Assessing Effects of Lateral Tilt on Cardiac Output Using a Non-invasive Technique

Aortocaval compression compromising tissue perfusion has always been of a concern in term pregnant women undergoing caesarian delivery or regional anesthesia when placed in the supine position. It is believed that this phenomena happens when the gravid uterus compresses the inferior vena cava (IVC)resulting in decreased venous return and hence cardiac output (CO) leading to low placental perfusion and associated fetal heart rate changes. Hence, due to these concerns, left lateral tilt is currently a common practice in obstetrics and it is believed to relief aortocaval compression and to improve blood flow to the fetus. Supporting evidence for this intervention remains controversial, and shows conflicting results. Some studies suggest that lateral tilt does not affect neonatal outcomes (1) or changes in cardiac output in patients with no regional anesthesia (2). While others suggest it can actually increase the volume of the IVC, especially when the patient is tilted 30 degrees or more (3) and may lead to increases in CO (4). Non-invasive hemodynamic monitoring (NICOM, Cheetah Medical), an FDA approved device, is currently being used to detect changes in CO in the United States. Its use has been validated in different clinical settings (5,6). Our hypothesis is that CO is increased in pregnant women that were placed in the lateral tilt position. We intend to compare CO measurements using the non-invasive hemodynamic monitoring among term pregnant patients in supine vs lateral tilt position.