Early Fasciotomy and Limb Salvage and Complications in Military Lower Extremity Vascular Injury.

BACKGROUND: Military guidelines endorse early fasciotomy after revascularization of lower extremity injuries to prevent compartment syndrome, but the real-world impact is unknown. We assessed the association between fasciotomy and amputation and limb complications among lower extremitys with vascular injury. METHODS: A retrospectively collected lower extremity injury database was queried for limbs undergoing attempted salvage with vascular procedure (2004-2012). Limbs were categorized as having undergone fasciotomy or not. Injury and treatment characteristics were collected, as were intervention timing data when available. The primary outcome measure was amputation. Multivariate models examined the impact of fasciotomy on limb outcomes. RESULTS: Inclusion criteria were met by 515 limbs, 335 (65%) with fasciotomy (median 7.7 h postinjury). Of 212 limbs, 174 (84%) with timing data had fasciotomy within 30 min of initial surgery. Compartment syndrome and suspicion of elevated pressure was documented in 127 limbs (25%; 122 had fasciotomy). Tourniquet and shunt use, fracture, multiple arterial and combined arteriovenous injuries, popliteal involvement, and graft reconstruction were more common in fasciotomy limbs. Isolated venous injury and vascular ligation were more common in nonfasciotomy limbs. Fasciotomy timing was not associated with amputation. Controlling for limb injury severity, fasciotomy was not associated with amputation but was associated with limb infection, motor dysfunction, and contracture. Sixty-three percent of fasciotomies were open for >7 d, and 43% had multiple closure procedures. Fasciotomy revision (17%) was not associated with increased amputation or complications. CONCLUSIONS: Fasciotomy after military lower extremity vascular injury is predominantly performed early, frequently without documented compartment pressure elevation. Early fasciotomy is generally performed in severely injured limbs with a subsequent high rate of limb complications.

Utility of the Mangled Extremity Severity Score in Predicting Amputation in Military Lower Extremity Arterial Injury.

BACKGROUND: Effective amputation prediction may help inform appropriate early limb salvage efforts in military lower extremity (LE) arterial injury. The Mangled Extremity Severity Score (MESS) is the most commonly applied system for early amputation prediction but its utility in military trauma is unknown. METHODS: Retrospective cohort study of Iraq and Afghanistan casualties with LE arterial injury who underwent a vascular limb salvage attempt. Retrospectively assessed MESS was statistically explored as an amputation predictor and MESS component surrogates (mechanism, vascular injury characteristics, tourniquet use, and transfusion volume) were used to characterize limb injuries by presenting characteristics and evaluated for amputation prediction. RESULTS: A total of 439 limbs were included with 99 (23%) amputations, 29 (7%) within 48 hr of injury. Median MESS was 5 (interquartile range 4-6) among salvaged limbs and 7 (5-9) among amputations (P < 0.0001). An MESS cutoff of ≥7 had a better receiver operating characteristic sensitivity/specificity profile (area under the curve 0.696 overall, 0.765 amputation within 48 hr) than MESS ≥8 (0.593, 0.621), but amputation rates were only 43% for MESS ≥7 and 50% for ≥8. MESS ≥7 was significantly associated with age, polytrauma, blast or crush mechanism, fracture, tourniquet use, distal (popliteal/tibial) and multiple arterial injuries, and massive transfusion. Amputation was significantly associated with polytrauma, blast or crush mechanism, fracture, and massive transfusion; however, 83 casualties had all 4 characteristics with an amputation rate of only 46%. CONCLUSIONS: In combat casualties with arterial injury, LE amputation after attempted vascular limb salvage is inadequately predicted by existing scoring systems or the presenting characteristics available in this registry. Limb loss is predominantly late and likely because of factors not projectable at initial presentation.

Outcomes of Arterial Grafts for the Reconstruction of Military Lower Extremity Arterial Injuries.

