Methylene Blue-Enhanced Ultrafiltration Improves Outcomes After Cardiopulmonary Bypass

METHYLENE BLUE-ENHANCED BLOOD WASHING DURING ZERO-BALANCE ULTRAFILTRATION REDUCES FLUID OVERLOAD AND INFLAMMATORY RESPONSE FOLLOWING CARDIOPULMONARY BYPASS: A RANDOMIZED CLINICAL TRIAL

Introduction: Fluid overload and systemic inflammation are major contributors to postoperative complications in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Objective: To evaluate the effects of blood washing with methylene blue during zero-balance ultrafiltration (ZBUF) on fluid overload and systemic inflammatory response. Methodology: Fluid status was assessed using the InBody S10 precision bioimpedance device, measuring extracellular water (ECW), total body water (TBW), intracellular water (ICW), and the ECW/TBW ratio. Pulmonary congestion and intravascular volume were evaluated separately using a Philips Lumify S4-1 transducer with a Samsung tablet. Pulmonary congestion was confirmed by the presence of B-lines on lung ultrasound. Intravascular volume was assessed via the inferior vena cava (IVC) distensibility index (DI) during mechanical ventilation and collapsibility index (CI) during spontaneous breathing. Inflammatory cytokine levels were measured using a Luminex xMAP-based multiplex immunoassay.

Study Overview

• Status: Completed
• Conditions: Aortic Valve Surgery; Cardiopulmonary Bypass Surgery; Mitral Valve Surgery; Myocardial Revascularization Surgery With Extracorporeal Circulation
• Intervention / Treatment: Drug: Methylene Blue; Procedure: Conventional ultrafiltration; Procedure: Zero-balance ultrafiltration

• Study Type: Interventional
• Enrollment (Actual): 124
• Phase: Phase 2

Contacts and Locations

Study Locations

• Brazil
  • São Paulo
    • Ribeirão Preto, São Paulo, Brazil, 14049-900
      • University of São Paulo Medical School in Ribeirão Preto

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Clinical diagnosis of cardiac disease requiring surgery with cardiopulmonary bypass (CPB)

Age ≥ 18 years

Ability to provide informed consent

Exclusion Criteria:

