Metalloproteinase Expression is Associated with Traumatic Wound Failure

Advanced technologies in trauma critical care management

Care of critically injured patients has evolved over the 50 years since Shoemaker established one of the first trauma units at Cook County Hospital in 1962. Modern trauma intensive care units offer a high nurse-to-patient ratio, physicians and midlevel providers who manage the patients, and technologically advanced monitors and therapeutic devices designed to optimize the care of patients. This article describes advances that have transformed trauma critical care, including bedside ultrasonography, novel patient monitoring techniques, extracorporeal support, and negative pressure dressings. It also discusses how to evaluate the safety and efficacy of future advances in trauma critical care.

Guidelines for the prevention of infections associated with combat-related injuries: 2011 update: endorsed by the Infectious Diseases Society of America and the Surgical Infection Society

Despite advances in resuscitation and surgical management of combat wounds, infection remains a concerning and potentially preventable complication of combat-related injuries. Interventions currently used to prevent these infections have not been either clearly defined or subjected to rigorous clinical trials. Current infection prevention measures and wound management practices are derived from retrospective review of wartime experiences, from civilian trauma data, and from in vitro and animal data. This update to the guidelines published in 2008 incorporates evidence that has become available since 2007. These guidelines focus on care provided within hours to days of injury, chiefly within the combat zone, to those combat-injured patients with open wounds or burns. New in this update are a consolidation of antimicrobial agent recommendations to a backbone of high-dose cefazolin with or without metronidazole for most postinjury indications, and recommendations for redosing of antimicrobial agents, for use of negative pressure wound therapy, and for oxygen supplementation in flight.

Prevention of infections associated with combat-related extremity injuries

During combat operations, extremities continue to be the most common sites of injury with associated high rates of infectious complications. Overall, ∼ 15% of patients with extremity injuries develop osteomyelitis, and ∼ 17% of those infections relapse or recur. The bacteria infecting these wounds have included multidrug-resistant bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, extended-spectrum β-lactamase-producing Klebsiella species and Escherichia coli, and methicillin-resistant Staphylococcus aureus. The goals of extremity injury care are to prevent infection, promote fracture healing, and restore function. In this review, we use a systematic assessment of military and civilian extremity trauma data to provide evidence-based recommendations for the varying management strategies to care for combat-related extremity injuries to decrease infection rates. We emphasize postinjury antimicrobial therapy, debridement and irrigation, and surgical wound management including addressing ongoing areas of controversy and needed research. In addition, we address adjuvants that are increasingly being examined, including local antimicrobial therapy, flap closure, oxygen therapy, negative pressure wound therapy, and wound effluent characterization. This evidence-based medicine review was produced to support the Guidelines for the Prevention of Infections Associated With Combat-Related Injuries: 2011 Update contained in this supplement of Journal of Trauma.

The effect of bacterial infection on the biomechanical properties of biological mesh in a rat model

BACKGROUND

The use of biologic mesh to repair abdominal wall defects in contaminated surgical fields is becoming the standard of practice. However, failure rates and infections of these materials persist clinically. The purpose of this study was to determine the mechanical properties of biologic mesh in response to a bacterial encounter.

METHODS

A rat model of Staphylococcus aureus colonization and infection of subcutaneously implanted biologic mesh was used. Samples of biologic meshes (acellular human dermis (ADM) and porcine small intestine submucosa (SIS)) were inoculated with various concentrations of methicillin-resistant Staphylococcus aureus [10(5), 10(9) colony-forming units] or saline (control) prior to wound closure (n = 6 per group). After 10 or 20 days, meshes were explanted, and cultured for bacteria. Histological changes and bacterial recovery together with biomechanical properties were assessed. Data were compared using a 1-way ANOVA or a Mann-Whitney test, with p<0.05.

RESULTS

The overall rate of staphylococcal mesh colonization was 81% and was comparable in the ADM and SIS groups. Initially (day 0) both biologic meshes had similar biomechanical properties. However after implantation, the SIS control material was significantly weaker than ADM at 20 days (p = 0.03), but their corresponding modulus of elasticity were similar at this time point (p>0.05). After inoculation with MRSA, a time, dose and material dependent decrease in the ultimate tensile strength and modulus of elasticity of SIS and ADM were noted compared to control values.

CONCLUSION

The biomechanical properties of biologic mesh significantly decline after colonization with MRSA. Surgeons selecting a repair material should be aware of its biomechanical fate relative to other biologic materials when placed in a contaminated environment.

Decreased mechanical properties of heart valve tissue constructs cultured in platelet lysate as compared to fetal bovine serum

In autologous heart valve tissue engineering, there is an ongoing search for alternatives of fetal bovine serum (FBS). Human platelet-lysate (PL) might be a promising substitute. In the present article, we aimed to examine the tissue formation, functionality, and mechanical properties of engineered three-dimensional tissue constructs cultured in PL as a substitute for FBS. Our results show that tissue constructs that were cultured in PL and FBS produce similar amounts of collagen, glycosoaminoglycans, and collagen crosslinks, and that the cellular phenotype remains unchanged. Nevertheless, mechanical testing showed that the ultimate tensile strength in PL constructs was on average approximately three times lower as compared to FBS (0.25 vs. 0.74 MPa, respectively, p<0.01), and also the elastic modulus was almost three times lower (1.33 MPa of PL constructs vs. 3.94 MPa of FBS constructs, p<0.01). Additional tests indicated that this difference might be explained by different collagen fiber architecture possibly due to increased production of matrix-degrading proteases by cells cultured in PL. In summary, our results indicate that PL is not preferred for the culture of strong heart valve tissue constructs.

Biomarkers to predict wound healing: the future of complex war wound management

BACKGROUND

Currently, no biological assay exists to objectively assess wounds to aid in timing of wound closure and guide therapy. In this article, the authors review military investigations in biomarkers as a method of objectively determining acute traumatic wound physiology and their applicability in predicting healing of complex soft-tissue wounds.

METHODS

The civilian literature related to biomarkers and wound physiology related to chronic and acute wounds was reviewed as a basis for current research into acute traumatic soft-tissue wounds.

RESULTS

Analysis of serum and wound effluent from traumatic extremity soft-tissue combat wounds revealed changes in specific proinflammatory matrix metalloproteinases associated with impaired wound healing. Forsberg et al. analyzed serum and wound effluent for chemokines and cytokines. An increase in serum procalcitonin levels correlated with wound dehiscence. Lastly, serum, wound effluent, and wound bed tissue biopsy specimens were analyzed by Hawksworth et al. Consistent with previous studies, elevation in proinflammatory cytokines was associated with wound dehiscence.

CONCLUSIONS

Changes in levels of proteases, protease inhibitors, and inflammatory markers have been correlated with wound healing. These findings further support the idea that inflammatory dysregulation and a persistent inflammatory state leads to failure of wound healing in the acute setting. These findings highlight potential targets for the development of a biological assay to individualize management of complex soft-tissue wounds, based on patient physiology and response, that would be applicable to not only military trauma but also civilian trauma. Ultimately, this would result in earlier wound closure, reduction in the number of operating room trips, and reduced health care costs.

Biomarker use in tailored combat casualty care

Modern war wounds are complex and primarily involve extremities. They require multiple operative interventions to achieve wound closure and begin rehabilitation. Current assessment of the suitability of surgical wound closure is based upon subjective methods coupled with a semiquantitative determination of the wound bacterial burden. Measurement of the systemic and local response to injury using inflammatory biomarkers may allow for accelerated wound closure and treatment of other combat-related morbidity. This article presents the introduction of personalized medicine into combat casualty care.