Individualized Hemodynamic Optimization by Indirect Measurement of the Respiratory Quotient in Major Surgery: Prospective Randomized Multicentre Open-Label Study (OPHIQUE) Individualized Optimization by Indirect Measurement of the Respiratory Quotient

The measurement of the inspired / expired fractions in O2 and CO2 is part of the daily monitoring of the intubated-ventilated patient in the operating theater. The ratio of VCO2 to VO2 (respiratory quotient (RQ)) is a non-invasive indirect measure of anaerobic metabolism of the patient, and an indirect reflection of tissue perfusion. We hypothesize that a hemodynamic optimization in major surgery individualized by non-invasive continuous measurement of the RQ would optimize TaO2 more specifically by informing us about the installation of a VO2 dependence, and therefore of an anaerobic metabolism. Patients are randomized in 2 groups : Control group: hemodynamic management of patients is done according to usual practices by maintenance of blood pressure by norepinephrine as well as optimization of Systolic Voume (SV) by vascular filling and use of dobutamine if necessary. Experimental group: perioperative hemodynamic management is based on an algorithm that includes RQ measurement and includes volume expansion, norepinephrine, FiO2 enhancement, RBC transfusion and dobutamine. Primary and secondary outcomes are recorded 1,2,7 and 30 days after the surgery.

• Background : The measurement of the inspired / expired fractions in O2 and CO2 is part of the daily monitoring of the intubated-ventilated patient in the operating theater. Changes in EtCO2 may reflect changes in metabolic CO2 production (VCO2), and oxygen extraction from the body (SvO2). The inspired / exhaled oxygen difference is an indirect reflection of the oxygen consumption (VO2). The ratio of VCO2 to VO2 (respiratory quotient (RQ)) is a non-invasive indirect measure of anaerobic metabolism of the patient, and an indirect reflection of tissue perfusion.

Some studies, including a recent one carried out by our center, showed that the RQ was linked to the appearance of anaerobic metabolism and to the postoperative evolution of the patient. The RQ was correlated with arterial lactate levels and predicted the occurrence of postoperative complications. Thus, the RQ can be a reliable, continuous, non-invasive marker of anaerobic metabolism in the operating room and therefore of the adequacy of arterial oxygen Transport (TaO2) with respect to the VO2 of the patient

* Purpose : Th investigators hypothesize that a hemodynamic optimization in major surgery individualized by non-invasive continuous measurement of the RQ would optimize TaO2 more specifically by informing us about the installation of a VO2 dependence, and therefore of an anaerobic metabolism.
* Brief summary:

The measurement of the inspired / expired fractions in O2 and CO2 is part of the daily monitoring of the intubated-ventilated patient in the operating theater. The ratio of VCO2 to VO2 (respiratory quotient (RQ)) is a non-invasive indirect measure of anaerobic metabolism of the patient, and an indirect reflection of tissue perfusion. We hypothesize that a hemodynamic optimization in major surgery individualized by non-invasive continuous measurement of the RQ would optimize TaO2 more specifically by informing us about the installation of a VO2 dependence, and therefore of an anaerobic metabolism. Patients are randomized in 2 groups : Control group: hemodynamic management of patients is done according to usual practices by maintenance of blood pressure by norepinephrine as well as optimization of Systolic Voume (SV) by vascular filling and use of dobutamine if necessary. Experimental group: perioperative hemodynamic management is based on an algorithm that includes RQ measurement and includes volume expansion, norepinephrine, FiO2 enhancement, RBC transfusion and dobutamine. Primary and secondary outcomes are recorded 1,2,7 and 30 days after the surgery.

Number of groups and description of groups :

2 groups Control group: hemodynamic management of patients is done according to usual practices by maintenance of blood pressure by norepinephrine as well as optimization of SV by vascular filling and use of dobutamine if necessary.

Experimental group: perioperative hemodynamic management is based on an algorithm that includes RQ measurement and includes volume expansion, norepinephrine, FiO2 enhancement, RBC transfusion and dobutamine.

• Interventions : Control group: hemodynamic management of patients is done according to usual practices by maintenance of blood pressure by norepinephrine as well as optimization of SV by vascular filling and use of dobutamine if necessary.

Experimental group: perioperative hemodynamic management is based on an algorithm that includes RQ measurement and includes volume expansion, norepinephrine, FiO2 enhancement, RBC transfusion and dobutamine.

The primary outcome is defined by at least one organ failure within 7 days postoperatively.

The duration of participation of each patient is 30 days and total research term is 49 months

* Number of subjects : 350
* Statistical analysis : The null hypothesis will be rejected in favor of the alternative hypothesis (there is a difference) using a test of χ2 or a Fisher test according to the frequency of the complications with a risk of the first bilateral species of 5%.
* Key-words : respiratory quotient, post opérative complications, anaerobic metabolism.

Eligibility Criteria:
Inclusion Criteria:

* Abdominal, orthopedic or vascular surgery with general anesthesia
* ASA score ≥ II
* Estimated duration of surgery\> 2 hours
* Consent signed.
* Affiliation to a social security scheme

Exclusion Criteria:

* Untreated or unbalanced severe hypertension under treatment.
* Preoperative renal failure dialyzed.
* Acute heart failure.
* Acute coronary insufficiency.
* Vascular surgery with kidney plasty.
* Cardiac surgery.
* Permanent laparoscopy.
* Preoperative shock state.
* Refusal of patient's participation
* Pregnant woman, parturient or breastfeeding.
* Patient under guardianship or trusteeship, under the protection of justice or private public law.
* Anesthesia with loco-regional anesthesia (spinal anesthesia and epidural).
* Acute respiratory distress syndrome (PaO2 / FiO2 ratio \<300).
* Chronic Respiratory Failure with Home Oxygen Therapy.
* Patient already included in another therapeutic trial with an experimental molecule.
* Emergency anesthesia