NEW YORK (Reuters Health) – In most infants who undergo fluoroscopy guided lumbar puncture (LP), the procedure will introduce red blood cells into the cerebrospinal fluid, which can cause diagnostic problems, new research shows.

The rate of these so-called traumatic LPs in children 1 year of age or younger is 58.8%, whereas in older patients the rate is just 3.2%, according to the report in the March issue of the American Journal of Neuroradiology.

“The findings suggest that in infants, physicians may opt to use ultrasound to guide the needle for lumbar puncture or work without the cerebrospinal fluid altogether,” senior researcher Dr. Annette J. Johnson, from Wake Forest University School of Medicine, Winston-Salem, North Carolina, said in a statement.

She added that “it’s just not worth the radiation and high chance of failure or bleeding that fluoroscopy-guided LP carries in these very young patients.”

The findings also show that a LP at the L4-L5 level carries a failure rate of 19% compared with rates of around 9% for those at the L2-L3 and L3-L4 levels.

The results stem from a review of all 756 patients who underwent fluoroscopy-guided LP at the researchers’ centers in 2005 and 2006. A traumatic LP was considered one in which the red blood cell count was 500 cells/mL or higher without xanthochromia.

The overall traumatic LP rate was 13.3%, the report indicates.

Although very young patients had the highest risk of LP failure, very old patients also had an elevated risk. In subjects over 80 years of age, the failure rate was 25.9%, roughly double the 12.4% rate seen in younger patients.

By contrast, gender and needle size did not influence the success of LP, the authors report.

“Lumbar punctures will very likely continue to be a common medical procedure,” Dr. Johnson said. “The findings of this study should help ordering physicians decide how best to order this test and should help radiologist physicians choose at which levels to perform the procedure.”

Reference:
Am J Neuroradiol 2009.