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Hemodynamic evaluation of the prone position by transesophageal echocardiography
Study Objective:
To evaluate the hemodynamic response in the prone position in surgical patients by measuring the effects of prone positioning on cardiac function using transesophageal echocardiography (TEE).
Design:
Prospective study.
Setting:
Elective surgery at a university hospital.
Patients:
15 adult ASA physical status I and II patients free of significant coexisting disease undergoing lumbar laminectomy.
Interventions And Measurements:
Approximately 15 minutes after the induction of general anesthesia, we measured heart rate, blood pressure, and central venous pressure. We also measured left ventricular area (LVA) and fractional area change (FAC) automatically and calculated left ventricular volume (LVV), stroke volume index (SVI), cardiac index (CI), left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), pulmonary venous flow velocity (PVFV), and pulmonary venous velocity time integral (PVVTI) via TEE. The same measurements were performed approximately 15 minutes after changing to the prone position with longitudinal bolsters.
Main Results:
In the prone position, there was significant reduction in end-systolic and end-diastolic LVA and LVV. There was a significant increase in LVEF, LVFS, and FAC in the prone position. In addition, there was diminishment of systolic PVFV and PVVTI and enhancement of diastolic PVFV and PVVTI. SVI and CI did not change significantly in the prone position.
Conclusion:
The prone position caused LVV to decrease. The prone position also led to decreased systolic PVFV and PVVTI and enhancement of diastolic PVFV and PVVTI. These changes were probably due to a decrease in the venous return due to inferior vena caval compression, and decreased left ventricular compliance due to increased intrathoracic pressure in the prone position.