The investigators will be comparing two different filtration methods on cardiopulmonary bypass for pediatric heart surgery patients. Three blood tests will be taken from the patient to compare which filtration method is better at decreasing post-cardiopulmonary bypass inflammation caused by the heart-lung machine.

The study holds promise to evaluate the efficacy of dilutional ultrafiltration (DUF) compared to the currently utilized conventional ultrafiltration method in a prospective randomized controlled trial. A disposable hemoconcentrator is included in the cardiopulmonary bypass circuit which allows for removal of plasma water and solutes with a molecular weight below 65,000 Daltons. Alternatively, dilutional ultrafiltration (DUF) is a process during cardiopulmonary bypass that uses a hemoconcentrator to remove effluent containing inflammatory mediators but also return equal amounts of Plasmalyte to the patient's blood volume through the cardiopulmonary bypass circuit. Plasmalyte is a balanced crystalloid solution that has a similar concentration of electrolytes, osmolality, and pH to human plasma. The "dilutional effect" in DUF is caused by adding Plasmalyte and reducing inflammatory mediators in a patient's entire blood volume while also replacing necessary electrolytes lost during ultrafiltration. The purpose of this study is to examine plasma C-Reactive Protein levels pre-bypass, 12 hours post-bypass, and 24 hours post-bypass comparing the two filtration methods to discover if there is a measurable decrease in postoperative inflammation using dilutional ultrafiltration (DUF) compared to conventional ultrafiltration (CUF). The primary objective of this trial is to evaluate the efficacy of dilutional ultrafiltration (DUF) compared to conventional ultrafiltration (CUF) on cardiopulmonary bypass patients by measuring the outcome of C-Reactive Protein (CRP). The secondary objective is to track postoperative clinical measurements associated with inflammation such as postoperative fluid balance, alveolar arterial gradient, inotrope score, diuretic need, time to negative fluid balance, postoperative length of intubation, and length of ICU stay.

Inclusion Criteria:

• Males and females less than 5 years of age
• Cardiac operations utilizing CPB
• Cardiac reoperations utilizing CPB

Exclusion Criteria:

• Patients greater than 5 years of age.
• Any active SYSTEMIC noncardiac disease expected to raise patient baseline CRP levels to above normal levels (>1mg/dL). Since CRP levels correlate with the severity of most skin disease, patients with active dermatitis issues on the day of surgery will be excluded from the study. Patients with autoimmune diseases including RA, SLE, IBD (Crohn's disease, ulcerative colitis), Kawasaki disease and patients experiencing active infections will be excluded from the study.
• Any noncardiac disease not well controlled (ex. Asthma not properly controlled with medication, etc.)
• Recent viral illness (ex. Positive COVID/flu test 30 days prior to surgery)
• All patients receive solumedrol (10mg/kg dose) from anesthesia as part of the prebypass protocol. Any patient currently taking steroids will also be excluded from the study
• Non-cardiopulmonary bypass cases (Off pump CoA, Vascular ring surgery, etc.)
• ECMO patients
• Emergent cases

Patients having cardiac surgery with cardiopulmonary bypass who meet inclusion criteria.