This is a research study to evaluate the safety and effectiveness of Niyad (nafamostat mesylate) as a blood thinner used during continuous renal replacement therapy (CRRT). CRRT is a standard treatment much like dialysis that is used to temporarily take the place of kidney function when one's kidneys are injured. Like your kidneys, CRRT helps to clean your blood and remove waste products.

Niyad is experimental which means that it is being tested and is not approved by the United States Food and Drug Administration (FDA). There is no guarantee that you will receive direct benefit as a result of your participation in this study. Possible benefits of Niyad include preventing your blood from clotting the dialysis filter so that the CRRT machine works more effectively and it also may reduce your need for a transfusion. The study results may help people in the future.

Participation voluntary and is expected to last up to 28 days. The length of time you may be exposed to Niyad is up to 7 days and safety assessments may last up to 28 days.

There will be no additional cost to you for procedures required in this research study. All routine clinical care that you would have undergone without participation in the study, including testing and procedures, will be billed to you/your insurance company. All study-related tests and procedures will be paid for by the Sponsor.

Some insurance plans will not pay for these services for people taking part in research studies. You will be responsible for any charges that your insurance does not cover including co-payments and deductibles.

Up to 67% of patients undergoing heart surgery may experience complications after surgery. These complications may include longer stay in the intensive care unit (ICU), more time on a ventilator (also known as a breathing machine), longer overall stay in the hospital, having to return to the hospital soon after being discharged, and even death.

This research study is being performed to see whether RBT-1, an investigational new drug, can reduce complications after heart surgery

In this research study, you will have a 50% chance of being assigned to receive RBT-1 and a 50% chance of being assigned to receive placebo.

If you decide to participate, you will receive a single intravenous (IV) infusion (an infusion into your vein) of either: 1) RBT-1 at a dose level of 45 mg SnPP/240 mg FeS or 2) placebo in the form of normal saline (salt water solution). You cannot choose whether you are given RBT-1 or placebo.