Comparison of ultrasound imaging in transverse median and parasagittal oblique planes for thoracic epidurals: A pilot study

BACKGROUND AND AIMS: The use of ultrasound (US) scanning to assess the depth of epidural space to prevent neurological complications is established in current practice. In this study, we hypothesised that pre-puncture US scanning for estimating the depth of epidural space for thoracic epidurals is comparable between transverse median (TM) and paramedian sagittal oblique (PSO) planes. METHODS: We performed pre-puncture US scanning in 32 patients, posted for open abdominal surgeries. The imaging was done to detect the depth of epidural space from skin (ultrasound depth [UD]) and needle insertion point, in parasagittal oblique plane in PSO group and transverse median plane in TM group. Subsequently, epidural space was localised through the predetermined insertion point by ‘loss of resistance’ technique and needle depth (ND) to the epidural space was marked. Correlation between the UD and actual ND was calculated and concordance correlation coefficient (CCC) was used to determine the degree of agreement between UD and ND in both the planes. RESULTS: The primary outcome, i.e., the comparison between UD and ND, done using Pearson correlation coefficient, was 0.99 in both PSO and TM groups, and the CCC was 0.93 (95% confidence interval [95% CI]: 0.81–0.97) and 0.90 (95% CI: 0.74–0.96) in PSO and TM groups respectively, which shows a strong positive association between UD and ND in both groups. CONCLUSION: The use of pre-puncture US scanning in both PSO and TM planes for estimating the depth of epidural space at the level of mid- and lower-thoracic spine is comparable.