A case of acute hypercapnia occurring during a session of bicarbonate hemodialysis is reported. The 82-year old female patient was affected by cardiac insufficiency, pulmonary hypertension and chronic obstructive lung disease. She developed acute symptomatic respiratory acidosis immediately after the beginning of a bicarbonate hemodialysis session, with arterial pH of 7.25 and paCO2 of 48.1 mmHg. This was related to the well known, but frequently forgotten, CO2 load from bicarbonate-based dialysate. We treated her with acetate-free biofiltration, with stable paCO2 throughout the session. Physiopathology of blood gas dynamics during hemodialysis is reviewed.
