Preanesthetic Ultrasonography Assessment of Inferior Vena Cava Diameter in the Supine Position, Left Lateral Tilt Position, and with the Left Uterine Displacement Maneuver in Full-Term Pregnant Women: A Randomized Cross-Over Design Study

Background: We used preanesthetic ultrasonography evaluation to study the effectiveness of left lateral tilt position (LLT) and the left uterine displacement maneuver (LUD) on increasing inferior vena cava diameter (IVCD) in healthy full-term pregnant women, using a randomized, single blinded, cross-over design study.MethodsTwenty-two parturients scheduled for elective cesarean section under spinal anesthesia were recruited. All patients were sequentially placed in the supine position (SPN), LLT and with LUD before induction of spinal anesthesia. Indices of IVCD, measured by subxiphoid ultrasonography, including maximum IVCD (IVCDmax), minimum IVCD (IVCDmin) and collapsibility index (CI), and hemodynamic parameters, such as heart rate and blood pressure, were recorded in each of the postures. Mean or median values of all measurements were compared among the postures.ResultsThe mean values of IVCDmax observed with both LLT and LUD were significantly larger than those in the SPN, respectively (SPN vs. LLT: P <0.05, SPN vs. LUD: P <0.01), although there were no significant differences between IVCDmax with LLT and LUD. There were no significant differences in IVCDmin, CI and hemodynamic parameters between any of the postures. IVCDmax was highest with LUD in 11 patients (55%), in the LLT position in seven patients (35%) and in the SPN in two patients (10%).ConclusionsLLT and LUD might be equally effective in enlarging the narrowed IVCD as compared to SPN. However, both LLT and LUD might not necessarily be appropriate treatment to relieve IVC compression in some cases.Trial registrationThis study was registered in the “UMIN Clinical Trials Registry” (ID no.: 000024344, date. 10th October 2016).