Topical glyceryl trinitrate for increasing radial arterial diameter in neonates: a randomised controlled trial

BACKGROUND: We evaluated the efficacy of topical Glyceryl trinitrate (GTN) in increasing the radial artery diameter (RAD) in neonates. METHODS: This single-centre randomised controlled trial was conducted in the tertiary neonatal intensive care unit (NICU) in Western Australia from August 2023 to July 2024. Hemodynamically stable neonates (gestation >34 weeks) admitted to the NICU were included. Neonates were randomised to GTN patch application for 30 min or 45 min or 60 min or placebo group. Primary outcome was change in ipsilateral RAD from baseline to post-intervention. Secondary outcomes were the absolute and percentage change from baseline in RAD in both limbs and safety (hypotension and methemoglobinemia). RESULTS: Mean RAD at baseline in ipsilateral limb in the anteroposterior view (AP) was [0.87 (SD 0.09), 0.89 (0.14), 0.86 (0.11) and 0.86 (0.12) mm, respectively,in the placebo, 30 min, 45 min and 60 min GTN groups; p value on ANOVA = 0.80]. Post-intervention, there was notable increase in AP-RAD in all the three GTN patch groups [1.20 (0.17), 1.16 (0.15), 1.16 (0.15)] Vs 0.93 (0.11) in placebo (p value < 0.001). Similar increase in RAD was noted in the transverse view at 30, 45 and 60 minutes. Post-GTN RAD did not increase with longer duration of application (p > 0.5). Post-intervention, there were no statistically significant differences between the groups in heart rate, blood pressure, oxygen saturation and methaemoglobin levels. CONCLUSION: Topical application of GTN increased RAD without clinically significant hypotension and methemoglobinemia in stable neonates. However, potential systemic effects warrant caution and further evaluation in critically ill infants. TRIAL REGISTRATION: anzctr.org.au Identifier ACTRN 12623000509662p. IMPACT: First RCT in neonates evaluating the effect of topical glyceryl trinitrate (GTN) patch on radial artery diameter (RAD). Topical GTN increases RAD on both sides. Systemic side effects of topical GTN require careful monitoring in sick neonates. These findings provide a framework for future trials evaluating the impact of topical GTN on arterial cannulation success rates, and radial artery spasm.