Chronic renal failure

Recent cardiac catheterization within the past month

Planned cardiac surgeries with an estimated CPB time of less than 60 minutes

Aortic surgery

Significantly impaired hepatic function

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Conventional ultrafiltration; Conventional ultrafiltration (G-CUF) patients in this group underwent conventional ultrafiltration widely used in cardiac surgery with extracorporeal circulation.	Drug: Methylene Blue; This protocol was designed to perform intraoperative blood lavage with methylene blue at the end of surgery, with a duration of 20 minutes. A low dose of 1 mg/kg of body weight was administered. The objective was not to elicit hemodynamic effects, which require higher doses, but rather to exploit the anti-inflammatory and antioxidant properties of methylene blue. Methylene blue was diluted in 1000 mL of 0.9% saline. An equivalent volume of fluid was removed simultaneously by zero-balance ultrafiltration, maintaining a fluid-equilibrium state throughout the 20-minute procedure. For this purpose, a dedicated circuit was developed to enable concurrent blood lavage and ultrafiltration. Blood was withdrawn through a dedicated port integrated into the SORIN oxygenator and directed by a centrifugal pump to a small reservoir containing the methylene blue solution. From this reservoir, the blood passed through a hemoc; Other Names: zero-balance ultrafiltration; Procedure: Conventional ultrafiltration; Conventional ultrafiltration (CUF). CUF during cardiopulmonary bypass (CPB) is performed to remove excess fluid and solutes from the patient's blood during cardiac surgery, thereby limiting fluid accumulation and attenuating pro-inflammatory effects. This technique increases hematocrit, improves cardiopulmonary function, and reduces the need for blood transfusions. Unlike modified ultrafiltration (MUF), which is performed after weaning from CPB, CUF is carried out simultaneously with CPB while the heart-lung machine remains in operation.; Procedure: Zero-balance ultrafiltration; Zero-balance ultrafiltration (Z-BUF). Z-BUF is performed during cardiopulmonary bypass (CPB) to maintain fluid equilibrium by removing plasma water and solutes while simultaneously infusing an equal volume of replacement fluid, thereby achieving a net zero fluid balance. This technique has been shown to decrease urine output, reduce tissue edema and the inflammatory response, improve arterial oxygenation (PaO₂), and lower the need for postoperative blood transfusions.
Placebo Comparator: Blood washing with physiological solution combined with zero-balance ultrafiltration; Blood washing with physiological solution combined with zero-balanced ultrafiltration (G-ZBUF) patients in this group underwent zero-balanced ultrafiltration, and for this purpose, the simulation was performed with physiological solution.	Drug: Methylene Blue; This protocol was designed to perform intraoperative blood lavage with methylene blue at the end of surgery, with a duration of 20 minutes. A low dose of 1 mg/kg of body weight was administered. The objective was not to elicit hemodynamic effects, which require higher doses, but rather to exploit the anti-inflammatory and antioxidant properties of methylene blue. Methylene blue was diluted in 1000 mL of 0.9% saline. An equivalent volume of fluid was removed simultaneously by zero-balance ultrafiltration, maintaining a fluid-equilibrium state throughout the 20-minute procedure. For this purpose, a dedicated circuit was developed to enable concurrent blood lavage and ultrafiltration. Blood was withdrawn through a dedicated port integrated into the SORIN oxygenator and directed by a centrifugal pump to a small reservoir containing the methylene blue solution. From this reservoir, the blood passed through a hemoc; Other Names: zero-balance ultrafiltration; Procedure: Conventional ultrafiltration; Conventional ultrafiltration (CUF). CUF during cardiopulmonary bypass (CPB) is performed to remove excess fluid and solutes from the patient's blood during cardiac surgery, thereby limiting fluid accumulation and attenuating pro-inflammatory effects. This technique increases hematocrit, improves cardiopulmonary function, and reduces the need for blood transfusions. Unlike modified ultrafiltration (MUF), which is performed after weaning from CPB, CUF is carried out simultaneously with CPB while the heart-lung machine remains in operation.; Procedure: Zero-balance ultrafiltration; Zero-balance ultrafiltration (Z-BUF). Z-BUF is performed during cardiopulmonary bypass (CPB) to maintain fluid equilibrium by removing plasma water and solutes while simultaneously infusing an equal volume of replacement fluid, thereby achieving a net zero fluid balance. This technique has been shown to decrease urine output, reduce tissue edema and the inflammatory response, improve arterial oxygenation (PaO₂), and lower the need for postoperative blood transfusions.
Experimental: Methylene blue wash combined with zero-balanced ultrafiltration; Methylene blue lavage combined with zero-balance ultrafiltration (MB+G-ZBUF). Patients assigned to this group underwent zero-balance ultrafiltration with concomitant blood lavage using methylene blue at a low dose of 1 mg/kg of body weight. Methylene blue was diluted in 1000 mL of 0.9% saline. An equivalent volume of fluid was simultaneously removed by zero-balance ultrafiltration, ensuring a balanced fluid state throughout the 20-minute procedure. For this purpose, a dedicated circuit was developed to allow simultaneous blood lavage and ultrafiltration. Blood was withdrawn through a dedicated port integrated into the SORIN oxygenator and directed by a centrifugal pump to a small reservoir containing the methylene blue solution. From this reservoir, the blood passed through a hemoconcentrator for filtration before being returned to the central reservoir of the cardiopulmonary bypass (CPB) circuit.	