INTRODUCTION: Lower extremity (LE) arterial injuries are common in military casualties and limb salvage is a primary goal. Bypass grafts are the most common reconstructions; however, their specific outcomes are largely unreported. We sought to describe the outcomes of LE arterial grafts among combat casualties and their association with limb loss. METHODS: Retrospective cohort study of 2004-2012 Iraq/Afghanistan casualties with LE arterial injury undergoing bypass graft from a database containing follow-up until amputation, death, or military discharge. Primary outcome was composite graft complications (GC-thrombosis, stenosis, pseudoaneurysm, blowout, and/or arteriovenous fistula). RESULTS: Two hundred and twenty-two grafts were included (99 femoral, 73 popliteal, 48 tibial). 56 (26%) had at least one GC; thrombosis was most common in femoral, stenosis most common in popliteal and tibial. GC was not associated with graft level but was associated with synthetic conduit (P = 0.01) and trended towards an association with multiple-level arterial injuries (P = 0.07). Four of eight (50%) synthetic grafts had amputations, all within 72h. Two of the eight synthetic grafts thrombosed, and both limbs were amputated. There were 52 total amputations. Amputation was performed in 13 (23%) of limbs with a GC and 24% of those without (P = 0.93) Overall, 24 (11%) of grafts thrombosed, 16 within 48h and 13 (25%) in limbs undergoing amputation (P = 0.001 for association of thrombosis with amputation). CONCLUSION: GC are common among LE bypass grafts in combat casualties but are not associated with limb loss. Thrombosis is predominantly early and is associated with amputation. Closer attention to ensuring early patency may improve limb salvage.

Impact of Staged Vascular Management on Limb Outcomes in Wartime Femoropopliteal Arterial Injury.

BACKGROUND: By necessity, wartime arterial injuries undergo staged management. Initial procedures may occur at a forward surgical team (role 2), where temporary shunts can be placed before transfer to a larger field hospital (role 3) for definitive reconstruction. Our objective was to evaluate the impact of staging femoropopliteal injury care on limb outcomes. METHODS: A military vascular injury database was queried for Iraq/Afghanistan casualties with femoropopliteal arterial injuries undergoing attempted reconstruction (2004-2012). Cases were grouped by initial arterial management: shunt placed at role 2 (R2SHUNT), reconstruction at role 2 (R2RECON), and initial management at role 3 (R3MGT). The primary outcome was limb salvage; secondary outcomes were limb-specific complications. Descriptive and intergroup comparative statistics were performed with significance defined at P ≤ 0.05. RESULTS: Of 257 cases, all but 4 had definitive reconstruction before evacuation to Germany (median, 2 days): 46 R2SHUNT, 84 R2RECON, and 127 R3MGT; median Mangled Extremity Severity Score was 6 for all groups. R2SHUNT had median extremity Abbreviated Injury Scale--vascular of 4 (other groups, 3; P < 0.05) and was more likely to have concomitant venous injury and to undergo fasciotomy. Shunts were used for 5 ± 3 hr. About 24% of R2RECON repairs were revised at role 3. Limb salvage rate of 80% was similar between groups, and 62% of amputations performed within 48 hr of injury. Rates of limb and composite graft complications were similar between groups. Thrombosis was more common in R2SHUNT (22%) than R2RECONST (6%) or R3MGT (12%) (P = 0.03). Late (>48 hr) thrombosis rates were similar, whereas 60% of R2SHUNT thromboses occurred on day of injury (P = 0.003 vs. 25% and 0%). CONCLUSIONS: Staged femoropopliteal injury care is associated with similar limb salvage to initial role 3 management. Early thrombosis is likely because of shunt failure but does not lead to limb loss. Current military practice guidelines are appropriate and may inform civilian vascular injury management protocols.

Can Dynamic Contrast-Enhanced CT Quantify Perfusion in a Stimulated Muscle of Limited Size? A Rat Model.

