Postoperative respiratory failure (PRF) is a dreaded complication that imposes a significant burden through unplanned admission to the ICU, post discharge disability and mortality. Despite widespread implementation of intraoperative lung-protective ventilation strategies over the past decade, results remain inconsistent. Interventions targeting individual parameters like tidal volume or positive end-expiratory pressure (PEEP) have shown equivocal results. The use of high PEEP and recruitment maneuvers raises safety concerns by possible negative hemodynamic effects. Recent studies suggest that individualizing ventilation strategies based on mechanical power-a composite parameter integrating tidal volume, plateau pressure, PEEP, and ventilator frequency-may better predict and help prevent PRF, independently of patients' baseline respiratory system compliance. These studies identified this parameter as interventional targets to reduce lung injury during mechanical ventilation. However, no multicenter randomized controlled trial has been performed in the field of ventilatory settings titration during invasive mechanical ventilation in operating room. The investigators hypothesize that a ventilation strategy aimed at decreasing mechanical power will reduce the incidence of PRF and mortality in patients undergoing abdominal surgery, compared with a standard strategy using fixed tidal volume and PEEP
Postoperative respiratory failure (PRF) is a dreaded complication that imposes a significant burden through unplanned admission to the intensive care unit (ICU) and post discharge disability. Respiratory failure evident by tracheal intubations 1 month following nonemergent, noncardiac surgeries has been associated with a nine-fold increase in mortality. Efforts to reduce the rates of PRF have incorporated intraoperative ventilation strategies as a central element, with lung-protective ventilation following recommendations for the ICU setting being broadly implemented over the past decade. Interventions targeting individual parameters like tidal volume have shown equivocal results. To summarize, two randomized clinical trials showed lung-protective ventilation with low tidal volume (VT) in addition to high positive end-expiratory pressure (PEEP) and recruitment maneuver (RM) to prevent against postoperative pulmonary complications when compared with ventilation with high VT plus low PEEP without RM. Two other large, randomized trials found no benefit of high PEEP with RM compared with low PEEP without RM in this setting, suggesting that beneficial effects arise primarily from the use of low VT ventilation. Concerns have also been raised about possible negative hemodynamic effects of high PEEP and RMs in these studies. One size does not fit all. Individualized strategies are needed, such as ones using driving pressure (plateau pressure - PEEP), to perform PEEP titration. Using this calculated parameter, reduced incidence of postoperative pulmonary complications has been demonstrated in small randomized controlled trials, and not achieved in others. However, tidal volume and respiratory rate are also important parameters to limit ventilator induced injuries, and are not considered when assessing driving pressure. Mechanical power, a concept that in addition to tidal volume, plateau pressure and positive end-expiratory pressure (PEEP) also integrates the ventilatory frequency, has been recently associated with a higher risk of PRF. This formula is now implemented in the most recent operating room ventilators, and used in routine by some teams, with lack of evidence showing an efficacy of this strategy to set ventilatory settings. Although it has become clear that high mechanical power identifies patients at risk of PRF both in the operating room and ICU, there is an ongoing debate about whether they are linked to PRF, or whether these parameters merely represent an epiphenomenon in patients with impaired respiratory system mechanics and elevated risk at baseline. Recently, several studies showed that high mechanical power was associated with PRF independent from patients' baseline respiratory system compliance. These studies identified this parameter as interventional targets to reduce lung injury during mechanical ventilation. However, no multicenter randomized controlled trial has been performed in the field of ventilatory settings titration during invasive mechanical ventilation in operating room. The investigators made the hypothesis that a strategy aimed at decreasing mechanical power (tidal volume, respiratory rate and PEEP individually titrated to minimize the mechanical power) will reduce PRF and mortality in patients undergoing abdominal surgery, when compared with that of a strategy of standard care (with fixed level of tidal volume and PEEP). The investigators expect decreased PRF and mortality rate in the group "mechanical power-guided ventilatory settings". The investigators also expect in this group reduced duration of postoperative mechanical ventilation, reduced incidence of postoperative organ dysfunction, and reduced duration of hospital stay.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
490
1. Tidal volume 7ml/kg PBW and RR titrated for EtCO2 between 40-50mmHg. See calculated Mechanical power:0,049\*tidal volume\*RR\*driving pressure. 2. Set PEEP 15cmH2O and perform recruitment maneuver at 30cmH2O for 20s. Decrease PEEP from 15 by steps of 2cmH2O until the lower level of PEEP minimizing mechanical power. Note mechanical power. Stop maneuver and/or decrease level of PEEP if decrease\>20% of cardiac output during the maneuver, when compared to baseline. 3. Repeat this step using 9 ml/kg PBW and choose the optimal tidal volume with lowest mechanical power. During the surgery, adjust RR to maintain EtCO2 between 40-50mmHg, with an inspiratory-to-expiratory time ratio of 1:2 to 1:1, an end-inspiratory pause of 30%, an FiO2 adjusted to maintain SpO2≥94%. Recruitment maneuvers will be performed after intubation, in case of ventilator disconnection, coelioscopy insufflation, change of position, at the end of surgery, or if mechanical power \>30%.
