Unexpected Turn

A 45-year-old woman with sickle cell disease is admitted for a pain crisis and worsening anemia, with a hemoglobin level of 65 g/L. She is ordered two units of packed red blood cells (PRBCs) for transfusion. Thirty minutes after starting the transfusion, she develops high fever (39.2°C / 102.6°F), severe lower back and flank pain, dark red urine, nausea and vomiting, and diffuse chest tightness. Her vitals show blood pressure of 80/45 mmHg, heart rate of 140 bpm, respiratory rate of 28 breaths/min, and oxygen saturation of 94% on room air. The transfusion is immediately stopped. Urinalysis shows hemoglobinuria and laboratory tests reveal:

Hemoglobin: 59 g/L (115–155)

LDH: 950 IU/L (100–205)

Indirect bilirubin: 85.5 µmol/L (3–17)

Haptoglobin:  0.1 g/L (0.3-2.0)

Potassium: 5.3 mmol/L (3.5–5.1)

Creatinine: 159.2 µmol/L (22–75; baseline 79.56 µmol/L)

Direct Coombs test: Positive