Efficacy of quadriceps femoris fasciculation induced by low-current nerve stimulation when used to assist ultrasound-guided lumbar plexus block

Abstract

Objective To evaluate the efficacy of quadriceps femoris fasciculation induced by low-current nerve stimulation when used to assist ultrasound-guided lumbar plexus block. Methods One hundred patients of both sexes, aged 18-45 yr, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, weighing 50-85 kg, scheduled for elective unilateral knee arthroscopy, were selected and randomly divided into 2 groups(n=50 each)using a random number table: ultrasound assisted by nerve stimulator group(group SU)and ultrasound group(group U). The shamrock method was used to perform the ultrasound-guided lumbar plexus block in two groups.In group SU, the nerve stimulator with current 0.35 mA and frequency 1 Hz was used in the process of puncture, and 0.5% ropivacaine 0.4 ml/kg was administrated when quadriceps femoris fasciculation was induced.In group U, when the tip of the nerve stimulating needle was located around the lumbar plexus, which was confirmed by ultrasound, 0.5% ropivacaine 0.4 ml/kg was administrated.The time of puncture, depth of needle insertion, onset time of block and effective block were recorded.Motor block was assessed using the modified knee score, and the development of complications was recorded within 24 h after block. Results Compared with group U, the onset time of block was significantly shortened, the rate of effective block was increased, the degree of motor block was aggravated(P 0.05). No complications were observed in two groups. Conclusion Low-current(0.35 mA)nerve stimulation-induced quadriceps femoris fasciculation when used to assist location can improve the efficacy of ultrasound-guided lumbar plexus block. Key words: Transcutaneous electric nerve stimulation; Ultrasonography; Lumbosacral plexus; Nerve block