HEMODYNAMIC EVALUATION OF THE PRONE POSITION BY TRANSESOPHAGEAL ECHOCARDIOGRAPHY

Study Objective: To evaluate the hemodynamic response in the prone pos ition in surgical patients by measuring the effects of prone positioni ng on cardiac function using transesophageal echocardiography (TEE). D esign: Prospective study. Setting: Elective surgery at a university ho spital. Patients: 15 Adult ASA physical status I and II patients free of significant coexisting disease undergoing lumbar laminectomy. Inter ventions and Measurements: Approximately 15 minutes after the inductio n of general anesthesia, we measured heart rate, blood pressure, and c entral venous pressure. We also measured left ventricular area (LVA) a nd fractional area change (FAC) automatically and calculated left vent ricular volume (LVV), stroke volume index (SVT), cardiac index (CI), l eft ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), pulmonary venous flow velocity (PVFV), and pulmonar y venous velocity time integral (PVVTI) via TEE. The same measurements were performed approximately 15 minutes after changing to the prone p osition with longitudinal bolsters. Main Results: In the prone positio n, there was significant reduction in end-systolic and end-diastolic L VA and LVV. There was a significant increase in LVEF, LVFS, and FAC in the prone position. In addition, there was diminishment of systolic P VFV and PVVTI and enhancement of diastolic PVFV and PVVTI. SVI and CI did not change significantly in the prone position. Conclusion: The pr one position caused LVV to decrease. The prone position also led to de creased systolic PVFV and PVVTI and enhancement of diastolic PVFV and PVVTI. These changes were probably due to a decrease in the venous ret urn due to inferior vena caval compression, and decreased left ventric ular compliance due to increased intrathoracic pressure in the prone p osition.