Causes of Death in Military Working Dogs During Operation Iraqi Freedom and Operation Enduring Freedom, 2001-2013.

BACKGROUND: Military working dogs (MWDs) are a major asset in the theater of operations. Their unique abilities make them ideal for tasks such as tracking, patrol, and scent detection. MWDs deployed to a war zone are exposed to harsh environments and battlefield dangers that increase their risk of disease, injuries, and death. Although canines have been used extensively in Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF), no published studies have reported detailed causes of death among MWDs deployed to these conflicts. MATERIALS AND METHODS: Potential cases were defined as U.S. military-owned MWDs that died while deployed in Iraq (OIF) or Afghanistan (OEF) from January 1, 2001 through December 31, 2013 and identified from both official sources and unofficial sources, that is, online searches. Cases included in this study were limited to MWDs with data on cause of death obtained by abstraction from official veterinary treatment records (VTRs) from the Department of Defense Military Working Dog Veterinary Service, Joint Base San Antonio-Lackland Air Force Base, San Antonio, Texas, and Special Operations Forces units. RESULTS: We identified 92 MWDs that died while deployed to OEF/OIF from 2001 through 2013 and had cause of death information from official VTRs. For both OEF and OIF, the most common training program was Multi-Purpose Canine (36.5% and 51.7%, respectively), followed by Improvised Explosive Detector Dog for OEF (34.9%) and Patrol Explosive Detector Dog for OIF (34.5%). Injuries were the primary cause of death for 77.2% of the MWDs for which we had cause of death data. The most frequent external injuries were gunshot wounds (GSW) (31.5%), explosion or blast (26.1%), and heat stress (9.8%). The proportion of deaths due to GSW was similar for OEF and OIF (30.2% vs. and 34.5%, respectively). However, a greater proportion of MWDs died from explosions during OEF than during OIF (30.2% vs. 17.2%, respectively). Diseases were the cause of death in 23.0% of the MWDs. The most common diseases were gastric dilation and volvulus (GDV, n = 3), pleuritis (n = 2), and sepsis (n = 3). Two deaths were associated with anesthesia-related medical procedures. A total of 8.7% of cases were missing cause of death, 8.7% were missing age, 32.6% of cases were missing data on necropsy, and 14.1% were missing data on final disposition of the body. Other variables of interest including number of deployments and duration of training had a very high proportion of missing values and thus could not be analyzed. CONCLUSIONS: Our study is the most comprehensive to date that reports causes of death of MWDs deployed to OIF and OEF. However, limitations in the available data lessen the potential of our results to inform improvements in training and point of injury medical care. Better documentation in VTRs and systematic data collection into an official MWD trauma registry could lead to improved training and facilitate further development and evaluation of guidelines to improve care of wounded MWDs in future conflicts.

Sealing of Corneal Lacerations Using Photoactivated Rose Bengal Dye and Amniotic Membrane.

PURPOSE: Watertight closure of perforating corneoscleral lacerations is necessary to prevent epithelial ingrowth, infection, and potential loss of the eye. Complex lacerations can be difficult to treat, and repair with sutures alone is often inadequate. In this study, we evaluated a potentially sutureless technology for sealing complex corneal and scleral lacerations that bonds the amniotic membrane (AM) to the wound using only green light and rose bengal dye. METHODS: The AM was impregnated with rose bengal and then sealed over lacerations using green light to bond the AM to the deepithelialized corneal surface. This process was compared with suture repair of 3 laceration configurations in New Zealand White rabbits in 3 arms of the study. A fourth study arm assessed the side effect profile including viability of cells in the iris, damage to the blood-retinal barrier, retinal photoreceptors, retinal pigment epithelium, and choriocapillaris in Dutch Belted rabbits. RESULTS: Analyses of the first 3 arms revealed a clinically insignificant increase in polymorphonuclear inflammation. In the fourth arm, iris cells appeared unaffected and no evidence of breakdown of the blood-retinal barrier was detected. The retina from green light laser-treated eyes showed normal retinal pigment epithelium, intact outer segments, and normal outer nuclear layer thickness. CONCLUSIONS: The results of these studies established that a light-activated method to cross-link AM to the cornea can be used for sealing complex penetrating wounds in the cornea and sclera with minimal inflammation or secondary effects.

