Variation in spread of analgesia and loss of temperature discrimination during intermittent postoperative epidural bupivacaine administration

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Abstract
The proximal-distal and bilateral extent of analgesia and loss of temperature discrimination were assessed during the initial 34.5 h after major abdominal surgery in ten patients receiving intermittent epidural bupivacaine injections according to a fixed dose regimen. Segmental spread of loss of temperature discrimination was invariably larger than analgesia at all times. During the later postoperative period (24-34 h) and a pronounced intra-individual variation in both proximal-distal and bilateral spread of analgesia was observed despite identical epidural injections of bupivacaine. This variation in extent of analgesia was observed during injections of both 0.5% and 0.25% bupivacaine. The explanation of this observation is unknown but it may be shifts in catheter position, a variable disposition of the local anesthetic agent or changes in the epidural space rather than tachyphylaxis.