Hyperosmolar Hyperglycemic State (HHS)
Formal Definition
Hyperosmolar Hyperglycemic State (formerly HHNK — hyperosmolar hyperglycemic nonketotic coma) — a life-threatening complication of type 2 diabetes characterized by severe hyperglycemia (typically >600 mg/dL, often >1,000), profound dehydration (fluid deficits of 8-12 L), hyperosmolarity (>320 mOsm/kg), absence of significant ketoacidosis, and altered mental status; mortality 10-20%, much higher than DKA; usually seen in elderly patients with type 2 diabetes triggered by infection, MI, medication non-adherence, or other physiologic stress.
How It's Used on the Ward
"HHS" — the diabetes emergency with sky-high sugar but no ketones (unlike DKA); the patient is in a profoundly dehydrated, altered state with sugar often >600 and sodium appearing falsely normal due to osmotic shifts; typically elderly T2DM patients who let their sugars run unchecked for days.
Example
""78-year-old nursing home resident with T2DM found confused and lethargic. Fingerstick glucose "HI" (meter max 600mg/dL). Labs: glucose 1,142 mg/dL, Na 158 (corrected 178), BUN 68, Cr 2.1, serum osm 358 mOsm/kg. Urinalysis: no ketones. ABG: pH 7.39, no acidosis. Diagnosis: HHS. Aggressive IV fluid resuscitation with NS started (1L over first hour), insulin drip at 0.1 U/kg/h, hourly glucose and electrolyte monitoring. ICU admission.""
Clinical Context
HHS vs DKA: HHS — T2DM (usually older), glucose >600 mg/dL, no/little ketoacidosis (pH >7.3, bicarb >15), osm >320, severe dehydration, altered mental status prominently. DKA — T1DM or insulin-dependent T2DM, glucose typically 250-600, significant ketoacidosis (pH <7.3, bicarb <15), osm usually <320, more rapid onset. Both share: total body K+ depletion (even with normal serum K — insulin deficiency + acidosis shifts K out of cells, urinary losses drop total body stores), need for aggressive fluids + insulin + K+ replacement. Triggers for HHS: infection (UTI, pneumonia, sepsis), MI, stroke, missed insulin doses, dehydration from gastroenteritis, new medications (steroids, SGLT2 inhibitors). Treatment protocol: (1) Aggressive fluids (NS 1L first hour, then 250-500 mL/h based on response), (2) insulin drip 0.1 U/kg/h (after K confirmed >3.3), (3) K+ replacement when <5.2, (4) hourly glucose, electrolytes, osm, mental status. Goal: glucose drop 50-75 mg/dL/h, osm drop 3 mOsm/L/h, replace fluid deficit over 24-36h. Watch for cerebral edema from rapid osm shifts (rare in HHS vs DKA).