Clinical Case Scenario

A 48-year-old woman with type 2 diabetes mellitus and hypertension presented with a 2-day history of fever and dysuria. She had been taking oral antibiotics prescribed at a local clinic. Despite this, the fever persisted, and she developed multiple episodes of vomiting with poor oral intake. She also complained of dull, diffuse abdominal pain.

Her regular medications include amlodipine, telmisartan-hydrochlorothiazide, metformin, glimepiride, and dapagliflozin.

On examination:

• Conscious, oriented
• BP 90/45 mmHg
• HR 120/min
• RR 22/min
• SpO₂ 97% on room air
• Per-abdomen examination: soft, non-distended, and non-tender.

ABG:

• pH 7.42
• PaCO₂ 34 mmHg
• HCO₃⁻ 23 mmol/L

Laboratory values:

• Na 124 mmol/L
• K 5.8 mmol/L
• Cl 83 mmol/L
• Glucose 180 mg/dL
• Lactate 0.8 mmol/L
• Albumin 3.0 g/dL
• Serum osmolality: 270 mOsm/kg H₂O
• Urine spot sodium: 62 mmol/L
• Urine osmolality: 630 mOsm/kg H₂O
• Blood urea: 77 mg/dL
• Serum creatinine: 0.8 mg/dL

Wrong Answer: ❌ A. Salbutamol may transiently lower potassium but does not treat the underlying ketoacidosis.

Wrong Answer: ❌ B. There are no clinical features (no tenderness) suggesting an acute surgical abdomen requiring urgent CECT.

Wrong Answer: ❌ C. Mild asymptomatic hypovolemic hyponatremia does not require hypertonic saline; isotonic fluid replacement is appropriate.

Right Answer: ✅ D. Fluid resuscitation with normal saline and insulin-dextrose infusion; observe in ICU

Explanation:

Corrected Anion Gap
o AG = Na − (Cl + HCO₃) = 124 − (83 + 23) = 18
o Albumin correction = AG + 2.5 × (4 − 3) = 20.5 mEq/L

Delta Ratio
o ΔAG = 20.5 − 12 = 8.5
o ΔHCO₃ = 24 − 23 = 1
o Delta ratio = 8.5
This indicates a high anion gap metabolic acidosis with concurrent metabolic alkalosis

Mixed Disorder Diagnosis
A normal pH does not exclude a significant acid-base disorder. Compensation alone cannot completely normalize the pH; therefore, a normal pH in the presence of an abnormal anion gap should raise suspicion for a mixed acid-base disorder.
In this patient, the corrected anion gap is elevated (20.5 mEq/L), indicating a high anion gap metabolic acidosis. The near-normal bicarbonate and elevated delta ratio suggest concomitant metabolic alkalosis, likely due to vomiting and diuretic use, resulting in a deceptively normal pH.



This case fits the last pattern, emphasizing the importance of calculating the anion gap even when pH, PaCO₂, and HCO₃⁻ appear normal.

Key Learning Point
A normal pH does not exclude a significant acid-base disorder. Despite a seemingly normal ABG, the elevated corrected anion gap indicates an underlying high anion gap metabolic acidosis. In this patient, SGLT2 inhibitor use, vomiting, poor oral intake, abdominal pain, relatively normal glucose with high anion gap strongly suggest euglycemic diabetic ketoacidosis (euDKA). Blood ketone testing (preferably serum β-hydroxybutyrate) should be performed to evaluate for ketoacidosis.
The presence of fever and dysuria is consistent with a urinary tract infection, a recognized precipitating factor for DKA. In addition, SGLT2 inhibitors are associated with both euglycemic diabetic ketoacidosis (euDKA) and genitourinary infections. Concurrent vomiting and thiazide use produce metabolic alkalosis, masking the acidosis and resulting in a near-normal pH. Treatment includes volume resuscitation with crystalloids, appropriate antimicrobial therapy, discontinuation of the SGLT2 inhibitor, and standard DKA management with insulin and dextrose.

CLINICAL PEARLS

💎 Always calculate the anion gap—even when pH, PaCO₂, and bicarbonate appear normal.
🎯 SGLT2 inhibitor + abdominal pain + normal glucose → Think euglycemic DKA.
🎯 Normal pH + elevated anion gap → Search for a mixed acid-base disorder.
🎯 Volume depletion + thiazide use + vomiting → Common causes of concomitant metabolic alkalosis.