title: Correlation between the distribution of contrast medium and the extent of blockade during epidural anesthesia.
abstract: BACKGROUND
  If the epidural spread of contrast medium can be well correlated with the spread of local anesthetics, epidurography can predict the dermatomal distribution of the anesthetic block. The authors evaluated the relation between radiographic and analgesic spread.
  
  
  METHODS
  An epidural catheter was inserted in 90 patients, and predicted catheter tip position was recorded. The analgesic area was determined by pinprick after a 5-ml injection of 1.5% lidocaine, and epidurography was performed after a 5-ml injection of 240 mg I/ml iotrolan. Patients were assigned to three groups according to catheter tip position (group C: C-T4; group T: T5-T10; group L: T11-L), and patterns of spread were compared. In 16 of 90 subjects, radiographic and analgesic spread was further investigated after an additional 5-ml injection of iotrolan and lidocaine.
  
  
  RESULTS
  The total radiographic spread correlated well with analgesic spread (right side: Y = 0.84 X + 0.16, r = 0.92, P < 0.01; left side: Y = 0.78 X + 0.45, r = 0.91, P < 0.01). The mean radiographic spread in the cephalad and caudal directions from the catheter tip also correlated well with mean analgesic spread (r = 0.97, P < 0.01, each direction). The mean distance between the predicted catheter tip and radiographically determined positions was 1.0 +/- 0.8 segments: the value in group T was significantly larger than that in groups C (P < 0.05) and L (P < 0.01). Although the correlation of radiographic spread with age was statistically significantly (r = 0.39, P < 0.01), great individual variation in spreading pattern was seen. In 16 subjects, mean radiographic spread correlated well with analgesic spread after 5- and 10-ml injections of iotrolan and lidocaine.
  
  
  CONCLUSIONS
  Epidurography is useful to indicate epidural catheter position and can help to predict the exact dermatomal distribution of analgesic block.
authors.affiliation: Department of Anesthesiology and Resuscitology, Okayama Medical School, Okayama City, Okayama, Japan. masayoko@cc.okayama-u.ac.jp
authors.forename: Masataka
authors.initials: M
authors.lastname: Yokoyama
authors.forename: Motohiko
authors.initials: M
authors.lastname: Hanazaki
authors.forename: Hiromi
authors.initials: H
authors.lastname: Fujii
authors.forename: Satoshi
authors.initials: S
authors.lastname: Mizobuchi
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakatsuka
authors.forename: Toru
authors.initials: T
authors.lastname: Takahashi
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsumi
authors.forename: Mamoru
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Morita
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000767:Anesthesia, Epidural / Q000379:methods*; D003287:Contrast Media / Q000032:analysis* / Q000494:pharmacology; D006801:Humans; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D011859:Radiography; D013116:Spinal Cord / Q000000981:diagnostic imaging* / Q000187:drug effects
chemical_list: D003287:Contrast Media