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

Vanessa Marques Ferreira Méndez,Carlos Gun,Patrícia Andrade Xavier,Adriana Do Nascimento Baião,Iracema I K Umeda,Mayron F Oliveira,Priscila A Sperandio

doi:10.1186/s40945-016-0030-4

Abstract

BackgroundCardiac 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.MethodsSeventy 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.ResultsAs 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.ConclusionIncreased 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.

Highlights

Cardiac surgery is widely used in the treatment of cardiovascular diseases
All patients were admitted at intensive care unit (ICU) and followed the institutional mechanical ventilation protocol with volume-controlled (PEEP 5 cmH2O, respiratory rate 14 breaths per minute, FiO2 0.4, tidal volume of 6–8 mL/kg) and Positive end expiratory pressure (PEEP) was increased to 12 cmH2O for 30 min in all patients with arterial hypoxemia (PaO2/FiO2 ratio
There were a higher percentage of male patients (77%) (Table 1) and, during surgery procedure, 50 patients (71%) had positive volemic status, and it remained positive during the stay in the intensive care unit, at both PEEP 5 cmH2O (180 ± 82 mL) and PEEP 12 cmH2O (197 ± 78 mL) (p > 0.05)

Summary

Introduction

Cardiac surgery is widely used in the treatment of cardiovascular diseases. several complications can be observed during the postoperative period. 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. Coronary artery bypass (CAB) surgery is widely used in cardiovascular treatment and, during procedure, patients are exposed to anesthesia and cardiopulmonary bypass. This exposure is one of the most important cause of pulmonary dysfunction in the postoperative period with higher levels of morbidities [1]. The influence of PEEP on cardiac output and tissue oxygenation can be measured by oxygen saturation of central venous blood (ScvO2) [3] and values under 70% suggest low oxygen delivery/utilization and are predictive of a poor prognosis during postoperative period [3].

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