COMBAT-C: COntrol of Major Bleeding by Application of Tourniquets over Clothing.

INTRODUCTION: External bleeding is the leading cause of preventable trauma-related death. In certain circumstances, tourniquet application over clothing may be necessary. Therefore, the aim of this study was to assess the effectiveness of tourniquets over different clothing setups. METHODS: Three windlass tourniquets (CAT, SAMXT, SOFTT-W) were applied over nine different clothing setups and without clothing on the Hapmed™ Tourniquet Trainer. We compared each tourniquet in each clothing setup to the tourniquet trainer that was not dressed, and we compared the three tourniquets within each clothing setup concerning blood loss, applied pressure and application time. Regression analysis of the effect of thickness, mean weight, mean deformation, application time, and applied pressure on blood loss was performed. RESULTS: Although blood loss was significantly greater in the CAT and SAMXT tourniquets when they were applied over leather motorcycle trousers, the overall findings showed that the clothing setups significantly reduced or did not affect blood loss. The mean blood loss was the lowest with CAT and the highest with SOFTT-W. The measured mean pressures were lower than 180 mmHg in four out of nine clothing setups with SOFTT-W, but CAT and SAMXT always exceeded this threshold. CAT had the fastest application time. Blood loss was significantly influenced by applied pressure and application time but was influenced to a far lesser degree by clothing parameters. CONCLUSION: The effects of the clothing setups were of little clinical relevance, except for leather motorcycle trousers. The effects of rugged protective equipment, e.g., hazard suits, are conceivable and need to be tested for specific garments with the tourniquet intended for use. No clothing parameter for predicting tourniquet effectiveness could be identified.

Comparison of Laryngeal Mask Airway Seal Between Anesthesiologists and Individuals Without Previous Airway Experience.

BACKGROUND: Tracheal intubation is the gold standard for airway management in emergency medicine, but more difficult to apply for inexperienced individuals than laryngeal mask airway (LMA). OBJECTIVE: The aim of our study was to investigate if inexperienced individuals are able to secure the airway with the help of LMA after a short introduction. A second aim was to evaluate Thiel-fixed specimens against unfixed ones. METHODS: In a body donor model, LMA application was evaluated between medical students without previous airway experience and anesthesiologists by comparing the sealing of the larynx using a water column applied to the esophagus. RESULTS: LMAs were successfully applied in 46 out of 55 (83.6%) attempts by medical students and in 30 out of 39 (76.9%) attempts by anesthesiologists. Among medical students, 14.1% of all LMA applications were primarily leaky, compared with 18.8% in anesthesiologists. Esophageal sealing was better in Thiel-fixed specimens (leakage 10.9%) compared with unfixed specimens (leakage 22.9%). Our data showed no significant difference between anesthesiologists and medical students in terms of sealing of LMA. Therefore, we conclude that medical students without previous airway experience can quickly learn to apply LMA sufficiently and thus, achieve aspiration protection similar to anesthesiologists. CONCLUSION: Medical students without previous airway experience can successfully insert LMAs after a short introduction. Thiel-fixed specimens are suitable for studies as well as for training in LMA application.

Suspension syndrome: a scoping review and recommendations from the International Commission for Mountain Emergency Medicine (ICAR MEDCOM).

