Insulin promotes potassium entry into cells by mechanisms separate from glucose entry; glucose is also required to prevent hypoglycemia. There is no general agreement on the dose to be used. Commonly used prescriptions include 15 units of soluble insulin in 50 ml of 50 per cent glucose given centrally over 20 to 30 min, and 15 to 20 units of insulin in 500 ml of 10 or 20 per cent glucose over 30 to 60 min. All methods will reduce plasma potassium by approximately 1 mmol/l over a period of 30 to 60 min and will usually maintain potassium at the lower level for 3 to 6 h, after which the treatment may be repeated. This may be sufficient to maintain plasma potassium levels at acceptable levels, but is usually inadequate in hypercatabolic patients and those with established renal failure; in such cases it will buy time for definitive treatment.
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