Ultrasound Localization of Resuscitative Endovascular Balloon Occlusion of the Aorta in a Human Cadaver Model.

OBJECTIVE: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is a method of gaining proximal control of noncompressible torso hemorrhage (NCTH). Catheter placement is traditionally confirmed with fluoroscopy, but few studies have evaluated whether ultrasound (US) can be used. METHODS: Using a pressurized human cadaver model, a certified REBOA placer was shown one of four randomized cards that instructed them to place the REBOA either correctly or incorrectly in Zone 1 (the distal thoracic aorta extending from the celiac artery to the left subclavian artery) or Zone 3 (in the distal abdominal aorta, from the aortic bifurcation to the lowest renal artery). Once the REBOA was placed, 10 US-trained locators were asked to confirm balloon placement via US. The participants were given 3 minutes to determine whether the catheter had been correctly placed, repeating this 20 times on two cadavers. RESULTS: Overall, US exhibited an average sensitivity of 83%, specificity of 76%, and accuracy of 80%. For Zone 1, US showed a sensitivity of 78% and specificity of 83%, and for Zone 3, a sensitivity of 88% and specificity of 76%. In addition, US exhibited a likelihood positive ratio (LR+) of 3.73 and a likelihood negative ratio (LR-) of 0.22 for either position, with similar numbers for Zone 1 (+4.57, -0.26) and Zone 3 (+3.16, -0.16). CONCLUSION: Ultrasound could prove to be a useful tool for confirming placement of a REBOA catheter, especially in austere environments.

A comparison of efficacy, efficiency, and durability in novel tourniquet designs.

BACKGROUND: Exsanguination due to extremity hemorrhage is a major cause of preventable traumatic deaths. Extremity tourniquet use has been shown to be safe and improve survival. The purpose of this study was to compare the efficacy, efficiency, and durability of the Generation 7 Combat Application Tourniquet (CAT; North American Rescue, Greer, SC), the Tactical Mechanical Tourniquet (TMT; Combat Medical Systems, Harrisburg, NC), and the SOF Tactical Tourniquet-Wide (SOFTT-W; Tactical Medical Solutions, Anderson, SC). METHODS: This study was a three-phase randomized, cross-over trial. In successive trials, subjects were timed during the application of each tourniquet to the upper and lower extremity. Following successful lower extremity application, subjects low crawled 25 ft and then were dragged 25 ft, after which effectiveness was reassessed, as defined by the cessation of distal pulses by Doppler ultrasound. RESULTS: In arm application, both the CAT and TMT had significantly less failure rates than the SOFTT-W (5.56%, 19.44%, 58.33%), with the CAT being the fastest tourniquet when compared with TMT and SOFTT-W (37.8 seconds, 65.01 seconds, 63.07 seconds). In leg application, the CAT had significantly less rates of failure when compared with the SOFTT-W, but there was no other significant difference between the tourniquets (27.78%, 44.44%, 61.11%). In addition, the CAT was significantly faster than both the TMT and SOFTT-W when applied to the leg (8.33 seconds, 40.96 seconds, 34.5 seconds). There was no significant difference in tourniquet failure rates between the three tourniquets after subject maneuvers in phase 3 (34.29%, 42.86%, 45.45%). DISCUSSION: The CAT is as effective as the TMT and significantly more effective than the SOFTT-W. In addition, the CAT demonstrated shorter application times than either the TMT or SOFTT-W. However, there was no significant difference between the three tourniquets in their ability to maintain pulselessness after subject maneuvers. LEVEL OF EVIDENCE: Care management, level II.

Efficacy of Hemostatic Gauzes in a Swine Model of Prolonged Field Care with Limb Movement.

