Hyperosmolar hyperglycaemic state

HHS (formerly known as HONK or hyperosmolar non ketotic coma) is the typical hyperglycaemic emergency of type 2 diabetes. It is characterised by hyperglycaemia and significant hyper osmolality (serum osmolality, calculated as 2xNa+glucose, of greater than 320 mOsmol/kg) in the absence of significant ketosis.

Guidelines

The most authoritative guidelines on management of HHS are the 2012 JBDS guidelines

Fluid resuscitation forms the mainstay of HHS management and is arguably more important than insulin therapy as these patients are rarely completely insulin-deficient. The overriding concern when treating HHS is not to correct the fluid and electrolyte abnormalities too fast.

These patients have taken days or weeks to become severely dehydrated, the rate of rehydration should reflect this to some extent, moreover, they are often frail with little cardiovascular reserve and therefore tolerate aggressive fluid resuscitation poorly. 

Immediate management

Venous access should be obtained, investigations listed in the Investigations Section should be initiated and one litre of normal saline should be administered intravenously.

If the patient is not shocked then the first litre should go in over two hours, otherwise normal saline or colloid should be administered rapidly to achieve a systolic >100. If the systolic BP can not be brought above 100 mm Hg reasonably quickly, then senior help should be sought and the patient transferred to HDU/ITU.

A fixed-dose intravenous insulin infusion should be initiated. Fifty units of soluble insulin such as actrapid is diluted in 50 ml normal saline and given via a syringe driver at a rate of 0.1 units/kg body weight/hour. The ADA guidelines also recommend a bolus/priming dose of insulin be given, many UK physicians would not see this as essential.

An alternative to fixed dose insulin infusion is to institute a traditional Variable Rate Intravenous Insulin Infusion ("sliding scale") IV insulin regimen.

Subsequent fluid management

This should always be performed according to clinical assessment but as a rough guide - it is reasonable to expect the 'average' case of HHS to be in a 7-14 litre negative fluid balance and the aim should normally be to replace this over two to three days.

Thus, after the first litre, the next should go in over four hours, the next over six to eight, then continue eight hourly litre bags. But it must be stressed that these figures are only a guide.

Although the ADA guidelines recommend use of half normal saline as the intravenous fluid of choice, most UK physicians would start off with normal saline and only switch to half-normal later if there is persisting hypernatraemia (e.g. >155 mmol/L after the first 24 hours) or if the presenting osmolality was excessively high (e.g. >380-390 mOsmol/kg).

However, it must be stressed that bringing the osmolality down too fast caries a risk of neurological damage and/or precipitating heart failure by sheer volume overload. A steady rate of reduction of 1 mOsmol/kg/hr should therefore be the aim. A urinary catheter should also be passed in order to monitor urine output.

After the first hour, serum K+ should be re-assessed (no K+ should be given in the first bag of fluid). If the serum K+ is greater then 5.5 mmol/L then K+ supplementation should be withheld, between 3.5 and 5.5, 40 mmol K+ should go in to each bag and, if less than 3.5 mmol/L, the patient should be transferred to a high dependency clinical area where strong IV K+ can be administered centrally.

Monitoring regimen

It is essential that a monitoring regimen is instituted. Capillary blood glucose levels should be checked hourly.

Us+Es and lab glucose should be checked four hourly. In addition, the patient should be frequently clinically re-assessed, especially with respect to their volume status. Frequently re-calculate osmolality and check that it is not falling too fast. If it is, slow the rate of IV fluid administration and consider slowing the rate of insulin as well. The latter is a good strategy when the glucose level is falling fast and significantly contributing to the over-rapid correction of total osmolality.

What should the doctor do when the blood glucose level starts to fall?

If you are using fixed dose insulin infusion then once the glucose level falls below around 10-12 mmol/L, halve the rate of insulin infusion and switch to using 5% glucose as the IV fluid.

When should the patient be converted to a subcutaneous insulin regimen?

This should be undertaken once HHS is resolved and they are eating and drinking normally.

If the patient was not previously on insulin, prescribe a twice daily bisphasic insulin such as Humulin M3. Calculate the total daily insulin requirement by adding up the insulin requirement from the previous 24 hour’s insulin infusion and dividing it as 2/3 in the morning and 1/3 in the evening. This should be continued for at least a fortnight while they fully recover, before considering switching them back to OHAs. However, if the admitting HbA1c was high, then a switch back to the previous OHAs may not be in their best interests and this decision should be discussed thoroughly with the patient’s usual diabetologist.

If the patient was previously taking insulin, convert them back to their usual regimen but add an extra 20% to all doses as they are likely to be significantly more insulin resistant than usual.

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