Interventions to Improve Compliance to Surgical Safety Checklist Use: Before-and-After Study at a Tertiary Public Hospital in Croatia

<b>Background/Objectives:</b> The World Health Organization's Surgical Safety Checklist (WHO SSC) is known to reduce surgical complications and mortality, yet its implementation remains inconsistent across institutions. This study evaluated compliance with a modified SSC and assessed the impact of structured interventions to improve adherence at the University Hospital of Split, Croatia. <b>Methods:</b> A before-and-after study analyzed a sample of 1437 completed SSCs over four time points between April 2024 and May 2025: the baseline and after three successive interventions (an official letter from the hospital director emphasizing mandatory SSC use, individual meetings with department heads and head nurses reinforcing its importance, and a quality audit review of SSC completeness with leadership). Checklist completeness was assessed across five SSC sections: General Information, Sign In, Time Out, Sign Out, and Staff Info. <b>Results:</b> Overall checklist completeness increased from 78.3 ± 8.5% at baseline to 86.3 ± 2.5%, 92.0 ± 3.8%, and 94.7 ± 4.8% after the first, second, and third interventions, respectively (<i>p</i> < 0.001). All checklist sections improved significantly: General Info rose from 91.1 ± 6.0% to 98.6 ± 2.6% (<i>p</i> < 0.001); Sign In from 85.0 ± 11.4% to 97.0 ± 3.5% (<i>p</i> = 0.002); Time Out from 79.0 ± 14.6% to 96.4 ± 6.5% (<i>p</i> < 0.001); Sign Out from 70.2 ± 11.2% to 87.7 ± 11.0% (<i>p</i> = 0.003); and Staff Info from 70.7 ± 12.9% to 100.0 ± 0.0% (<i>p</i> < 0.001). Post hoc testing confirmed significant gains versus baseline for all three interventions (Dunnett's test), with a further significant improvement between the first and third interventions (Tukey's HSD, <i>p</i> = 0.011). <b>Conclusions:</b> Structured, low-cost interventions emphasizing administrative support, education, and communication significantly improved SSC adherence across a large tertiary hospital. This initiative represents a pioneering effort in Croatia and offers a scalable model for similar public healthcare systems aiming to enhance patient safety.