Hemodynamics and tissue oxygenation effects after increased in positive end-expiratory pressure in coronary artery...

Cardiac surgery is widely used in the treatment of cardiovascular diseases. However, several complications can be observed during the postoperative period. Positive end expiratory pressure (PEEP) improves gas exchange, but it might be related to decreased cardiac output and possible impairment of tissue oxygenation. The aim of this study was to investigate the hemodynamic effects and oxygen saturation of central venous blood (ScvO₂) after increasing PEEP in hypoxemic patients after coronary artery bypass (CAB) surgery.

Seventy post-cardiac surgery patients (CAB), 61 ± 7 years, without ventricular dysfunction (left ventricular ejection fraction 57 ± 2%), with hypoxemia (PaO₂/FiO₂ ratio <200) were enrolled. Heart rate, mean arterial pressure, arterial and venous blood samples were measured at intensive care unit and PEEP was increased to 12 cmH₂O for 30 min.

As expected, PEEP12 improved arterial oxygenation and PaO₂/FiO₂ ratio (p < 0.0001). Reduction in ScvO₂ was observed between PEEP5 (63 ± 2%) and PEEP12 (57 ± 1%; p = 0.01) with higher values of blood lactate in PEEP12 (p < 0.01). No hemodynamic effects (heart rate, mean arterial pressure, SpO₂; p > 0.05) were related.

Increased PEEP after cardiac surgery decreased ScvO₂ and increased blood lactate, even with higher O₂ delivery. PEEP did not interfere in hemodynamics status in CAB patients, suggesting that peripheral parameters must be controlled and measured during procedures involving increased PEEP in post-cardiac surgery patients in the intensive care unit.