Hyperosmolar hyperglycemic state (HHS): workup and management
HHS: severe hyperglycemia (usually ≥600 mg/dL) with effective serum osmolality >300 mOsm/kg, profound dehydration and often altered mental status, without significant ketoacidosis (pH ≥7.3, bicarbonate ≥15, β-hydroxybutyrate <3 mmol/L). Mortality is higher than DKA. Priorities are cautious-but-substantial fluid replacement, potassium, low-dose insulin once fluids alone stop working, and finding the trigger.
Working diagnosis
Adult · US guidelines
Draft · awaiting physician review
01Orient
What's new in the evidence
- 2024 consensus: IV insulin 0.05 unit/kg/h in HHS without significant ketosis, started once glucose stops falling with fluids alone
- Safety limits: glucose fall ≤90–120 mg/dL per hour, sodium fall ≤10 mEq/L per 24 hours, osmolality fall 3–8 mOsm/kg per hour
- A rise in measured sodium as glucose falls is expected and is not by itself a reason for hypotonic fluid
Differential diagnoses
- HHS (often older adults with type 2 diabetes)
- Mixed DKA–HHS (both ketoacidosis and hyperosmolality)
- Precipitant: infection (pneumonia, UTI, sepsis) (can't miss)
- Precipitant: MI or stroke (can't miss)
- Precipitant: missed or inadequate diabetes medication
- Drugs: glucocorticoids, thiazides, atypical antipsychotics, SGLT2 inhibitors
- Altered mental status from another cause (stroke, meningitis, hyponatremia)
02Assess
Risk scores and decision tools
- Effective osmolality = 2 × Na + glucose/18
- Corrected sodium
- GCS (reduced consciousness correlates with osmolality)
Key history questions
- Days to weeks of polyuria, polydipsia, weight loss, reduced intake
- Confusion, drowsiness or new focal neurological symptoms
- Infection symptoms, chest pain, stroke symptoms
- Diabetes medications, adherence and recent changes
- Steroids, antipsychotics, diuretics, SGLT2 inhibitors
- Access to water (nursing home residents, dementia)
Examination findings
- Severe dehydration: dry mucosa, tachycardia, hypotension, poor skin turgor
- Level of consciousness (GCS); seizures; focal deficits that may reverse with treatment
- Source of infection: chest, urine, skin, pressure ulcers
- No Kussmaul breathing unless mixed DKA–HHS
03Investigate
Initial investigations
- Glucose, β-hydroxybutyrate, venous blood gas
- BMP with calculated effective osmolality (2×Na + glucose/18) and corrected sodium
- Measured serum osmolality
- CBC, magnesium, phosphate, CK
- Urinalysis, ECG, troponin, chest X-ray
- Blood and urine cultures if any infection is possible
Advanced investigations
- CT head if focal signs or mental status out of proportion to osmolality
- Lipase if abdominal pain
- HbA1c to guide discharge regimen
04Treat
Immediate management
- 0.9% saline 1–1.5 L over the first hour, then guided by volume status, corrected sodium and urine output
- Aim for osmolality to fall about 3–8 mOsm/kg per hour; avoid faster falls
- Check potassium before insulin: replace if under 3.5 mEq/L and hold insulin until it is
- Start IV insulin 0.05 units/kg/h once glucose stops falling with fluids alone (earlier if ketonemia)
First-line treatment
- Add 20–30 mEq potassium per liter of fluid when K is 3.5–5.0 mEq/L
- Switch to 0.45% saline if corrected sodium is high or rising once perfusion is restored
- Add dextrose when glucose falls to about 250–300 mg/dL and keep glucose in that range until mental status and osmolality recover
- VTE prophylaxis (high thrombotic risk) unless contraindicated
- Treat the precipitant
Second-line treatment
- ICU for shock, coma or severe hyperosmolality
- Phosphate replacement only if under 1.0 mg/dL or with cardiac or respiratory compromise
Specialist referrals
- ICU for hemodynamic instability or reduced consciousness
- Diabetes or endocrinology team before discharge
05Disposition
Admission criteria
- All HHS requires admission, usually step-down or ICU
- Effective osmolality >320, GCS <12 or hemodynamic instability: ICU
Safe discharge criteria
- Osmolality and mental status back to baseline
- Eating and drinking; stable subcutaneous regimen
- Precipitant treated and follow-up arranged
Follow-up timing
- Diabetes follow-up within 1–2 weeks
Patient instructions
- Sick-day plan: keep drinking fluids, check glucose more often, seek help early
- Who to call if glucose stays above about 300 mg/dL
Monitoring
- Glucose hourly; BMP and osmolality every 2–4 hours
- Neurological status and fluid balance hourly
Clinical pearls and pitfalls
- Fluid deficit is often 8–12 L; correct it over 24–48 hours
- Measured sodium rises as glucose falls; use corrected sodium to judge free-water deficit
- Rapid osmolality falls risk cerebral edema and osmotic demyelination
- Many patients can go home on oral agents after recovery; reassess the long-term regimen
RefGuidelines and landmark evidence
For education only. Typical adult starting points; confirm doses against renal function, allergies, interactions and your institution's protocols. Not a substitute for clinical judgment or senior review.