Abdominal girth has a strong correlation with ultrasound-estimated epidural depth in parturients: a prospective observational study.

BACKGROUND: Preprocedural ultrasound examination of vertebral column guides to locate desired intervertebral space and provides a prevision of needle trajectory and estimated needle depth in parturients. The objective of this study was to assess the correlation between ultrasound-estimated epidural depth (ED) with abdominal girth (AG), body mass index (BMI), weight, height, and age.

METHODS: In this prospective, observational study, ultrasound imaging was done at L3-4 interspace in transverse median plane (TP) and paramedian sagittal oblique plane (PSO) to obtain ultrasound estimates of skin to epidural space depth. Combined spinal epidural anesthesia was performed at L3-4 interspace. AG, BMI, age, height, and weight were recorded for every parturient.

RESULTS: Data from 130 parturients were analyzed. Estimated ED was 56.5 ± 9.5 mm in TP, 57.5 ± 9.3 mm in PSO, and actual epidural depth was 57.9 ± 9.4 mm. Correlation coefficients between ED and AG were 0.797 in TP (95% CI 0.727-0.854, p < 0.001) and 0.803 in PSO (95% CI 0.733-0.857, p < 0.001). Correlation coefficients between ED and BMI were 0.543 in TP (95% CI 0.405-0.661, p < 0.001) and 0.566 in PSO (95% CI 0.428-0.680, p < 0.001). Correlation coefficients between ED and weight were 0.593 in TP (CI = 0.466-0.695, p < 0.001) and 0.615 in PSO (CI = 0.500-0.716, p < 0.001). Height and age had no significant correlation with ED.

CONCLUSIONS: Abdominal girth has a strong correlation with ultrasound-estimated epidural depth in parturients.