BACKGROUND: Suspension syndrome describes a multifactorial cardio-circulatory collapse during passive hanging on a rope or in a harness system in a vertical or near-vertical position. The pathophysiology is still debated controversially. AIMS: The International Commission for Mountain Emergency Medicine (ICAR MedCom) performed a scoping review to identify all articles with original epidemiological and medical data to understand the pathophysiology of suspension syndrome and develop updated recommendations for the definition, prevention, and management of suspension syndrome. METHODS: A literature search was performed in PubMed, Embase, Web of Science and the Cochrane library. The bibliographies of the eligible articles for this review were additionally screened. RESULTS: The online literature search yielded 210 articles, scanning of the references yielded another 30 articles. Finally, 23 articles were included into this work. CONCLUSIONS: Suspension Syndrome is a rare entity. A neurocardiogenic reflex may lead to bradycardia, arterial hypotension, loss of consciousness and cardiac arrest. Concomitant causes, such as pain from being suspended, traumatic injuries and accidental hypothermia may contribute to the development of the Suspension Syndrome. Preventive factors include using a well-fitting sit harness, which does not cause discomfort while being suspended, and activating the muscle pump of the legs. Expediting help to extricate the suspended person is key. In a peri-arrest situation, the person should be positioned supine and standard advanced life support should be initiated immediately. Reversible causes of cardiac arrest caused or aggravated by suspension syndrome, e.g., hyperkalaemia, pulmonary embolism, hypoxia, and hypothermia, should be considered. In the hospital, blood and further exams should assess organ injuries caused by suspension syndrome.

Analysis of tourniquet pressure over military winter clothing and a short review of combat casualty care in cold weather warfare.

Cold weather warfare is of increasing importance. Haemorrhage is the most common preventable cause of death in military conflicts. We analysed the pressure of the Combat Application Tourniquet® Generation 7 (CAT), the SAM® Extremity Tourniquet (SAMXT) and the SOF® Tactical Tourniquet Wide Generation 4 (SOFTT) over different military cold weather clothing setups with a leg tourniquet trainer. We conducted a selective PubMed search and supplemented this with own experiences in cold weather medicine. The CAT and the SAMXT both reached the cut off value of 180mmHg in almost all applications. The SOFTT was unable to reach the 180mmHg limit in less than 50% of all applications in some clothing setups. We outline the influence of cold during military operations by presenting differences between military and civilian cold exposure. We propose a classification of winter warfare and identify caveats and alterations of Tactical Combat Casualty Care in cold weather warfare, with a special focus on control of bleeding. The application of tourniquets over military winter clothing is successful in principle, but effectiveness may vary for different tourniquet models. Soldiers are more affected and impaired by cold than civilians. Military commanders must be made aware of medical alterations in cold weather warfare.

Hemostatics in patients with inhibited coagulation-A viscoelastic in-vitro analysis.

BACKGROUND: The military has used topical hemostatic agents to successfully treat life-threatening external bleeding for years. In contrast to the military environment, the general population are increasingly prescribed anticoagulants. There are only few comparative evaluations of topical hemostatic agents with anticoagulated human blood. It is important to understand the impact of these agents on those who take anticoagulants. STUDY DESIGN AND METHODS: Citrated blood of patients treated with enoxaparin, heparin, and acetylsalicylic acid, apixaban or phenprocoumon was incubated with different hemostatic agents (QuikClot Gauze, Celox Granules, Celox Gauze, Chito SAM 100, WoundClot Trauma Gauze, QuikClot Gauze Moulage Trainer and Kerlix) and rotational thromboelastometry was performed with non-activated thromboelastometry (NATEM reagent). RESULTS: All tested agents improved the onset of coagulation in all anticoagulants, mostly to a significant degree. Most significant improvements were produced by QuikClot Gauze and QuikClot Gauze Moulage Trainer, followed by the tested chitosans (Celox Granules, Celox Gauze, Chito SAM 100). Of the anticoagulant groups, the most significant improvements were seen in enoxaparin. This was followed in order by apixaban, heparin, and acetylsalicylic acid, and phenprocoumon. DISCUSSION: All the hemostatic agents tested were able to activate the clotting cascade earlier and initiate faster clot formation in anticoagulated blood. A definitive head-to-head comparison is not feasible, because of the limitations of an in-vitro analysis. However, the sometimes-presented hypothesis that kaolin-based hemostatic agents are ineffective in anticoagulated blood is inaccurate according to our data. Hemostasis with hemostatic agents appears most challenging with phenprocoumon.

Survival in a Collapsed Stable for 37 Days After Avalanche Burial in 1755.

