HHS (Hyperosmolar Hyperglycemic State): Fluids First, Gentle Insulin & Osmolality Math

Hyperosmolar hyperglycemic state is mostly a water problem. Think profound dehydration, sky-high glucose, and minimal ketosis. The priorities: fluids → potassium → low-dose insulin, while watching osmolality and sodium so you don’t drop them too fast.

Diagnosis — How HHS differs from DKA

• Severe hyperglycemia: often > 600 mg/dL (33 mmol/L).
• Effective osmolality: > 320 mOsm/kg.
• Minimal ketosis/acidosis: pH > 7.30, HCO₃⁻ > 18 mEq/L, small/absent ketones (β-hydroxybutyrate may be mildly ↑).
• Neurologic changes (confusion → coma) correlate with osmolality.

Useful formulas

• Effective osmolality (excludes urea): 2 × Na (mEq/L) + glucose/18.
• Corrected Na⁺ for hyperglycemia: add ~1.6 mEq/L (some use 2.4 at high glucose) for each 100 mg/dL glucose above 100.

First 10 minutes — Stabilize & screen for triggers

• Vitals, mental status, volume assessment, fall risk precautions.
• Two large-bore IVs, telemetry if ill; POCUS IVC/lungs/bladder if volume uncertainty.
• Labs: BMP (with Mg/Phos), VBG/ABG, β-hydroxybutyrate, CBC, serum osmolality (if available), UA/urine ketones, cultures if infection suspected.
• ECG (look for ischemia and potassium effects).
• Common precipitants: infection, MI, stroke, steroids/thiazides/atypical antipsychotics, poor access to water, missed insulin.

Step 1 — Fluids (the main therapy)

• Initial: give 1 L isotonic crystalloid over the first hour (adjust for CHF/CKD/elderly). Balanced crystalloids lower chloride load; 0.9% saline acceptable if that’s your protocol.
• Then: 250–500 mL/h guided by perfusion, urine output, and ultrasound.
• Choose tonicity using corrected Na⁺:
  • Corrected Na⁺ low/normal (≤145): continue isotonic (LR/NS).
  • Corrected Na⁺ high (>145): switch to 0.45% NaCl to slowly lower osmolality.
• Targets: drop effective osmolality by about 3 mOsm/kg/h (avoid rapid shifts); sodium fall ≤ 10–12 mEq/L per 24 h.

Step 2 — Potassium (before insulin)

• K⁺ <3.3 mEq/L: hold insulin; give IV KCl (e.g., 20–30 mEq/h) until ≥3.3.
• K⁺ 3.3–5.2: add 20–30 mEq K⁺ per liter of IV fluid; target K⁺ 4–5.
• K⁺ >5.2: withhold K⁺ initially and recheck every 2 h.
• Replete magnesium if low—helps retain K⁺ and stabilize myocardium.

Step 3 — Insulin (gentle and later than DKA)

• After 1–2 h of fluids (and once K⁺ is safe), start IV regular insulin at 0.05 units/kg/h (no bolus).
• Aim glucose fall of ~50–75 mg/dL per hour. If slower, titrate modestly.
• When glucose reaches ~300 mg/dL (17 mmol/L), add D5 to IV fluids (e.g., D5-LR or D5-½NS depending on Na⁺) and continue insulin to correct hyperosmolality carefully.

Step 4 — Phosphate & bicarbonate?

• Phosphate: routine replacement not required; replete if <1.0 mg/dL, rhabdomyolysis, respiratory muscle weakness, or cardiomyopathy (consider K-phos if K⁺ allows).
• Bicarbonate: generally not indicated (acidosis is usually mild); consider only for severe acidosis from another process.

Monitoring cadence

• Glucose hourly until trend steady; neuro checks each nursing round.
• Electrolytes (Na⁺, K⁺, HCO₃⁻), measured or calculated effective osmolality, phosphate, magnesium every 2–4 h initially.
• Track fluid balance, weights, and lung exam for overload.

Antithrombotic prophylaxis

• HHS carries a high VTE risk; give pharmacologic DVT prophylaxis (e.g., LMWH) unless contraindicated.

When is HHS “resolved”?

• Return of baseline mental status and hemodynamic stability,
• Effective osmolality < ~315–320 mOsm/kg with a safe downward trajectory,
• Glucose controlled (<300 mg/dL) with ongoing insulin plan.

Transition to subcutaneous insulin

• Calculate total daily dose (TDD) ~0.3–0.6 units/kg/day (individualize; older/frail on the lower side).
• Give basal insulin (e.g., glargine) 1–2 h before stopping IV insulin; start prandial/correctional when eating.
• Diabetes education, sick-day rules, and trigger mitigation before discharge.

Special populations & pitfalls

• Elderly/CKD/CHF: smaller boluses, slower titration, frequent lung/IVC reassessment.
• Mixed DKA/HHS: treat like DKA (earlier insulin) but still protect against rapid osmolality shifts.
• Avoid precipitous drops in Na⁺/osmolality—use ½NS or D5-containing fluids judiciously to keep changes gradual.
• Don’t forget infections/MI/stroke—treat the trigger or HHS will recur.

Patient FAQs

“Why are you giving so much fluid?” HHS causes severe dehydration; water replacement is the key to safely lowering sugar and osmolality.

“Why is my insulin drip so low?” In HHS we lower glucose and osmolality slowly to protect the brain from rapid shifts.

References & Notes

Practical HHS pathway: resuscitate first, correct Na⁺ and effective osmolality gradually, use low-dose insulin after potassium is safe, anticoagulate prophylactically, and overlap basal insulin at transition. Local protocols vary—follow institutional guidance. Educational only.