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Correspondence |
Tokyo, Japan
To the Editor:
Epidural anesthesia occasionally fails to provide adequate surgical analgesia. Evaluation of the effectiveness of epidural anesthesia is required at an early stage following the administration of local anesthetics. The increase in pulse amplitude from the toe has been utilized as an index of the degree of sympathetic block and may aid in the early detection of successful epidural block.1 Single electric stimulation provides a more reliable predictor of the adequacy of sensory block.2 We assessed the clinical efficacy (sensory block, motor block and sympathetic block) during the early stages of epidural block.
Eleven patients undergoing epidural block with 14 mL 2% lidocaine with 1:200000 epinephrine at L4–5 or L5–S1 were studied. Pain threshold after single electric stimulation was performed at L2 and S1. Motor block was evaluated by the Bromage scale. Sympathetic blockade was assessed by plethysmographic waveforms from the toe. Patients were divided into two groups based upon whether the pain threshold did (group A) or did not (group B) reach 60 mA within 20 min.
Demographic data was comparable between groups. The threshold significantly increased after ten minutes compared with zero minutes in each group (P <0.05). The threshold of L2 region in group A was significantly higher than in group B at 15 and 20 min (P <0.01) while the threshold of S1 region in group A was significantly higher than in group B at 20 min (P <0.05). The amplitude of plethysmographic waveforms significantly increased after five minutes (P <0.05) and the Bromage scale significantly increased at 20 min in group A (P <0.05; Figure
). These results might suggest that the significant increment of the amplitude of plethysmographic waveforms within five minutes is one of the predictive factors of successful lumbar epidural block.
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References
1 Mineo R, Sharrock NE. Pulse oximeter waveforms from the finger and toe during lumbar epidural anesthesia. Reg Anesth 1993; 18: 106–9.[Medline]
2 Dyhre H, Renck H, Andersson C. Assessment of sensory block in epidural anaesthesia by electric stimulation. Acta Anaesthesiol Scand 1994; 38: 594–600.[Medline]
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P <0.05, compared with zero minutes in group A. C, Changes of Bromage scale. There were no statistically significant differences between the two groups. +P <0.05, compared with zero minutes in group A. Values are mean ± SD.