Diagnostic Criteria for Hyperosmolar Hyperglycemic State (HHS)
The diagnostic criteria for Hyperosmolar Hyperglycemic State (HHS) include blood glucose ≥600 mg/dL, effective serum osmolality ≥320 mOsm/kg H₂O, arterial pH >7.3, serum bicarbonate >15 mEq/L, minimal or absent ketones in urine or serum, and altered mental status. 1
Key Diagnostic Parameters
| Parameter | HHS Criteria |
|---|---|
| Plasma glucose | ≥600 mg/dL |
| Arterial pH | >7.3 |
| Serum bicarbonate | >15 mEq/L |
| Urine ketones | Small/minimal |
| Serum ketones | Small/minimal |
| Effective serum osmolality | ≥320 mOsm/kg H₂O |
| Anion gap | Variable |
| Mental status | Stupor/coma (typically altered) |
Calculation of Effective Serum Osmolality
Effective serum osmolality is a critical diagnostic parameter for HHS and should be calculated using the following formula:
- Effective serum osmolality = 2[measured Na⁺ (mEq/L)] + glucose (mg/dL)/18 2
Clinical Presentation
HHS typically develops more gradually than DKA, often over many days, resulting in:
- Extreme dehydration (fluid losses of 100-220 mL/kg)
- Severe hyperglycemia (often >600 mg/dL)
- Altered mental status ranging from confusion to coma
- Minimal or no ketosis (distinguishing it from DKA)
- Higher mortality rate (10-20%) compared to DKA 1, 3
Important Distinctions from DKA
- HHS features minimal ketosis and minimal acidosis compared to DKA
- Mental status changes are more prominent in HHS due to extreme hyperosmolality
- HHS has a more gradual onset (days) compared to DKA (hours)
- Dehydration and metabolic disturbances are typically more severe in HHS 1, 4
Resolution Criteria
HHS is considered resolved when:
- Blood glucose <300 mg/dL
- Serum osmolality <315 mOsm/kg
- Patient is alert and able to ingest liquids 1
Common Pitfalls to Avoid
- Failing to recognize mixed DKA/HHS presentations, which require elements of both treatment protocols
- Initiating insulin before adequate fluid resuscitation, which may precipitate cardiovascular collapse
- Rapid correction of osmolality (>8 mOsm/kg/h), which may lead to cerebral edema or central pontine myelinolysis
- Overlooking underlying precipitating factors such as infection, stroke, myocardial infarction, or medication effects 1, 4, 3
HHS is a medical emergency requiring prompt diagnosis and management to reduce the high associated mortality. The diagnostic criteria focus on extreme hyperglycemia, hyperosmolality, minimal ketosis, and altered mental status, with treatment centered on careful fluid resuscitation and insulin therapy.