Repeat spinal anesthesia for intrapartum cesarean section after epidural labor analgesia: a retrospective cohort study of failure rate and the volume-risk relationship

Repeat SA following ELA carries a failure rate that exceeds accepted thresholds when cumulative epidural volume is high. The cumulative epidural volume is a readily quantifiable variable that can be integrated into risk-assessment algorithms. Prospective multicentre studies are warranted to validate this relationship and to test ancillary bedside measures (glucose reagent strips, pH testing or ultrasound) for confirming true subarachnoid placement before intrathecal injection.