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Cove, Matthew; Sen, Ayan; Federspiel, William; Kellum, John

doi: 10.1097/01.ccm.0000425235.36766.17
Poster: ABSTRACT Only

Introduction: Extracorporeal carbondioxide (CO2) removal (ECCOR) may enable lung protective ventilation (LPV) in Acute Respiratory Distress Syndrome (ARDS) by lowering minute ventilation and preventing hypercarbia. Bicarbonate dialysis offers an alternative, more available strategy, by removing CO2 in the form of bicarbonate. However, previous attempts using hemodialysis or hemofiltration have been limited, amongst other things, by metabolic acidosis.

Hypothesis: To develop a low bicarbonate dialysate which will maximize carbondioxide (CO2) removal in the form of bicarbonate during continuous venovenous hemodialysis without producing metabolic acidosis.

Methods: An in-vitro model was designed to develop and test a dialysate solution capable of removing bicarbonate. An artificial plasma solution with an electrolyte composition similar to plasma was created. CO2 was added to the plasma using a Minimax plus hollow fiber oxygenator (Medtronic, Anaheim CA, USA) with a sweep gas composed of N2 and CO2. The solution was pumped through an M10 dialysis filter (Gambro, Lyon France) with a surface area of 0.04 m-sq. A proprietary dialysate solution with differing levels of bicarbonate was used. Pre and post-filter acid-base was assessed using a blood gas analyzer.

Results: Our in vitro data shows successful removal of CO2 from a plasma-like solution using a low bicarbonate dialysate and a physiologic sodium concentration. The chloride concentration is slightly supra-physiologic (118 mmol/L), but it is well within tolerance limits. Our novel dialysate is designed to control the strong ion difference rather than replacing bicarbonate. A dialysate with 11 mmol/L bicarb removes the equivalent of 2 - 2.5 mmol/min of bicarbonate. To achieve maximal CO2 removal requires dialysate flow rates around seven times in excess of standard flow rates. Post-filter pH is maintained around 7.4, thus eliminating metabolic acidosis which hampered previous attempts.

Conclusions: Respiratory dialysis may help provide ECCOR without causing MA, facilitating application of LPV by limiting hypercarbia.

University of Pittsburgh Medical Center

University of Pittsburgh

University of Pittsburgh Medical Center

© 2012 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins