The umbilical arterial catheter: a formula for improved positioning in the very low birth weight infant.

OBJECTIVE: : An umbilical arterial catheter is often used to monitor blood pressure and take frequent blood samples in the very low birth weight newborn infant requiring neonatal intensive care. Incorrect placement of the umbilical arterial catheter increases catheter complications, and adjustment of catheter position after radiograph increases infant handling and infection risk. Current methods overestimate insertion length in very low birth weight babies. We suggest a new formula for calculating insertion length that is more appropriate for today's neonatal intensive care population. The Umbilical Arterial Catheter Calculation Study, Australian Perinatal Trials Register PT0398, was set up to investigate this technical change. Our hypothesis was that the new formula would improve the siting of umbilical arterial catheters in very low birth weight infants.

DESIGN: : Randomized control trial.

SETTING: : Tertiary referral neonatal intensive care unit.

PATIENTS: : All infants <1500 g who were free from major cardiovascular malformations and who received an umbilical arterial catheter for clinical reasons were eligible for the study.

INTERVENTIONS: : Infants were randomized to current practice, using a nomogram derived from Dunn (control), or to the new formula: insertional length (cm) = (4 x birth weight [kg]) + 7. Primary outcome was correct catheter position (T6-10) on initial radiograph.

MEASUREMENTS AND MAIN RESULTS: : Seventy-four randomized infants had catheters successfully inserted. There were no significant differences between the groups in birth weight, gestational age, or gender. There was a significant increase in correctly sited catheters (p = .003) with the new formula. Overinsertion of the umbilical arterial catheter was significantly less likely (p < .0001). Underinsertion was not significantly increased. Umbilical arterial catheter manipulation after radiograph was decreased from 50% to 5% (p = .007). There was no increase in adverse effects.

CONCLUSIONS: : The use of the new formula results in better overall placement and in significantly less overinsertion of umbilical artery catheters in very low birth weight infants.