Hyperglycaemic Hyperosmolar State (HHS) ✅

🚑 Hyperosmolar Hyperglycaemic State (HHS) is a life-threatening hyperglycaemic emergency usually seen in type 2 diabetes. It is characterised by severe hyperglycaemia, profound dehydration, and hyperosmolality, with minimal ketonaemia and little or no acidosis. Mortality (10–20%) is higher than diabetic ketoacidosis because patients are typically older and comorbid. Management follows the UK JBDS HHS guideline and focuses on slow correction of dehydration and osmolality.

⚡ Key Diagnostic Features (JBDS)

• Severe hyperglycaemia: glucose usually ≥ 30 mmol/L
• Hyperosmolality: ≥ 320 mOsm/kg
• Profound dehydration
• Minimal ketonaemia: ketones ≤ 3 mmol/L
• No significant acidosis: pH ≥ 7.3 and bicarbonate ≥ 15 mmol/L

🧮 Calculated osmolality: (2 × Na⁺) + glucose + urea (all mmol/L)

🧠 Pathophysiology

• Relative insulin deficiency prevents glucose uptake but enough insulin remains to suppress ketosis.
• Severe hyperglycaemia causes osmotic diuresis → loss of water > electrolytes.
• This produces extreme dehydration (often 6–13 L deficit).
• Rising serum osmolality leads to intracellular brain dehydration → confusion, seizures, coma.
• Rapid correction of osmolality can cause cerebral oedema, hence slow fluid replacement.

🧬 Common Precipitants

• 🦠 Infection (most common): pneumonia, UTI, cellulitis
• ❤️ Acute vascular events: MI, stroke
• 💊 Drugs: corticosteroids, thiazide diuretics, atypical antipsychotics
• 🚰 Dehydration: poor oral intake, elderly or care-home patients
• 🩺 New diagnosis of type 2 diabetes

🩺 Clinical Features

• Severe dehydration: dry mucosae, tachycardia, hypotension
• Polyuria and polydipsia
• Neurological symptoms:
  • Confusion
  • Seizures
  • Coma
• Usually no Kussmaul breathing or acetone breath unless mixed DKA/HHS

🔬 Investigations

• Capillary glucose and blood ketones
• Venous blood gas (pH, bicarbonate)
• Urea & electrolytes, creatinine
• Calculated osmolality
• FBC and CRP
• Blood cultures if infection suspected
• Urinalysis and culture
• ECG and troponin if ACS suspected
• CXR if pneumonia suspected

🛠️ Management (JBDS Approach)

✅ Principles: Fluids first → gradual osmolality correction → insulin only when indicated.

1️⃣ Initial resuscitation

• ABCDE assessment
• Insert IV access
• Start 0.9% sodium chloride
• Typical initial fluid target:
  • 2–3 L positive balance by 6 hours
  • 3–6 L by 12 hours
• Give prophylactic LMWH due to high thrombotic risk

2️⃣ Insulin therapy

• Often not required initially
• Start IV insulin infusion (FRIII) 0.05 units/kg/hour if:
• Glucose stops falling with fluids alone
• Ketones > 1 mmol/L
• If mixed DKA/HHS (ketones >3 mmol/L with acidosis) → treat using DKA protocol (0.1 units/kg/hour)

3️⃣ Electrolyte management

• Total body potassium is depleted despite normal serum levels.
• Replace potassium according to serum levels and urine output.
• A rising sodium is expected as glucose falls.
• Focus on osmolality reduction rather than sodium alone.

4️⃣ Monitoring

• Hourly glucose
• Hourly observations and neurological status
• Fluid balance and urine output
• U&E and osmolality every 1–2 hours initially

🎯 Treatment Targets

• Osmolality fall: 3–8 mOsm/kg/hour
• Glucose fall: ≤ 5 mmol/L/hour

⚠️ Complications

• Venous thromboembolism
• Acute kidney injury
• Electrolyte disturbances
• Seizures
• Aspiration pneumonia
• Rhabdomyolysis

✅ Resolution Criteria (JBDS)

• Osmolality < 300 mOsm/kg
• Glucose < 15 mmol/L
• Normal cognition
• Urine output ≥ 0.5 mL/kg/hour

🏁 Prevention and Discharge

• Identify and treat precipitating cause
• Review diabetes medications
• Provide sick-day advice
• Arrange diabetes team follow-up

📚 References

• JBDS Guideline: Management of Hyperosmolar Hyperglycaemic State (Adults)
• JBDS HHS Care Pathway (UK Hospitals)
• BNF/NICE – Diabetic hyperglycaemic emergencies
• NICE Clinical Knowledge Summary – Hyperglycaemic emergencies