Figure 2. SPIRIT schedule of enrolment, interventions and assessments. Filled circles indicate the time point at which each procedure or assessment is performed, across the enrolment (day of imaging, before the procedure), allocation, the intervention (first and any rescue attempts) and the post-procedure period (with the catheter in situ, up to a maximum of 4 hours). The primary outcome (first-attempt success) is highlighted. A-DIVA, Adult Difficult Intravenous Access; NIR, near-infrared; NRS, Numerical Rating Scale.