Tidal volume 7 ml/kg predicted body weight, calculated according to a predefined formula: 50+0.91 x (centimeters of height - 152.4) for males and 45.5+0.91 x (centimeters of height - 152.4) for females, fixed PEEP between 6 and 8 cmH20, recruitment maneuvers at the discretion of the physician. The respiratory rate will be adjusted to maintain end-tidal partial pressure of CO2 between 30 and 40 mmHg, a target reported to be used by approximately 90% of physicians according to a recent online survey administered to French anesthesiologists via the French Society of Anesthesia \& Intensive Care Medecine (SFAR), which will be published soon, with an inspiratory-to-expiratory time ratio of 1:2 to 1:1, an end-inspiratory pause of 30 %, and an FiO2 adjusted to maintain SpO2 ≥ 94%. Mechanical power will not be measured during the surgery to avoid any modification of the ventilatory setting by the physician in charge.
Composite of postoperative respiratory failure
Defined as failure to wean from the ventilator within the first 12 hours after surgery
Time frame: Up to 12 hours after surgery
Composite of postoperative respiratory failure
Defined as the need for unplanned reintubation following the end of surgery, once extubated
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Composite of postoperative respiratory failure
Defined as the need for therapeutic non-invasive ventilation following the end of surgery, once extubated
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
All-cause mortality
Defined as death from any cause occurring within 30 days following surgery. The time to death will be measured from the date of surgery to the date of death. Patients discharged from hospital alive before Day 30 or still alive at Day 30 will be considered censored at that time.
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Severity of postoperative pulmonary complications following surgery
The severity of pulmonary complications after surgery will be scored on a grade scale ranging from 0 to 4, with grade 0 representing the absence of any pulmonary complication and grades 1 through 4 representing successively the worse forms of pulmonary complications
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Renal dysfunction following surgery
Postoperative renal dysfunction will be assessed using the Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Classification, based on serum creatinine levels and urine output criteria. The KDIGO classification ranges from Stage 0 to Stage 3, where higher stages indicate more severe renal dysfunction (Stage 0 = no acute kidney injury; Stage 3 = most severe acute kidney injury). Renal dysfunction will be defined as KDIGO Stage 1 or higher.
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Sepsis and septic shock following surgery
Will be evaluated after surgery, according to the last recommendations on sepsis and septic shock
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Sepsis-related Organ Failure Assessment (SOFA)
The SOFA score will be collected at randomization, at Day 1, at Day 7 to evaluate the extent of organ dysfunction. The score includes six organ systems: respiratory, cardiovascular, hepatic, coagulation, renal, and neurological function. Each system is graded from 0 (normal function) to 4 (severe dysfunction) based on objective clinical or laboratory parameters. The Glasgow Coma Score will be excluded from the calculation
Time frame: At randomization (day 0), at Day 1, at Day 7
Ventilator-free days (VFDs)
A ventilator-free day is defined as the receipt as \< 2 hours of invasive mechanical ventilation or non-invasive mechanical ventilation (as curative therapy) within a 24-hour period
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Duration of invasive mechanical ventilation
Measured from the time of initiation of mechanical ventilation to the first tracheal extubation
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Total duration of mechanical ventilation
Total duration of invasive mechanical ventilation will be measured in days from the initiation of mechanical ventilation until final discontinuation during the follow-up period. All periods of invasive mechanical ventilation, including episodes requiring reintubation, will be included in the total duration calculation.
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Time to successful tracheal extubation
Successful extubation reflects both effective weaning from mechanical ventilation and the patient's ability to maintain adequate spontaneous breathing. it's defined as the interval from the time of initiation of mechanical ventilation to the tracheal extubation that is not followed by reintubation within 7 days
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
ICU-free days
Are defined as the number of days a patient is both alive and discharged from the intensive care unit (ICU) during the first 30 days following surgery. Patients who die before ICU discharge will be assigned zero ICU-free days. The outcome will be censored at 30 days postoperatively or at the time of hospital discharge, whichever occurs first
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Length of ICU stay
Will be measured from the date of ICU admission to the date of discharge from the ICU. Patients who are still in ICU on day 30 will be considered censored at that time
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Length of hospital stay
Will be measured from the date of hospital admission to the date of discharge from the hospital. Patients who are transferred to another type of healthcare facility (e.g., rehabilitation center) before Day 30 will be considered as having been discharged from the hospital. Patients who are still in hospital on day 30 will be considered censored at that time
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
Time to death (or censoring)
Is defined as the time from the date of surgery to the occurrence of death. Data will be collected up to Day 30, or until the date of hospital discharge, if this occurs before Day 30. Patients who do not die during this period will be considered censored at that time
Time frame: Up to 30 days after surgery, or by the date of hospital discharge, if this occurs before Day 30
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