An Ultrasonographic Assessment of Nerve Stimulation-Guided Median Nerve Block at the Elbow

Abstract

Nerve stimulation does not prevent intraneural injection. In the absence of intraneural injection, the presence of circumferential LA spread image seemed predictive of successful sensory block in almost 75% of the cases within the 30-minute evaluation period.

The Requisites of Needle-to-Nerve Proximity for Ultrasound-Guided Regional Anesthesia

“…While circumferential injection may be required for some nerves, such as the sciatic nerve 108,109 and median nerve, 110,111 it has not been shown to be a requirement for other nerves. Similarly, as with our understanding of sonographic nerve structure 112 and its associated connective tissue layers, 113 the sonographic characteristics of a safe versus dangerous injection are not known.…”

Ultrasound guidance, a win-win approach to peripheral nerve blockade

“…Among various localization techniques, low (0.5 mA) minimal stimulating current intensities may be associated with intraneural injections with a frequency of 43-83% [9][10][11]. This risk persists under ultrasound guidance with an incidence of 16-17% [12,13 & ].…”

Where should the tip of the needle be located in ultrasound-guided peripheral nerve blocks?

“…This efficacy is attributed to an injection in the common nerve sheath that still envelops both nerve components at this level and allows for local anaesthetic spread both distally and proximally toward the sciatic nerve and its divisions [7,9 && ,27 & ]. However, in another observational study, Dufour et al [29] used ultrasonography to assess the circumferential local anaesthetic spread after a nerve stimulationguided median nerve block at the elbow. Circumneural spread without intraneural injection was associated with (no more than) a 75% success rate of sensory blockade within the 30-min evaluation period [29].…”