Clinical Care Scenario
A 62-year-old woman with type 2 diabetes (on metformin 1g twice daily), chronic hypertension (on Lisinopril 100 mg BD), and peripheral arterial disease presents to the emergency department with a 2-day history of severe watery diarrhoea, nausea, and vomiting. She had been caring for her grandson, who recently had gastroenteritis. On arrival, she is confused and hypotensive (BP 70/39 mmHg). Laboratory findings reveal:
- Hb 7 g/dL, WBC 14,000/mm3, Platelets 80,000/ mm3
- LDH 700 U/L
- CRP 156 mg/L, PCT 1.1 ng/mL,
- Urea 65 mmol/L, Creatinine: 634 µmol/L
- Arterial blood gas (ABG): pH 6.8, HCO₃⁻ 3 mEq/L
- Sodium 134 mEq/L, K 5.6 mEq/L
- Anion gap: 28 mmol/L , Lactate: 17.3 mmol/L
She is diagnosed with severe lactic acidosis. Despite discontinuation of metformin and Lisinopril, aggressive fluid resuscitation, and vasopressor support, she develops pulseless electrical activity (PEA) cardiac arrest. After successful resuscitation, continuous renal replacement therapy (CRRT) is initiated in ICU. Blood culture is growing E. coli O157:H7.
What is the most likely primary cause of this patient’s life-threatening lactic acidosis?
