Protective mechanical ventilation during open surgery on the abdomen with general anaesthesia

Post-operative pulmonary complications composed of:
1. Mild respiratory failure (PaO2 less than 60 mmHg or SpO2 less than 90% in room air but responding to supplemental oxygen (excluding hypoventilation)
2. Severe respiratory failure (need for non-invasive or invasive mechanical ventilation or a PaO2 less than 60 mmHg or SpO2 less than 90% despite supplemental oxygen (excluding hypoventilation)
3. ALI/ARDS (by the consensus criteria - only in case of non-invasive or invasive mechanical ventilation)
4. Suspected pulmonary infection (in case patient receives antibiotics and meets at least one of the following criteria: new or changed sputum, new or changed lung opacities on chest X-ray when clinically indicated, timpanic temperature greater than 38.3°C, WBC count greater than 12,000/mm3)
5. Pulmonary infiltrate (chest X-ray demonstrating monolateral or bilateral infiltrate)
6. Pleural effusion (chest X-ray demonstrating blunting of the costophrenic angle, loss of the sharp silhouette of the ipsilateral hemidiaphragm in upright position, evidence of displacement of adjacent anatomical structures, or (in supine position) a hazy opacity in one hemi-thorax with preserved vascular shadows)
7. Atelectasis (suggested by lung opacification with shift of the mediastinum, hilum, or hemidiaphragm towards the affected area, and compensatory overinflation in the adjacent nonatelectatic lung)
8. Pneumothorax (defined as air in the pleural space with no vascular bed surrounding the visceral pleura)
9. Bronchospasm (defined as newly detected expiratory wheezing treated with bronchodilators)
10. Aspiration pneumonitis (defined as respiratory failure after the inhalation of regurgitated gastric contents)
11. Cardiopulmonary oedema (defined as clinical signs of congestion, including dyspnoea, oedema, rales and jugular venous distention, with the chest X-ray demonstrating increase in vascular markings and diffuse alveolar interstitial infiltrates)

These outcomes will primarily be presented as a total percentage of post-operative pulmonary complications.

Primary and secondary endpoints are assessed on day 1, 3 and 5 after surgery, and at the last day before discharge or on day 90, if patient is still admitted to the hospital at that time. Clinical data and the presence of pulmonary and extra-pulmonary post-operative complications will be scored; the day of development of any complication will be indicated.

1. Intra-operative complications (desaturation, barotrauma, hypotension during recruitment, need for vasopressors)
2. Need for ICU admission (if not as part of routine) or ICU readmission
3. Hospital-free days at day 90
4. Post-operative wound healing (devided in superficial, deep and organ/space)
5. Systemic levels of markers of pulmonary inflammation, markers of acute lung injury and markers of distal organ injury
6. Post-operative non-pulmonary organ function, defined as follows:
6.1. Systemic inflammatory response syndrome (SIRS); presence of two or more of the following findings:
6.1.1. Body temperature less than 36°C or greater than 38°C
6.1.2. Heart rate greater than 90 beats per minute
6.1.3. Respiratory rate greater than 20 breaths per minute or, on blood gas, a PaCO2 less than 32 mmHg (4.3 kPa)
6.1.4. White blood cell (WBC) count less than 4,000 cells/mm3 or greater than 12,000 cells/mm3 or greater than 10% band forms
6.2. Sepsis (SIRS in response to a confirmed infectious process; infection can be suspected or proven by culture, stain, or polymerase chain reaction [PCR]), or a clinical syndrome pathognomonic for infection. Specific evidence for infection includes WBCs in normally sterile fluid (such as urine or cerebrospinal fluid [CSF]), evidence of a perforated viscus (free air on abdominal x-ray or computed tomography [CT] scan, signs of acute peritonitis), abnormal chest x-ray (CXR) consistent with pneumonia (with focal opacification), or petechiae, purpura, or purpura fulminans
6.3. Severe sepsis (sepsis with organ dysfunction, hypoperfusion, or hypotension)
6.4. Septic shock: sepsis with refractory arterial hypotension or hypoperfusion abnormalities in spite of adequate fluid resuscitation; signs of systemic hypoperfusion may be either end-organ dysfunction or serum lactate greater than 4 mmol/dL. Other signs include oliguria and altered mental status. Patients are defined as having septic shock if they have sepsis plus hypotension after aggressive fluid resuscitation, typically upwards of 6 litres or 40 ml/kg of crystalloid.
6.5. Extra-pulmonary infection (wound infection or any other infection)
6.6. Coma (Glasgow Coma Score less than 8 in the absence of therapeutic coma or sedation)
6.7. Acute myocardial infarction (detection of rise and/or fall of cardiac markers (preferably troponin) with at least one value above the 99th percentile of the upper reference limit, together with: symptoms of ischaemia, ECG changes indicative of new ischaemia, development of pathological Q-waves, or imaging evidence of new loss of viable myocardium or new regional wall motion abnormality, or sudden unexpected cardiac death, involving cardiac arrest with symptoms suggestive of cardiac ischaemia (but death occurring before the appearance of cardiac markers in blood)
6.8. Acute renal failure: renal failure documented as follows -
6.8.1. Risk: increased creatinine x 1.5 or glomerular filtration rate (GFR) decrease greater than 25% or urine output (UO) less than 0.5 ml/kg/h x 6 hr
6.8.2. Injury: increased creatinine x 2 or GFR decrease greater than 50% or UO less than 0.5 ml/kg/h x 12 hr
6.8.3. Failure: increase creatinine x 3 or GFR decrease greater than 75% or UO less than 0.3 ml/kg/h x 24 hr or anuria x 12 hrs
6.8.4. Loss: persistent ARF = complete loss of kidney function greater than 4 weeks
6.9. Disseminated intravascular coagulation (DIC) score, documented as follows:
6.9.1. Platelet count less than 50 (2 points), less than 100 (1 point), or = 100 (0 points)
6.9.2. D-dimer greater than 4 µg/ml (2 points), greater than 0.39 µg/ml (1 point) or = 0.39 µg/ml (0 points)
6.9.3. Prothrombin time greater than 20.5 seconds (2 points), greater than 17.5 seconds (1 point) or = 17.5 seconds (0 points)
6.9.4. If = 5 points: overt DIC
6.10. Gastro-intestinal failure: gastro-intestinal bleeding or gastro-intestinal failure (GIF) score documented as follows: 0 = normal gastrointestinal function; 1 = enteral feeding with under 50% of calculated needs or no feeding 3 days after abdominal surgery; 2 = food intolerance (FI) or intra-abdominal hypertension (IAH); 3 = FI and IAH; and 4 = abdominal compartment syndrome (ACS)
6.11. Hepatic failure (serum bilirubin level greater than 2 mg/dL with elevation of the transaminase and lactic dehydrogenase levels above twice normal values)

Primary and secondary endpoints are assessed on day 1, 3 and 5 after surgery, and at the last day before discharge or on day 90, if patient is still admitted to the hospital at that time. Clinical data and the presence of pulmonary and extra-pulmonary post-operative complications will be scored; the day of development of any complication will be indicated.