Diabetic Ketoacidosis (DKA): A High-Yield USMLE Topic
Diabetic Ketoacidosis (DKA) is a life-threatening complication of diabetes mellitus, often seen in type 1 diabetes but can also occur in type 2 diabetes under stress conditions. It results from insulin deficiency and increased counter-regulatory hormones, leading to hyperglycemia, ketonemia, and metabolic acidosis.
Understanding DKA is essential for USMLE preparation, as it commonly appears in clinical vignettes involving acid-base disorders, electrolyte imbalances, and emergency medicine.
Pathophysiology of DKA
DKA develops due to absolute or relative insulin deficiency, causing:
↑ Gluconeogenesis & Glycogenolysis → Severe hyperglycemia
↑ Lipolysis → Free fatty acids → Ketogenesis → Metabolic acidosis
Osmotic diuresis → Severe dehydration and electrolyte imbalance
Mnemonic for DKA Causes: "The 5 I’s"
Infection (most common, e.g., pneumonia, UTI)
Insulin noncompliance (missed doses)
Infarction (MI, stroke)
Illness (trauma, pancreatitis)
Intravenous drug use
Clinical Presentation of DKA
Patients with DKA present with:
| Symptom | Explanation |
|---|---|
| Polyuria, Polydipsia | Due to osmotic diuresis from hyperglycemia |
| Dehydration, Hypotension | Severe volume loss |
| Kussmaul Respiration | Deep, rapid breathing to compensate for metabolic acidosis |
| Fruity Breath Odor | Due to ketones (acetone) |
| Abdominal Pain, Nausea, Vomiting | Common but non-specific symptoms |
| Altered Mental Status | Severe cases may lead to coma |
Key Diagnostic Tests for DKA
| Test | Expected Finding |
|---|---|
| Blood Glucose | > 250 mg/dL |
| Arterial Blood Gas (ABG) | Metabolic acidosis (pH < 7.3, HCO₃ < 18 mEq/L) |
| Serum Ketones | Positive (β-hydroxybutyrate elevated) |
| Anion Gap | Increased (> 12) |
| Serum Potassium | Initially high, but total body K+ depleted |
| Urinalysis | Ketones, glucosuria |
Management of DKA (4-Step Approach)
1️⃣ IV Fluids
Start with Normal Saline (0.9% NaCl) to correct dehydration
Switch to ½ NS + 5% Dextrose when glucose falls <250 mg/dL
2️⃣ Insulin Therapy
IV Regular Insulin (bolus + continuous infusion)
Monitor glucose & switch to subcutaneous insulin once ketosis resolves
3️⃣ Electrolyte Correction
Potassium: Despite initial hyperkalemia, total K+ is depleted → Replenish K+ if <5.3 mEq/L
Bicarbonate: Only in severe acidosis (pH <6.9)
4️⃣ Treat Underlying Cause
Infection: Start antibiotics if needed
Noncompliance: Patient education on insulin adherence
Special Considerations in DKA
| Patient Group | Consideration |
|---|---|
| Children | Risk of cerebral edema → Give IV mannitol if suspected |
| Elderly Patients | Higher mortality, careful fluid resuscitation needed |
| Pregnancy | DKA can harm the fetus → Urgent management required |
| Chronic Kidney Disease | Adjust fluids to prevent volume overload |
Key Takeaways for USMLE
DKA is caused by insulin deficiency and counter-regulatory hormone excess
Metabolic acidosis, hyperglycemia, and ketosis are the hallmarks
IV fluids, insulin, potassium replacement, and treating the cause are crucial
Monitor for cerebral edema in pediatric patients
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