BACKGROUND: Muscle injury may result in damage to the vasculature, rendering it unable to meet the metabolic demands of muscle regeneration and healing. Therefore, therapies frequently aim to maintain, restore, or improve blood supply to the injured muscle. Although there are several options to assess the vascular outcomes of these therapies, few are capable of spatially assessing perfusion in large volumes of tissue. QUESTIONS/PURPOSES: Can dynamic contrast-enhanced CT (DCE-CT) imaging acquired with a clinical CT scanner be used in a rat model to quantify perfusion in the anterior tibialis muscle at spatially relevant volumes, as assessed by (1) the blood flow rate and tissue blood volume in the muscle after three levels of muscle stimulation (low, medium, and maximum) relative to baseline as determined by the non-stimulated contralateral leg; and (2) how do these measurements compare with those obtained by the more standard approach of microsphere perfusion? METHODS: The right anterior tibialis muscles of adult male Sprague Dawley rats were randomized to low- (n = 10), medium- (n = 6), or maximum- (n = 3) level (duty cycles of 2.5%, 5.0%, and 20%, respectively) nerve electrode coupled muscle stimulation directly followed by DCE-CT imaging. Tissue blood flow and blood volume maps were created using commercial software and volumetrically measured using NIH software. Although differences in blood flow were detectable across the studied levels of muscle stimulation, a review of the evidence suggested the absolute blood flow quantified was underestimated. Therefore, at a later date, a separate set of adult male Sprague Dawley rats were randomized for microsphere perfusion (n = 7) to define blood flow in the animal model with an accepted standard. With this technique, intra-arterial particles sized to freely flow in blood but large enough to lodge in tissue capillaries were injected. Simultaneously, blood sampling at a fixed flow rate was simultaneously performed to provide a fixed blood flow rate sample. The tissues of interest were then explanted and assessed for the total number of particles per tissue volume. Tissue blood flow rate was then calculated based on the particle count ratio within the reference sample. Note that a tissue's blood volume cannot be calculated with this method. Comparison analysis to the non-stimulated baseline leg was performed using two-tailed paired student t-test. An ANOVA was used to compare difference between stimulation groups. RESULTS: DCE-CT measured (mean ± SD) increasing tissue blood flow differences in stimulated anterior tibialis muscle at 2.5% duty cycle (32 ± 5 cc/100 cc/min), 5.0% duty cycle (46 ± 13 cc/100 cc/min), and 20% duty cycle (73 ± 3 cc/100 cc/min) compared with the paired contralateral non-stimulated anterior tibialis muscle (10 ± 2 cc/100 cc/min, mean difference 21 cc/100 cc/min [95% CI 17.08 to 25.69]; 9 ± 1 cc/100 cc/min, mean difference 37 cc/100 cc/min [95% CI 23.06 to 50.11]; and 11 ± 2 cc/100 cc/min, mean difference 62 cc/100 cc/min [95% CI 53.67 to 70.03]; all p < 0.001). Similarly, DCE-CT showed increasing differences in tissue blood volumes within the stimulated anterior tibialis muscle at 2.5% duty cycle (23.2 ± 4.2 cc/100 cc), 5.0% duty cycle (39.2 ± 7.2 cc/100 cc), and 20% duty cycle (52.5 ± 13.1 cc/100 cc) compared with the paired contralateral non-stimulated anterior tibialis muscle (3.4 ± 0.7 cc/100 cc, mean difference 19.8 cc/100 cc [95% CI 16.46 to 23.20]; p < 0.001; 3.5 ± 0.4 cc/100 cc, mean difference 35.7 cc/100 cc [95% CI 28.44 to 43.00]; p < 0.001; and 4.2 ± 1.3 cc/100 cc, mean difference 48.3 cc/100 cc [95% CI 17.86 to 78.77]; p = 0.010). Microsphere perfusion measurements also showed an increasing difference in tissue blood flow in the stimulated anterior tibialis muscle at 2.5% duty cycle (62 ± 43 cc/100 cc/min), 5.0% duty cycle (89 ± 52 cc/100 cc/min), and 20% duty cycle (313 ± 269 cc/100 cc/min) compared with the paired contralateral non-stimulated anterior tibialis muscle (8 ± 4 cc/100 cc/min, mean difference 55 cc/100 cc/min [95% CI 15.49 to 94.24]; p = 0.007; 9 ± 9 cc/100 cc/min, mean difference 79 cc/100 cc/min [95% CI 33.83 to 125.09]; p = 0.003; and 18 ± 18 cc/100 cc/min, mean difference 295 cc/100 cc/min [95% CI 8.45 to 580.87]; p = 0.023). Qualitative comparison between the methods suggests that DCE-CT values underestimate tissue blood flow with a post-hoc ANOVA showing DCE-CT blood flow values within the 2.5% duty cycle group (32 ± 5 cc/100 cc/min) to be less than the microsphere perfusion value (62 ± 43 cc/100 cc/min) with a mean difference of 31 cc/100 cc/min (95% CI 2.46 to 60.23; p = 0.035). CONCLUSIONS: DCE-CT using a clinical scanner is a feasible modality to measure incremental changes of blood flow and tissue blood volume within a spatially challenged small animal model. Care should be taken in studies where true blood flow values are needed, as this particular small-volume muscle model suggests true blood flow is underestimated using the specific adaptions of DCE-CT acquisition and image processing chosen. CLINICAL RELEVANCE: CT perfusion is a clinically available modality allowing for translation of science from bench to bedside. Adapting the modality to fit small animal models that are relevant to muscle healing may hasten time to clinical utility.