In 1755 in Bergemoletto, Italy, an avalanche buried 4 people (2 women, a girl, and a boy) and several animals in a stable. After 37 d in a pitch-dark confined space, 3 of the 4 people were rescued alive. The 3 survivors had only goat milk, a few chestnuts, a few kg of raw kid meat, and meltwater for nutrition. We describe the longest-known survival in an avalanche burial and discuss the medical and psychological problems of the survivors. The boy died. When they were extricated, all 3 survivors were exhausted, cachectic, and unable to stand or walk. They were severely malnourished and were experiencing tingling, tremors, and weakness in the legs; constipation; changes in taste; and amenorrhea. One of the women had persistent eye problems and developed symptoms consistent with post-traumatic stress disorder. The survivors were given slow refeeding. It took from 1 to 6 wk before they could walk. We compare this case to other long-duration burials, especially mining accidents, and describe the rescue and patient care after long-duration burials. This case demonstrates that people can overcome extremely adverse conditions and survive.

Initial Treatment of High-Altitude Pulmonary Edema: Comparison of Oxygen and Auto-PEEP.

BACKGROUND: Improvement of oxygenation is the aim in the therapy of high-altitude pulmonary edema (HAPE). However, descent is often difficult and hyperbaric chambers, as well as bottled oxygen, are often not available. We compare Auto-PEEP (AP-Pat), a special kind of pursed lips breathing, against the application of bottled oxygen (O2-Pat) in two patients suffering from HAPE. METHODS: We compare the effect of these two different therapies on oxygen saturation measured by pulse oximetry (SpO2) over time. RESULT: In both patients SpO2 increased significantly from 65-70% to 95%. Above 80% this increase was slower in AP-Pat compared with O2-Pat. Therapy started immediately in AP-Pat but was delayed in O2-Pat because of organizational and logistic reasons. CONCLUSIONS: The well-established therapies of HAPE are always the option of choice, if available, and should be started as soon as possible. The advantage of Auto-PEEP is its all-time availability. It improves SpO2 nearly as well as 3 L/min oxygen and furthermore has a positive effect on oxygenation lasting for approximately 120 min after stopping. Auto-PEEP treatment does not appear inferior to oxygen treatment, at least in this cross-case comparison. Its immediate application after diagnosis probably plays an important role here.

Induced Hypothermia as Cold as 3°C in Humans: Forgotten Cases Rediscovered.

Zafren, Ken, Raimund Lechner, Peter Paal, Hermann Brugger, Giles Peek, and Tomasz Darocha. Induced hypothermia as cold as 3°C in humans: Forgotten cases rediscovered. High Alt Med Biol. 23:105-113.-The lowest temperature from which humans can be successfully rewarmed from accidental hypothermia is unknown. The lowest published core temperature with survival from accidental hypothermia is 11.8°C. We recently reported a rediscovered case series of patients in whom profound hypothermia was induced for surgery. The patient in this case series with the lowest core temperature, 4.2°C, survived neurologically intact. We subsequently rediscovered several additional case series of induced hypothermia to core temperatures below 11.8°C. In one case series, at least one patient was cooled to 3°C. We do not know if any patient survived cooling to 3°C. As in the previous case series, the authors of the additional reports presented physiological data at various core temperatures, showing wide variations in individual responses to hypothermia. These data add to our understanding of the physiology of profound hypothermia. Although induced hypothermia for surgery differs from accidental hypothermia, survival from very low temperatures in induced hypothermia provides evidence that humans with accidental hypothermia can be resuscitated successfully from temperatures much lower than 11.8°C. We continue to advise against using core temperature alone to decide if a hypothermic patient in cardiac arrest has a chance of survival.

Accidental Hypothermia: 2021 Update.