INTRODUCTION: Prolonged field care for junctional wounds is challenging and involves limb movement to facilitate transport. No studies to date have explored the efficacy of gauze products to limit rebleeding in these scenarios. MATERIALS AND METHODS: We randomly assigned 48 swine to QuikClot Combat Gauze, ChitoGauze, NuStat Tactical, or Kerlix treatment groups (12 each) and then inflicted a severe groin injury by utilizing a modified Kheirabadi model of a 6-mm femoral artery punch followed by unrestricted bleeding for 60 seconds. We reassessed rebleed following limb movement at 30 minutes of stabilization and 4 hours after stabilization. RESULTS: Swine treated with Combat Gauze proved to have the lowest incidence of rebleeding, and conversely, NuStat Tactical had the highest incidence of rebleeding at wounds after limb movement. Importantly, rebleeds occurred at a rate of 25%-58% across all swine treatment groups at 30 minutes postinjury and 0%-42% at 270 minutes postinjury demonstrating that limb movements universally challenge hemostatic junctional wounds. CONCLUSIONS: Our findings highlight the difficulty of controlling hemorrhage from junctional wounds with hemostatic gauze in the context of prolonged field care and casualty transport. Our research can guide selection of hemorrhage control gauze when patients have prolonged field extraction or difficult transport. Our data demonstrates the frequency of junctional wound rebleeding after movement and thus the importance of frequent patient reassessment.

Comparison of 10- versus 14-gauge angiocatheter for treatment of tension pneumothorax and tension-induced pulseless electrical activity with hemorrhagic shock: Bigger is still better.

BACKGROUND: Little is known regarding the effect of hemorrhagic shock on the diagnosis and treatment of tension pneumothorax (tPTX). Recently, the Tactical Combat Casualty Care guidelines included the 10-gauge angiocatheter (10-g AC) as an acceptable alternative to the 14-g AC. This study sought to compare these two devices for decompression of tPTX and rescue from tension-induced pulseless electric activity (tPEA) in the setting of a concomitant 30% estimated blood volume hemorrhage. METHODS: Following a controlled hemorrhage, carbon dioxide was insufflated into the chest to induce either tPTX or tPEA. Tension pneumothorax was defined as a reduction in cardiac output by 50%, and tPEA was defined as a loss of arterial waveform with mean arterial pressure less than 20 mm Hg. The affected hemithorax was decompressed using a randomized 14-g AC or 10-g AC while a persistent air leak was maintained after decompression. Successful rescue from tPTX was defined as 80% recovery of baseline systolic blood pressure, while successful return of spontaneous circulation following tPEA was defined as a mean arterial pressure greater than 20 mm Hg. Primary outcome was success of device. RESULTS: Eighty tPTX and 50 tPEA events were conducted in 38 adult Yorkshire swine. There were no significant differences in the baseline characteristics between animals or devices. In the tPTX model, the 10-g AC successfully rescued 90% of events, while 14-g AC rescued 80% of events (p = 0.350). In the tPEA model, the 10-g AC rescued 87% of events while the 14 AC rescued only 48% of events (p = 0.006). CONCLUSION: The 10-g AC was vastly superior to the 14-g AC for return of spontaneous circulation following tPEA in the setting of 30% hemorrhage. These findings further support the importance of larger caliber devices that facilitate rapid recovery from tPTX, particularly in the setting of polytrauma. LEVEL OF EVIDENCE: Therapeutic, level II.

Intravenous and Intraosseous Blood Transfusion With Three Different Pediatric Pressure Transfusion Strategies in an Immature Swine (Sus scrofa) Model of Hemorrhagic Shock: A Pilot Study.

INTRODUCTION: Exsanguination remains the leading cause of preventable death in military conflicts, and pediatric casualties are common. Transfusion is crucial to preserve life, but vascular access is challenging in children, so intraosseous (IO) access is often required. However, the optimal transfusion method is unclear. There was therefore the need for feasibility testing of a model for contrasting the efficacy of blood infusion devices via intravenous (IV) and IO access in immature swine with bone densities similar to children. MATERIALS AND METHODS: Eighteen immature swine (21 ± 1 kg) were bled 31% of estimated blood volume and then received autologous blood delivered by pressure bag, push-pull (PP), or LifeFlow Rapid Infuser via IO (15-gauge IO needle placed in the humeral head) or IV (auricular 20-gauge), with monitoring for 60 minutes. RESULTS: Flow rates for LifeFlow (172 ± 28 mL/kg) were 4-fold higher than pressure bag (44 ± 13 mL/kg, P < 0.001) and 80% higher than PP (95 ± 28 mL/kg, P < 0.02). However, higher hemolysis was evident in the IV LifeFlow condition, with 6-fold more plasma-free hemoglobin than other conditions (P < 0.0001). CONCLUSIONS: IV LifeFlow conferred higher flows, but higher hemolysis in this pilot study demonstrates the feasibility of an immature swine model toward determining optimal methods for resuscitating children with hemorrhagic shock.