A Porcine Urinary Bladder Matrix Does Not Recapitulate the Spatiotemporal Macrophage Response of Muscle Regeneration after Volumetric Muscle Loss Injury.

Volumetric muscle loss (VML) results in irrecoverable loss of muscle tissue making its repair challenging. VML repair with acellular extracellular matrix (ECM) scaffolds devoid of exogenous cells has shown improved muscle function, but limited de novo muscle fiber regeneration. On the other hand, studies using minced autologous and free autologous muscle grafts have reported appreciable muscle regeneration. This raises the fundamental question whether an acellular ECM scaffold can orchestrate the spatiotemporal cellular events necessary for appreciable muscle fiber regeneration. This study compares the macrophage and angiogenic responses including the remodeling outcomes of a commercially available porcine urinary bladder matrix, MatriStem™, and autologous muscle grafts. The early heightened and protracted M1 response of the scaffold indicates that the scaffold does not recapitulate the spatiotemporal macrophage response of the autograft tissue. Additionally, the scaffold only supports limited de novo muscle fiber formation and regressing vessel density. Furthermore, scaffold remodeling is accompanied by increased presence of transforming growth factor and α-smooth muscle actin, which is consistent with remodeling of the scaffold into a fibrotic scar-like tissue. The limited muscle formation and scaffold-mediated fibrosis noted in this study corroborates the findings of recent studies that investigated acellular ECM scaffolds (devoid of myogenic cells) for VML repair. Taken together, acellular ECM scaffolds when used for VML repair will likely remodel into a fibrotic scar-like tissue and support limited de novo muscle fiber regeneration primarily in the proximity of the injured musculature. This is a work of the US Government and is not subject to copyright protection in the USA. Foreign copyrights may apply. Published by S. Karger AG, Basel.

Postischemic conditioning does not reduce muscle injury after tourniquet-induced ischemia-reperfusion injury in rats.

BACKGROUND: The widespread application of tourniquets has reduced battlefield mortality related to extremity exsanguinations. Tourniquet-induced ischemia-reperfusion injury (I/R) can contribute to muscle loss. Postischemic conditioning (PostC) confers protection against I/R in cardiac muscle and skeletal muscle flaps. The objective of this study was to determine the effect of PostC on extremity muscle viability in an established rat hindlimb tourniquet model. METHODS: Rats were randomly assigned to PostC-1, PostC-2, or no conditioning ischemic groups (n = 10 per group). Postischemic conditioning, performed immediately after tourniquet release, consisted of four 15-second cycles (PostC-1) or eight 15-second cycles (PostC-2) of alternating occlusion and perfusion of hindlimbs. Twenty-four hours later, muscles were excised. The primary end points were muscle edema and viability; secondary end points were histologic and markers of oxidative stress. RESULTS: Ischemia-reperfusion injury decreased viability in all tourniquet limbs, but viability was not improved in either PostC group. Likewise, I/R resulted in substantial muscle edema that was not reduced by PostC. The predominant histologic feature was necrosis, but no significant differences were found among groups. Markers of oxidative stress were increased similarly among groups after I/R, although myeloperoxidase activity was significantly increased only in the no conditioning ischemic group. A protective effect from PostC was not observed in our model suggesting that PostC was not effective in reducing I/R skeletal muscle injury or any benefits of PostC were not sustained for 24 hours when tissues were assessed. CONCLUSION: These negative findings are pertinent as the military investigates different strategies to extend the safe time for tourniquet application.

Activity attenuates skeletal muscle fiber damage after ischemia and reperfusion.

