated lithium concentrations and features of impaired consciousness, tremor, and seizures.

Lithium has a narrow therapeutic range (0.5-1.0 mmol/L), and toxic effects are seen at levels above 1.0 mmol/L. Toxicity is more likely where there is electrolyte imbalance, or renal impairment. Some drugs also impair lithium excretion, in particular thiazide diuretics, ACE inhibitors, and NSAIDs.

At levels of 1-2 mmol/L lithium toxicity results in:

anorexia

vomiting

ataxia

dysarthria

blurring of vision

coarse tremor

diarrhoea

drowsiness, and

muscle weakness.

Higher levels, as seen here, result in severe toxicity which is characterised by:

circulatory failure

coma

convulsions

hyper-reflexia

oliguria

psychosis, and

death (in severe cases).

Mild to moderate toxicity (levels less than 2 mmol/L) can be treated with normal saline fluid resuscitation. Severe cases require haemodialysis. Sodium bicarbonate used to alkalinise urine has been suggested to increase lithium excretion, but there is little evidence of benefit. 10% of patients who survive severe lithium toxicity will be left with a neurological deficit.

Activated charcoal does not bind lithium effectively and is therefore ineffective except where co-ingestion of other poisons is suspected.

Furosemide is likely to decrease lithium excretion and is therefore inappropriate.

Measuring lithium concentration in two hours would be negligent because treatment needs to be initiated immediately.

Answer Statistics

1

93%

2

2%

3

4%

4

1%

5

2%

Times answered: 260