Diabetic Ketoacidosis: Types of Acidosis and Precipitating Causes
Diabetic ketoacidosis (DKA) primarily presents as a high anion gap metabolic acidosis caused by the accumulation of ketone bodies (β-hydroxybutyrate and acetoacetate), but frequently occurs with mixed acid-base disorders that can significantly alter the clinical presentation.
Types of Acidosis in DKA
Primary Acidosis: High Anion Gap Metabolic Acidosis
The hallmark of DKA is high anion gap metabolic acidosis resulting from unrestrained hepatic fatty acid oxidation to ketone bodies (β-hydroxybutyrate and acetoacetate) 1. This occurs due to:
- Absolute or relative insulin deficiency
- Elevated counterregulatory hormones (glucagon, catecholamines, cortisol, growth hormone)
- Increased lipolysis releasing free fatty acids
- Unregulated ketogenesis in the liver
β-hydroxybutyrate is the strongest and most prevalent acid in DKA, though standard nitroprusside testing only measures acetoacetate and acetone 2, 1.
Mixed Acid-Base Disorders
DKA commonly presents with mixed acid-base disorders, not pure metabolic acidosis 3. The clinical presentation spectrum includes:
- Traditional acidemic DKA (pH ≤7.3): 48.9% of cases
- DKA with mild acidemia (pH 7.3-7.4): 27.8% of cases
- Diabetic ketoalkalosis (pH >7.4): 23.3% of cases 4
Specific Mixed Patterns:
Hyperchloremic metabolic acidosis develops in 69.3% of patients during treatment, typically appearing around 6 hours into therapy and increasing to 80% by 24 hours 5. This occurs from:
- Chloride overload from intravenous hydration fluids
- Better hydration status paradoxically increases risk 3
- Can mask resolution of ketoacidosis when monitoring pH alone
Concurrent metabolic alkalosis occurs in approximately 9-47% of cases 4, 3, particularly in:
- Severely dehydrated patients with recurrent vomiting
- Those with significant gastrointestinal losses
Concurrent respiratory alkalosis appears in 81.1% of diabetic ketoalkalosis cases 4 and in patients with:
- Pneumonia
- Gram-negative septicemia
- Kussmaul respirations (compensatory hyperventilation)
Concurrent respiratory acidosis occurs in 11.3% of cases 4, typically in patients with respiratory depression.
Critical Clinical Pitfall
34% of patients with diabetic ketoalkalosis (pH >7.4) have severe ketoacidosis (β-hydroxybutyrate ≥3 mmol/L) and require the same aggressive treatment as traditional DKA 4. Do not be falsely reassured by normal or elevated pH—check anion gap and ketone levels directly.
Common Precipitating Causes
Most Common: Infection (Primary Trigger)
Infection is the most common precipitating factor for both DKA and HHS, accounting for approximately 69% of cases 1, 6, 1, 7. Specific infections include:
- Pneumonia: 38.7% of infection-related DKA 7
- Urinary tract infections: 30.6% of infection-related DKA 7
- Other bacterial infections, particularly gram-negative septicemia
Important note: Patients may be normothermic or even hypothermic due to peripheral vasodilation; hypothermia is a poor prognostic sign 1.
Insulin-Related Causes
- Non-compliance to insulin therapy: 53.5% of cases 7
- New-onset type 1 diabetes: Common presentation
- Discontinuation or inadequate insulin dosing in established type 1 diabetes 1, 6, 1
- Psychological factors in young patients with type 1 diabetes (20% of recurrent cases): fear of weight gain, fear of hypoglycemia, rebellion, eating disorders 2
Cardiovascular Events
- Myocardial infarction
- Cerebrovascular accident (stroke)
Other Medical Conditions
- Pancreatitis
- Trauma
- Alcohol abuse (note: combined diabetes and alcohol dependency increases ketoacidosis risk 3.8-fold compared to diabetes alone) 8
Medications That Precipitate DKA
Drugs affecting carbohydrate metabolism 1, 2:
- Corticosteroids
- Thiazide diuretics
- Sympathomimetic agents (dobutamine, terbutaline)
- SGLT2 inhibitors: Can cause euglycemic DKA, particularly perioperatively 9, 10
High-Risk Populations
- Elderly individuals with new-onset diabetes, especially nursing home residents
- Patients unable to recognize hyperglycemia or access fluids
- Those with known diabetes who become hyperglycemic and cannot maintain hydration 1
Monitoring Considerations
During treatment, monitor anion gap, blood ketones (β-hydroxybutyrate preferred), and Cl⁻/Na⁺ ratio in addition to routine pH and bicarbonate 5. This helps differentiate:
- Resolving DKA from developing hyperchloremic acidosis
- True metabolic improvement from treatment-induced acid-base changes
- Need for continued versus discontinued intravenous therapy
The nitroprusside method should not guide therapy decisions as it misses β-hydroxybutyrate and may falsely suggest worsening ketosis during treatment when β-hydroxybutyrate converts to acetoacetate 2, 1.