[Identification of the lumbosacral nerve plexus during the extreme lateral interbody fusion procedure].

PURPOSE OF THE STUDY

The aim of this clinical observation study was to determine the extent to which muscle relaxation induced by anesthesia must be intra-operatively reversed for a reliable identification, by intra-operative monitoring, of the lumbosacral (LS) nerve roots during extreme lateral interbody fusion (XLIF). MATERAL AND METHODS: General anesthesia (midazolam, propofol, sufentanil, oxygen/air/sevofluran - rocuronium) was administrated to all pa - tients. Train-of-four (TOF) stimulation of the ulnar nerve at 10-second intervals and an electromyographic response of the adductor pollicis muscle were used, and the duration of neuromuscular block was measured by the value of the TOF-ratio. When the level of recovery from neuromuscular block was TOF-count = 2, reversion to normal function was still accelerated by sugammadex administration at a dose of 2 mg.kg-1. Subsequently, it was determined at which level of muscle relaxation subsidence the first responses to LS nerve root stimulation were evident. Intra-operative neurophysiologial monitoring (IOM) with use of the NIM - Neuro® 3.0 device allowed for assessment of a triggered electromyographic reaction (tEMG) of LS roots to stimulation during surgery. The neuromuscular reactions were evaluated in 11 patients, five men and six women. The results were analysed by descriptive statistics and presented as median and interquartile-range values.

RESULTS

In all patients a reliable monitoring of the depth of muscle relaxation was established. The value of supramaximal impulse was 46 mA (38 to 64 mA). The period from rocuronium administration to a spontaneous recovery of the TOF-count = 2 took 33 min (29 to 35 min). Duration from sugammadex administration to a TOF ratio of . 0.70 was 90 seconds (50 to 140) and to a TOF ratio of . 0.90 was 190 seconds (100 to 220 s). A reliable tEMG response of LS nerve roots to electric stimulation at 10 mA intensity was recorded at a TOF ratio of 0.68 (0.56 to 0.77) and at a 5 mA intensity it was reliable at a TOF ratio of 0.86 (0.75 to 0.90).. None of the patients reported radicular symptoms after surgery.

DISCUSSION

From the anatomy of the greater psoas muscle and varied patterns of its LS plexus it is obvious that none of the zones is absolutely safe. In XLIF procedures it is therefore recommended to disect the psoas muscle under both visual and IOM control. Intra-operative checking of the depth of muscle relaxation then will provide information that conditions not affected by rocuronium administration and necessary for the detection of LS roots have been provided.

CONCLUSIONS

1. For a reliable intra-operative identification of LS nerve roots by electric stimulation at a 10 mA intensity it is recommended to achieve the value of TOF ratio equal to at least 0.70. When stimulation at a lower intensity (5 mA) is used, a TOF ratio of . 0.90 is necessary. 2. Administration of sugammadex to reverse an action of the muscle relaxant rocuronium is an effective and quick method to achieve the values required.