Prolongation of Subarachnoid Block With Concomitant Use of Intravenous Dexmedetomidine: An Evidence-based Review

A failed subarachnoid block due to prolonged surgical duration continues to be a challenging problem for anesthesia providers. This evidence-based review updates a 2013 systematic review describing the use of intravenous dexmedetomidine as an extrathecal spinal adjunct capable of extending the duration of a subarachnoid block. Eight randomized controlled trials published after the 2013 systematic review met the inclusion criteria. The evidence continues to support the use of intravenous dexmedetomidine as an effective method for prolonging the duration of motor and sensory blockade and postoperative analgesia in a subarachnoid block, with minimal side effects. This updated review reported a more consistent use of assessment tools measuring motor and sensory recovery, expanded the volume of evidence related to postoperative analgesia, and further validated the safe and efficacious use of intravenous dexmedetomidine in extending the duration of a subarachnoid block. Future studies are needed to evaluate the rescue benefit of intravenous dexmedetomidine in failed subarachnoid blocks converted to general anesthesia resulting from prolonged surgical times.