A randomized study to validate a midspinal canal depth nomogram in neonates.

Improving the accuracy of lumbar puncture (LP) in neonates should reduce the incidence of hemorrhagic contamination of cerebrospinal fluid (CSF) samples. We have previously demonstrated a linear correlation between neonatal weight and midspinal canal depth (MSCD), generating a nomogram and simple formula to allow MSCD estimation. In this study, we attempted to validate the nomogram by improving the quality of the CSF samples obtained. We consecutively randomized 99 infants in whom LP was clinically warranted to receive either a standard, "blind" ( N = 48) or "measured" ( N = 51) procedure. If allocated to the measured technique, the operator marked the LP needle with a Steri-Strip (TM) at the predicted depth of insertion (i.e., MSCD) derived from the weight-based nomogram. CSF samples were classified as clear (<500 red blood cells [rbc]/mL), mildly bloodstained (500 to 10,000 rbc/mL), heavily bloodstained (>10,000 rbc/mL or clotted), or failed procedures. Clear and mildly bloodstained LPs were "successful." Heavily bloodstained or failed procedures were considered "unsuccessful." We also recorded the number of attempts required to obtain a CSF sample. The overall success rate (