Pre-Ejection Period to Estimate Cardiac Preload Dependency in Mechanically Ventilated Pigs Submitted to Severe Hemorrhagic Shock

Abstract

Respiratory change in pre-ejection period (ΔPEP) has been described as a potential parameter for monitoring cardiac preload dependency in critically ill patients. This study was designed to describe the relationship between ΔPEP and pulse pressure variation (PPV) in pigs submitted to severe hemorrhagic shock. In 17 paralyzed, anesthetized mechanically ventilated pigs, electrocardiography, arterial pressure, and cardiac output derived from pulmonary artery catheter were recorded. Hemorrhagic shock was induced by removal of blood volume followed by restoration. PEP was defined as the time interval between the beginning of the Q wave on the electrocardiogram and the upstroke of the invasive radial arterial pressure curve. At baseline, ΔPEP and PPVs were both <12% with PPV significantly correlated with ΔPEP (r = 0.96, p < 0.001). Volume loss induced by hemorrhage significantly increased PPV and ΔPEP values (p < 0.05). During severe hemorrhage, PPV correlated well with ΔPEP (r = 0.88, p < 0.001) with PPV values significantly higher than ΔPEP (p < 0.05). However, the reproducibility of ΔPEP measurements was significantly better than PPV during this step (p < 0.05). Retransfusion significantly decreased PPV and ΔPEP (p < 0.05) with PPV significantly correlated to ΔPEP (r = 0.94, p < 0.001). Available correlations between PPV and ΔPEP at each time of the study were observed, meaning that ΔPEP is a reliable parameter to estimate and track the changes in cardiac preload dependency. Moreover, during the severe hemorrhagic shock period, ΔPEP measurements were more reproducible than PPV values.