Effects of PEEP on Parameters of Tissue Perfusion in Patients Post Cardiac Surgery

Study Overview
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Brief Summary
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Pulmonary dysfunction is a condition inherent in cardiac surgery because of various interventions, such as general anesthesia, a median sternotomy, cardiopulmonary bypass and establishment of internal thoracic artery dissection. In situations when there is a deterioration in oxygenation, increased positive pressure on the airways end pressure (PEEP) can be used as therapeutic mode by reversing severe hypoxemia resulting pulmonary shunt. But the use of PEEP has been associated to reduced cardiac output, due mainly to decrease systemic venous return consequent to increased intrathoracic pressure, and thus might reduce tissue oxygenation. Moreover, the increased transpulmonary gradient may also impair right ventricular ejection exacerbating the hemodynamic consequences in some patients, which in clinical practice this diagnosis may be difficult to perform. In hypovolemic patients or those with cardiac changes may become even more pronounced, resulting in accentuation of low flow and systemic hypotension entailing changes in markers of tissue perfusion commonly measured by venous saturation central difference venoarterial carbon dioxide and lactate. The hypothesis of the investigators is that PEEP of 10 cmH2O and 15 cmH2O can be applied to reverse lung damage in patients in the immediate postoperative myocardial revascularization without repercussion tissue importantly in markers of tissue perfusion. The objective is to evaluate the effects of different optimization levels of PEEP on gas exchange and influences the tissue perfusion after coronary artery bypass graft surgery.

Detailed Description
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This is a prospective, randomized study and will be performed on patients who accept coronary artery bypass grafting with cardiopulmonary bypass, the conscious openness to participate in the study. Age, sex, body mass index (BMI), smoking habits, diagnosis, additional diseases, drugs used, surgery, intervention, peroperative supportive treatments, left ventricular ejection fraction, post operative blood and cardiopulmonary bypass (CPB) time (min), cross clamp time (min), duration of operation, postoperative extubation period, intensive care day of hospitalization, day of hospitalization will be recorded.The study was planned in 3 groups. Group G5 (control group: no changes will be made to the value of PEEP). Group G10 [after 30 minutes of admission (time 0) the PEEP will be raised to 10 cmH2O (time1) for 30 minutes and then returned to 5 cmH2O (time 2)]. Group G15 [after 30 minutes of admission (time 0) the PEEP will be raised to 15 cmH2O (time 1) for 30 minutes and then returned to 5 cm H2O (time 2)]. At each time of protocol (0, 1 and 2) will be collected: arterial blood gas measurements (partial pressure of arterial oxygen [PaO2] and partial pressure of carbon dioxide ([PaCO2]), the ratio between the partial oxygen pressure, inspired oxygen fraction (PaO2/FiO2) and pH. Also, will be performed parameters of tissue perfusion: central venous oxygen saturation ([SVO2]), arterial blood lactate, venoarterial CO2 difference ([Dif VA CO2]) and vital signs. In all other respects, treatment will follow the standard of care.

Official Title
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Effects of PEEP on Parameters of Tissue Perfusion and Clinical Outcomes After Coronary Artery Bypass Graft Surgery - a Randomized Clinical Trial

Conditions
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Coronary Artery Disease, Coronary Artery Bypass Grafting, Acute Lung Injury

Intervention / Treatment
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* Other: Group G5
* Other: Group G10
* Other: Group G15


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: elective and isolated CABG, ejection fraction greater than 40% Exclusion Criteria: patients with a diagnosis of pulmonary disease, emergency surgery and mechanical ventilation prior to surgery. Postoperative patients who had radiological abnormalities suggestive of pneumothorax, atrial or ventricular arrhythmias, electrical ischemic changes on ECG, pulse pressure variation of more than 13, hemodynamic instability characterized by mean arterial pressure less than 60 mmHg, nor epinephrine greater than 0.5 mcg/Kg/ min and the presence of increased bleeding through the drains (greater than 2 ml \ kg \ h) the protocol was discontinued and the patient excluded from the study.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 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: Treatment
Allocation: Randomized
Intervention Model: Sequential Assignment
Interventional Model Description: The study was planned in 3 groups. Group G5 (control group: no changes will be made to the value of PEEP). Group G10 [after 30 minutes of admission (time 0) the PEEP will be raised to 10 cmH2O (time1) for 30 minutes and then returned to 5 cm H2O (time 2)]. Group G15 [after 30 minutes of admission (time 0) the PEEP will be raised to 15 cmH2O (time 1) for 30 minutes and then returned to 5 cm H2O (time 2)].
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Sham Comparator: Group G5<br>Patients submitted to CABG and peep 5 | Other: Group G5<br>* Submitted to peep 5<br>|
| Experimental: Group G10<br>Patients submitted to CABG and peep 10 | Other: Group G10<br>* Submitted to peep 10<br>|
| Experimental: Group G15<br>Patients submitted to CABG and peep 15 | Other: Group G15<br>* Submitted to peep 15<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pulmonary events | Pleural effusion was considered relevant when exceeding the phrenicocostal angle and fluid drainage was monitored hourly. Atelectasis was acknowledged when a clear atelectasis radiologic shadow exceeded 15 mm in width, with linear atelectasis | Through study completion, an average of 24 hours after surgery | 
| Arterial oxygenation | arterial blood gas measurements (partial pressure of arterial oxygen [PaO2] | Immediately after arrival at the intensive care unit until the end of protocol (around 5 hours) | 
| Tissue oxygenation | (central venous oxygen saturation , arterial blood lactate and venoarterial CO2 difference | Immediately after arrival at the intensive care unit until the end of protocol (around 5 hours) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Length of intensive care unit (ICU) stay | Days since surgery until ICU discharge | From the day of surgery up to ICU discharge, maximum censoring at day 28 after surgery ] | 
| Length of Hospital Stay | Days since surgery until Hospital discharge | From the day of surgery up to Hospital discharge, maximum censoring at day 28 after surgery ] | 
| Duration of mechanical ventilation | Hours since surgery until extubation | Through study completion, an average of 24 hours after surgery | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Acute Lung Injury, postoperative of cardiac surgery