Accidental hypothermia is an unintentional drop of core temperature below 35 °C. Annually, thousands die of primary hypothermia and an unknown number die of secondary hypothermia worldwide. Hypothermia can be expected in emergency patients in the prehospital phase. Injured and intoxicated patients cool quickly even in subtropical regions. Preventive measures are important to avoid hypothermia or cooling in ill or injured patients. Diagnosis and assessment of the risk of cardiac arrest are based on clinical signs and core temperature measurement when available. Hypothermic patients with risk factors for imminent cardiac arrest (temperature < 30 °C in young and healthy patients and <32 °C in elderly persons, or patients with multiple comorbidities), ventricular dysrhythmias, or systolic blood pressure < 90 mmHg) and hypothermic patients who are already in cardiac arrest, should be transferred directly to an extracorporeal life support (ECLS) centre. If a hypothermic patient arrests, continuous cardiopulmonary resuscitation (CPR) should be performed. In hypothermic patients, the chances of survival and good neurological outcome are higher than for normothermic patients for witnessed, unwitnessed and asystolic cardiac arrest. Mechanical CPR devices should be used for prolonged rescue, if available. In severely hypothermic patients in cardiac arrest, if continuous or mechanical CPR is not possible, intermittent CPR should be used. Rewarming can be accomplished by passive and active techniques. Most often, passive and active external techniques are used. Only in patients with refractory hypothermia or cardiac arrest are internal rewarming techniques required. ECLS rewarming should be performed with extracorporeal membrane oxygenation (ECMO). A post-resuscitation care bundle should complement treatment.

Resuscitation of an Unconscious Victim of Accidental Hypothermia in 1805.

In 1805, W.D., a 16-y-old boy, became hypothermic after he was left alone on a grounded boat in Leith Harbour, near Edinburgh, Scotland. He was brought to his own house and resuscitated with warm blankets, smelling salts, and massage by Dr. George Kellie. W.D. made an uneventful recovery. We discuss the pathophysiology and treatment of accidental hypothermia, contrasting treatment in 1805 with treatment today. W.D. was hypothermic when found by passersby. Although he appeared dead, he was rewarmed with help from Dr. Kellie and his assistants over 200 y ago using simple methods. One concept that has not changed is the critical importance of attempting resuscitation, even if it seems to be futile. Don't give up!

[Prehospital Strategies to Stop the Bleeding]. / Prähospitale Strategien zur Minimierung des Blutverlustes.

Seriously injured patients represent only a small group of patients in the emergency medical service with 0.5% (ground based) to 5% (HEMS), but they are associated with a high mortality rate. Among people younger than 45, trauma is the most common cause of death, mostly as a result of severe traumatic brain injury (TBI) and/or extreme hemorrhage. As the outcome of severe TBI prehospitally can only be influenced to a very limited extent, a majority of preventable deaths in prehospital setting are caused by "critical" bleeding. The "critical" bleeding is defined by its life-threatening dimension. Anticoagulation medication can have a reinforcing effect. Adequate prehospital therapy strategies exist for external bleeding. In contrast, internal bleeding regularly evades a causal prehospital care, so that in such cases, transport prioritization and rapid definitive surgical intervention remain the only option. In the civilian environment the tested and evaluated "ABCDE" scheme must be preceded by the (for "critical bleeding") in order to react time-critically to compressible external bleeding, possibly even prior to airway management. These findings have found their way into the current version of the S3 guideline on treatment of multi system trauma by the German Society for Trauma Surgery (DGU). According to this "severely bleeding injuries that can impair vital functions should be treated with priority". Thus, this publication focuses on prehospital bleeding control.

Induced Hypothermia to 4.2°C with Neurologically Intact Survival: A Forgotten Case Series.

The lowest recorded core temperature from which a person with accidental hypothermia has survived neurologically intact is 11.8°C in a 2-y-old boy. The lowest recorded temperature from which an adult has been resuscitated neurologically intact is 13.7°C in a 29-y-old woman. The lowest core temperature with survival from induced hypothermia has been quoted as 9°C. We discovered a case series (n=50) from 1961 in which 5 patients with core temperatures below 11.8°C survived neurologically intact. The lowest core temperature in this group was 4.2°C. The authors also presented cardiovascular and other physiologic data at various core temperatures. The patients in the case series showed a wide variation in individual physiological responses to hypothermia. It is not known whether survival from accidental hypothermia is possible with a core temperature below 11.8°C, but this case series suggests that the lower limit for successful resuscitation may be far lower. We advise against using core temperature alone to decide whether a hypothermic patient in cardiac arrest has a chance of survival.

