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

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) 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 anaesthetic agent or changes in the epidural space rather than tachyphylaxis.