ported that epidural puncture was successful by one-time trial in 179/180 patients (99.4%). Yamashita and Tsuji [17] applied the drip infusion method to identify the epidural space in 350 infants (300 in the spinal region and 50 in the thoracic vertebra region) under the age of nine and reported that it was accurately performed in 342 infants (97.7%). However, in our case, although we performed the drip infusion method to avoid the problems of pseudo positive loss of resistance method listed previously, the Tuohy nee- dle was unable to penetrate through the ligamentum fla- vum, the catheter deviated to the spinal lamina region at the entrance of the ligamentum flavum, and it proceeded into the near erecter spinae muscle, as revealed by cervical and thoracic CT. The methods used to verify accurate nee- dle placement - hanging drop, loss of resistance, and drip infusion - were performed in the space just before the lig- amentum flavum. Thus, the operator mistakenly consid- ered this to be the epidural space and inserted the cathe- ter, which led to the failure of the epidural anesthesia. The reason why the results from all three methods were found to be positive is unclear. As described previously, possible causes include the accompaniment of interspinous liga- ment degeneration or tissue breakdown by fluid overload due to chronic renal failure [18]. Clinically, epidural anesthesia sometimes fails even when the loss of resistance and hanging drop tests show positive results, and the catheter is inserted without any particular difficulty. Although C-arm guidance is employed from time to time, it is undeniably true that epidural anes- thesia is most often performed without an imaging instrument. We identified the causes of epidural anesthesia failure using CT and recommend the use of C-arm guid- ance for epidural anesthesia, if possible, to reduce the fre- quency of pseudo positive cases of the loss of resistance. REFERENCES 1. Howell TK, Prosser DP, Harmer M. A change in resistance? A survey of epidural practice amongst obstetric anaesthetists. Anaesthesia 1998; 53: 238-43. 2. Kil HK, Cho JE, Kim WO, Koo BN, Han SW, Kim JY. Prepuncture ultrasound-measured distance: an accurate reflection of epidural depth in infants and small children. Reg Anesth Pain Med 2007; 32: 102-6. 3. Rapp HJ, Folger A, Grau T. Ultrasound-guided epidural SJ Lee, et al / Epidural Catheter Malposition 47 catheter insertion in children. Anesth Analg 2005; 101: 333-9. 4. Kim SH, Lee KH, Yoon KB, Park WY, Yoon DM. Sonographic estimation of needle depth for cervical epidural blocks. Anesth Analg 2008; 106: 1542-7. 5. Suwa T, Inomata S, Saito S, Toyooka H. Pressure-guided method for identification of the epidural space in children. Anesthesiology 1998; 89: 546-8. 6. Matsuda K. Identification of the epidural space using a drip infusion set. Masui 1977; 26: 956-7. 7. Yamashita M, Tsuji M. Identification of the epidural space in children. The application of a micro-drip infusion set. Anaesthesia 1991; 46: 872-4. 8. Yokoyama T, Ushida T, Yamasaki F, Inoue S, Sluka KA. Epidural puncture can be confirmed by the Quecken- stedt-test procedure in patients with cervical spinal canal stenosis. Acta Anaesthesiol Scand 2008; 52: 256-61. 9. Lechner TJ, van Wijk MG, Maas AJ, van Dorsten FR, Drost RA, Langenberg CJ, et al. Clinical results with the acoustic puncture assist device, a new acoustic device to identify the epidural space. Anesth Analg 2003; 96: 1183-7. 10. Tsui BC, Gupta S, Finucane B. Confirmation of epidural catheter placement using nerve stimulation. Can J Anaesth 1998; 45: 640-4. 11. Lee YB, Kim SY, Park JT, Han YK, Yoon KB. On the accuracy of cervicothoracic vertebral level determination by palpation of spinous processes. Korean J Anesthesiol 1999; 37: 608-12. 12. Uchino T, Hagiwara S, Iwasaka H, Kudo K, Takatani J, Mizutani A, et al. Use of imaging agent to determine postoperative indwelling epidural catheter position. Korean J Pain 2010; 23: 247-53. 13. Rissanen PM. The surgical anatomy and pathology of the supraspinous and interspinous ligaments of the lumbar spine with special reference to ligament ruptures. Acta Orthop Scand Suppl 1960; 46: 1-100. 14. Sharrock NE. Recordings of, and an anatomical explanation for, false positive loss of resistance during lumbar extradural analgesia. Br J Anaesth 1979; 51: 253-8. 15. Gupta B, Sharma S, D'souza N, Kaur M. Pseudo loss of resistance in epidural space localization. Saudi J Anaesth 2010; 4: 117-8. 16. Lirk P, Kolbitsch C, Putz G, Colvin J, Colvin HP, Lorenz I, et al. Cervical and high thoracic ligamentum flavum frequently fails to fuse in the midline. Anesthesiology 2003; 99: 1387-90. 17. Yamashita M, Tsuji M. Identification of the epidural space in children. The application of a micro-drip infusion set. Anaesthesia 1991; 46: 872-4. 18. Rimmelé T, Kellum JA. Oliguria and fluid overload. Contrib Nephrol 2010; 164: 39-45.