Oxygen Consumption, Hypoperfusion and Organ Injury After Cardio-pulmonary Bypass

Uppsala University Hospital65 enrolled

Overview

The goal of this observational study is to understand how oxygen consumption after heart surgery relates to blood flow problems and organ injury. The study focuses on patients over 18 years old who are having planned heart surgery with a heart-lung machine (cardiopulmonary bypass). The main questions the study aims to answer are: 1. How does oxygen consumption in the early hours after surgery relate to lactate levels (a sign of low oxygen supply to the tissues)? 2. How is oxygen consumption linked to signs of poor blood flow and organ injury (such as heart, kidney, liver, brain, and gut damage)? Researchers will measure oxygen consumption after surgery using a technique called indirect calorimetry. They will also track blood flow and oxygen use during surgery and check for signs of organ injury the day after the procedure. The study will include 65 participants. People with certain health conditions, like severe anemia, high lactate levels before surgery, or needing intensive care or extra oxygen supply before surgery, will not be included. By understanding how oxygen consumption relates to blood flow and organ injury, this research may help to better manage patients after heart surgery and reduce complications.

Study Type

OBSERVATIONAL

Enrollment

Conditions

Cardiac Surgery Requiring Cardiopulmonary Bypass

Interventions

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

Inclusion Criteria: * Elective cardiac surgery requiring cardiopulmonary bypass Exclusion Criteria: * Combined, redo or annuloplasty procedures * Surgical procedures involving other vascular cannulation than standard direct, such as bicaval or femoral cannulation * Preoperative hyperlactatemia (\>2mmol/L) or anaemia (Hb \<90 g/dL) * Preoperative need for supplementary oxygen or ICU care * Consent not obtainable.

Outcomes

Primary Outcomes

Difference in oxygen consumption in early postoperative hypoperfusion

Difference in oxygen consumption (VO2I via indirect calorimetry) in ml min-1 m-2 between patients with and without early hyperlactatemia (\>2mmol/L)

Time frame: 0-4 hours after surgery

Secondary Outcomes

Evaluation of hypoperfusion parameters as predictors of postoperative oxygen consumption

Hypoperfusion parameters will be evaluated as a predictors of postoperative oxygen consumption (VO2I, ml min-1 m-2 via indirect calorimetry). Blood gas parameters taken preoperatively and at spaced time-points up to 24 hrs after start of surgery: 1\) Central venous oxygen saturation (ScvO2, %, central venous blood gas), 2) Arterial lactate (mmol/L, arterial blood gas), 3) Base excess (BE, mmol/L, arterial blood gas), 4) Venous-to-arterial CO2 difference (ΔPCO2, mmHg, arterial and central venous blood gas) and its ratio with arterial -central venous oxygen content. Clinical variables measured hourly or otherwise specified: 5\) Heart rate (beats/min), 6) Mean arterial pressure (MAP, mmHg), 7) Central venous pressure (CVP, mmHg), 8) Vasopressor or inotrope requirement (Y/N, low-intermediate-high), 9) Urine output (mL/24 hours), and 10) net fluid balance (mL/24 hours). Additional explorative data analyses for hypothesis generating purposes can be performed.

Time frame: 0-24 hours after surgery

Evaluation of oxygen delivery and consumption during cardiopulmonary bypass as predictors of postoperative oxygen consumption

Oxygen delivery (DO2I, ml min-1 m-2) and oxygen consumption (VO2I ml min-1 m-2) will be measured during cardiopulmonary bypass by continuous blood parameter monitoring or calculated by blood oxygen content and pump flow. Both mean levels and repeated measures will be analysed as predictors for postoperative oxygen consumption. Additional explorative data analyses for hypothesis generating purposes can be performed.

Time frame: 0-4 hours during and after surgery

Evaluation of organ injury biomarkers as predictors of postoperative oxygen consumption

Organ injury markers will be evaluated as predictors for postoperative oxygen consumption. Absolute levels, changes from preoperative values, and above normal predicted value (yes/no) will be used in the analysis. Blood sampling preoperatively and the day after surgery. 1. Renal: Creatinine (mmol L-1), Estimated glomerular filtration rate; eGFR (ml min-1 1.73 m-2): 2. Cardiac: Troponin T; TnT, creatinine kinase-MB; CK-MB, probrain natriuretic peptide; Nt-proBNP (ng L-1) 3. Hepatic: Aspartate aminotransferase; ASAT, alanine aminotransferase; ALAT(mikrokat L-1) 4. Brain: Neurofilament light chain; NFL, Glial fibrillary acidic protein, GFAP (ng L-1) 5. Gut: Medium chain fatty acids; MCFA, Short chain fatty acids; SCFA, conjugated and non-conjugated bile acids (ng ml-1) Additional explorative data analyses for hypothesis generating purposes can be performed.

Time frame: Preoperative and the day after surgery