Internal Medicine · Year 3 · from Internal Medicine
Case 1: Diabetic Ketoacidosis
Patient Presentation
A 28-year-old woman with type 1 diabetes mellitus presents with nausea, vomiting, and abdominal pain for 2 days. She reports increased thirst and urinary frequency over the past week. She admits to running out of her insulin 3 days ago and being unable to afford a refill. She denies fever, dysuria, or respiratory symptoms.
Vital Signs
- Blood Pressure: 98/62 mmHg
- Heart Rate: 118 bpm
- Respiratory Rate: 28/min (Kussmaul respirations)
- Oxygen Saturation: 99% on room air
- Temperature: 37.2°C
Physical Examination
- General: Ill-appearing, drowsy but arousable, fruity breath odor
- HEENT: Dry mucous membranes, sunken eyes
- Cardiovascular: Tachycardic, regular rhythm
- Pulmonary: Deep, rapid respirations; lungs clear
- Abdomen: Diffusely tender without rebound or guarding
- Skin: Decreased turgor, no rashes
- Neurologic: Alert and oriented, no focal deficits
Initial Workup
- Glucose: 485 mg/dL
- Sodium: 128 mEq/L
- Potassium: 5.8 mEq/L
- Chloride: 95 mEq/L
- Bicarbonate: 8 mEq/L
- BUN/Creatinine: 32/1.8 mg/dL
- Anion gap: 25 mEq/L
- Arterial pH: 7.18
- Serum ketones: Large
- Urinalysis: Glucose 4+, ketones 3+, no leukocytes
Clinical Image
Figure 1: Diagram illustrating Kussmaul respirations - deep, labored breathing pattern representing respiratory compensation for metabolic acidosis in diabetic ketoacidosis.
Image Source: Educational illustration for teaching purposes.
Questions
- What are the diagnostic criteria for diabetic ketoacidosis (DKA)?
- A) Glucose >200, pH <7.35, bicarbonate <18, ketones positive
- B) Glucose >250, pH <7.30, bicarbonate <18, ketones positive, anion gap >12
- C) Glucose >400, pH <7.20, bicarbonate <15, ketones positive
- D) Glucose >300, pH <7.25, bicarbonate <20, anion gap >10
- What is the corrected sodium in this patient?
- A) 128 mEq/L
- B) 132 mEq/L
- C) 134 mEq/L
- D) 136 mEq/L
- What is the most critical electrolyte to monitor during DKA treatment?
- A) Sodium
- B) Potassium
- C) Calcium
- D) Phosphorus
- Outline the initial management priorities in treating DKA.
- When should sodium bicarbonate be administered in DKA?
Answers
- B) Glucose >250, pH <7.30, bicarbonate <18, ketones positive, anion gap >12 - DKA is characterized by hyperglycemia (>250 mg/dL), metabolic acidosis (pH <7.30, bicarbonate <18), positive serum/urine ketones, and elevated anion gap (>12).
- C) 134 mEq/L - Corrected sodium = measured sodium + 1.6 × [(glucose - 100)/100]. Here: 128 + 1.6 × [(485-100)/100] = 128 + 6.16 ≈ 134 mEq/L. This corrects for dilutional hyponatremia from hyperglycemia.
- B) Potassium - Although serum potassium may be normal or elevated on presentation, total body potassium is depleted. Insulin administration drives potassium intracellularly, risking severe hypokalemia. Do not start insulin until K+ >3.3 mEq/L.
- Initial management priorities:
- Fluids: Normal saline 1-1.5 L/hour initially; switch to 0.45% saline when sodium normalizes
- Insulin: Regular insulin 0.1 units/kg bolus, then 0.1 units/kg/hour infusion (after confirming K+ >3.3)
- Potassium: Add 20-40 mEq/L to fluids when K+ <5.3 mEq/L
- Monitor: Glucose hourly, electrolytes every 2-4 hours
- Dextrose: Add D5 to fluids when glucose <200-250 mg/dL
- Search for precipitant: Infection, medication non-adherence, MI, etc.
- Bicarbonate administration:
- Only indicated when pH <6.9
- 100 mEq sodium bicarbonate in 400 mL sterile water with 20 mEq KCl over 2 hours
- Routine bicarbonate administration is not recommended for pH ≥6.9
- May cause paradoxical CNS acidosis and hypokalemia