Changes in cardiac output after acute blood loss and position change in man

Abstract

Thoracic bioimpedance cardiac output (Q̇tbi) was measured at 1-min intervals in 27 volunteers before, during, and after withdrawing 500 ml (3.7 to 8.5 ml/kg; mean 5.8) of blood. The effects of passive leg raising (PLR) and standing on Q̇tbi were measured before and after blood withdrawal. Arterial oxygen saturation (SaO2), transcutaneous oxygen tension (PtcO2), mean arterial BP (MAP), and heart rate (HR) were also measured before and after blood withdrawal. Thoracic bioimpedance cardiac index (CI) decreased 18% (0.8 ± 0.1 L/min · m2, p < .0001). PLR can increase stroke volume and cardiac output in hypovolemic humans.