• Gianluca Cappelleri, Andrea Luigi Ambrosoli, Marco Gemma, Cedrati Valeria Libera Eva VLE, Federico Bizzarri, and Giorgio Francesco Danelli.
• From the Anesthesia, Intensive Care and Pain Therapy, AUSL, IRCCS (Scientific Research and Care Institute), Reggio Emilia, Italy (G.C., F.B., G.F.D.) the Anesthesia, Intensive Care and Pain Therapy, Ospedale di Circolo, Varese, Italy (A.L.A.) the Anesthesia and Intensive Care, IRCCS Ospedale San Raffaele, Italy (M.G.) the Anesthesia and Pain Therapy, ASST Gaetano Pini-CTO, Milano, Italy (V.L.E.C.).
• Anesthesiology. 2018 Aug 1; 129 (2): 241-248.

What We Already Know About This TopicWHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Both extra- and intraneural sciatic injection resulted in significant axonal nerve damage. This study aimed to establish the minimum effective volume of intraneural ropivacaine 1% for complete sensory-motor sciatic nerve block in 90% of patients, and related electrophysiologic variations.MethodsForty-seven consecutive American Society of Anesthesiologists physical status I-II patients received an ultrasound-guided popliteal intraneural nerve block following the up-and-down biased coin design. The starting volume was 15 ml. Baseline, 5-week, and 6-month electrophysiologic tests were performed. Amplitude, latency, and velocity were evaluated. A follow-up telephone call at 6 months was also performed.ResultsThe minimum effective volume of ropivacaine 1% in 90% of patients for complete sensory-motor sciatic nerve block resulted in 6.6 ml (95% CI, 6.4 to 6.7) with an onset time of 19 ± 12 min. Success rate was 98%. Baseline amplitude of action potential (mV) at ankle, fibula, malleolus, and popliteus were 8.4 ± 2.3, 7.1 ± 2.0, 15.4 ± 6.5, and 11.7 ± 5.1 respectively. They were significantly reduced at the fifth week (4.3 ± 2.1, 3.5 ± 1.8, 6.9 ± 3.7, and 5.2 ± 3.0) and at the sixth month (5.9 ± 2.3, 5.1 ± 2.1, 10.3 ± 4.0, and 7.5 ± 2.7) (P < 0.001 in all cases). Latency and velocity did not change from the baseline. No patient reported neurologic symptoms at 6-month follow-up.ConclusionsThe intraneural ultrasound-guided popliteal local anesthetic injection significantly reduces the local anesthetic dose to achieve an effective sensory-motor block, decreasing the risk of systemic toxicity. Persistent electrophysiologic changes suggest possible axonal damage that will require further investigation.

26 keywords...

hide…