Intraoperative Protective Ventilation for Obese Patients Undergoing Gynaecological Laparoscopic Surgery

Study Overview
=================
Brief Summary
-----------------
Background. The use of a comprehensive strategy providing low tidal volumes, peep and recruiting maneuvers in patients undergoing open abdominal surgery improves postoperative respiratory function and clinical outcome. It is unknown whether such ventilatory approach may be feasible and/or beneficial in patients undergoing laparoscopy, as pneumoperitoneum and Trendelenburg position may alter lung volumes and chest-wall elastance. Objective. The investigators designed a randomized, controlled trial to assess the effect of a lung-protective ventilation strategy on postoperative oxygenation in obese patients undergoing laparoscopic surgery.

Official Title
-----------------
Intraoperative Protective Ventilation for Obese Patients Undergoing Gynaecological Laparoscopic Surgery. A Single-centre Randomized, Controlled Trial

Conditions
-----------------
Anesthesia, Surgery--Complications

Intervention / Treatment
-----------------
* Drug: Intravenous anesthetic
* Drug: Crystalloid Solutions
* Diagnostic Test: Esophageal pressure measurement
* Diagnostic Test: Lung volume measurement with the nitrogen washin-washout technique


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: scheduled for gynaecological laparoscopic surgery in the Trendelenburg position Obesity with body mass index>35 kg/m^2 written informed consent Exclusion Criteria: Clinical history or signs of chronic heart failure history of neuromuscular disease history of thoracic surgery pregnancy chronic respiratory failure requiring long-term oxygen administration

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
Female

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Protective ventilation<br>Volume controlled ventilation with tidal volume 6-7 ml/kg of predicted body weight (45.5 + 0.91 (height [cm] -152.4)), FiO2 0.4 and PEEP 10 cmH2O during the whole study period. Respiratory rate will be titrated to keep end-tidal CO2 values between 30 and 40 mmHg. I:E ratio will be set in order to obtain an inspiratory time of 0.8 seconds and an inspiratory pause of 0.3 seconds and FiO2 will be kept unchanged during the whole study period. In patients in this group, recruiting maneuvers will be performed throughout a stepwise 5 cmH2O PEEP increase every 30 seconds to achieve a PEEP of 35 cmH2O during Pressure Controlled Ventilation (10 cmH2O of inspiratory pressure while keeping respiratory rate unmodified), followed by a stepwise 5 cmH2O PEEP reduction every 30 seconds until the baseline set peep is reached. | Drug: Intravenous anesthetic<br>* Anaesthesia induction will be obtained with i.v. 2-3 mg/kg propofol, 0,6-0,8 mcg/kg fentanyl, and 0.9-1,2 mg/kg rocuronium. Anaesthesia will be maintained with i.v. propofol continuous infusion, with a dose titrated to achieve a bi-spectral index value between 40 and 50<br>Drug: Crystalloid Solutions<br>* Balanced crystalloids will be administered to patients in both groups as a standard rate of 3-5 ml/kg/h. Treatment of eventual hemodynamic instability will be left to the attending physician<br>Diagnostic Test: Esophageal pressure measurement<br>* A nasogastric polyfunctional tube (Nutrivent, Sidam, Italy) will be placed after anaesthesia induction in all enrolled patients to measure esophageal pressure, estimate pleural pressure and compute transpulmonary pressure<br>Diagnostic Test: Lung volume measurement with the nitrogen washin-washout technique<br>* Lung volume will be measured through nitrogen wash-in wash-out technique and low-flow Pressure-volume curve will be recorded to estimate differences in alveolar recruitment between the two study groups.<br>|
| Active Comparator: Standard Ventilation<br>Volume controlled ventilation with tidal volume 10 ml/kg of PBW (45.5 + 0.91 (height [cm] -152.4)), FiO2 0.4 and PEEP 5 cmH2O during the whole study period. Respiratory rate will be titrated to keep end-tidal CO2 values between 30 mmHg and 40 mmHg. I:E ratio will be set in order to obtain an inspiratory time of 0.8-1 seconds and an inspiratory pause of 0.3 second | Drug: Intravenous anesthetic<br>* Anaesthesia induction will be obtained with i.v. 2-3 mg/kg propofol, 0,6-0,8 mcg/kg fentanyl, and 0.9-1,2 mg/kg rocuronium. Anaesthesia will be maintained with i.v. propofol continuous infusion, with a dose titrated to achieve a bi-spectral index value between 40 and 50<br>Drug: Crystalloid Solutions<br>* Balanced crystalloids will be administered to patients in both groups as a standard rate of 3-5 ml/kg/h. Treatment of eventual hemodynamic instability will be left to the attending physician<br>Diagnostic Test: Esophageal pressure measurement<br>* A nasogastric polyfunctional tube (Nutrivent, Sidam, Italy) will be placed after anaesthesia induction in all enrolled patients to measure esophageal pressure, estimate pleural pressure and compute transpulmonary pressure<br>Diagnostic Test: Lung volume measurement with the nitrogen washin-washout technique<br>* Lung volume will be measured through nitrogen wash-in wash-out technique and low-flow Pressure-volume curve will be recorded to estimate differences in alveolar recruitment between the two study groups.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative oxygenation | PaO2/FiO2 ratio 1 hour after extubation, while the patient is receiving oxygen through VenturiMask 40% | One hour after extubation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Postoperative forced expiratory volume in 1 second (FEV1) | volume exhaled during the first second of a forced expiratory maneuver started from the level of total lung capacity | 48 hours after the end of surgery | 
| Postoperative forced vital capacity (FVC) | the total amount of air exhaled during a forced expiratory maneuver started from the level of total lung capacity | 48 hours after the end of surgery | 
| Postoperative Tiffeneau index | computed as FEV1/FVC | 48 hours after the end of surgery | 
| Postoperative Dyspnea | Dyspnea assessed by Borg dyspnea scale | 1 hour after surgery | 
| Pulmonary infection | modified clinical pulmonary infection score (mCPIS) | 24 hours after the end of surgery | 
| Postoperative pulmonary infiltrates | Evaluated with the chest x-ray by two independent clinicians blinded to treatment assignment | 24 hours after the end of surgery | 
| Intraoperative driving pressure | driving pressure, computed as Plateau pressure-PEEP | during surgery, recorded on a 60-minute basis | 
| Intraoperative lung driving pressure | transpulmonary driving pressure, computed as Transpulmonary end-inspiratory pressure-transpulmonary total end-expiratory pressure | during surgery, recorded on a 60-minute basis | 
| Intraoperative oxygenation | PaO2/FiO2 | during surgery, recorded on a 60-minute basis | 
| Intraoperative dead space | Approximated as the difference between End-tidal CO2 and PaCO2 divided by PaCO2 | during surgery, recorded on a 60-minute basis | 
| Lung recruitment | lung recruitment/changes in end expiratory lung volume between the two groups | during surgery, recorded on a 60-minute basis | 
| Intraoperative blood pressure | Arterial blood pressure | during surgery, recorded on a 60-minute basis | 
| Intraoperative respiratory system compliance | computed as Tidal volume/airway driving pressure | during surgery, recorded on a 60-minute basis | 
| Intraoperative lung compliance | computed as Tidal volume/lung driving pressure | during surgery, recorded on a 60-minute basis | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Mechanical ventilation