Warning: Tourniquets Risk Frostbite in Cold Weather.

We sought to better understand the frostbite risk during first-aid tourniquet use by reviewing information relevant to an association between tourniquet use and frostbite. However, there is little information concerning this subject, which may be of increasing importance because future conflicts against near-peer competitors may involve extreme cold weather environments. Historically, clinical frostbite cases with tourniquet use occurred in low frequency but in high severity when leading to limb amputation. The physiologic response of vasoconstriction to cold exposure leads to limb cooling and causes a reduction of limb blood flow, but cold-induced vasodilation ensues as periodic fluctuations that increase blood flow to hands and feet. In animal experiments, tourniquet use increased the development of frostbite. Evidence from human experiments also supports an association between tourniquet use and frostbite. Clinical guidance for caregiving to casualties at risk for frostbite with tourniquet use had previously been provided but slowly and progressively dropped out of documents. Conclusions: The cause of frostbite was deduced to be a sufficiently negative heat-transfer trend in local tissues, which tourniquet use may worsen because of decreasing tissue perfusion. An association between tourniquet use and frostbite exists but not as cause and effect. Tourniquet use increased the risk of the cold causing frostbite by allowing faster cooling of a limb because of reduced blood flow and lack of cold-induced vasodilation. Care providers above the level of the lay public are warned that first-aid tourniquet use in low-temperature (<0°C [<32°F]) environmental conditions risks frostbite.

Good outcomes after pediatric intraperitoneal kidney transplant.

BACKGROUND: Kidney transplantation in small children is technically challenging. Consideration of whether to use intraperitoneal versus extraperitoneal placement of the graft depends on patient size, clinical history, anatomy, and surgical preference. We report a large single-center experience of intraperitoneal kidney transplantation and their outcomes. METHODS: We conducted a retrospective review of pediatric patients who underwent kidney transplantation from April 2011 to March 2018 at a single large volume center. We identified those with intraperitoneal placement and assessed their outcomes, including graft and patient survival, rejection episodes, and surgical or non-surgical complications. RESULTS: Forty-six of 168 pediatric kidney transplants (27%) were placed intraperitoneally in children mean age 5.5 ± 2.3 years (range 1.6-10 years) with median body weight 18.2 ± 5 kg (range 11.4-28.6 kg) during the study period. Two patients (4%) had vascular complications; 10 (22%) had urologic complications requiring intervention; all retained graft function. Thirteen patients (28%) had prolonged post-operative ileus. Eight (17%) patients had rejection episodes ≤6 months post-transplant. Only one case resulted in graft loss and was associated with recurrent focal segmental glomerular sclerosis (FSGS). Two patients (4%) had chronic rejection and subsequent graft loss by 5-year follow-up. At 7-year follow-up, graft survival was 93% and patient survival was 98%. CONCLUSIONS: The intraperitoneal approach offers access to the great vessels, which allows greater inflow and outflow and more abdominal capacity for an adult donor kidney, which is beneficial in very small patients. Risk of graft failure and surgical complications were not increased when compared to other published data on pediatric kidney transplants.

Crew-Friendly Countermeasures Against Musculoskeletal Injuries in Aviation and Spaceflight.

Aviation and space medicine face many common musculoskeletal challenges that manifest in crew of rotary-wing aircraft (RWA), high-performance jet aircraft (HPJA), and spacecraft. Furthermore, many astronauts are former pilots of RWA or HPJA. Flight crew are exposed to recurrent musculoskeletal risk relating to the extreme environments in which they operate, including high-gravitational force equivalents (g-forces), altered gravitational vectors, vibratory loading, and interaction with equipment. Several countermeasures have been implemented or are currently under development to reduce the magnitude and frequency of these injuries. Cervical and lumbar spine, as well as extremity injuries, are common to aviators and astronauts, and occur in training and operational environments. Stress on the spinal column secondary to gravitational loading and unloading, ± vibration are implicated in the development of pain syndromes and intervertebral disk pathology. While necessary for operation in extreme environments, crew-support equipment can contribute to musculoskeletal strain or trauma. Crew-focused injury prevention measures such as stretching, exercise, and conditioning programs have demonstrated the potential to prevent pre-flight, in-flight, and post-flight injuries. Equipment countermeasures, especially those addressing helmet mass and center of gravity and spacesuit ergonomics, are also key in injury prevention. Furthermore, behavioral and training interventions are required to ensure that crew are prepared to safely operate when faced with these exposures. The common operational exposures and risk factors between RWA and HPJA pilots and astronauts lend themselves to collaborative studies to develop and improve countermeasures. Countermeasures require time and resources, and careful consideration is warranted to ensure that crew have access to equipment and expertise necessary to implement them. Further investigation is required to demonstrate long-term success of these interventions and inform flight surgeon decision-making about individualized treatment. Lessons learned from each population must be applied to the others to mitigate adverse effects on crew health and well-being and mission readiness.

Tibial Interference Screw Positioning Relative to the Bone Plug in ACL Reconstruction: A Biomechanical Comparison of Cortical Versus Cancellous-Sided Placement.

