A Comparison of Sartorius Vs. Quadriceps Evoked Motor Response for Femoral Nerve to Prevent Secondary Catheter Failure

Background:

Continuous femoral nerve block (c FNB) is a widely used regional anesthetic technique for many lower limb operations. It provides superior pain relief, faster ambulation, and shorter hospital stay and less risk of side effects when compared with patient controlled analgesia (PCA).

Stimulating catheters (SC): SC were introduced back in 1999 to provide an objective end point to guide the catheter position by maintaining the desired evoked muscle response.

Stimulating catheter for continuous femoral nerve block: Salinas et al compared stimulating catheters vs. non-stimulating catheter in volunteers having femoral nerve block. They maintained a quadriceps evoked muscle twitch < 0.5 mA through the stimulating catheter . They reported a block success of 100% via the stimulating catheters versus 85% via the non-stimulating catheters (P = 0.07) and a much dense motor block and pain scores with SC as compared to NSC.

Motor responses of the femoral nerve: With peripheral nerve stimulation of the femoral nerve, two responses may be elicited, sartorius muscle contraction (contraction of the sartorius muscle through stimulation of its muscular branch) or quadriceps muscle contraction or patella twitch (contraction of the quadriceps muscle through stimulation its respective muscular branches). The two divisions of the femoral nerve are in fact medial and lateral divisions rather than anterior and posterior . The medial division supplies the sartorius muscle and the lateral division supplies the quadriceps muscle and both divisions lay within close proximity in the same fascial plane. Several regional anesthesia texts states that the anterior branch, supplying a motor branch to sartorius is above the fascia iliaca and this is partly why this stimulation should not be sought for FNB because there would be inadequate spread around the femoral nerve. An anatomical study by Gustafson et al and other anatomical text have forfeited this theory , . Furthermore, the rectus femoris of quadriceps often gets part of its innervation from the same division supplying the sartorius muscle.