Abstract
BackgroundThere is no consensus on the ventilation management during cardiopulmonary bypass (CPB), and the anesthesiologists or the surgeons usually ventilate the lungs with different ventilation strategies or keep them static. Better outcomes are more likely to occur when the ventilation is administered during CPB according to the existing literatures. However, the use of high fraction of inspired oxygen (FiO2) is debatable in cardiac surgery. And the potential effects of strategies combining low tidal volume (VT) ventilation with different FiO2 during CPB on postoperative pulmonary complications (PPCs) are unclear.DesignThe VONTCPB trial is a single-center, prospective, double-blinded, randomized, controlled trial. We are going to recruit total 420 elective cardiac surgery patients with median sternotomy under CPB, who will be equally randomized into three different ventilation strategy groups: NoV, LOV and HOV. (1) The NoV group receives no mechanical ventilation during CPB; (2) the LOV group receives a low VT of 3-4 ml/kg of ideal body weight (IBW) with the respiratory rate (RR) of 10–12 acts/min, and the positive end-expiratory pressure (PEEP) of 5–8 cmH2O during CPB; the FiO2 is 30%; (3) the HOV group receives a low VT of 3-4 ml/kg of IBW with the RR of 10–12 acts/min, and the PEEP of 5–8 cmH2O during CPB; the FiO2 is 80%. The primary endpoints are the incidence of the composite of PPCs and the PPCs score. The secondary endpoints refer to the incidence of the oxygenation index (PaO2/FiO2 ratio) < 300 mmHg at three time points (the moment arriving in the ICU, 6 and 12 h after arrival in the ICU), the surgical incision healing grade, the intubation time, the stay of ICU, the length of hospital stay, and mortality at 30 days after the surgery.DiscussionThe VONTCPB trial is the first study to assess the effects of strategies combining low tidal volume (VT) ventilation with different FiO2 during CPB on patients’ outcomes.Trial registrationChiCTR1800015261. Registered on 20 March 2018.
Highlights
There is no consensus on the ventilation management during cardiopulmonary bypass (CPB), and the anesthesiologists or the surgeons usually ventilate the lungs with different ventilation strategies or keep them static
The VONTCPB trial is the first study to assess the effects of strategies combining low tidal volume (VT) ventilation with different Inhaled oxygen concentration (FiO2) during CPB on patients’ outcomes
FiO2 is adjusted according to the Arterial blood partial pressure of oxygen (PaO2) by performing arterial blood gas (ABG) analyses: if PaO2 ≥ 150 mmHg, it is decreased by 10%; but if PaO2 ≤ 80 mmHg, it is increased by 10%; minimum FiO2 is 30%
Summary
There is no consensus on the ventilation management during cardiopulmonary bypass (CPB), and the anesthesiologists or the surgeons usually ventilate the lungs with different ventilation strategies or keep them static. The PPCs have the forms of respiratory failure, respiratory infection, pleural effusion resulting in thoracentesis, atelectasis, pneumothorax, bronchospasm, aspiration pneumonitis [2] These complications extend the length of mechanical ventilation and intensive care unit (ICU) stay, indicating worse prognosis [3, 4]. While two sets of independent circulation systems composing the blood delivery system of the lungs, the bronchial arteries supply only about 3–5% of the pulmonary blood flow system, which may be reduced to one-tenth of the original upon experimental conditions of CPB in pigs model. Those reduced blood flow may be difficult to meet the physiological metabolic needs of the lungs [5]. Those factors, in addition to the strikes of pulmonary ischemia-reperfusion and reoxygenation, oxygen-free radicals, inflammatory response make the lungs especially vulnerable in the dedicated phases [4]
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