The biomechanical strength of a bone-patellar tendon-bone graft in the tibia may vary depending on whether the interference screw abuts the cancellous vs the cortical surface of the bone plug. In a porcine model, 10×20-mm bone-patellar tendon-bone grafts were prepared and fixed in a 10-mm diameter tibial tunnel using a 9×25-mm titanium interference screw. The screw was positioned on the cancellous surface of the graft in group A (n=13) vs the cortical side of the graft in group B (n=14). Specimens underwent precycling, cyclic loading, and load-to-failure testing. The mean ultimate failure load was 493±245 N for group A vs 304±145 N for group B (P=.008). Sixty-nine percent of specimens in group A survived 1000 cycles of load testing compared with 21% of specimens in group B. Forty-three percent of specimens in group B sustained intratendinous failure adjacent to the bone plug compared with 15% of specimens in group A. Orientation of the tibial interference screw along the cancellous vs the cortical side of the graft results in superior cyclic loading and ultimate failure load characteristics. Additionally, screw placement along the cortical side may weaken the tendon interface and lead to tendon failure under load. This study indicates that placement of the tibial interference screw along the cancellous side of the graft is biomechanically favorable. However, the clinical ramifications of these findings are not clear. [Orthopedics. 2018; 41(6):337-342.].

Cat on a Hot Tin Roof: Mechanical Testing of Models of Tourniquets After Environmental Exposure.

BACKGROUND: The purpose of the present study was to mechanically assess models of emergency tourniquet after 18 months of environmental exposure to weather to better understand risk of component damage. MATERIALS AND METHODS: An experiment was designed to test tourniquet performance on a manikin thigh. Three tourniquet models were assessed: Special Operations Forces Tactical Tourniquet Wide, Ratcheting Medical Tourniquet, and Combat Application Tourniquet. Unexposed tourniquets formed a control group stored in a laboratory; exposed tourniquets were placed outdoors on a metal roof for 18 months in San Antonio, Texas. Two users, a military cadet and a scientist, made 300 assessments in total. Assessment included major damage (yes-no), effectiveness (hemorrhage control, yes-no), casualty survival (alive-dead), time to stop bleeding, pressure, and blood loss. Time, pressure, and blood loss were reported in tests with effectiveness. RESULTS: Exposed devices had worse results than unexposed devices for major damage (3% [4/150] versus 0% [0/150]; ρ = .018), effectiveness (89% versus 99%; ρ = .002), and survival of casualties (89% versus 100%; ρ < .001). In tests for effectiveness, exposed devices had worse results than unexposed devices for time to stop bleeding (29 seconds versus 26 seconds; ρ = .01) and pressure (200mmHg versus 204mmHg; ρ = .03, respectively), but blood loss volume did not differ significantly. CONCLUSION: Compared with unexposed control devices, environmentally exposed tourniquets had worse results in tests of component damage, effectiveness, and casualty survival.

Evaluation of Virulence Gene Expression Patterns in Acinetobacter baumannii Using Quantitative Real-Time Polymerase Chain Reaction Array.

According to the Centers for Disease Control's recently devised National Strategy for Combating Antibiotic-Resistant Bacteria, Acinetobacter baumannii is a "serious" threat level pathogen. A. baumannii's notoriety stems from the fact that a large number of modern strains are multidrug resistant and persist in the hospital setting, thus causing numerous deaths per year. It is imperative that research focus on a more fundamental understanding of the factors responsible for the success of A. baumannii. Toward this end, our group investigated virulence gene expression patterns in a recently characterized wound isolate, AB5075, using quantitative real-time polymerase chain reaction array. Notably, several genes showed statistically significant upregulation at 37°C compared to 25°C; MviM, Wbbj, CarO, and certain genes of the Bas, Bar, and Csu operons. Additionally, we found that in vitro biofilm formation by Csu transposon insertion mutant strains is attenuated. These findings validate previous reports that suggest a link between the Csu operon and biofilm formation. More importantly, our results demonstrate a successful method for evaluating the significance of previously identified virulence factors in a modern and clinically relevant strain of A. baumannii, thereby providing a path toward a more fundamental understanding of the pathogenicity of A. baumannii.

Substrate concentration influences effective radial diffusion coefficient in canine cortical bone.

Transport of nutrients and waste across osseous tissue is dependent on the dynamic micro and macrostructure of the tissue; however little quantitative data exists examining how this transport occurs across the entire tissue. Here we investigate in vitro radial diffusion across a section of canine tissue, at dimensions of several hundred microns to millimeters, specifically between several osteons connected through a porous microstructure of Volkmann's canals and canaliculi. The effective diffusion coefficient is measured by a "sample immersion" technique presented here, in which the tissue sample was immersed in solution for 18-30 h, image analysis software was used to quantify the solute concentration profile in the tissue, and the data were fit to a mathematical model of diffusion in the tissue. Measurements of the effective diffusivity of sodium fluorescein using this technique were confirmed using a standard two-chamber diffusion system. As the solute concentration increased, the effective diffusivity decreased, ranging from 1.6 × 10(-7) ± 3.2 × 10(-8) cm(2)/s at 0.3 µM to 1.4 × 10(-8) ± 1.9 × 10(-9) cm(2)/s at 300 µM. The results show that there is no significant difference in mean diffusivity obtained using the two measurement techniques on the same sample, 3.3 × 10(-8) ± 3.3 × 10(-9) cm(2)/s (sample immersion), compared to 4.4 × 10(-8) ± 1.1 × 10(-8) cm(2)/s (diffusion chamber).