Prevention of Acute Kidney Injury by Nitric Oxide in Prolonged Cardiopulmonary Bypass. A Double Blind Controlled Randomized Trial in Cardiac Surgical Patients With Endothelial Dysfunction.

I. SUBJECT ENROLLMENT

1. Methods of enrollment, including procedures for patient registration. Patients will be screened in the "Cardiac surgery pre-operative clinic", Massachusetts General Hospital (MGH) Cox building floor 6 (before surgery). If the patient is eligible and after obtaining the consent of the primary cardiac surgeon, the patient will be approached for consent to participate in this clinical trial. Consent will be obtained exclusively from the patient, and not from a surrogate, because cardiac surgery is usually a scheduled procedure. The obtaining of the consent directly from the patient is preferred, since there will be the opportunity of interaction with the patient when he/she is fully awake. After consent is obtained, the patient will be randomized to the study group. A de-identified code will be assigned to the patient and registered on a dedicated enrollment log.
2. Procedures for obtaining informed consent (including timing of consent process). Patients will be screened in the "Cardiac surgery pre-operative clinic", MGH Cox building floor 6 (before surgery). If a patient is eligible for the study and after obtaining the consent of the primary cardiac surgeon, the patient will be approached to consent to participate in the clinical trial. There is no need for surrogate consent for this trial, as explained above. Signing the Informed Consent Form will be requested for participation in the study. Personal Medical Information (PMI) will be accessed by the investigator(s) only for study purposes. Patients who choose not to participate in this study will receive standard care according to the procedures of the ICU, without any repercussion.
3. Treatment assignment and randomization (if applicable). To ensure a robust and unbiased approach, randomization should account for demographic characteristics of the patients (i.e.: age, sex) and glomerular filtration rate (GFR). Only patients who are cared for by experienced anesthesiologists and cardiac surgeons (more than 5 years of staff experience) will participate in this study. The patients will be randomized to receive either NO (study drug) or N2 (placebo) alone. In order to account for an elevated baseline pulmonary artery pressure, patients with pre-operative mean PAP ≥30 mmHg will be allocated equally to the two groups during the stratified randomization process. The random allocation sequence will be created using a computerized random generation program. The randomization will be in blocks of 10 patients. The intervention will consist of administering the test gas via the cardiopulmonary bypass (CPB) machine and after CPB via the inspiratory limb of the anesthetic or ventilator circuit, and thereafter via the mechanical ventilator in the Intensive Care Unit (ICU). When patients are extubated they will breathe test gas via a facemask or nasal prongs. Test gas administration will commence at the onset of CPB and last for 24 hours. At the end of 24 hours, inhaled NO (iNO) will be weaned and discontinued while carefully monitoring hemodynamics for a period of 2-4 hours. Local guidelines for NO gas discontinuation will be followed. Using commercially available tanks of Nitric Oxide (Airgas Inc, Radnor Township, Pennsylvania) or volumetrically-calibrated flowmeters, pure N2 (placebo) or 850 ppm NO gas in N2 will be mixed with pure oxygen (O2) or air to obtain the desired concentration of O2 and, in the NO treatment group, a final concentration of 80 ppm NO. For safety, nitric oxide, nitrogen dioxide (NO2), O2 and methemoglobin (Met-Hb) levels will be continuously monitored by the personnel unblinded to the study. Patients in the placebo (N2) group will receive nitrogen test gas during the same 24 hour-period. The inspired oxygen levels will be maintained at the usual levels required for routine post-operative care. No changes to the usual and customary standards of care for any intraoperative or postoperative treatment will be made during the study period.
4. Blinding procedure for Nitric Oxide and Nitrogen delivery. A double-blind study will be performed to avoid potential patient and investigator bias, the study is blinded to: participants, perfusionists, surgeons, anesthesiologists, ICU physicians and the nursing staff. The test gas tank and the gas delivery system in the operating room (OR) and at the bedside will be masked. The respiratory therapist in the ICU and a member of the study staff will be unblinded and will prepare the appropriate test gas tanks and NO/N2 meters. Blood Met-Hb levels and NO/NO2 concentrations are safety concerns that the respiratory therapist and one member of the study staff will monitor and regulate (NO2 levels will be maintained below 5 ppm, and Met-Hb below 5%, if necessary by reducing NO concentration to 40 ppm or less according to MGH guidelines NO therapy).

II. STUDY PROCEDURES a. Study visits and parameters to be measured (e.g., laboratory tests, x-rays, and other testing). SCREENING visit: Screening will take place in the "Cardiac surgery pre-operative clinic", MGH Cox building floor 6 (before surgery). Patients will be screened if they require prolonged CPB (>90 minutes on CPB, i.e., valve replacement ± coronary artery bypass grafting (CABG)) and if the primary cardiac surgeon of the patient agrees on enrolling the patient in the study.

Screening consists of:

• Review eligibility entry criteria of the study: inclusion/exclusion criteria will be reviewed.
• Review the research protocol: This is a protected time for the subject to ask questions and become familiar with all aspects of the study protocol.
• Administration of a brief questionnaire to determine endothelial function with the subject verbal assent on the day of pre-surgical evaluation. The questionnaire evaluates medical history, integrating clinical and laboratory data of screened patients. In males > 40 year old and females > 50 year old, endothelial dysfunction has been shown to be associated with at least one the following criteria: Previous coronary artery bypass graft or PTCA (+ stent); History or presence of intermittent claudication; Critical limb ischemia, or peripheral vascular disease with the Exception of vasculitis; History of transient ischemic attack and/or ischemic stroke; Diagnosis of diabetes (IDDM or NIDDM) requiring oral hypoglycemic agents or insulin; Hypercholesterolemia (total cholesterol > 200 mg/dl or LDL > 160 mg/dl) treated with statins, ion- exchange resins or other oral agents; BMI > 40; Hypertension (SBP 140 ≥ mmHg) treated with antihypertensive drugs; Active smoking ≥ 10 pack - years
• Consent form: The subject will be asked to sign the consent form.