Ultrasound-guided Nerve Blocks for the Sciatic and Saphenous Nerves: Characteristics of the Single Penetration Dual Injection (SPEDI) Technique

Background and aims: Ultrasound-guided (USG) nerve blocks of the sciatic nerve (popliteal level = PL) and the saphenous nerve (mid-femoral level = MFL) provides analgesia following leg surgery. Traditionally two separate injections are performed. The aim was to describe a novel, faster USG block combination requiring only one skin penetration to block the sciatic and saphenous nerves; i.e. the SPEDI block = Single PEnetration Dual Injection. Methods: A randomized, controlled and double-blinded trial. Following ethics committee approval 60 patients will be randomized to the administration of an USG SPEDI block compared to two separate USG blocks of the saphenous (MFL) and sciatic (PL) nerves. Blocks will be performed after induction of general anaesthesia. Outcome measures will be performance time (primary outcome measure), Post-Anaesthesia Care Unit pain scores (VAS scores 0-10), block difficulty level (easy, middle, difficult), opioid consumption (in the PACU), serum-ropivacaine pharmacokinetics (blood sample 0-180 minutes). Both block combinations will be evaluated by MR imaging (MRI). Hypothesis: The USG SPEDI block combination is expected to be performed significantly faster without moving the leg, and achieve successful perioperative pain management. The SPEDI block may find important use in the emergency setting.