Ventilation During Cardiopulmonary Bypass
Condition: Lung Injury; Postoperative Complications; Pulmonary Collapse
MeSH terms: Lung Injury; Pulmonary Atelectasis; Postoperative Complications
Study type: Interventional

Summary: 
      Postoperative pulmonary dysfunction (PPD) is a widely reported complication of
      cardiopulmonary bypass (CPB) although there is improvement in perioperative management, that
      leads to increased morbidity and mortality in cardiac surgery.

      Many surgical-related factors can predispose to postoperative pulmonary complications such as
      the effects of general anesthesia combined with the effects of a median sternotomy, CPB, and
      the use of topical cooling for myocardial protection.

      Main clinical manifestations of PPD include atelectasis, pleural effusion, and postoperative
      hypoxemia without clinical symptoms in addition to acute respiratory distress syndrome which
      is rare to happen but leads to high mortality Different strategies including perioperative
      management of mechanical ventilation (MV), restrictive transfusion, technical modifications
      of CPB, and medication administration such as steroids and aprotinin have been developed to
      lessen impairment of pulmonary function.

      A recent meta-analysis identified improvement in oxygenation after weaning from CPB when low
      tidal volume (LTV) ventilation was maintained or after lung recruitment maneuvers (LRM), as
      compared to when there was no ventilation (noV). Also, maintaining mechanical ventilation may
      reduce the inflammation response and tissue damage. So far, available researches regarding
      whether ventilation during CPB could improve respiratory outcomes is still controversial
      especially in pediatric patients undergoing corrective surgeries for congenital heart
      defects.
    

Detailed description: 
      Our study is designed to determine the effect of different strategies of ventilation during
      CPB on arterial oxygenation and PPD in pediatrics undergoing corrective cardiac surgeries for
      non-cyanotic congenital anomalies.

      Preoperative:

      First, a proper and detailed history from the parents will be taken followed by a full and
      detailed examination of the child then the investigators will check all investigations
      including complete blood count(CBC), coagulation profile, liver enzymes, kidney function
      tests, chest X-ray (CXR), echocardiography, and blood grouping.

      All patients will be premedicated with atropine 0.01 mg/kg, and midazolam 0.02 mg/kg
      intramuscular(IM), 30 minutes before induction of anesthesia.

      Intraoperative:

      the investigators will start with Standard Monitoring as ECG, Pulse oximetry, and
      non-invasive blood pressure. Then the investigators will proceed to induction using
      sevoflurane in 50% FiO2 followed by Placement of peripheral IV cannula and IV administration
      of fentanyl (2 µg/kg) and cisatracurium 0.1 mg/kg then Oral endotracheal intubation and the
      Capnogram will be connected to monitor End-tidal carbon dioxide(CO2).

      The patient will be mechanically ventilated using pressure-controlled mode with a fraction of
      inspired oxygen(FiO2) 50%, Inspiration to expiration time ratio of 1:2, peak inspiratory
      pressure (PIP), and respiratory rate will be set according to the age to maintain the range
      of end-tidal carbon dioxide pressure at 35-45 mmHg in all groups.

      Maintenance of anesthesia will be achieved using sevoflurane 2 % in 1:1 oxygen: air,
      cisatracurium infusion 1-2 mcg/kg/min and Fentanyl 1-5 µg/kg till the time of CPB (1 µg/kg
      before skin incision,2 µg/kg before sternotomy,2 µg/kg during cannulation) Advanced
      monitoring where nasopharyngeal temperature probe will be placed, a Central venous catheter
      to monitor central venous pressure(CVP), and Arterial cannula to monitor invasive blood
      pressure, then antibiotic will be given after skin test, Standard CPB technique will be used
      in all patients. Before aortic cannulation, patients will receive IV heparin 300-400 U.kg-1
      aiming to produce activated clotting time (ACT) value > 400 sec. A membrane oxygenator
      (minimax plus; Medtronic's Inc., Anaheim, CA) will be used during CPB. Priming solution in
      the form of isotonic saline solution supplemented with heparin will be added to fresh whole
      blood in appropriate amounts to achieve a hematocrit of 20-25% during CPB. Furosemide in a
      dose of 1 mg/kg will be given to all patients. Anesthesia during CPB will be given by
      Sevoflurane administrated via a vaporizer inserted into the oxygenator gas supply with a
      constant gas flow of 3 liters/min. A non-pulsatile roller pump (model10.10.00; Stockett
      instruments; Munich, Germany) will be used and the pump flow will be adjusted at 2.4 to 2.6
      L/min /m2 during the normothermic period targeting mean arterial blood pressure between 40
      and 60 mmHg, Alpha-stat pH management was used and replacement fluids were added as blood
      (packed red cells), colloid or crystalloid as indicated.

      After application of aortic cross-clamp, cold blood cardioplegia (20 mL/kg for initial dose)
      with 30 milliequivalent(mEq)/L of potassium, sodium bicarbonate 25 mEq/L, Xylocaine 120 mg/L
      will be injected into the aortic root, also topical myocardial cooling will be used.

      During CPB the patients enrolled in the study will be randomly assigned to three groups using
      a computer-generated random sequence of numbers.

        -  Group A (n=20) the lungs will be kept inflated by delivery of oxygen: air 3 liters/min
           with FiO2 50% pressure-controlled mode, respiratory rate(RR) 20-30/min according to age,
           PIP will be adjusted to keep Vt 2 mL/kg as possible.

        -  Group B (n=20) their lungs will be kept inflated by delivery of oxygen: air 3 liters/min
           with FiO2 50% and continuous positive airway pressure(CPAP) will be maintained via a
           circle system with airway pressure maintained at 5 cmH2O by positive end expiratory
           pressure(PEEP) valve. This will be verified by a previously calibrated, in-circuit
           Bourdon gauge.

        -  Group C (control group) (n=20) their lungs will be deflated by disconnecting the
           breathing circuit from the ventilator (passive deflation).

      Post CPB, the patient will be mechanically ventilated using pressure-controlled mode with
      FiO2 50%, Inspiration to expiration time ratio of 1:2, peak inspiratory pressure (PIP), and
      respiratory rate will be set according to the age to maintain the range of end-tidal carbon
      dioxide pressure at 35-45 mmHg in all groups.
    

Intervention name(s): ventilation
Intervention type(s): Other
Intervention description(s): low volume positive pressure ventilation is better than continuous positive airway pressure and passive deflation on arterial oxygenation and PPD after CPB in pediatrics undergoing cardiac surgeries for non-cyanotic congenital heart defects.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Care Provider, Outcomes Assessor)
Primary purpose: Prevention