Vaccination with a live attenuated Acinetobacter baumannii deficient in thioredoxin provides protection against systemic Acinetobacter infection.

Multi-drug resistant Acinetobacter baumannii (MDR-Ab), an opportunistic pathogen associated with nosocomial and combat related infections, has a high mortality due to its virulence and limited treatment options. Deletion of the thioredoxin gene (TrxA) from a clinical isolate of MDR-Ab resulted in a 100-fold increase in 50% lethal dose (LD50) in a systemic challenge murine model. Thus, we investigated the potential use of this attenuated strain as a live vaccine against MDR-Ab. Mice were vaccinated by subcutaneous (s.c.) injection of 2×105 CFU of the ΔtrxA mutant, boosted 14days later with an equivalent inoculum, and then challenged 30days post-vaccination by i.p. injection with 10 LD50 of the wild type (WT) Ci79 strain. Efficacy of vaccination was evaluated by monitoring MDR-Ab specific antibody titers and cytokine production, observing pathology and organ burdens after WT challenge, and measuring levels of serum pentraxin-3, a molecular correlate of A. baumannii infection severity, before and after challenge. Mice vaccinated with ΔtrxA were fully protected against the lethal challenge of WT. However, minimal immunoglobulin class switching was observed with IgM predominating. Spleens harvested from vaccinated mice exhibited negligible levels of IL-4, IFN-γ and IL-17 production when stimulated with UV-inactivated WT Ci79. Importantly, tissues obtained from vaccinated mice displayed reduced pathology and organ burden compared to challenged non-vaccinated mice. Additionally, serum pentraxin-3 concentrations were not increased 24h after challenge in vaccinated mice, correlating with reduction of WT MDR-Ab infection in ΔtrxA immunized mice. Furthermore, passive immunization with ΔtrxA-immune sera provided protection against lethal systemic Ci79 challenge. Collectively, the defined live attenuated ΔtrxA strain is a vaccine candidate against emerging MDR Acinetobacter infection.

Does small-volume resuscitation with crystalloids or colloids influence hemostasis and survival of rabbits subjected to lethal uncontrolled hemorrhage?

BACKGROUND: Prehospital, small-volume resuscitation of combat casualties with a synthetic colloid (6% hydroxyethyl starch [HES] 670/0.75) has been recommended when blood or blood components are unavailable. We studied hemostatic effects of a newer synthetic colloid (6% HES, 130/0.4) compared with either a natural colloid (albumin) or to crystalloids in an uncontrolled hemorrhage model. METHODS: Spontaneously breathing New Zealand white rabbits (3.4 ± 0.1 kg) were anesthetized, instrumented, and subjected to a splenic injury with uncontrolled bleeding. Fifteen minutes after injury, rabbits were in shock (mean arterial pressure [MAP] = 26 ± 1.3 mm Hg, and received colloids (6% HES, 130/0.4 or 5% albumin at 15 mL/kg), or crystalloids (normal saline at 30 mL/kg or 5% hypertonic saline at 7.5 mL/kg) for resuscitation in two intravenous bolus injections (15 minutes apart) to raise their MAP to 65 mm Hg, n = 9/group. Animals were monitored for 2.5 hours or until death, and blood losses were measured. Blood samples were analyzed for arterial blood gas, complete blood count, and coagulation measures. RESULTS: There were no differences among groups in baseline measures and initial hemorrhage volume (11.9 ± 0.6 mL/kg) at 15 minutes postinjury. Twenty minutes after fluid resuscitation (1 hour postinjury), MAP was higher, shock indices were lower, and blood pH was higher in colloids versus. crystalloids groups (p < 0.05). Administration of 6% HES 130/0.4 colloid produced the largest hemodilution (54% decrease in hematocrit, p < 0.05 vs. hypertonic saline). Activated partial thromboplastin time increased approximately 35% above baseline in all groups except in 6% HES 130/0.4 group in which it doubled. Clot strength was reduced (15%) only in the 6% HES 130/0.4 group. 6% HES 130/0.4 resuscitation produced the largest blood loss and 33% survival rate that was not different than the crystalloid groups. Albumin produced the best hemostatic and survival outcomes (78%). CONCLUSION: Small-volume resuscitation with crystalloids appeared inadequate to treat hypovolemic shock and prevent death. 6% HES 130/0.4 was effective hemodynamically but detrimental to hemostasis. Albumin produced the best outcomes consistent with our previous observations. Further studies are needed to prove benefit of albumin solution as a possible resuscitation fluid for treating combat casualties at the point of injury.

