Management Differences Between HHS and DKA
The primary difference in managing HHS versus DKA is that fluid resuscitation is the cornerstone of HHS treatment while insulin therapy is the cornerstone of DKA treatment, though both require aggressive fluid replacement, insulin, and electrolyte monitoring. 1
Key Diagnostic Thresholds
DKA criteria:
- Glucose ≥250 mg/dL
- pH <7.3
- Bicarbonate <15 mEq/L
- Moderate ketonuria/ketonemia 2
HHS criteria:
- Glucose ≥600 mg/dL (some guidelines use ≥30-33.3 mmol/L)
- pH ≥7.3
- Bicarbonate ≥15 mEq/L
- Altered mental status or severe dehydration
- Osmolality ≥320 mOsm/kg 2, 3
Fluid Management: The Critical Difference
HHS Approach
- More aggressive fluid replacement is essential - HHS patients have more profound dehydration (typically 8-10L deficit vs 3-6L in DKA)
- Replace approximately 50% of estimated fluid loss within first 12 hours 3
- Initial rate: 15-20 mL/kg/h or 1-1.5 L/h of 0.9% normal saline 3
- Target osmolality correction: <3 mOsm/kg/h (some UK guidelines accept 3-8 mOsm/kg/h) 3
- Fluid replacement takes priority over insulin in HHS 1
DKA Approach
- Standard fluid resuscitation at typical rates
- Fluid is important but insulin therapy is the primary treatment focus 1
Insulin Therapy: Dosing Differences
DKA
- Continuous IV insulin infusion preferred for moderate-to-severe cases 4, 2
- Standard rate: 0.1 units/kg/h 2
- Mild DKA can use subcutaneous insulin with priming dose of 0.4-0.6 units/kg (half IV bolus, half SC/IM), then 0.1 unit/kg SC/IM hourly 2
- Target glucose decline: 50-75 mg/dL/h 2
HHS
- Lower insulin infusion rate: 0.05 units/kg/h, increasing by 1 unit/h as needed 3
- When glucose reaches 300 mg/dL in HHS (vs 250 mg/dL in DKA), start insulin infusion 2
- Insulin is secondary to fluid resuscitation in treatment priority 1
Monitoring Differences
DKA-Specific
- Monitor ketones directly - β-hydroxybutyrate is preferred over nitroprusside method 2
- Ketonemia takes longer to clear than hyperglycemia 2
- Follow venous pH and anion gap every 2-4 hours 2
HHS-Specific
- Monitor osmolality closely - primary marker of treatment response
- Mental status changes correlate with osmolality
- Less frequent need for pH/ketone monitoring
Resolution Criteria
DKA Resolution
- Glucose <200 mg/dL
- Bicarbonate ≥18 mEq/L
- Venous pH >7.3 2
HHS Resolution
- Osmolality normalized
- Mental status improved
- Adequate hydration restored
Critical Pitfalls
Hypokalaemia occurs in ~50% during treatment and severe hypokalaemia (<2.5 mEq/L) increases mortality - monitor potassium every 2-4 hours in both conditions 4
In adults with mixed DKA/HHS features (occurs in up to one-third of cases):
- Administer fluids more rapidly than in pure DKA
- Risk of fatal cerebral edema is low in adults
- Undertreatment causes vascular occlusion and increased mortality 1, 5
In pediatric patients with mixed features:
- Avoid rapid correction to prevent cerebral edema
- Do NOT give initial insulin bolus 2
- Use more conservative fluid rates (1.5× maintenance, not exceeding 2× maintenance) 2
Transition to Subcutaneous Insulin
Continue IV insulin 1-2 hours after starting subcutaneous regimen to prevent rebound hyperglycemia - abrupt discontinuation leads to poor control 2
Mortality rates differ significantly: HHS mortality is 5-16% (10× higher than DKA which is <1%), making aggressive early management even more critical 6