Nerve stimulator and multiple injection technique for upper and lower limbblockade: Failure rate, patient acceptance, and neurologic complications

To evaluate the failure rate, patient acceptance, effective volumes of loca l anesthetic solution, and incidence of neurologic complications after peri pheral nerve block performed using the multiple injection technique with a nerve stimulator, we prospectively studied 3996 patients undergoing combine d sciatic-femoral nerve block (n = 2175), axillary blocks (n = 1650), and i nterscalene blocks (n = 171). The success rate and mean injected volumes of local anesthetic were: 93% with 22.6 +/- 4.5 mL in the axillary, 94% with 24.5 +/- 5.4 mL in the interscalene, and 93% with 28.1 +/- 4.4 mL in the sc iatic-femoral nerve blocks. Patients receiving combined sciatic-femoral ner ve block showed more discomfort during block placement and worse acceptance of the anesthetic procedure than patients receiving brachial plexus anesth esia. During the first month after surgery, 69 patients (1.7%) developed ne urologic dysfunction on the operated limb. Complete recovery required 4-12 wk in all patients but one, who required 25 wk. The only variable showing s ignificant association with the development of postoperative neurologic dys function was the tourniquet inflation pressure (<400 mm Hg compared with >4 00 mm Hg, odds ratio 2.9, 95% confidence intervals 1.6-5.4; P < 0.001). We conclude that using the multiple injections technique with a nerve stimulat or results in a success rate of >90% with a volume of <30 mL of local anest hetic solution and an incidence of transient neurologic complication of <2% . Implications: Based on a prospective evaluation of 3996 consecutive perip heral nerve blocks, the multiple injection technique with nerve stimulator allows for up to 94% successful nerve block with <30 mL of local anesthetic solution. Although the data collection regarding neurologic dysfunction wa s limited, the withdrawal and redirection of the stimulating needle was not associated with an increased incidence of neurologic complications. Sedati on/analgesia should be advocated during block placement to improve patient acceptance.