Physiological Consequences of Abdominal Aortic and Junctional Tourniquet (AAJT) Application to Control Hemorrhage in a Swine Model.

INTRODUCTION: Specialized tourniquets such as Abdominal Aortic and Junctional Tourniquet (AAJT) have been deployed for control of junctional hemorrhage with limited information concerning their efficacy and safety. We examined physiological effects of a 2-h abdominal application of AAJT to control groin hemorrhage in a swine model. METHODS: Anesthetized pigs were subjected to 25% controlled hemorrhage and a groin arterial injury. Resulting hemorrhage from the groin wound was controlled for 2 h by applying AAJT on each pig's abdomen. After AAJT removal, the artery was repaired and blood flow was fully restored for 1 h. CT angiography and blood analyses were done and tissues collected for histology. Experiments were conducted in three groups of pigs (n = 6/group): mechanically ventilated (MV); spontaneously breathing (SB); and spontaneously breathing during AAJT application but transitioned to mechanical ventilation (SB-MV) before AAJT release. RESULTS: AAJT application produced sharp increases in blood pressure and heart rate. SB animals experienced labored and rapid respiration, but their PaO2 and PaCO2 were unaffected. Their respiration suddenly stopped when the AAJT was released requiring manual respiratory assistance. However, three pigs in SB group eventually died from cardiac and respiratory arrests, which coincided with hyperkalemia and metabolic acidosis that occurred after reflow. These changes were less severe in other groups. Other measures including increased hematocrit, tissue injury biomarkers, and kidney function indicators were similar in all groups. Histological changes were mild and reversible. CONCLUSION: The ischemia-induced hyperkalemia and metabolic acidosis associated with AAJT application are life-threatening in spontaneously breathing subjects. Cardiopulmonary resuscitation appears necessary when AAJT is released to prevent life-threatening consequences.

Influences of limited resuscitation with plasma or plasma protein solutions on hemostasis and survival of rabbits with noncompressible hemorrhage.

BACKGROUND: Plasma infusion with or without red blood cells is the current military standard of care for prehospital resuscitation of combat casualties. We examined possible advantages of early and limited resuscitation with fresh plasma compared with a single plasma protein or crystalloid solutions in an uncontrolled hemorrhage model in rabbits. METHODS: Anesthetized spontaneously breathing rabbits (3.3 ± 0.1 kg) were instrumented and subjected to a splenic uncontrolled hemorrhage. Rabbits in shock were resuscitated at 15 minutes with Plasma-Lyte (PAL; 30 mL/kg), PAL + fibrinogen (PAL + F; 30 mL + 100 mg/kg), fresh rabbit plasma (15 mL/kg), or 25% albumin (ALB; 5 mL/kg) solution, all given in two bolus intravenous injections (15 minutes apart) to achieve a mean arterial pressure of 65 mm Hg, n = 8 to 9/group. Animals were monitored for 2 hours or until death, and blood loss was measured. Blood samples and tissues were collected and analyzed. RESULTS: There were no differences among groups in baseline measures and their initial bleeding volume at 15 minutes. At 60 minutes after injury, mean arterial pressure was higher with ALB than with crystalloids (PAL or PAL + F), but shock indices were not different despite the large differences in resuscitation volumes. Fibrinogen addition to PAL only increased clot strength. Plasma resuscitation increased survival rate (75%) without significant improvement in coagulation measures. Albumin administration replenished total plasma protein and increased survival rate to 100% (p < .05 vs. crystalloids). No histological adverse events were identified in the vital organs. CONCLUSIONS: Fibrinogen administration added to a compatible crystalloid did not improve hemostatic outcomes. Plasma resuscitation increased survival rate; however, its effects did not differ from those obtained with 25% ALB at one-third of the volume. The ALB advantage was consistent with our previous findings in which 5% ALB was used at a volume equal to plasma. The benefit of plasma for resuscitation may be mostly due to its ALB content rather than its coagulation proteins.