Simple and accurate formula to estimate umbilical arterial catheter length of high placement.

OBJECTIVE The present study aimed to derive the new simple, reliable, and accurate formula based on a body measurement parameter and not on reference graphs, to determine umbilical arterial catheter length of high placement, between the sixth to tenth thoracic vertebral (T6-T10) levels. Accuracy among a variety offormulas was also examined. MATERIAL AND METHOD A prospective recruitment of 40 babies who had an umbilical arterial catheter placed in the NICU, Thammasat University Hospital was studied Insertional length for high placement was measured. The body measurement parameters were measured twice on each patient to indicate their reliability properties. Three individual umbilical arterial lengths, from umbilical ring to anatomical points of T6, T8, and T10 levels accordingly, were estimated by verifying the catheter tip against those anatomical points on chest and abdominal radiograph. Correlation coefficient (r) between each parameter and the umbilical arterial length to the T8 level was calculated. RESULTS Suprasternal notch to superior iliac spine length (SSSL) was the selected parameter to derive a new formula because of high reliability coefficient of 0.964, high correlation to the umbilical arterial length to the T8 level (r = 0.906), and its simplicity to measure. The accuracy of the 'SSSL' to position the catheter tip at T6-T10 was 90%. CONCLUSION The SSSL is simple and accurate for predetermination of the umbilical arterial catheter length to position the catheter tip at T6-T10. It can be an alternative formula, especially where birth weight and total body length are not available.