Ultrasound Imaging Reduces Failed Epidural Catheterizations

April 29, 2013

Using ultrasound imaging before an epidural catheterization or lumbar puncture can reduce the risk of failed or traumatic procedures and can lower the number of needle insertions and redirections, according to the findings of a systematic review and meta-analysis.

Using ultrasound imaging before an epidural catheterization or lumbar puncture can reduce the risk of failed or traumatic procedures and can lower the number of needle insertions and redirections, according to the findings of a systematic review and meta-analysis.1
   
The successful placement of an epidural catheter or a lumbar puncture is largely dependent on palpation of anatomical landmarks, which obesity, edema, or anatomical variation can obscure, explain the authors. Other factors that affect the performance of these procedures are the angle of needle progression and the distance from the skin to the target space, which cannot be determined by palpation and are solely controlled by operator skill. Use of ultrasound scanning before an epidural catheterization or lumbar puncture can help the clinician identify the intended vertebral interspace level, the midline of the spine, the optimal puncture point and needle insertion angle, and the depth to the spinal canal.1 Another advantage of ultrasound is that it is relatively inexpensive, readily available, and involves no radiation.
   
A total of 14 studies were reviewed, and 12 studies provided data for the meta-analysis.1 Of 624 procedures conducted in the ultrasound group, there were 6 failed procedures (1%). The failure rate was higher in the control group, which involved 44 failures (7.2%) out of 610 procedures. The use of ultrasound imaging significantly reduced the risk of a failed procedure (risk ratio, 0.21; P<0.001; number needed to treat [NNT], 16). Ultrasound imaging also significantly reduced the risk of traumatic procedures (risk ratio, 0.27; P=0.005; NNT, 17) and the number of insertion attempts and needle redirections (mean difference, -0.44 and -1.0, respectively; P<0.001).
   
Although these results show a beneficial effect of using ultrasound imaging before epidural catheterization or lumbar puncture, the implications for clinical practice are uncertain. “Because the baseline rate of failed procedures was low even when ultrasound was not used, it is unclear whether ultrasound imaging should be used for all lumbar punctures and epidural catheterizations,” they write.1 They suggest that ultrasound imaging may be best used for patients who may be at greater risk for a difficult procedure, such as those who are obese or who have significant swelling in the lower back, or as a rescue modality after a failed or traumatic attempt.

Pertinent Points:
- Failed epidural catheterizations and lumbar punctures are significantly reduced when pre-procedure ultrasound scanning is performed.
- Ultrasound imaging can reduce the number of traumatic procedures and the number of needle insertions and needle redirections.
 

References:

1. Shaikh F, Brzezinski J, Alexander S, et al. Ultrasound imaging for lumbar punctures and epidural catheterisations: a systematic review and meta-analysis. BMJ. 2013;346:f1720. doi: 10.1136/bmj.f1720.