I read with interest the article recently published by Chen et al. ,1“Ultrasound Guidance in Caudal Epidural Needle Placement.” The authors demonstrated that ultrasound can be used as an alternative tool to guide needle placement. The advantage of ultrasound is radiation free. The disadvantage is that ultrasound cannot monitor the depth of the inserted needle, as the authors indicated.1However, other disadvantages of ultrasound guiding caudal epidural needle placement should be discussed.

Complications of caudal epidural injection include intravascular placement or dural puncture. Aspirating the needle to check for blood or cerebrospinal fluid is helpful if positive, but the incidence of false-negative aspiration is too high to rely on this technique alone.2Fluoroscopic guidance and radiographic contrast administration can confirm needle position and rule out intravascular or subarachnoid placement immediately. The complication rate is significantly low when contrast is also used to verify the epidural needle placement. Johnson et al.  3reported only 4 minor complications in 5,334 cases when epidural steroid injection was done using fluoroscopy and contrast at various spinal level.

Placement of epidural steroid injection close to the level of pathology can optimize patient response to treatment.4,5Fluoroscopic guidance and contrast administration are essential to assess spread of epidural injectate into the desired target level during caudal epidural steroid injection.

Anesthesiologists of Greater Orlando, Orlando, Florida. jeffrey_j_huang@hotmail.com

Chen CPC, Tang SFT, Hsu TC, Tsai WC, Liu HP, Chen MJL, Date E, Lew HL: Ultrasound guidance in caudal epidural needle placement. Anesthesiology 2004; 101:181–4
Bernards CM: Epidural and spinal anesthesia, Clinical Anesthesia, 4th edition. Edited by Barash PG, Cullen BF, Stoelting RK. Philadelphia, Lippincott-Raven, 2000, pp 689–713Epidural and spinal anesthesia,Barash PG, Cullen BF, Stoelting RK
Johnson BA, Schellhas KP, Pollei SR: Epidurography and therapeutic epidural injections: Technical considerations and experience with 5334 cases. AJNR Am J Neuroradiol 1999; 20:697–705
Winnie AP, Hartman JT, Meyers HL, Ramamurthy S, Barangan V: Intradural and extradural corticosteroids for sciatica. Anesth Analg 1972; 51:990–1003
Renfrew DL, Moore TE, Kathol MH, el-Khoury GY, Lemke JH, Walker CW: Correct placement of epidural steroid injections: Fluoroscopic guidance and contrast administration. AJNR Am J Neuroradiol 1991; 12:1003–7