INTRODUCTION: In this investigation we aimed to determine whether: (1) physical activity protects rat skeletal muscle from ischemia/reperfusion (I/R) injury; and (2) continued activity after I/R improves the rate of healing. METHODS: Rats were divided into sedentary or active (voluntary wheel running) groups. Active rats ran for 4 weeks before I/R or 4 weeks before plus 4 weeks after I/R. RESULTS: Activity before I/R resulted in 73.2% less muscle damage (Evans blue dye inclusion). Sedentary and active rats had a similar decline in neural-evoked (∼ 99%) and directly stimulated (∼ 70%) in vivo muscle torque, and a similar reduction in junctophilin 1. Active rats produced 19% and 15% greater neural-evoked torque compared with sedentary rats at 14 and 28 days postinjury, respectively, although the rate of recovery appeared similar. CONCLUSIONS: Activity protects against long-term muscle damage, but not short-term neural injury or excitation-contraction uncoupling. Continued activity neither accelerates nor hinders the rate of functional recovery.

Amelioration of ischemia-reperfusion-induced muscle injury by the recombinant human MG53 protein.

INTRODUCTION: Ischemia-reperfusion injury (I-R) in skeletal muscle requires timely treatment. METHODS: Rodent models of I-R injury were used to test the efficacy of recombinant human MG53 (rhMG53) protein for protecting skeletal muscle. RESULTS: In a mouse I-R injury model, we found that mg53,-/- mice are more susceptible to I-R injury. rhMG53 applied intravenously to the wild-type mice protected I-R injured muscle, as demonstrated by reduced CK release and Evans blue staining. Histochemical studies confirmed beneficial effects of rhMG53. Of interest, rhMG53 did not protect against I-R injury in rat skeletal muscle. This was likely due to the fact that the plasma level of endogenous MG53 protein is high in rats. CONCLUSIONS: Our data suggest that rhMG53 may be a potential therapy for protection against muscle trauma. A mouse model appears to be a better choice than a rat model for evaluating potential treatments for protecting skeletal muscle.

Transfusion for shock in US military war casualties with and without tourniquet use.

STUDY OBJECTIVE: We assess whether emergency tourniquet use for transfused war casualties admitted to military hospitals is associated with survival. METHODS: A retrospective review of trauma registry data was made of US casualties in Afghanistan and Iraq. Patients with major limb trauma, transfusion, and tourniquet use were compared with similar patients who did not receive tourniquet use. A propensity-matching analysis was performed by stratifying for injury type and severity by tourniquet-use status. Additionally, direct comparison without propensity matching was made between tourniquet use and no-tourniquet use groups. RESULTS: There were 720 casualties in the tourniquet use and 693 in the no-tourniquet use groups. Of the 1,413 casualties, 66% (928) also had nonextremity injury. Casualties with tourniquet use had worse signs of hemorrhagic shock (admission base deficit, admission hemoglobin, admission pulse, and transfusion units required) than those without. Survival rates were similar between the 2 groups (1% difference; 95% confidence interval -2.5% to 4.2%), but casualties who received tourniquets had worse shock and received more blood products. In propensity-matched casualties, survival rates were not different (2% difference; 95% confidence interval -6.7% to 2.7%) between the 2 groups. CONCLUSION: Tourniquet use was associated with worse shock and more transfusion requirements among hospital-admitted casualties, yet those who received tourniquets had survival rates similar to those of comparable, transfused casualties who did not receive tourniquets.

Performance of Junctional Tourniquets in Normal Human Volunteers.

BACKGROUND: Inguinal bleeding is a common and preventable cause of death on the battlefield. Four FDA-cleared junctional tourniquets (Combat Ready Clamp [CRoC], Abdominal Aortic and Junctional Tourniquet [AAJT], Junctional Emergency Treatment Tool [JETT], and SAM Junctional Tourniquet [SJT]) were assessed in a laboratory on volunteers in order to describe differential performance of models. OBJECTIVE: To examine safety and effectiveness of junctional tourniquets in order to inform the discussions of device selection for possible fielding to military units. METHODS: The experiment measured safety and effectiveness parameters over timed, repeated applications. Lower extremity pulses were measured in 10 volunteers before and after junctional tourniquet application aimed at stopping the distal pulse assessed by Doppler auscultation. Safety was determined as the absence of adverse events during the time of application. RESULTS: The CRoC, SJT, and JETT were most effective; their effectiveness did not differ (p > 0.05). All tourniquets were applied safely and successfully in at least one instance each, but pain varied by model. Subjects assessed the CRoC as most tolerable. The CRoC and SJT were the fastest to apply. Users ranked CRoC and SJT equally as performing best. CONCLUSION: The CRoC and SJT were the best-performing junctional tourniquets using this model.

