Topical glyceryl trinitrate to increase radial artery diameter in neonates: study protocol for a randomized controlled trial.

Background: Newborn infants admitted to the neonatal intensive care unit require arterial cannulation for hemodynamic monitoring and blood sampling. Arterial access is achieved through catheterization of umbilical or peripheral arteries. Peripheral artery cannulation is performed in critically ill newborns, but artery localization and cannulation is often challenging and unsuccessful. Therefore, increasing the internal diameter and preventing vasospasm are important for successful peripheral artery cannulation in neonates. Topical glyceryl trinitrate has the potential to increase cannulation success by relaxing arterial smooth muscles and thus increasing the internal diameter. We aim to conduct a pilot randomized controlled trial to evaluate the efficacy and safety of topycal glyceryl trinitrate in increasing the diameter of the radial artery in neonates.

Methods/design: This study will be a single-center, observer-blind, randomized, placebo-controlled trial conducted in the neonatal intensive care unit of Perth Children's Hospital, Western Australia. A total of 60 infants born at >34 weeks of gestation who are admitted for elective surgery or medical reasons and for whom a peripheral arterial line is needed for sampling or blood pressure monitoring will be recruited after informed parental consent is obtained. The primary outcome will be the change in radial arterial diameter from baseline to postintervention. Secondary outcomes will be the absolute and percentage change from baseline in the radial arterial diameter in both limbs and safety (hypotension and methemoglobinemia).

Discussion: This will be the first randomized controlled trial evaluating the use of topical glyceryl trinitrate to facilitate peripheral artery cannulation in neonates. If our pilot randomized controlled trial confirms the benefits of glyceryl trinitrate patches, it will pave the way for large multicenter randomized controlled trials in this field.