RESUMO
OBJECTIVE: To provide a gestation age- and weight-specific mathematical formula for predicting the optimal depth of spinal needle insertion. METHODS: The study included 127 neonates between 28 and 40 weeks of gestation and weighing 700 to 4000 grams, and a total of 202 ultrasound examinations were performed. Anterior and posterior borders were delineated using ultrasound and measured as spinal canal depth in lateral decubitus position at L3- L4 vertebral interspace. The mid-spinal canal depth (MSCD) was calculated. RESULTS: Spinal canal dimensions showed an increasing trend with an increase in weight and post-menstrual age of the babies. The best correlation was found between weight and MSCD with an r2 of 0.85, which is given by the formula MSCD (cm) = 0.2 X weight in kg + 0.45. CONCLUSION: Knowledge of the spinal canal depth using the formula may facilitate accurate needle placement, thereby decreasing traumatic lumbar puncture.