Effect of recombinant human MG53 protein on tourniquet-induced ischemia-reperfusion injury in rat muscle.

INTRODUCTION: Skeletal muscle ischemia-reperfusion injury (I-R) is a complex injury process that includes damage to the sarcolemmal membrane, contributing to necrosis and apoptosis. MG53, a muscle-specific TRIM family protein, has been shown to be essential for regulating membrane repair and has been shown to be protective against cardiac I-R and various forms of skeletal muscle injury. The purpose of this study was to determine if recombinant human MG53 (rhMG53) administration offered protection against I-R. METHODS: rhMG53 was administered to rats immediately before tourniquet-induced ischemia and again immediately before reperfusion. Two days later muscle damage was assessed histologically. RESULTS: rhMG53 offered no protective effect, as evidenced primarily by similar Evans blue dye inclusion in the muscles of rats administered rhMG53 or saline. CONCLUSIONS: Administration of rhMG53 does not offer protection against I-R in rat skeletal muscle. Additional studies are required to determine if the lack of a response is species-specific.

Severe burn and disuse in the rat independently adversely impact body composition and adipokines.

INTRODUCTION: Severe trauma is accompanied by a period of hypermetabolism and disuse. In this study, a rat model was used to determine the effects of burn and disuse independently and in combination on body composition, food intake and adipokines. METHODS: Male rats were assigned to four groups 1) sham ambulatory (SA), 2) sham hindlimb unloaded (SH), 3) 40% total body surface area full thickness scald burn ambulatory (BA) and 4) burn and hindlimb unloaded (BH). Animals designated to the SH and BH groups were placed in a tail traction system and their hindlimbs unloaded. Animals were followed for 14 days. Plasma, urine, fecal and tissue samples were analyzed. RESULTS: SA had a progressive increase in body mass (BM), SH and BA no change and BH a reduction. Compared to SA, BM was reduced by 10% in both SH and BA and by 17% when combined in BH. Compared to SA, all groups had reductions in lean and fat body mass with BH being greater. The decrease in lean mass was associated with the rate of urinary corticosterone excretion. The loss in fat mass was associated with decreases in plasma leptin and adiponectin and an increase in ghrelin. Following the acute response to injury, BH had a greater food intake per 100 g BM. Food intake was associated with the levels of leptin, adiponectin and ghrelin. CONCLUSIONS: The effects of the combination of burn and disuse in this animal model were additive, therefore in assessing metabolic changes with severe trauma both injury and disuse should be considered. Furthermore, the observed changes in adipokines, corticosterone and ghrelin provide insights for interventions to attenuate the hypermetabolic state following injury, possibly reducing catabolism and muscle loss and subsequent adverse effects on recovery and function.

Slow-adhering stem cells derived from injured skeletal muscle have improved regenerative capacity.

A wide variety of myogenic cell sources have been used for repair of injured and diseased muscle including muscle stem cells, which can be isolated from skeletal muscle as a group of slow-adhering cells on a collagen-coated surface. The therapeutic use of muscle stem cells for improving muscle regeneration is promising; however, the effect of injury on their characteristics and engraftment potential has yet to be described. In the present study, slow-adhering stem cells (SASCs) from both laceration-injured and control noninjured skeletal muscles in mice were isolated and studied. Migration and proliferation rates, multidifferentiation potentials, and differences in gene expression in both groups of cells were compared in vitro. Results demonstrated that a larger population of SASCs could be isolated from injured muscle than from control noninjured muscle. In addition, SASCs derived from injured muscle demonstrated improved migration, a higher rate of proliferation and multidifferentiation, and increased expression of Notch1, STAT3, Msx1, and MMP2. Moreover, when transplanted into dystrophic muscle in MDX/SCID mice, SASCs from injured muscle generated greater engraftments with a higher capillary density than did SASCs from control noninjured muscle. These data suggest that traumatic injury may modify stem cell characteristics through trophic factors and improve the transplantation potential of SASCs in alleviating skeletal muscle injuries and diseases.

Administration of particulate oxygen generators improves skeletal muscle contractile function after ischemia-reperfusion injury in the rat hindlimb.

