Effect of nerve stimulation on the success rate of ultrasound-guided subsartorial saphenous nerve block?

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Effect of nerve stimulation on the success rate of ultrasound-guided subsartorial saphenous nerve block?

Ultrasound-guided subsartorial saphenous nerve block is frequently used to furnish the complete surgical anesthesia of the foot and ankle, alongwith with a popliteal sciatic nerve block. Nonetheless, the saphenous nerve is more strenuous to reliably block than the sciatic nerve in the popliteal fossa. This may be due to its small caliber and absence of a prominent vascular landmark in the subsartorial plane distal to the adductor canal. Since saphenous nerve is a sensory nerve only, neurostimulation can be used to induce a “tapping” sensation on the anteromedial aspect of the lower leg extending towards the medial malleolus.

A study by Shaylyn H and colleaguess aimed to examine the hypothesis that the addition of nerve stimulation use to an ultrasound (US)-guided technique will surge the success rate of subsartorial saphenous nerve block.

A total of 80 patients were enrolled with institutional human ethics board approval and participants' written informed consent undergoing foot and ankle surgery in a randomized, single-blinded, parallel-group clinical trial. The patients were randomly designated to receive US-guided subsartorial saphenous nerve block either alone (US group) or with the use of additional nerve stimulation (NS group; time limit, 5 minutes). All patients received 10 mL of 0.5% ropivacaine for saphenous nerve blockade. Primary end point depicted complete absence of sensation to pinprick at 30 minutes at two different anatomic regions in the distribution of the saphenous nerve (2 cm proximal to the medial malleolus and 10 cm distal to the medial tibial condyle). Secondary end points revealed reduced sensation at 30 minutes and block failure (normal sensation) at 30 minutes.

This trail was completed by 80 patients (40 patients in each group). At both anatomic areas of assessment (Fisher exact test, P=0.25 [one sided]; 95% confidence interval (CI) of difference in proportions, −11.9% to 31.9%), 22 patients (55%) in the NS group versus 18 (45%) in the US group had complete absence of sensation to pinprick at 30 minutes. At 30 minutes, the percentages of patients with any confirmation of block (decreased or complete absence of sensation) at both areas were 92.5% (NS) and 97.5% (US), respectively (P = 0.62 [two sided]); corresponding failure rates (normal sensation) were 7.5% (NS) and 2.5% (US). Within 5 minutes of stimulation time limit in 20% of patients (n=8), no response in the saphenous nerve distribution was evoked in the NS group. All the patients in the NS group with normal sensation at 30 minutes (n=3) were amid this subcohort.

It was culminated that the addition of the use of nerve stimulation did not ameliorate the success rate of US-guided subsartorial saphenous nerve block. But, in the NS group, an inability to induce a “tapping” sensation in the saphenous nerve distribution was related with block failure.

Source:

Regional Anesthesia and Acute Pain

Link to the source:

journals.lww.com/rapm/Abstract/2017/01000/Effect_of_Nerve_Stimulation_Use_on_the_Success.4.aspx

Original title of article:

Effect of Nerve Stimulation Use on the Success Rate of Ultrasound-Guided Subsartorial Saphenous Nerve Block: A Randomized Controlled Trial

Authors:

Shaylyn H. et al.

Regional Anesthesia and Acute Pain
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