Abstract
Background This study compared the hemodynamic effects and gas exchange under several different ventilator settings—with regard to tidal volume, respiratory rate, and end-expiratory pressure—in patients after coronary artery bypass grafting (CABG). Methods Prospective interventional cohort study with a controlled group in a single cardiosurgical ICU involving 119 patients following on-pump CABG surgery. During the 1st postoperative hour, the intervention group patients were ventilated with Vt 10 ml × kg−1, RR 14/min, PEEP 5 cmH2O (“conventional ventilation”). During the 2nd hour, RR was reduced to 8/min (“reduced RR ventilation”). At 3 hrs, Vt was decreased to 6 ml × kg−1, RR returned to 14/min, and PEEP increased to 10 cmH2O (“low Vt-high PEEP ventilation”). Results Patients in the “low Vt-high PEEP” ventilation period showed significantly lower alveolar ventilation and thoraco-pulmonary compliance than during “reduced RR” ventilation. Mean airway pressure and Vds/Vt peaked during low Vt-high PEEP ventilation; however, driving pressure was lower. Vt decrease and PEEP increase did not lead to oxygenation improvement and worsened CO2 elimination. Hemodynamically, the study revealed significant cardiac output decrease during low Vt-high PEEP ventilation. In 23.2% of patients, catecholamine therapy was initiated. Conclusions In postoperative cardiosurgical patients, MV with Vt 6 ml × kg−1 and PEEP 10 cm H2O is characterized by worsened oxygenation and elimination of CO2 and a less favorable hemodynamic profile than ventilation with Vt 10 ml × kg−1 and PEEP 5 cmH2O. New and Noteworthy. (i) Patients after CABG may be especially sensitive to low tidal volume and increased PEEP as it negatively affects hemodynamic profile by means of the right heart preload decrease and afterload increase. (ii) Mechanical ventilation settings aiming to minimize mean airway pressure reduce the negative effects of positive inspiratory pressure and are favorable for hemodynamics.
Highlights
Mechanical ventilation (MV) affects both respiratory and cardiovascular systems as a result of positive inspiratory pressure [1]. e “lung-protective strategy” characterized by the use of a relatively small tidal volume (Vt) of 6 ml × kg−1 and by variable adjustment of positive end-expiratory pressure (PEEP) is spreading widely across different categories of patients [2]. is strategy helps to defend the lungs from baro- and volumotrauma and to improve outcomes in patients with acute respiratory distress syndrome (ARDS) [3]. e lung-protective approach is recommended to patients without gas exchange disorders and those who undergo surgery under anesthesia [4]
E results of the PReVENT trial conducted to determine whether a ventilation strategy using low Vt (4–6 ml × kg−1 of predicted body weight (PBW)) is superior to one with intermediate Vt (8–10 ml × kg−1 PBW) in critically ill patients without ARDS [6] did not demonstrate an advantage to a low Vt strategy
Due to the interdependence of heart-lung physiology—in which an increased intrathoracic pressure has a depressing effect on cardiac output (CO), affecting right heart performance especially [11,12,13]—one of the most serious problems in postcardiac surgery care is the setting of proper MV parameters for patients with compromised respiratory and hemodynamic profiles, and in those having decreased myocardial contractility
Summary
Heart-Protective Mechanical Ventilation in Postoperative Cardiosurgical Patients. Vadim Mazurok , Igor Kasherininov, Andrey Bautin, Olga Kulemina, and Ryta Rzheutskaya. During the 1st postoperative hour, the intervention group patients were ventilated with Vt 10 ml × kg−1, RR 14/min, PEEP 5 cmH2O (“conventional ventilation”). The study revealed significant cardiac output decrease during low Vt-high PEEP ventilation. MV with Vt 6 ml × kg−1 and PEEP 10 cm H2O is characterized by worsened oxygenation and elimination of CO2 and a less favorable hemodynamic profile than ventilation with Vt 10 ml × kg−1 and PEEP 5 cmH2O. (i) Patients after CABG may be especially sensitive to low tidal volume and increased PEEP as it negatively affects hemodynamic profile by means of the right heart preload decrease and afterload increase. (ii) Mechanical ventilation settings aiming to minimize mean airway pressure reduce the negative effects of positive inspiratory pressure and are favorable for hemodynamics New and Noteworthy. (i) Patients after CABG may be especially sensitive to low tidal volume and increased PEEP as it negatively affects hemodynamic profile by means of the right heart preload decrease and afterload increase. (ii) Mechanical ventilation settings aiming to minimize mean airway pressure reduce the negative effects of positive inspiratory pressure and are favorable for hemodynamics
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