GGC Medicines

Adult Therapeutics Handbook

Management of Hyperglycaemic Hyperosmolar State / Hyperosmolar Non-Ketotic Coma (HONC)

Management of Hyperglycaemic Hyperosmolar State (HHS) / Hyperosmolar Non-Ketotic Coma (HONC)

This condition carries a significant mortality and close monitoring within a well staffed clinical area is essential. The following regimen is a guide only; because of the co-morbidities associated with this condition each case must be treated on an individual basis.


Diagnostic criteria include:

  • Severe hyperglycaemia (blood glucose >30mmol/L)
  • Total osmolality >340mosmol/kg
  • Serum bicarbonate >15mmol/L (not acidotic)
  • Urinary ketones ≤ + plus

Clinical features include:

  • Insidious onset
  • Severe dehydration
  • Impaired level of consciousness (degree correlates with plasma osmolality).
  • May have concurrent illness e.g. MI, stroke or pneumonia.

This condition occurs in patients with type 2 diabetes mellitus (which may or may not have been previously diagnosed). There is marked hyperglycaemia and dehydration without significant ketosis and acidosis. The condition usually develops over a period of days, often made worse by diuretics and consumption of glucose rich drinks.

The aim should be for a gradual restoration of blood biochemistry avoiding a rapid reduction in plasma osmolality (which can precipitate cerebral oedema). These patients commonly have coexisting medical problems and mortality is much higher than for DKA. There is also a significant risk of thromboembolism and thromboprophylaxis should always be used in the absence of contraindication.

Key steps in the management of HHS / HONC

  • Establish correct diagnosis
  • Monitor closely in a well staffed clinical area
  • Aim to reduce blood glucose gradually
  • Appropriate fluid resuscitation must be guided by clinical assessment, hydration status and co-morbidity.
  • Regular monitoring of potassium level must guide appropriate replacement
  • Consider and treat the underlying cause.

Assessment / monitoring

  • Glucose – often exceeds 40mmol/L
  • U&Es – patient is dehydrated and can be hypernatraemic
  • Venous blood gases – are relatively normal (not acidotic as seen in diabetic ketoacidosis (DKA))
  • Osmolality – is calculated by [2 x (Na+ + K+) + urea + glucose]. It is usually >350mosmol/kg
  • FBC – increase in Hb and WCC may indicate dehydration and infection
  • ECG – may show ischaemia or infarction
  • Chest x-ray
  • Urinalysis
  • MSSU / blood cultures

General management and drug therapy

IV insulin and IV fluid replacement are the mainstays of treatment but both should be used more cautiously compared to DKA (see below).

  • Give oxygen therapy.
  • Central venous pressure (CVP) monitoring may be required to guide fluid replacement.
  • Insert nasogastric tube if consciousness level is reduced or protracted vomiting.
  • Insert urinary catheter.
  • Give thromboprophylaxis SC (if no contraindications) – Enoxaparin SC 40mg once daily (or 20mg once daily if the eGFR is <30ml/minute/1.73m2).

IV Fluids

Administer: Sodium chloride IV 0.9% –

  • Give 1st litre over 1 hour,
  • 2nd litre over 2 hours
  • 3rd litre over 4 hours
  • 4th litre over 6 hours and
  • 5th litre over 8 hours.


  • Faster rehydration is inappropriate in hyperosmolar coma. The above regimen is a guide and should be reviewed in the elderly or patients with cardiac disease according to clinical assessment of hydration and taking into account co-morbidities.
  • If the corrected sodium concentration is high (>155mmol/L) after the initial 1–2 litres of sodium chloride, then 0.45% sodium chloride should be considered after discussion with the consultant on-call or diabetes team. Serum electrolytes should be monitored closely.
  • When blood glucose (BG) level falls below 14mmol/L add in 10% glucose at a rate of 100ml/hour.
  • Review the patient closely to determine hydration status and consider the need for, and rate of rehydration with sodium chloride 0.9% solution.

IV Insulin (soluble insulin e.g. Actrapid® or Humulin S®)

Preparation: Add 50units of soluble insulin (Actrapid® or Humulin S®), drawn up using an insulin syringe, to 50ml of 0.9% sodium chloride in a 50ml syringe (1unit/ml infusion). Infuse intravenously using a syringe pump.

A starting infusion rate similar to the one used in DKA can be used. Start at 6units/hour of insulin. Aim for a target blood glucose of between 9–14mmol/L. The additional supporting guidance from DKA care pathway 4 hours–discharge (here) can be used to adjust insulin dose when blood glucose has fallen to <14mmol/L.


  • Aim for a gradual reduction in blood sugar in order to prevent sudden osmotic shifts.
  • Aim for a fall in BG at a rate of 2–3 mmol/hour. It may be necessary to adjust the infusion rate to achieve this. If the fall in BG is too rapid with 6units/hour of insulin then consider reducing the rate to 3units/hour.
  • When BG falls below 14mmol/L add in 10% glucose 100ml/hour.
  • Be prepared to adjust insulin infusion rate to maintain BG within the target range.
  • If BG level is not falling, always check pump devices, IV lines and IV cannulae to ensure patients are getting prescribed insulin dose. Consider other causes that could be contributing: sepsis, steroid therapy, obesity or liver disease.

Potassium monitoring and replacement

  • The initial serum potassium can be normal or elevated but the potassium level may fall in response to the patient being treated with insulin. It is therefore essential that U&Es are checked on admission, and at 2 hours and at 4 hours into admission to guide appropriate potassium replacement.
  • Aim for a serum potassium of 4–5 mmol/L. IV fluids containing potassium (unless patient anuric) can be used to maintain potassium within this range.
Serum Potassium (mmol/L) Potassium chloride to be given (mmol/L)
(N.B. Potassium bags are available as 20mmol/500ml)
>5 0
3.5–5 20#
<3.5 40
# To give potassium chloride 20mmol/L, give one 500ml bag of fluid containing potassium chloride 20mmol and then run through a bag of 500ml fluid not containing any potassium.
  • The usual maximum rate of potassium administration is 10mmol/hour. Faster rates can be given but ensure ECG monitoring is done.
  • N.B. Do not administer potassium chloride at a rate >20mmol/hour under any circumstances.

Important points

  1. This regimen is a guide and should be modified according to response to therapy.
  2. U&Es should be checked at least four times daily to guide potassium administration but may need to be more frequent depending on clinical scenario.
  3. Continue IV fluids and insulin until normal biochemistry is restored and patient is eating and drinking normally. This may take up to 48–72 hours.
  4. Recommence insulin or oral hypoglycaemics in patients previously treated. Many patients who were previously undiagnosed can be managed on diet therapy alone. Some will require oral hypoglycaemics (see Types of Antidiabetic Drugs).
  5. Discuss with a member of the Diabetes Team pre-discharge.

If you are unsure of how to review or how to adjust any of these parameters please contact a member of your local Diabetes Team.