[The spread of contrast medium in the epidural space and the analgesic area in epidural anesthesia in elderly patients].

We evaluated the relationship between the spread of contrast medium in epidural space and the analgesia area in epidural anesthesia in elderly patients. The spread of contrast medium was examined radiographically after the injection of iotrolan 5 ml through the epidural catheter and the analgesia area was examined by pin prick following the epidural injection of the same volume of 1% lidocaine. In lumbar group (group L) (n = 10), the radiographic spread was 10.4 (4-17) segments (mean, minimum-maximum) and the analgesic area was 8.5 (4-15) dermatomes. In cervical or thoracic group (group C/T) (n = 10), the radiographic spread was 12.4 (8-17) segments and the analgesic area was 10.4 (6-15) dermatomes. The dose of local anesthetics required to get analgesia per. one dermatome was 0.7 (0.3-1.3) ml in group L and 0.5 (0.3-0.8) ml in group C/T. The spread of contrast medium correlated well with the analgesic area in both groups (group L:Y = 0.79X + 0.31, r = 0.92, group C/ T:Y = 0.80X + 0.52, r = 0.79). The mean dose of local anesthetics required for analgesia was smaller than that of previous reports although individual variations were large. We conclude that the spread of contrast medium is useful for predicting the spread of epidural block.