Rapid ascents of Mt Everest: normobaric hypoxic preacclimatization.

BACKGROUND: Acclimatization to high altitude is time consuming. An expedition to Mt Everest (8848 m) requires roughly 8 weeks. Therefore it seems very attractive to reach the summit within 3 weeks from home, which is currently promised by some expedition tour operators. These rapid ascent expeditions are based on two main components, normobaric hypoxic training (NHT) prior to the expedition and the use of high flow supplemental oxygen (HFSO2). We attempted to assess the relative importance of these two elements. METHODS: We evaluated the effect of NHT on the basis of the available information of these rapid ascent expeditions and our experiences made during an expedition to Manaslu (8163 m) where we used NHT for preacclimatization. To evaluate the effect of an increased O2 flow rate we calculated its effect at various activity levels at altitudes of 8000 m and above. RESULTS: So far rapid ascents to Mt Everest have been successful. The participants carried out 8 weeks of NHT, reaching sleeping altitudes = 7100 m and spent at least 300 h in NH. At rest a flow rate of 2 l O2/min is sufficient to keep the partial pressure of inspired oxygen (PIO2) close to 50 mm Hg even at the summit. For ativities of ~80% of the maximum rate of oxygen consumption (VO2max) at the summit 6 l O2/min are required to maintain a PIO2 above 50 mm Hg. DISCUSSION: NHT for preacclimatization seems to be the decisive element of the offered rapid ascent expeditions. An increased O2 flow rate of 8 l/min is not mandatory for climbing Mt Everest. CONCLUSIONS: Preacclimatization using normobaric hypoxica (NH) is far more important than the use of HFSO2. We think that NHT will be widely used in the future. The most effective regimen of preacclimatization in NH, the duration of each session and the optimal FIO2 are still unclear and require further study.

In-vitro study of species-specific coagulation differences in animals and humans using rotational thromboelastometry (ROTEM).

Animal tests are conducted in all fields of trauma research, but transferability of these data to humans is limited. For example, it is still unclear which animal species is most similar to humans in terms of physiology of blood coagulation. To improve transferability and raise awareness of the existing differences, we compared human coagulation to coagulation of different animals. Rotational thromboelastometry was used to analyse the blood of pigs, sheep, rabbits and dogs. Animal data were compared with human coagulation based on the number of significant differences of the test parameters and on a descriptive comparison of the extent of relative deviation of the single values. All animal species showed significant differences in coagulation properties when compared with humans. Coagulation parameters of dogs and sheep were on average most similar to humans. However, there is no animal which is most similar to humans concerning all aspects of coagulation. Differences in coagulation between humans and animals are significant. This must be taken into account when transferring animal test data to humans.

Challenges of Military Health Service Support in Mountain Warfare.

INTRODUCTION: History is full of examples of the influence of the mountain environment on warfare. The aim of this article is to identify the main environmental hazards and summarize countermeasures to mitigate the impact of this unique environment. METHODS: A selective PubMed and Internet search was conducted. Additionally, we searched bibliographies for useful supplemental literature and included the recommendations of the leading mountain medicine and wilderness medicine societies. RESULTS: A definition of mountain warfare mainly derived from environmental influences on body functions is introduced to help identify the main environmental hazards. Cold, rugged terrain, hypoxic exposure, and often a combination and mutual aggravation of these factors are the most important environmental factors of mountain environment. Underestimating this environmental influence has decreased combat strength and caused thousands of casualties during past conflicts. Some marked differences between military and civilian mountaineering further complicate mission planning and operational sustainability. CONCLUSIONS: To overcome the restrictions of mountain environments, proper planning and preparation, including sustained mountain mobility training, in-depth mountain medicine training with a special emphasize on prolonged field care, knowledge of acclimatization strategies, adapted time calculations, mountain-specific equipment, air rescue strategies and makeshift evacuation strategies, and thorough personnel selection, are vital to guarantee the best possible medical support. The specifics of managing risks in mountain environments are also critical for civilian rescue missions and humanitarian aid.

