Hyperosmolar Hyperglycemic State (HHS)

A note on the name

This condition was once called hyperosmolar hyperglycemic nonketotic state or coma, because, unlike diabetic ketoacidosis (DKA), ketones are absent or only mildly raised. Some people have features of both HHS and DKA. "Hyperosmolar" means the blood is unusually concentrated because of high sugar and water loss.

How HHS develops

In type 2 diabetes there is usually enough insulin to stop the body breaking down fat into ketones, but not enough to control blood sugar under stress. Blood sugar climbs. The kidneys pass sugar into the urine, taking large amounts of water with it. Over days to weeks, the person becomes severely dehydrated, often losing 8 to 12 liters of body water. Older adults may not feel thirsty or may not be able to drink, so the cycle worsens. As blood becomes more concentrated, brain cells lose water, causing confusion and coma.

Causes and triggers

• infections, the most common trigger: pneumonia, urinary tract infection, skin infections, sepsis
• stroke, heart attack, pancreatitis
• missed or stopped diabetes medicines
• medicines that raise blood sugar: steroids, thiazide diuretics, some antipsychotics
• not drinking enough: older adults in care homes, people with dementia
• undiagnosed type 2 diabetes (HHS can be the first sign)
• alcohol or drug use

Symptoms

Symptoms build over several days or weeks:

• extreme thirst and dry mouth
• frequent urination, then reduced urine as dehydration worsens
• weakness and tiredness
• weight loss
• blurred vision
• leg cramps
• confusion, drowsiness, hallucinations
• seizures, weakness on one side, or coma in severe cases

HHS vs DKA

Diagnosis

Blood tests confirm HHS:

• blood glucose, typically 600 mg/dL (33.3 mmol/L) or higher
• serum osmolality above 300 to 320 mOsm/kg
• little or no ketones, and near-normal blood pH and bicarbonate
• sodium, potassium, kidney function
• tests for the trigger: urine and blood cultures, chest X-ray, ECG, cardiac markers, sometimes brain imaging

Treatment

HHS is treated in hospital, often in intensive or high-dependency care:

• IV fluids: the most important treatment. Fluids are replaced gradually over 24 to 48 hours to avoid shifting water into the brain too quickly.
• Insulin: given intravenously, usually at a low dose and often started after fluids have begun lowering blood sugar.
• Electrolytes: potassium, and sometimes phosphate and magnesium, are replaced and closely monitored.
• Treating the trigger: antibiotics for infection, stroke or heart care as needed.
• Blood clot prevention, as thickened blood raises the risk of clots.
• Monitoring of glucose, sodium, osmolality, mental status, urine output and heart rhythm.

After recovery, most people continue on insulin or adjusted diabetes medicines, with education on preventing recurrence.

Complications

• blood clots in legs, lungs or brain
• stroke and heart attack
• kidney failure
• seizures and brain swelling (rare, especially if correction is too fast)
• death, particularly in older adults with serious triggering illness

Prevention

• check blood sugar more often when unwell
• follow sick day rules: keep drinking fluids, keep taking diabetes medicines unless told otherwise, and contact your care team early
• caregivers of older adults with diabetes should watch fluid intake and blood sugar, especially during infections or heat
• attend regular diabetes reviews
• know the symptoms of very high blood sugar

Frequently asked questions

What is hyperosmolar hyperglycemic state?

HHS is a diabetes emergency in which blood sugar becomes extremely high and the body becomes severely dehydrated, making the blood very concentrated. It mostly affects older adults with type 2 diabetes and can cause confusion, seizures and coma.

What is the difference between HHS and DKA?

Both are diabetes emergencies with high blood sugar. DKA involves high ketones and acidic blood and develops quickly, usually in type 1 diabetes. HHS involves even higher blood sugar and severe dehydration with few ketones, develops over days to weeks, and usually affects older people with type 2 diabetes.

What triggers HHS?

Infections such as pneumonia and urinary tract infections are the most common triggers. Others include stroke, heart attack, missed diabetes medicines, steroids, and not drinking enough fluids. It can also be the first sign of undiagnosed type 2 diabetes.

Can HHS be fatal?

Yes. HHS has a higher death rate than DKA, mainly because it affects older people and is often triggered by serious illness. Early recognition and hospital treatment with fluids, insulin and treatment of the trigger greatly improve survival.