Most nurses know diabetic ketoacidosis (DKA). Fewer are as familiar with hyperosmolar hyperglycaemic state (HHS), a diabetes emergency that typically affects older people with type 2 diabetes, often undiagnosed. It develops slowly over days, causes profound dehydration, and has a higher mortality than DKA. Recognising it and treating it carefully saves lives.
HHS vs DKA
| DKA | HHS | |
|---|---|---|
| Typical patient | Type 1 diabetes, often younger | Type 2 diabetes, often older |
| Onset | Hours to a day | Days to weeks |
| Blood glucose | Raised (often above 11 mmol/L) | Very high (often 30 mmol/L or more) |
| Ketones | High | Low or absent (not significantly raised) |
| Acidosis | Yes | Usually not significant |
| Osmolality | Variable | Very high (often above 320 mOsm/kg) |
| Dehydration | Significant | Severe (often 10–22% of body water) |
Mixed presentations with features of both also occur.
Triggers
- Infection (pneumonia, urinary tract infection, sepsis).
- Missed diabetes medicines.
- Medicines such as steroids and thiazide diuretics.
- Stroke, myocardial infarction.
- Not drinking enough (older adults, dementia, hot weather).
- Sugary drinks consumed to quench thirst, worsening hyperglycaemia.
Signs
- Several days of excessive urination and thirst.
- Signs of severe dehydration: dry mouth, sunken eyes, low BP, fast heart rate.
- Confusion, drowsiness, seizures, focal neurological signs, coma.
- Very high capillary glucose (“HI” on many meters).
Treatment principles: slow and steady
Unlike DKA, the cornerstone of HHS treatment is careful fluid replacement, not early aggressive insulin.
- IV 0.9% sodium chloride to restore circulating volume; fluid alone lowers glucose.
- Insulin is usually started at a low fixed rate only when glucose stops falling with fluids alone, or earlier if significant ketones are present, according to guidelines such as JBDS.
- Aim for a gradual fall in glucose (e.g. around 4–6 mmol/L per hour) and in osmolality, because rapid changes risk cerebral oedema and osmotic demyelination.
- Monitor sodium: it often rises initially as glucose falls; this is expected but must be watched.
- Replace potassium as guided by levels.
Nursing priorities
- Hourly capillary glucose; regular bloods for sodium, potassium, urea, osmolality as ordered.
- Strict fluid balance; urinary catheter may be needed.
- Neurological observations (GCS).
- Watch for fluid overload, especially in older patients with heart disease.
- VTE prophylaxis: HHS causes very high clot risk due to dehydration and hyperviscosity. See VTE prevention.
- Foot protection: older, immobile patients with diabetes are at high risk of heel pressure ulcers. See diabetic foot care.
- Find and treat the trigger.
Prevention
Teach “sick day rules”, encourage fluid intake (water, not sugary drinks), and ensure older people with diabetes are checked when unwell. See type 2 diabetes education.
Based on Joint British Diabetes Societies (JBDS) guideline on HHS in adults and ADA consensus on hyperglycaemic crises. Educational content: follow local protocols.