Residency training: a failed lumbar puncture is more about obesity than lack of ability

To identify factors influencing the success of lumbar puncture (LP) performed by neurology residents in an outpatient clinic.

There is a need to understand the specific influence of patient or operator characteristics in LP performance in order to identify situations at high risk for failure that could benefit from compensatory interventions.

We performed a retrospective analysis of all consecutive patients who underwent elective LP in the Neurology Clinic at the University of Iowa between 2009 and 2012. We recorded demographic, anthropometric, and clinical information, and the level of training of the resident performing the procedure. Outcomes measure was unsuccessful LP, defined as no quantifiable CSF. This study was previously approved by the University of Iowa institutional review board.

A total of 328 patients (59% women) were included. Men were significantly older than women, and the indication of the procedure differed by sex. Headache or possible multiple sclerosis were more common indications in women than in men. Nineteen percent of the LPs were unsuccessful. We found a strong correlation between patient body mass index (BMI) and unsuccessful outcome (p < 0.0001). Age of the patient and level of training of the operator did not predict unsuccessful LP.

Patient BMI is the key factor that determines an unsuccessful LP by neurology residents in an outpatient setting, an association that might be applicable to different clinical settings. The high failure rate in patients with BMI >35 suggests that implementing compensatory interventions such as the use of imaging guidance might be cost-effective and better tolerated by these patients.