TRANSESOPHAGEAL ECHOCARDIOGRAPHY - AN OBJECTIVE TOOL IN DEFINING MAXIMUM VENTRICULAR RESPONSE TO INTRAVENOUS FLUID THERAPY

Ventricular preload is an important determinant of cardiac function, w hich is indirectly measured in the clinical setting by the pulmonary c apillary wedge pressure (PCWP). Transesophageal echocardiography (TEE) is rapidly gaining acceptance as a monitor of cardiac func tion. Alth ough it provides high-resolution images of cardiac structures, clinica l assessment of ventricular preload using TEE has been subjective, sin ce quantitative measurements have been difficult to perform in a timel y fashion. Automated border detection (ABD) is a new technology used i n conjunction with TEE that allows quantitative real-time, two-dimensi onal measurement of cavity areas. To determine whether end-diastolic a rea (EDA) measured by ABD can be used to determine an appropriate end point for intravenous fluid administration, nine mongrel dogs were stu died. Anesthetized animals were hemorrhaged to achieve a central venou s pressure of 0-5 mm Hg. Each animal was then given intravenous fluid( autologous blood followed by hetastarch) until a peak in thermodilutio n cardiac output (GO) was achieved. Measures of PCWP, EDA, CO, and lef t ventricular stroke work (LVSW) were obtained after each fluid bolus. Bivariate plots displaying administered volume versus CO, LVSW, and E DA revealed parallel curves for each of these variables with peaks evi dent at cumulative volumes of 50-55 mL/kg. Multiple regression with mi xed model anal ysis of covariance was performed to determine the signi ficance of EDA in relation to changes in CO and LVSW. Analysis was lik ewise performed comparing the relationship between PCWP and changes in CO or LVSW. A significant relationship was demonstrated when comparin g EDA to changes in CO and LVSW (P = 0.03 and P < 0.0001, respectively ). Similar analysis comparing PCWP to changes in CO and LVSW failed to demonstrate a significant relationship (P = 0.54 and P = 0.36, respec tively). These data suggest that changes in EDA measured using TEE wit h ABD are related to trends in cardiac function and can suggest an app ropriate end point for intravenous fluid administration as defined by maximum CO and LVSW. PCWP did not demonstrate a significant relationsh ip to changes in CO and LVSW.