High Versus Low Positive End Expiratory Pressure With Alveolar Recruitment Maneuver in Laparoscopic Bariatric Surgeries

Study Overview
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Brief Summary
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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
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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): Abort any recruitment maneuver in low PEEP+ RM group. Gradual decrease PEEP by 5 cmH2O in stepwise manner in higher PEEP group. Give 500 ml bolus colloid and correct fluid status with blood transfusion if indicated. Noradrenalin infusion as last resort

Official Title
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Low Positive End Expiratory Pressure With Alveolar Recruitment Maneveurs Versus High Positive End Expiratory Pressure as Lung Protective Strategy in Laparoscopic Bariatric Surgeries

Conditions
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Anesthesia

Intervention / Treatment
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* Device: Recruitment with low PEEP
* Device: High PEEP without RM


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiologists (ASA) physical status II and III. Patients included in the study having body mass index ≥35kg/m2. Both genders. Age ≥ 20 years old. Exclusion Criteria: Major cardiovascular diseases (heart failure and ejection fraction below 40%). Sever obstructive pulmonary diseases (FEV1 < 50 and FVC < 50) Hepatic and renal impairment. Younger than 20 years old.

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Supportive Care
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Mechanical ventilation with either recruitment maneuver and low PEEP versus conventional mechanical ventilation and high PEEP
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Recruitment with low PEEP<br>Recruitment maneuver ( RM) will carried out during 2 minutes with increasing PEEP in stepwise manner.PEEP increase from 5 to 10 cmH2O (3 breaths),then to 15 cm H2O (3 breaths), PEEP to 20 cmH2O (10 breaths).Then decrease by 5 cmH2O every 3 breaths till back to preset PEEP 5 cmH2O .Recruitment carried out at the following times: post intubation(T1) , after insuflation(T2) ,after desuflation (T3) and before extubation(T4) . The peak airway pressure should not exceed 40cmH2O . | Device: Recruitment with low PEEP<br>* 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 .<br>* Other names: Low PEEP + RM;|
| Active Comparator: High PEEP without RM<br>Patients will receive from the start during anesthesia high PEEP (15 cmH2O) with maintaining the peak airway pressure below 40 cm H2O. Monitoring times: after intubation(T1), post-insufflation(T2), after desuflation (T3) and before extubation(T4). | Device: High PEEP without RM<br>* 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.<br>* Other names: High PEEP;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Dynamic lung compliance | To achieve nearly 20% increase in dynamic lung compliance (Cdyn) during anesthesia for obese patients undergoing bariatric surgery. | During intra-operative mechanical ventilation | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Horowitz ratio | Improvement of intraoperative oxygenation with Horowitz ratio (Pao2/Fio2) more than 350. | During mechanical ventilation | 
| Alveolar dead space ratio | Achievement of the least alveolar dead space ratio (vd/vt). | During mechanical ventilation | 
| Systolic blood pressure | Maintain systolic blood pressure above 100 mmHg. | During mechanical ventilation | 
| Diastolic blood pressure | Maintain diastolic blood pressure above 50 mmHg. | During mechanical ventilation | 
| Mean blood pressure | Maintain mean blood pressure above 65 mmHg. | During mechanical ventilation | 
| Heart rate | Maintain heart rate within the range of 60-90 (bpm ). | During mechanical ventilation | 
| Analgesia | postoperative visual analogue score less than 4. | postoperative time for 24 hours | 
| Atelectasis | Chest X-ray for evidences of atelectasis | postoperative time for 24 hours |