Effects of Nitric Oxide on the Endothelium During Hemolysis.

Study Overview
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Brief Summary
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This study is an ancillary (add-on) study to the clinical trial entitled Effect of Nitric Oxide in Cardiac Surgery Patients With Endothelial Dysfunction, which has Clinical Trials.gov identifier NCT02836899. NCT02836899 trial randomizes cardiac surgical patients to receive either Nitric Oxide (NO) or a placebo during and after cardiac surgery. This ancillary study aims to assess the effects of Nitric Oxide on vascular responsiveness and on endothelial function during hemolysis in patients with pre-operative endothelial dysfunction undergoing cardiac surgery requiring prolonged cardiopulmonary bypass.

Detailed Description
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Endothelial cells regulate tissue perfusion by releasing nitric oxide (NO), a potent endogenous dilator of vascular smooth muscle cells, which modifies vascular tone. Under normal physiological conditions, vascular NO is released by endothelial NO synthase (eNOS). Impairment of the eNOS, as seen in patients with atherosclerosis, peripheral vascular disease, hypertension, obesity, and diabetes, is a feature of endothelial dysfunction.The inability to increment eNOS activity is particularly evident in conditions of decreased vascular NO bioavailability, such as during hemolysis associated with prolonged cardiopulmonary bypass (CPB>90 min). During hemolysis, ferrous plasma free hemoglobin (Oxy-Hb) is released into the circulation and can be injurious for the endothelial cells by exerting an oxidative and proinflammatory effect. Moreover, plasma free Oxy-Hb can scavenge vascular NO, reducing its bioavailability as ferrous Oxy-Hb is transformed into ferric methemoglobin (Met-Hb). The clinical results of reduced bioavailability of vascular NO have been found to be associated with both systemic and pulmonary vasoconstriction, ultimately leading to reduced tissue perfusion. The exogenous administration of NO has been shown to prevent the scavenging of endogenous NO by inactivating the highly oxidative-reactive ferrous plasma Oxy-Hb to ferric Met-Hb. Our group is conducting a randomized controlled trial at Massachusetts General Hospital (Boston, USA) in patients with signs and symptoms of endothelial dysfunction, undergoing cardiac surgery requiring prolonged CPB and randomized to receive NO or placebo. However, the mechanisms underlying the beneficial systemic effects of NO administration have still to be determined. This is an ancillary study that aims to (I) assess the effects of hemolysis on vascular responsiveness and on endothelial function in patients with pre-operative endothelial dysfunction and (II) to determine the vascular protective effects of NO administration.

Official Title
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Effects of Nitric Oxide on Vascular Responsiveness and on Endothelial Cells During Hemolysis in Patients With Pre-operative Endothelial Dysfunction Undergoing Prolonged Cardiopulmonary Bypass.

Conditions
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Endothelial Dysfunction, Hemolysis Intravascular, Cardiovascular Diseases, Cardiovascular Risk Factor

Intervention / Treatment
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* Drug: Nitric Oxide
* Diagnostic Test: Reactive Hyperemia Index
* Procedure: Endothelial Cells Collection


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Eligible and randomized in the trial NCT02836899 Provide written informed consent Age ≥ 18 years of age Elective cardiac or aortic surgery with CPB >90 minutes Clinical evidence of endothelial dysfunction assessed by a specifically designed questionnaire Exclusion Criteria: Estimated Glomerular Filtration Rate less than 30 ml/min/1.73 m2 Emergent cardiac surgery Life expectancy < 1 year at the time of enrollment Hemodynamic instability as defined by a systolic blood pressure <90 mmHg. Mean pulmonary artery pressure ≥ 40 mm Hg and PVR > 4 Wood Units. Left ventricular ejection fraction < 30% by echocardiography obtained within three months of enrollment Administration of one or more Packed Red Blood Cell (PRBC) transfusions in the week prior to enrollment X-ray contrast infusion less than 48 hours before surgery Evidence of hemolysis from any other origin: a. Intravascular: i. Intrinsic RBC defects leading to hemolytic anemia (eg, enzyme deficiencies, hemoglobinopathies, membrane defects) ii. Extrinsic: liver disease, hypersplenism, infections (eg, bartonella, babesia, malaria), treatment with oxidizing exogenous agents (eg, dapsone, nitrites, aniline dyes), exposure to other hemolytic agents (eg, lead, snake and spider bites), lymphocyte leukemia, autoimmune hemolytic disorders b. Extravascular: Infection (eg, clostridial sepsis, severe malaria), paroxysmal cold hemoglobinuria, cold agglutinin disease, paroxysmal nocturnal hemoglobinuria, iv infusion of Rho(D) immune globulin, iv infusion of hypotonic solutions

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Control<br>Inhaled nitrogen will be administered 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). Test gas administration will commence at the onset of CPB and last for 24 hours. | Diagnostic Test: Reactive Hyperemia Index<br>* Vascular responsiveness will be assessed with peripheral arterial tonometry which measures the transient increase in forearm blood flow (Reactive Hyperemia Index, RHI) in response to a five-minute occlusion of the brachial artery with a pressure cuff.<br>Procedure: Endothelial Cells Collection<br>* Endothelial cells are collected before and after surgery from a peripheral vessel using a soft J-shaped wire inserted through an intravascular catheter.<br>|
| Experimental: Nitric Oxide<br>Inhaled nitric oxide (iNO) will be administered via the CPB machine and after CPB via the inspiratory limb of the anesthetic or ventilator circuit, and thereafter via the mechanical ventilator in the ICU. Test gas administration will commence at the onset of CPB and last for 24 hours. At the end of 24 hours, iNO will be weaned and discontinued. | Drug: Nitric Oxide<br>* Inhaled nitric oxide (iNO) will be administered via the CPB machine and after CPB via the inspiratory limb of the anesthetic or ventilator circuit, and thereafter via the mechanical ventilator in the ICU. Test gas administration will commence at the onset of CPB and last for 24 hours. At the end of 24 hours, iNO will be weaned and discontinued.<br>* Other names: iNO;Diagnostic Test: Reactive Hyperemia Index<br>* Vascular responsiveness will be assessed with peripheral arterial tonometry which measures the transient increase in forearm blood flow (Reactive Hyperemia Index, RHI) in response to a five-minute occlusion of the brachial artery with a pressure cuff.<br>Procedure: Endothelial Cells Collection<br>* Endothelial cells are collected before and after surgery from a peripheral vessel using a soft J-shaped wire inserted through an intravascular catheter.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Reactive Hyperemia Index (RHI) | A finger plethysmograph will measure the transient increase in forearm blood flow (Reactive Hyperemia Index, RHI) in response to a 5 minutes occlusion of the brachial artery with a pressure cuff (Peripheral Artery Tonometry). | The test will be performed perioperatively before anesthesia induction and at 24 hours after CPB during ICU admission. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Cardiac Surgery, Cardiopulmonary Bypass, Reactive Hyperemia Index, Nitric Oxide