Feasibility of electromyography (sEMG) in measuring muscular activity during spinal anaesthesia in patients undergoing knee arthroplasty.
BACKGROUND
Bromage scale (0-3) is used to measure the degree of motor block during spinal anaesthesia. However, an estimation of motor block is difficult during surgery. The purpose of this study was to evaluate the feasibility of surface EMG describing spontaneous muscular activity in the lower extremities during spinal anaesthesia.


METHODS
In part I of the study, 13 patients undergoing day case surgery were studied. They received 10 mg hyperbaric bupivacaine at interspace L3-4. EMG, sensory and muscular block were measured at 5-min intervals during the first 30 min and then every 15 min until the patient was able to flex the knee. In part II of the study, 16 patients undergoing knee arthroplasty received 10 mg bupivacaine through spinal catheter at interspace L3-4 (Group CSA). An additional bolus of 2.5 mg was administered using EMG-guidance, if needed. Another group, 15 patients, received a single bolus of bupivacaine (15-20 mg) at L3-4 (Group Bolus). EMG, muscular and sensory block were monitored as described above. The epidural catheter was used as rescue.


RESULTS
Part I: EMG compared to modified Bromage scale showed a significant correlation (P < 0.01, Spearman rank correlation). Part II: The amount of bupivacaine was significantly reduced with EMG guidance when compared with the single bolus group (14.0 mg vs. 17.0 mg) (P < 0.05 Mann-Whitney U). Motor block started to recover before the sensory block in 7/15 CSA patients vs. 1/15 Bolus patient.


CONCLUSIONS
Stable maximal sensory block does not necessarily correlate with adequate motor block in patients receiving spinal anaesthesia induced with small bolus doses. In spite of electrical noise, EMG-guided administration of spinal anaesthesia significantly reduced the amount of bupivacaine compared to the hospital routine. Further studies are needed to develop the method.
Niemi-Murola
L
L
Department of Anaesthesia and Intensive Care Medicine, Helsinki University Central Hospital, Helsinki, Finland.
Paloheimo
M
M
D000328:Adult; D000368:Aged; D000556:Ambulatory Surgical Procedures; D000775:Anesthesia, Spinal; D019645:Arthroplasty, Replacement, Knee; D004311:Double-Blind Method; D004576:Electromyography / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D018482:Muscle, Skeletal / Q000502:physiology*