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Left ventricular end-systolic cavity obliteration as an estimate of intraoperative hypovolemia
1Department of Anesthesiology, University of California, San Francisco 94115.
Background:
Transesophageal echocardiography is increasingly used intraoperatively as a monitor of ventricular function and volume. Although obliteration of the left ventricular (LV) cavity at end-systole is interpreted as indicative of intraoperative hypovolemia, this relation has not been demonstrated directly.
Methods:
We continuously monitored the LV short axis by using transesophageal echocardiography and determined the relation between acute changes in LV area and hemodynamic variables in 139 patients undergoing elective coronary artery bypass graft surgery. The end-diastolic areas (EDA) and end-systolic areas were calculated during the control state (after anesthetic induction) and during 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 cm2, P = 0.0001). The corresponding mean LV EDA also significantly decreased from the control to obliterated state (18.18 +/- 4.36 to 12.92 +/- 3.74 cm2, P = 0.0001). Mean ejection fraction area increased from 0.609 +/- 0.095 (control) to 0.692 +/- 0.083 (obliteration) (P < 0.0001). Of these 39 episodes, 31 (80%) were 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 additional 4 (10%) with no substantial change in either the EDA or ejection fraction area. Overall, LV cavity obliteration was not associated with hemodynamic 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 intraoperative transesophageal echocardiography is frequently associated with decreases in EDA, not every instance of end-systolic cavity obliteration is indicative of decreased left ventricular filling.