Abstract: A novel system and method for fluid management for accurate continuous venovenous hemofiltration (CWH) in extracorporeal membrane oxygenation (ECMO). The fluid management or CWH system is automated and configured for operation as a stand alone unit and can be easily integrated with an ECMO system. The fluid management system is capable of producing either perfect or negative fluid balance between ultrafiltrate removal and replacement fluid delivery. The fluid management system can achieve electrolyte replacement over a range of flow rates needed to care for patients ranging from neonates to adults. Finally, the novel fluid management system preserves patient safety, maintains sterility during operation, is easy to operate, and is compact enough to fit near a patient's bed.