Clean Shot: Bacterial Contamination After Positive Pressure Irrigation of Low-Velocity Gunshot Wounds.

OBJECTIVE: Low-velocity gunshot wounds (LV-GSWs) are a common reason for emergency department visits. Optimal nonsurgical treatment has not been thoroughly studied and is not standardized. The goal of this study was to determine whether positive pressure irrigation reduces the bacterial contamination after a simulated GSW to soft tissue. METHODS: Nineteen lamb shank specimens were prepared with denim inoculated with Serratia marcescens cultures. A 9-mm pistol round was fired from a distance of 3 m through the contaminated denim into the lamb shank. A culture swab was placed in the wound directly after firing, after 250 cubic-centimeters (cc) irrigation with normal saline, and after an additional 250 cc irrigation (for a total of 500 cc). Swabs were then cultured to determine the amount of bacterial growth. RESULTS: Before irrigation, 0 (0%) plates showed no growth, 2 (10.5%) showed rare growth, 8 (42.1%) showed few growth, 6 (31.6%) showed moderate growth, and 3 (15.8%) showed many growth. After 500 cc irrigation, 2 (10.5%) showed no growth, 1 (5.3%) showed rare growth, 11 (57.9%) showed few growth, 2 (10.5%) showed moderate growth, and 3 (15.8%) showed many growth. Fisher exact test confirmed no significant change in bacterial concentration after irrigation ( P = 0.59). A Pearson test found no correlation between irrigation and bacterial growth (r = -0.15, P = -0.25). CONCLUSIONS: Positive pressure irrigation with up to 500 cc normal saline did not significantly alter the quantity of bacterial growth within a simulated GSW cavity. The data suggest that bedside positive pressure irrigation may not be beneficial in the initial emergency department treatment of LV-GSWs.

Detection of traumatic elbow arthrotomies: computed tomography scan vs. saline load test.

BACKGROUND: Traumatic elbow arthrotomies are common injuries evaluated for by orthopedic services; however, failed identification of a traumatic arthrotomy leads to a high risk of developing septic arthritis. Currently these injuries are evaluated by either a saline load test or a computed tomography (CT) scan, yet there is little published evidence regarding detection of traumatic elbow arthrotomies. HYPOTHESIS: In our study, we hypothesized better sensitivity and specificity of detecting a traumatic elbow arthrotomy with a CT scan over a saline load test. STUDY DESIGN: Descriptive cadaveric laboratory study. METHODS: Ten fresh-frozen cadaveric transhumeral upper extremity amputation specimens were thawed for trial. Specimens were brought through CT scan prior to arthrotomy, arthrotomy was made, and then post arthrotomy a repeat CT scan was performed. A saline load test was then performed after all CT scans were completed. RESULTS: Zero CT scans before (0/10) and after (0/10) the arthrotomies were positive for intra-articular air in the elbow joint with a 0% sensitivity and specificity. The saline load test had an average positive test at 19 mL with a 100% sensitivity and 100% specificity. CONCLUSION: After our study and based on the recommendations of the brief literature on this topic, we advise evaluating for traumatic elbow arthrotomies with a saline load test as the primary method of detection.

Thermal Energy Produced by Medium Velocity Pistol Projectiles and the Effects on Peripheral Nerve Tissue.

CONTEXT: Sidearm pistols are more frequently involved in violent crimes due to their relatively small size and ability to be concealed. The extent to which the thermal energy released from such medium velocity pistol projectiles contributes to peripheral nerve injury requires further testing. The purpose of this paper is to describe a method to quantify how much thermal energy is released during impact of medium velocity pistol projectiles and report how thermal energy contributes to peripheral nerve injury. METHODS: Eleven seven-centimeter segments of radial, median, and ulnar nerves were dissected from a thawed fresh frozen cadaver. The nerve segments were placed in a 10% ballistics gel block, one centimeter from the end of the block nearest the shooter. A series of 115-grain 9 mm. NATO-classified ammunitions were fired through the nerve and ballistics gel construct with a pistol. The impacts were recorded with a high-speed infrared camera and nerve samples were sent for histologic analysis by two board-certified pathologists. RESULTS: The average velocity of the projectiles were 391m/s, 95% CI [387-395 m/s], with an average kinetic energy of 572.0 J, 95% CI [560.0-583.0J]. The average observable temperature of the ballistics gel/nerve prior to impact was 28.8°C±0.6ºC, 95% CI [26.4-30.3°C]. Average observable temperature of the surrounding ballistics gel/nerve during projectile impact was 55.1°C±2.4ºC, 95% CI [51.3- 62.1°C], yielding an average observable increase of 26.4°C±3.2ºC, 95% CI [20.2- 35.4°C]. An adjusted temperature increase was also surprisingly high 63.4°C ± 3.2, 95% CI [57.2 - 72.4ºC]. Histology reports of the impacted nerve tissue failed to show any sign of thermal or even crush injury. CONCLUSIONS: Medium velocity handgun projectiles release a significant amount of heat energy when impacting a substance similar to human tissue. The authors' temperature data points were greater than those previously reported to cause thermal injury to peripheral nerves. The authors' findings suggest that nerve injury after collision with pistol projectiles may be secondary to thermal injury in addition to the classic model of concussion and penetration given our documented levels of heat generated during impact.