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Using ultrasound in a case of difficult epidural needle placement

Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Canada, E-mail: philip.peng{at}uhn.on.ca

To the Editor:

Ultrasound imaging provides important information for epidural or spinal needle placement and can be a valuable tool in managing patients with potentially difficult anatomy.^1,2 We recently used ultrasonography to facilitate successful epidural needle placement in a patient with a documented history of difficult epidural insertion. A 50-yr-old lady with a body mass index of 43 was referred for epidural steroid injection. She had a known history of failed back surgery, in which she had persistent back and leg pain following previous L4-5 discectomy. During the first epidural steroid injection, an epidural needle was inserted at the L2-3 level in the sitting position with loss-of-air resistance technique. Despite numerous attempts at this level and the adjacent levels, the anesthesiologist was unable to locate the epidural space. Because the patient became distressed, the procedure was postponed. Several weeks later, with the use of ultrasound imaging (Philips ATL HDI 5000 unit, Philips Medical Systems ATL Ultrasound, Bothell, WA, USA), both the mid-line plane and the interspinous space were identified. Successful epidural needle placement was achieved on the second attempt. Although the role of ultrasound imaging in facilitating epidural placement has been well described, this is the first reported observation of the potential role of ultrasound in rescuing an established difficult epidural needle insertion.

There are many reasons for failed epidural needle placement: poor patient cooperation, difficult anatomy (enlarged facet joints, calcified or ossified ligamentum flavum in degenerative disorder or ankylosing spondylitis) and failure to appreciate the midline plane, interlamellar space and rotation of vertebrae (in scoliosis). The target for epidural needle is the interlamellar space, which is the widest in the midline (Figure). However, in obese patients and those with impalpable spinous processes, definition of the midline can be difficult. In chronic pain practice, anatomic challenges can be overcome using fluoroscopy with the patient prone. However, fluoroscopy is not readily accessible in daily anesthesia practice. Prepuncture ultrasound imaging can be used to define the sagittal plane and the level of interspinous space. For the purpose of defining the sagittal plane of spinous process, we used the Philips ATL. However, less expensive ultrasound models, such as those used for central line placement, are quite adequate. This ultrasound equipment is much more accessible to anesthesiologists working in the operating room.

View larger version (99K): [in this window] [in a new window]   FIGURE Fluoroscopy of the lumbar spine showing the interlamellar space as outlined by dark arrows.

Footnotes

Accepted for publication November 6, 2005.

References

1 Grau T, Leipold RW, Conradi R, Martin E, Motsch J. Efficacy of ultrasound imaging in obstetric epidural anesthesia. J Clin Anesth 2002; 14: 169–75.[Medline]

2 McLeod A, Roche A, Fennelly M. Case series: Ultrasonography may assist epidural insertion in scoliosis patients. Can J Anesth 2005; 52: 717–20.[Abstract/Free Full Text]

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