257 - Does Bullet Caliber Matter with Clinical Outcomes? A Pilot Study of Nonfatal Pediatric Firearm Injuries

Publication Number: 2247.257

Tyler Lennon, Medical College of Wisconsin, Milwaukee, WI, United States; Shane Huang, Medical College of Wisconsin, Milwaukee, WI, United States; Constance Kostelac, Medical College of Wisconsin, Milwaukee, WI, United States; Samantha P. Leonard, Medical College of Wisconsin, Milwaukee, WI, United States; Kellie C. Snooks, Medical College of Wisconsin, Milwaukee, WI, United States; Katherine FlynnO’Brien, Medical College of Wisconsin, Milwaukee, WI, United States; David J. Milia, Medical College of Wisconsin, Whitefish Bay, WI, United States; Stephen W. Hargarten, Medical College of Wisconsin - Milwaukee, WI, Shorewood, WI, United States

Background: Firearms remain a major cause of injury in the United States, and the leading cause of death for children ages 1-19 years old. However, little is known about the morbidity associated with bullet caliber, which has the potential to influence clinical outcomes and public health policy.

Objective: To examine the association between bullet caliber and clinical outcomes among children with nonfatal firearm injuries.

Design/Methods: We conducted a cross-sectional analysis of single-caliber nonfatal firearm injuries among children ages 0-17 years from January 1, 2016, to December 31, 2024. Police records from the Milwaukee Police Department were matched to trauma registry data from the city's only pediatric Level 1 trauma center using name, age, and incident date. Bullet caliber was categorized as high (10mm, .40, .44, .357, .45), medium (9mm), or low (.22, .25, .32, .38, .380, 5.7). Descriptive statistics were used to present survivor demographics, injury characteristics, and clinical outcomes. Proportions of incidents by caliber were compared over time. Fisher's exact and Kruskal-Wallis rank sum tests were used, p < 0.05 was significant. IRB approval and police data consent were obtained.

Results: We successfully linked 211 nonfatal cases (41.1% link rate) from the police to trauma data; 19.4% (n=41) of cases involved a high caliber bullet, 73.5% (n=155) medium caliber, and 7.1% (n=15) low caliber. Cases involving medium caliber increased over time (Fig 1). In the linked sample, median age was 15 years, 77.7% were male, and 88.2% were Black. Children with high caliber injuries were more likely to require the operating room (50% high vs. 24% medium vs. 38% low, p = 0.006), surgery for hemorrhage control (17.1% high vs. 8.4% medium vs. 6.7% low, p = 0.031), and greater volumes of plasma (788 mL high vs. 306 mL medium vs. 0 mL low, p=0.026) and platelets (395 mL high vs. 0 mL medium vs. 0 mL low, p=0.004) within 24 hours. There were no differences in new injury severity score (NISS), intensive care unit days, total hospital length of stay, complications, or other blood products used.

Conclusion(s): Police and trauma registry data can be linked to better understand the association between bullet caliber and clinical outcomes. Among pediatric patients with nonfatal firearm injuries, a higher caliber bullet was associated with greater operative intervention and increased blood product use within the first 24 hours. Future work will expand the analysis to include additional injury characteristics and multiple cities.

Figure 1. Trends in Nonfatal Pediatric Firearm Injuries by Bullet Caliber, 2016-2024