Extended tourniquet application, often associated with battlefield extremity trauma, can lead to severe ischemia-reperfusion (I/R) injury in skeletal muscle. Particulate oxygen generators (POGs) can be directly injected into tissue to supply oxygen to attenuate the effects of I/R injury in muscle. The goal of this study was to investigate the efficacy of a sodium percarbonate (SPO)-based POG formulation in reducing ischemic damage in a rat hindlimb during tourniquet application. Male Lewis rats were anesthetized and underwent tourniquet application for 3 h at a pressure of 300 mmHg. Shortly after tourniquet inflation, animals received intramuscular injections of either 0.2 mg/mL SPO with catalase (n = 6) or 2.0 mg/mL SPO with catalase (n = 6) directly into the tibialis anterior (TA) muscle. An additional Tourniquet-Only group (n = 12) received no intervention. Functional recovery was monitored by in vivo contractile testing of the hindlimb at 1, 2, and 4 wk after injury. By the 4 wk time point, the Low-Dose POG group continued to show improved functional recovery (85% of baseline) compared with the Tourniquet-Only (48%) and High-Dose POG (56%) groups. In short, the low-dose POG formulation appeared, at least in part, to mitigate the impact of ischemic tissue injury, thus improving contractile function after tourniquet application. Functional improvement correlated with maintenance of larger muscle fiber cross-sectional area and the presence of fewer fibers containing centrally located nuclei. As such, POGs represent a potentially attractive therapeutic solution for addressing I/R injuries associated with extremity trauma.NEW & NOTEWORTHY Skeletal muscle contraction was evaluated in the same animals at multiple time points up to 4 wk after injury, following administration of particulate oxygen generators (POGs) in a clinically relevant rat hindlimb model of tourniquet-induced ischemia. The observed POG-mediated improvement of muscle function over time confirms and extends previous studies to further document the potential clinical applications of POGs. Of particular significance in austere environments, this technology can be applied in the absence of an intact circulation.

Treatment of tourniquet-induced ischemia reperfusion injury with muscle progenitor cells.

BACKGROUND: Acute ischemia reperfusion injury (IRI) results in muscle atrophy and functional loss. Although studies have shown that stem cells can improve muscle function in chronic ischemia caused by vascular diseases, none investigated whether stem cells can improve muscle function following acute IRI. The primary purpose of this study was to determine whether transplantation of muscle progenitor cells (MPCs) improves recovery of muscle function after tourniquet (TK) induced IRI. METHODS: IRI was induced in rat hind limb muscles with a pneumatic TK (250 mmHg) for 3 h. Rats were then divided into two groups; receiving either intramuscular injection of MPCs or vehicle control into the injured tibialis anterior muscle 48 h after tourniquet application. Muscle mass, isometric contractile properties, and selected histologic properties were evaluated at 2 wk after ischemia. RESULTS: IRI resulted in significant reductions in absolute muscle force (N) and specific muscle force (N/cm(2)). MPC treatment significantly prevented the loss in muscle specific force compared with vehicle controls. The mass and cross sectional areas of the muscles were similar between treatment groups. Histologic results showed that a small number of transplanted cells differentiated and formed muscle fibers, which could potentially contribute to force generation. IRI caused significant fibrosis and inflammation, both of which could affect muscle-specific force, of which inflammation was reduced by MPCs treatment. CONCLUSIONS: Intramuscular injection of MPCs may provide a beneficial treatment for improving functional recovery following IRI, and the beneficial effects are mainly through improving muscle quality (specific force) but not quantity (mass).

Poloxamer-188 reduces muscular edema after tourniquet-induced ischemia-reperfusion injury in rats.

