Fluid replacement for adults with hyperosmolar hyperglycaemia
Intravenous fluid replacement is the mainstay of management for patients with hyperosmolar hyperglycaemia. Patients are often very dehydrated; fluid losses may be around 100 to 220 mL/kg (eg 9 to 20 L in a 90 kg patient). The aim of fluid replacement therapy is to slowly and safely replace fluid and electrolyte losses, normalise the osmolality and normalise the blood glucose concentration. Fluid replacement alone will start to reduce blood glucose concentration and serum osmolality.
Do not replace fluid losses rapidly and excessively because if the metabolic changes are reversed too rapidly it can be harmful (eg glucose and sodium normalisation).
Intravenous fluid replacement using sodium chloride 0.9% is usually started immediately to restore circulating volume and reverse dehydration. The aim of treatment should be to replace approximately 50% of estimated fluid loss within the first 12 hours and the remainder in the following 12 to 36 hours; however, initial severity of the hyperosmolar hyperglycaemia, degree of kidney impairment and presence of comorbidities may limit the speed of correction. Complete normalisation of electrolytes may take up to 72 hours.
Serum osmolality must be measured or calculated hourly1. The rate of fluid replacement should be adjusted to give a positive fluid balance sufficient to cause a gradual decline in osmolality, such as 3 mmol/kg/hour. Serum sodium concentration may rise as the blood glucose concentration falls, but this is not a concern unless osmolality is not decreasing at the same time. Follow specialist advice on adjusting the rate of fluid replacement.
If osmolality is not decreasing despite adequate fluid replacement with sodium chloride 0.9% and blood glucose concentration is not decreasing, sodium chloride 0.45% may be substituted. Follow local hospital protocols if available or seek specialist advice.