In pediatric and neonatal intensive care units, assessing the severity of extravasation is difficult, considering the specificity of this population. The purpose of this study was to demonstrate the ability to improve the measurement of extravasation by nurses with the establishment of a standardized instrument suitable for children. Sixty-six nurses, randomly assigned to two groups, assessed the severity of extravasations by looking at fifteen clinical vignettes. The intervention group used the Pediatric Peripheral Intravenous Infiltration Scale (PIV scale) (n=33) and the control group based their assessment on clinical judgment only (n=33). The references were obtained from a group of experts. For both groups, concordance and sensitivity were calculated. Concordance was improved by the use of the PIV scale—κ=0,62 (IC 95%; 0,57-0,67) vs. κ=0,51 (IC 95 %; 0,45-0,57) for the control group, as was sensitivity—69% vs. 60% (p<0,001) for the control group. The assessment of the severity of extravasation on peripheral venous accesses by nurses was improved with the use of the PIV scale, compared to clinical judgment. As this study was based on clinical vignettes, further studies are needed to confirm these results in a clinical setting.