Clinical Case Scenario
A 62-year-old male with a history of hypertension and dyslipidaemia presents to the emergency department with severe retrosternal chest pain, sweating, and shortness of breath. A 12-lead ECG shows ST-segment elevation myocardial infarction (STEMI). The patient rapidly deteriorates, developing profound hypotension and signs of cardiogenic shock. The patient is intubated and he is started on inotrope infusion, and the patient is transferred to the ICU.
In ICU, shock persists despite escalating doses of inotropes. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is initiated via the femoral artery and femoral vein. Gradually an improvement in haemodynamics is observed.
Over the next few hours, the ICU team notes that the patient's lower extremities remain warm and well-perfused, with good pulse oximetry readings. However, the upper extremities and face appear cyanotic. Arterial blood gas (ABG) analysis reveals a significant discrepancy: blood from the right radial artery (upper body) shows ‘PaO₂ 45 mmHg,’ while blood from the femoral arterial line (lower body, ECMO-supported) shows ‘PaO₂ 95 mmHg.’
Over the next 24 hours, the patient develops oliguria (urine output 100 mL in last 24 hours). Laboratory findings include:
- Serum creatinine: 2.4 mg/dL (trends up from 1.0 mg/dL)
- Blood urea nitrogen (BUN): 48 mg/dL (trends up from 11 mg/dL)
- K⁺: 5.8 mEq/L
- pH: 7.18, HCO₃⁻: 14 mEq/L
- Urinalysis: Muddy brown granular casts
Which of the following is the most appropriate next step in management?
