CASE PRESENTATION: A 74-year old man with a five-year history of Waldenström’s macroglobulinemia was admitted to our intensive care unit (ICU) with melena 17 days after fludarabine initiation, his fourth chemotherapy regimen. He was hemodynamically stable, afebrile, and had no other focal complaints. Pertinent laboratory data showed pancytopenia with lactate of 11.7 mmol/L (normal 0.6-2.3 mmol/L), anion gap 33.4 mg/dL, arterial pH 7.40, pCO2 20 mmHg, IgM 2030 mg/dL (normal 50-300 mg/dL), and LDH 2350 U/L (normal 122-222 U/L). Initially suspecting septic shock due to his immunosuppressed state and lactic acidosis, broad spectrum antibiotics were initiated with vancomycin, piperacillin-tazobactam, and caspofungin. Blood (bacterial and fungal) and urine cultures returned negative as part of an extensive workup for infection. Computerized Tomography of his abdomen showed no signs of ischemic bowel. Over the next two days, lactate rose to 17.7 mmol/L and pH downtrended to 7.06 (Fig 1). Non-fluid responsive hypotension developed, prompting initiation of vasopressor support. He was intubated due to respiratory distress. Comfort care was initiated on Hospital Day 3, and the patient expired the following day.