BACKGROUND: Skeletal muscle injury can result in significant edema, which can in turn lead to the development of acute extremity compartment syndrome (CS). Poloxamer-188 (P-188), a multiblock copolymer surfactant, has been shown to decrease edema by sealing damaged membranes in a number of tissues after a variety of injury modalities. The objective is to determine whether the administration of P-188 significantly reduces skeletal muscle edema associated with ischemia/reperfusion injury (I-R). METHODS: Male Sprague-Dawley rats underwent 180 minutes of tourniquet-induced ischemia. Five minutes before tourniquet release, rats received either a bolus of (1) P-188 (150 mg/kg; P-188 group) or (2) vehicle (Vehicle group) via a jugular catheter (n=10 per group). After 240 minutes reperfusion, both groups received a second bolus of either P-188 (P-188) or vehicle (Vehicle) via a tail vein catheter. Sixteen hours later, rats were killed; muscle weights were determined, infarct size (2,3,5-triphenyltetrazolium chloride method), and blinded histologic analysis (hematoxylin and eosin) were performed on the gastrocnemius and tibialis anterior muscles, as well as indices of antioxidant status. RESULTS: P-188 resulted in significantly less edema (wet weight) and reduced an index of lipid peroxidation compared with Vehicle (p<0.05). Wet:dry weight ratios were less in the P-188 group (indicating less edema). Muscle viability as indicated by 2,3,5-triphenyltetrazolium chloride staining or routine histology did not reveal statistically significant differences between groups. CONCLUSION: P-188 significantly reduced ischemia-reperfusion-related muscle edema and lipid peroxidation but did not impact muscle viability. Excess edema can lead to acute extremity CS, which is associated with significant morbidity and mortality. P-188 may provide a potential adjunctive treatment for the reduction of CS.

Battle casualty survival with emergency tourniquet use to stop limb bleeding.

BACKGROUND: In a previous study conducted at a combat support hospital in Iraq, we reported the major lifesaving benefits of emergency tourniquets to stop bleeding in major limb trauma. Morbidity associated with tourniquet use was minor. STUDY OBJECTIVES: The objective of this study is to further analyze emergency tourniquet use in combat casualty care. DESIGN AND SETTING: This report is a continuation of our previous study of tourniquet use in casualties admitted to a combat support hospital (NCT00517166 at www.ClinicalTrials.gov). METHODS: After verifying comparable methodologies for the first study and the current study, we compared patient results for these two time periods and then pooled data to analyze outcomes with a larger sample size. RESULTS: The total study population was 499 (232 in the previous study and 267 in the current study). In all, 862 tourniquets were applied on 651 limbs. Survival was 87% for both study periods. Morbidity rates for palsies at the level of the tourniquet were 1.7% for study 1 and 1.5% for study 2; major limb shortening was 0.4% for both. Survival was associated with prehospital application (89% vs. 78% hospital, p < 0.01) and application before the onset of shock (96% vs. 4% after). CONCLUSIONS: This study shows consistent lifesaving benefits and low risk of emergency tourniquets to stop bleeding in major limb trauma.

The military emergency tourniquet program's lessons learned with devices and designs.

OBJECTIVE: The purpose of this study is to report the device lessons learned from an emergency tourniquet program and, in particular, to emphasize analysis of discarded devices recovered after clinical use. METHODS: Discarded tourniquet devices were analyzed after use in emergency care of war casualties to determine wear and tear patterns, effectiveness rates, and associations among device designs. RESULTS: The 159 devices recovered comprised seven designs. Emergency & Military Tourniquet (92%) and Combat Application Tourniquet (79%) effectiveness rates were significantly different from each other and better than other tourniquets (p < 0.002) as the most effective ambulance and field tourniquets, respectively. Designs had specific pitfalls (e.g., sand-clogged ratchets) and strengths (the pneumatic design was least painful). Every device had wear, abrasions, or deformity about the band edges or bladder. User understanding of how devices work best helped attain better results. Some desirable traits (e.g., one-handed application, use for entrapped limbs) were rarely needed. Tourniquets fit casualty limbs well. CONCLUSIONS: Correct user actions (e.g., following the instructions to remove slack before twisting) led to device effectiveness, but misuse did not. Users often assumed that optimal use required more force, but this was associated with misuse. Training should include tourniquet pearls and pitfalls.

Minor morbidity with emergency tourniquet use to stop bleeding in severe limb trauma: research, history, and reconciling advocates and abolitionists.

BACKGROUND: In prior reports of active data collection, we demonstrated that early use of emergency tourniquets is associated with improved survival and only minor morbidity. To check these new and important results, we continued critical evaluation of tourniquet use for 6 more months in the current study to see if results were consistent. METHODS: We continued a prospective survey of casualties and their records at a combat support hospital in Baghdad who had tourniquets used at a combat hospital in Baghdad (NCT00517166 at ClinicalTrials.gov). RESULTS: After comparable methods were verified for both the first and current studies, we report the results of 499 patients who had 862 tourniquets applied on 651 limbs. The clinical results were consistent. No limbs were lost from tourniquet use. CONCLUSION: We found that morbidity was minor in light of major survival benefits consistent with prior reports.