The association between foot temperature and asymmetrical epidural blockade

This study was designed to explore the correlation between sensory block asymmetry and a disparity in foot temperature following epidural bupivacaine administration in labour. Sixty parturients requesting epidural analgesia had epidural catheters sited at L 3/4 while in the lateral position. A test dose was followed 5 min later by a main dose of 25-30 mg of plain bupivacaine. A thermistor thermometer recorded the temperature of the feet before and 5, 10, 15, 20 and 30 min after the end of the main dose. The upper and lower limits of sensory blockade on both the left and right sides were recorded at the same time intervals. Spearman's coefficient of rank correlation between sensory block asymmetry and foot temperature difference were at 5 min: 0.4, 10 min: 0.39, 15 min: 0.54, 20 min: 0.59 and 30 min: 0.6. This was significant at 5 and 10 min (P < 0.05) and highly significant at 15, 20 and 30 min (P < 0.001). During the 30 min period after the end of the main dose, 45 midwives, junior and senior medical staff (up to 4 observers per patient) were asked if they could detect foot temperature asymmetry. Their observations were compared with the thermistor readings. Most staff were able to detect a foot temperature difference > 1 degrees C. Our findings indicate a clear association between sensory block asymmetry and the difference between the temperature of the feet. This difference can be detected simply by feeling the feet.