Can blood loss be assessed by echocardiography? An experimental study on a controlled hemorrhagic shock model in piglets.

Abstract

Assessment of the volemic loss is a major challenge during the management of hemorrhagic shock. Echocardiography is an increasingly used noninvasive tool for hemodynamic assessment. In mechanically ventilated patients, some studies suggest that respiratory variations of mean subaortic time-velocity integral (∆VTI) would be predictive of fluid filling response. An experimental model of controlled hemorrhagic shock provides a precise approach to study correlation between blood volume and cardiac ultrasonographic parameters. The main objective was to analyze the ∆VTI changes during hemorrhage in an anesthetized-piglet model of controlled hemorrhagic shock. The secondary objective was to evaluate ∆VTI during the resuscitation process after hemorrhage and other echocardiographic parameters changes during the whole protocol. Twenty-four anesthetized and ventilated piglets were bled until mean arterial pressure reached 40 mm Hg. Controlled hemorrhage was maintained for 30 minutes before randomizing the piglets to two resuscitation groups: fluid filling group resuscitated with saline solution and noradrenaline group resuscitated with saline solution and noradrenaline. Echocardiography and hemodynamic measures, including pulsed pressure variations (PPV), were performed at different stages of the protocol. The correlation coefficient between ΔVTI and PPV with the volume of bleeding during the hemorrhagic phase were respectively 0.24 (95% confidence interval, 0.08-0.39; p < 0.01) and 0.57 (95% CI, 0.44-0.67; p < 0.01). Two parameters had a moderate correlation coefficient with hemorrhage volume (over 0.5): mean subaortic time-velocity index (VTI) and mitral annulus diastolic tissular velocity (E'). In this hemorrhagic shock model, ΔVTI had a low correlation with the volume of bleeding, but VTI and E' had a correlation with blood volume comparable to that of PPV.