EMG Assessment of Analgesia in Treatment of Posttonsillectomy Pain

OBJECTIVES: Surface electromyographic (sEMG) study of posttonsillectomy swallow-evoked muscular reactions was performed to assess validity of EMG in evaluation of analgesic drugs. METHODS: Sixty randomly chosen operated adults were divided into group 1 (n=30) treated with oxycodone, and group 2 (n=30) treated with placebo. Pain assessment included visual analog scale (VAS) pain score and EMG data: the timing, electric amplitude, and graphic patterns of muscular activity. We investigated masseter, infrahyoid, and submental-submandibular muscles. Records from trapezius muscle were used for control. The results were compared with previously established normative database. The sEMG data were compared with VAS score. RESULTS: Oxycodone significantly reduced VAS pain score and changed muscle reactions to analgesia (amplitude) as was recorded by sEMG, whereas placebo reduced VAS pain score nonsignificantly and changed the reaction of the trapezius muscle only. Analgesia smoothes the recorded swallow peaks and increases time of deglutition. Statistically significant difference in muscle reactions was detected between the 2 groups. CONCLUSIONS: sEMG might be used for quantitative evaluation of analgesic drugs by assessment of muscular reactions to pain and to analgesia. This method might add quantitative justification to the information obtained by VAS pain testing and clinical data.