Motor response evaluation during brachial plexus block anesthesia: An ultrasonography aided study

Abstract

Background:The sparing of ulnar nerve often leads to the failure of the upper limb blockade. It has been claimed that local anesthetic injection at the site of stimulator evoked finger flexion response is associated with highest success rate of a successful block. The lower trunk stimulation of plexus should yield similar results as this trunk contributes significantly for median and ulnar nerves of hand and forearm.Materials and Methods:The patients with intact anatomical upper limb structures underwent (a) combined ultrasound (USG) assisted nerve stimulator evoked motor response evaluation or in (b) open brachial plexus trunk stimulation evaluations. The individual patient's lower trunk stimulation motor responses were documented.Results:When combined the results of both USG and open plexus groups, wrist flexion was seen in 52%, finger flexion in 61% and forearm pronation or twitches of anterior compartment in 48% of total subjects studied. These responses were noted either separately or in combinations.Conclusion:We conclude other than finger flexion, the wrist flexion the forearm twitches, pronation and wrist adduction may be used for lower trunk blockade and thus for higher accuracy.

Comparison of the anesthesia effect of ultrasound-guided middle and low interscalene brachial plexus block: a randomized, controlled, non-inferiority trial

“…Similarly to previous studies, no extension of the wrist or fingers but the contraction of the triceps brachii was observed in our study with a current set at 0.4 mA when stimulated in the ventral ramus C7, which contributed largely to the radial nerve, so the contraction of the triceps brachii was considered to be the motor response to the stimulation of the middle trunk [ 18 , 19 ]. Due to the high accuracy feature, flexion of the fingers was considered the motor response elicited by the inferior trunk [ 20 , 21 ]. In the present study, for the first injection, the percentage of patients in the MISB group with fingers elicited motor response was lower (17.9% vs. 62.2%, P < 0.001) but higher with triceps brachii elicited motor response (59% vs. 29.7%, P = 0.01), compared with LISB group.…”