Sorbent regenerative hemodialysis as a potential cause of acute hypercapnia

Commercially available sorbent regenerative hemodialysis systems offer a convenient method of either acetate or bicarbonate hemodialysis. Sorbent dialysis requires only a small volume of dialysate (5 to 6 liters), which is continuously regenerated (production of “fresh” dialysate from that containing uremic solutes) by a cartridge containing urease, anion and cation exchangers, and activated charcoal. The convenience of bicarbonate hemodialysis and the small dialysate volume in this system makes sorbent regenerative hemodialysis particularly suited for intensive care units. In fact, this system has been recommended for critically ill patients [1]. Carbon dioxide is known to be generated during sorbent regenerative hemodialysis, but the magnitude and potential consequences of this carbon dioxide production in altering acid-base homeostasis has not been evaluated [2–4]. Our interest in acid-base changes during sorbent dialysis was stimulated after observing profound acute respiratory acidosis in a mechanically ventilated patient during hemodialysis with this system. We, then, prospectively evaluated acid-base changes during sorbent regenerative hemodialysis in 15 patients