Comparison of thromboelastography versus conventional coagulation tests in simulated Crotalus atrox envenomation using human blood.

INTRODUCTION: Pit viper bites are a source of significant morbidity and mortality. Pit viper bites can cause venom-induced consumptive coagulopathy (VICC), typically evaluated with laboratory-based conventional coagulation tests (CCTs). However, CCTs require a laboratory and average 1 h to conduct. Thromboelastography (TEG) provides real-time, point-of-care tests of coagulation that are fast and require no separate laboratory facilities, which could be advantageous in both hospital and austere settings. However, the relative efficacy of TEG versus CCTs was unclear, particularly at low venom concentrations. Therefore, the objectives of this study were to test human blood with various concentrations of pit viper venom using CCTs and TEG to determine dose-dependent changes, lowest observed effect concentration (LOEC), and sensitivity to detecting samples out of normal diagnostic range. METHODS: Blood samples from 20 volunteers were mixed with varying concentrations of western diamond back rattlesnake (Crotalus atrox) venom based on the mouse LD50IV (none, 0.5%, 1%, 2%, 33%, 66%, and 100% LD50IV). Samples were split and assessed with both CCTs including prothrombin time (PT), international normalized ratio (INR), partial thromboplastin time (PTT), fibrinogen, and D-dimer, along with TEG measures of reaction time (R), kinetic time (K), rate of clot formation (α-angle), and clot strength (MA). Data were analyzed as dose-dependent concentration-based changes in raw values and in percent of samples exceeding diagnostic thresholds using ANOVA and nonparametric statistics at the p < .05 threshold. RESULTS: All evaluations showed significant concentration-dependent changes, and 100% of samples exceeded diagnostic thresholds at 33%LD50IV and above, save D-dimer. At 0.5%LD50IV, R, K, α-angle, PT, and INR were significantly different from controls, and at 1%LD50IV, mean values exceeded diagnostic thresholds for R, K, α-angle, MA, PT, and INR, but not for PTT, D-dimer, or fibrinogen. At 2%LD50IV, 100% of samples were out of normal range for K, α-angle, and PT. CONCLUSION: TEG is effective in coagulopathy evaluations of in vitro simulated pit viper envenomation. At low venom concentrations, TEG performed as well or better than the majority of CCTs. These findings provide empirical evidence supporting the use of TEG to rapidly and accurately evaluate VICC.

Impact of Marine Exposure on Hemostatic Gauzes Using Thromboelastography.

BACKGROUND: Military forces render emergency care in marine environments, where care for exsanguination is challenging. However, the effect of saltwater on the functionality of hemostatic agents is unknown. In this study, we used thromboelastography (TEG) to quantify the effect of saltwater on the efficacy of five gauze products. METHODS: Blood from 24 healthy adult men was diluted by 30% with hetastarch to mimic hemodilution. Dry and saltwater-soaked Kerlix™, ChitoGauze®, Combat Gauze®, NuStat™, and WoundClot™ were contrasted in terms of the TEG parameters of speed of clot initiation (R), clot amplification (K), α angle (i.e., clot formation rate), and maximum amplitude of clot (MA), using repeated-measures analysis of variance at the p < .05 statistical significance threshold. RESULTS: Compared with untreated dilute blood, R was significantly faster when any dry or wet gauze was added, with the fastest R values recorded for Combat Gauze. K and α angle findings were mixed. MA was greater than diluted blood for dry hemostatic gauze, but in the wet condition, only the MA for Combat Gauze was significantly greater than that of diluted blood. CONCLUSION: Gauze products, wet or dry, improved clotting compared to diluted blood without gauze. Saltwater exposure did not significantly detract from this benefit. Our findings suggest that Combat Gauze may be the choice hemostatic gauze for maritime environments.