Ultrasound-determined landmarks decrease pressure pain at epidural insertion site in immediate post-partum period

BACKGROUND: Women have blamed epidurals for their post-partum back pain for decades. Survey-based studies have shown similar incidence of chronic back pain between women who delivered with epidurals compared to those who did not. However, epidural insertion site pain has yet to be evaluated by a quantitative measure: pressure pain threshold (PPT). Algometer measured PPT has been shown to be accurate and reproducible in acute, chronic, and postoperative pain studies. This study determines the effect of ultrasound-based landmarks on the PPT at the epidural insertion site in the post-partum period. METHODS: Participants were randomized into either the ultrasound or sham groups. In addition, a non-randomized control group (no epidural) participated. Ultrasound of the lumbar region was used to mark mid intervertebral levels in the US group but not in the sham group. Epidural were placed using the marks in the US group or palpated bony landmarks in the sham group. PPT at each intervertebral space measured before and after the use of epidural. RESULTS: Epidural placement did significantly decreased PPT in US (68%) and US sham (79%) groups and less in the control group (21%). US group showed decreased PPT only at insertion site whereas US sham group also showed decreased PPT at insertion site and adjacent levels. CONCLUSIONS: We showed that epidural placed with ultrasound-determined landmarks not only improves the success of epidural placement but also minimizes the number of intervertebral levels with decreased PPT.