LEFT-VENTRICULAR END-SYSTOLIC CAVITY OBLITERATION AS AN ESTIMATE OF INTRAOPERATIVE HYPOVOLEMIA

Background: Transesophageal echocardiography is increasingly used intr aoperatively as a monitor of ventricular function and volume. Although obliteration of the left ventricular (LV) cavity at end-systole is in terpreted as indicative of intraoperative hypovolemia, this relation h as not been demonstrated directly. Methods: We continuously monitored the LV short axis by using transesophageal echocardiography and determ ined the relation between acute changes in LV area and hemodynamic var iables in 139 patients undergoing elective coronary artery bypass graf t surgery. The end-diastolic areas (EDA) and end-systolic areas were c alculated during the control state (after anesthetic induction) and du ring LV end-systolic cavity obliteration. Results: Thirty-nine of 139 patients had episodes of LV cavity obliteration. Mean LV end-systolic area decreased significantly from the control to obliterated state (7. 29 +/- 2.56 to 4.00 +/- 1.46 cm(2), P = 0.0001). The corresponding mea n LV EDA also significantly decreased from the control to obliterated state (18.18 +/- 4.36 to 12.92 +/- 3.74 cm(2), P = 0.0001). Mean eject ion fraction area increased from 0.609 +/- 0.095 (control) to 0.692 +/ - 0.083 (obliteration) (P < 0.0001). Of these 39 episodes, 31 (80%) we re associated with a greater than 10% decrease in EDA relative to the initial value after induction of anesthesia and tracheal intubation; 4 (10%) with increases in ejection fraction area only; and an additiona l 4 (10%) with no substantial change in either the EDA or ejection fra ction area. Overall, LV cavity obliteration was not associated with he modynamic changes. Conclusions: Our study demonstrates that LV cavity obliteration is rarely preceded by any acute alteration in hemodynamic parameters. Although end-systolic cavity obliteration detected by int raoperative transesophageal echocardiography is frequently associated with decreases in EDA, not every instance of end-systolic cavity oblit eration is indicative of decreased left ventricular filling.