Drug: Methylene Blue; This protocol was designed to perform intraoperative blood lavage with methylene blue at the end of surgery, with a duration of 20 minutes. A low dose of 1 mg/kg of body weight was administered. The objective was not to elicit hemodynamic effects, which require higher doses, but rather to exploit the anti-inflammatory and antioxidant properties of methylene blue. Methylene blue was diluted in 1000 mL of 0.9% saline. An equivalent volume of fluid was removed simultaneously by zero-balance ultrafiltration, maintaining a fluid-equilibrium state throughout the 20-minute procedure. For this purpose, a dedicated circuit was developed to enable concurrent blood lavage and ultrafiltration. Blood was withdrawn through a dedicated port integrated into the SORIN oxygenator and directed by a centrifugal pump to a small reservoir containing the methylene blue solution. From this reservoir, the blood passed through a hemoc; Other Names: zero-balance ultrafiltration; Procedure: Conventional ultrafiltration; Conventional ultrafiltration (CUF). CUF during cardiopulmonary bypass (CPB) is performed to remove excess fluid and solutes from the patient's blood during cardiac surgery, thereby limiting fluid accumulation and attenuating pro-inflammatory effects. This technique increases hematocrit, improves cardiopulmonary function, and reduces the need for blood transfusions. Unlike modified ultrafiltration (MUF), which is performed after weaning from CPB, CUF is carried out simultaneously with CPB while the heart-lung machine remains in operation.; Procedure: Zero-balance ultrafiltration; Zero-balance ultrafiltration (Z-BUF). Z-BUF is performed during cardiopulmonary bypass (CPB) to maintain fluid equilibrium by removing plasma water and solutes while simultaneously infusing an equal volume of replacement fluid, thereby achieving a net zero fluid balance. This technique has been shown to decrease urine output, reduce tissue edema and the inflammatory response, improve arterial oxygenation (PaO₂), and lower the need for postoperative blood transfusions.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Systemic Inflammation	To assess systemic inflammation, blood samples were collected via central venous access through the internal jugular vein at five time points: before surgery, during surgery, 10 minutes after cannulation, 10 minutes after blood lavage with methylene blue and ultrafiltration, and 4 hours after ICU admission. Samples were drawn into EDTA-containing syringes (50 mM, pH 8.0) at one-tenth of the total blood volume. Plasma was separated by centrifugation at 1,700 × g for 10 minutes at 4 °C, transferred to new tubes avoiding the buffy coat, and centrifuged again at 11,000 × g for 2 minutes at 4 °C. Plasma was aliquoted and stored at -80 °C. Cytokine concentrations were quantified using a Luminex xMAP multiplex immunoassay (8-27-plex) in triplicate, enabling simultaneous measurement of up to seven cytokines, chemokines, and interleukins from 50 μL plasma.	Three years
Water overload	Fluid balance was meticulously monitored, including fluids removed by conventional ultrafiltration, surgical suction, sponges, and urine output. Discrepancies between infused and removed volumes were corrected using zero-balance ultrafiltration (ZBUF), removing excess fluid or compensating deficits to match preoperative volemic status. For example, if 100 mL more than planned had been removed, only 900 mL were withdrawn. Body fluid composition was assessed with the InBody S10 bioimpedance device. Extracellular water (ECW) was measured at 5 kHz, total body water (TBW) at 250 kHz, and intracellular water (ICW) calculated as TBW-ECW. The ECW/TBW ratio served as the primary parameter to monitor fluid status and detect overload.	Three years
Intravascular volume assessment using IVC indices	Intravascular volume will be evaluated by analyzing mechanical and hemodynamic changes in the inferior vena cava (IVC) using subcostal ultrasound images. The collapsibility index (CI = (IVCmax - IVCmin)/IVCmax) will be used during spontaneous breathing, and the distensibility index (DI = (IVCmax - IVCmin)/IVCmin) during mechanical ventilation. Time Frame: Preoperatively, immediately postoperatively, and 24 hours after surgery. Unit of Measure: Percentage (%).	Three years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Length of stay in the intensive care unit (ICU)	Secondary outcomes included the length of stay in the intensive care unit (ICU), measured in hours, to evaluate the clinical impact of zero-balance ultrafiltration with methylene blue. This parameter was recorded for all patients and analyzed in relation to fluid balance, pulmonary congestion, intravascular volume, and systemic inflammatory markers, providing a comprehensive assessment of the intervention's effects on postoperative recovery.	Three years

Collaborators and Investigators

• Sponsor: University of Sao Paulo

Study record dates

Study Major Dates

• Study Start (Actual): April 12, 2021
• Primary Completion (Actual): August 25, 2023
• Study Completion (Actual): March 16, 2024

Study Registration Dates

• First Submitted: September 23, 2025
• First Submitted That Met QC Criteria: October 1, 2025
• First Posted (Estimated): October 8, 2025

Study Record Updates

• Last Update Posted (Estimated): October 8, 2025
• Last Update Submitted That Met QC Criteria: October 1, 2025
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Keywords: cardiopulmonary bypass; Cardiac surgery; methylene blue; pulmonary congestion; water overload; intravascular volemia; zero-balance ultrafiltration
• Additional Relevant MeSH Terms: Sulfur Compounds; Organic Chemicals; Heterocyclic Compounds; Heterocyclic Compounds, Fused-Ring; Heterocyclic Compounds, 3-Ring; Phenothiazines; Methylene Blue
• Other Study ID Numbers: 2.462.520

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No