Forced alkaline diuresis

Forced alkaline diuresis is indicated in the treatment of moderate salicylate poisoning except if the patient is:

• in shock
• in heart failure
• has impaired renal function

Urinary pH should be maintained above 7.5, ideally 8.0 -8.5. Increasing the pH of the urine from 7 to 8 results in a ten fold increase in the concentration of aspirin in the urine.

Any potassium deficit must be corrected otherwise it may be difficult to achieve a sufficiently alkaline urine without causing a rise in plasma pH. The volume of the diuresis need not be more than 500 ml per hour.

In the first hour infuse:

• 500 ml 5% dextrose
• 500 ml bicarbonate 1.4%
• 500 ml dextrose 5%

Potassium chloride should be added to keep serum potassium above 3.5 mmol/l.

Administer 1.5-2.0 litres of i.v. fluids per hour for 3 hours or to maintain urine volume greater than 500 ml per hour. Urine pH should be measured every 30 min and action taken to maintain the pH between 7.5 and 8.5. Alkaline diuresis should be discontinued at 1 hour if the urine flow is less than 3 ml per minute.

Otherwise, continue alkaline diuresis beyond 3 hours at 1 litre per hour until blood salicylate is less than 2.5 mmol per litre.

For children, infuse at rate of 30 mg per kilogram per hour.