Ultra-long duration of a peripheral nerve block: A possible consequence of intraneural (subepineural) local anaesthetic injection

Abstract

A 29-year-old patient was scheduled for bilateral halllux valgus surgery and a lateral sciatic popliteal nerve block was performed on each side using ropivacaine and lidocaine using nerve stimulation. Although the sensory and motor block had usual duration on the left side, the block lasted more than 48 hours on the right side with both sensory and motor impairment. An MRI performed on day 2 on the blocked side showed extra- and intraneural fluid accumulation with cephalad and distal spread. Sensory and motor function progressively recovered within the next day and was complete on the fourth day. We postulate that this case of extremely long duration of a peripheral nerve block can be ascribed to subepineural trapping of the local anaesthetic. Part of the variability in the duration of the sensory and motor block after peripheral nerve blocks might be explained by the variable amount of drug injected intraneurally.