High Versus Low Positive End Expiratory Pressure With Alveolar Recruitment Maneuver in Laparoscopic Bariatric Surgeries
Condition: Anesthesia
Study type: Interventional

Summary: 
      For the patients undergoing laparoscopic bariatric surgery, application of low (PEEP) with
      frequent alveolar recruitment maneuver could be beneficial and superior to conventional
      ventilation with a high (PEEP) in improving lung compliance, better oxygenation and less dead
      space .This hypothesis could be achieved by minimizing the expected lung atelectasis during
      anesthesia for this particular kind of laparoscopic surgery without any haemodynamics
      alterations.This trial was designed to study the effects of alveolar recruitment strategy
      with low PEEP versus conventional mechanical ventilation with higher PEEP on the patients
      undergoing laparoscopic bariatric surgeries. The primary end point of the study will be the
      achievement of the highest dynamic lung compliance (Cdyn). Improvement of intraoperative
      oxygenation (Pao2/Fio2) and achievement of a lower dead space ratio (vd/vt), with stable
      intraoperative haemodynamics will be considered as secondary outcome
    

Detailed description: 
      The use of a alveolar recruitment maneuver(RM) effectively increases end expiratory lung
      volume and reopens lung atelectasis during anesthesia and reproduces better oxygenation for
      surgical obese patients .Alveolar recruitment maneuver with PEEP could decreases atelectasis
      and improved oxygenation in obese surgical patients .This concept indicate that the
      maintenance of low PEEP after multiple alveolar recruitment maneuver during anesthesia may
      improve its benefits without complications. Patients will randomly divided by computerized
      randomization sequence method into two groups (30 patients in each study group):

      Both groups receive volume controlled ventilation, tidal volume was 6-8 ml/kg for predicted
      body weight. The PBW calculated according to a formula: 50 + 0.91 × {height (cm)-152.4} for
      men and 45.5 + 0.91 × {height (cm) - 152.4} for women. The respiratory rate was adjusted to
      keep the EtCO2= 35-40 mmHg. The inspiratory to expiratory ratio (I:E ratio) was 1:2 and the
      FiO2 was 0.40.

      Low PEEP+RM group: Patients receive PEEP of 5cmH2O. Recruitment maneuver ( RM) will be done
      by increasing the PEEP in stepwise manner. First PEEP was increased to 10 cmH2O (3
      breaths),then to 15 cm H2O (3 breaths).Finally, PEEP was raised to 20 cmH2O (10 breaths).Then
      decreased for 15cmH2O for (3 breaths),10cmH2O for(3 breaths), and finally returned back to
      original PEEP 5 cmH2O.The total procedure took 2 min. Recruitment will be carried out at the
      following times: post intubation(T1) , after peritoneal insuflation(T2) ,after desuflation
      (T3) and before extubation(T4) . The peak airway pressure should not exceed 40cmH2O.

      High PEEP group: Patients receive throughout ventilation 15 cm H2O PEEP with maintaining the
      peak airway pressure below 40 cm H2O.

      Monitoring :after intubation(T1), post-insufflation(T2), after disinflation (T3) and before
      extubation(T4) for the fillowoing.1--Minute volume ,respiratory rate and tidal volume
      2-Arterial blood gas( PaO2, PaCO2,pH).3-Hemodynamics : heart rate and invasive arterial blood
      pressure.4-Calculated dynamic Lung compliance by equation: T V/peak airway pressure- PEEP
      .5-calculated driving pressure by equation: Pplat-PEEP.6-Calculated dead space ratio (VD/VT)
      by equation :PaCO2-ETCO2)/ PaCO2.

      Rescue strategies:

      A) Intraoperative hypoxemia (SpO2≤92%): In both groups ,rescue primarily will be performed by
      an increase in FiO2 by 0.1 till reaching oxygen (100% ) .If failed and hypoxia persist a
      recruitment maneuver will be carried out with stepwise incremental PEEP irrespective of the
      group allocation.

      The time of the event of hypoxia and its management will be recorded.

      B) Intraoperative hypotension (systolic blood pressure <90 mmHg):

        1. Abort any recruitment maneuver in low PEEP+ RM group.

        2. Gradual decrease PEEP by 5 cmH2O in stepwise manner in higher PEEP group.

        3. Give 500 ml bolus colloid and correct fluid status with blood transfusion if indicated.

        4. Noradrenalin infusion as last resort
    

Intervention name(s): Recruitment with low PEEP; High PEEP without RM
Intervention type(s): Device; Device
Intervention description(s): Volume controlled ventilation with TV 6-8 ml/PBW . RR adjusted to keep the EtCO2 35-40 mmHg. I/E ratio1:2 and FiO2 0.40.Patients will receive PEEP of 5cmH2O. RM will be done by increasing the PEEP in stepwise manner. First PEEP increase to 10 cmH2O (3 breaths),then to 15 cm H2O (3 breaths) and finally PEEP raise to 20 cmH2O (10 breaths).Then PEEP decrease by 5 cmH2O increments every (3 breaths) until back to PEEP 5 cmH2O. RM will take 2 minutes. RM will be carried out at the following times: post intubation(T1) , after peritoneal insuflation(T2) ,after desuflation (T3) and before extubation(T4) . The peak airway pressure should not exceed 40 cmH2O. Monitoring of the following parameters :Dynamic lung compliance ,Horowitz index ,dead space and driving pressure .; Volume controlled ventilation will carried out with tidal volume 6-8 ml/kg for predicted body weight. The PBW calculated according to the formula : 50 + 0.91 × {height (cm)-152.4} for men and 45.5 + 0.91 × {height (cm) - 152.4} for women. The respiratory rate adjusted to keep the EtCO2= 35-40 mmHg. The inspiratory to expiratory ratio (I:E ratio) 1:2 and FiO2 0.40.Patients will receive high PEEP of 15cmH2O from the start and continue all through the procedure . Monitoring of dynamic lung compliance,Horowitz index,dead space and driving pressure will be carried out at the following times: post intubation(T1) , after peritoneal insuflation(T2) ,after desuflation (T3) and before extubation(T4) . The peak airway pressure should not exceed 40cmH2O.
Other intervention name(s): Low PEEP + RM; High PEEP
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Mechanical ventilation with either recruitment maneuver and low PEEP versus conventional mechanical ventilation and high PEEP
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Supportive Care