Oxygen saturation increases over the course of the night in mountaineers at high altitude (3050-6354 m).

BACKGROUND: Blood oxygen saturation (SpO 2 ) is frequently measured to determine acclimatization status in high-altitude travellers. However, little is known about nocturnal time course of SpO 2 (SpO 2N ), but alterations in SpO 2N might be practically relevant as well. To this end, we describe the time-course of SpO 2N in mountaineers at high altitude. METHODS: SpO 2N was continuously measured in ten male mountaineers during a three-week expedition in Peru (3,050-6,354m). Average SpO 2N of the first (SpO 2N1 ) and second half (SpO 2N2 ) of an individual's sleep duration was calculated from 2h intervals of uninterrupted sleep. Heart rate oscillations and sleep dairies were used to exclude periods of wakefulness. SpO 2 was also measured at rest in the morning. RESULTS: SpO 2N significantly increased from SpO 2N1 to SpO 2N2 . The magnitude of this increase (ΔSpO 2 ) was reduced with time spent at altitude. On night 1 (3,050m) SpO 2 increased from 83.4% (N1) to 86.3% (N2). At the same location on night 21, SpO 2 increased from 88.3% to 90.1%, which is a relative change of 4.7% and 2.0%, respectively. This pattern of increase in SpO 2N was perturbed when individual acclimatization was poor or altitude was extreme (5630m). SpO 2N was significantly lower than SpO 2 at rest in the morning. CONCLUSIONS: This study is the first to demonstrate an increase of SpO 2 during the night in mountaineers at high altitude (3,050-6,354m) with high consistency between and within subjects. The magnitude of ΔSpO 2N decreased as acclimatization improved, suggesting that these changes in ΔSpO 2 between nights might be a valuable indicator of individual acclimatization. In addition, the failure of any increase in SpO 2N during the night might indicate insufficient acclimatization. Even though underlying mechanisms for the nocturnal increase remain unclear, the timing of SpO 2N measurement is obviously of utmost importance for its interpretation. Finally our study illustrates the detailed effects of ventilatory acclimatization over several weeks.

The effect of a combined thoracic and soft-tissue trauma on blood flow and tissue formation in fracture healing in rats.

INTRODUCTION: Previously, it was found that fracture healing is impaired by blunt chest trauma and an additional soft-tissue trauma. The mechanisms leading to this disturbance are largely unknown. Here, we investigated the effect of thoracic and soft-tissue trauma on blood flow of the injured lower leg and on tissue differentiation and callus formation during fracture healing. MATERIALS AND METHODS: Male Wistar rats received either a mid-shaft fracture of the tibia alone (group A), an additional chest trauma (group B), or additional chest and soft-tissue traumas (group C). Peripheral blood flow was determined by Laser Doppler Flowmetry before and after the injury, and on observation days 1, 3, 7, 14, and 28. Quantitative histological analysis was performed to assess callus size and composition. RESULTS: All groups displayed an initial decrease in blood flow during the first 3 days post-trauma. A recovery of the blood flow that even exceeded preoperative levels occurred in group A and later and to a lesser degree in group B, but not in group C. The amount of callus formation decreased with increasing trauma load. More cartilage was formed after 7 days in groups B and C than in group A. At later healing time points, callus composition did not differ significantly. CONCLUSIONS: An increasing injury burden causes a decreasing blood supply capacity and revascularization, and leads to impaired callus formation and an increasing delay in bone healing.

Biomechanical in vitro comparison of radiofrequency kyphoplasty and balloon kyphoplasty.

PURPOSE: Balloon kyphoplasty (BK) has emerged as a popular method for treating osteoporosis vertebral compression fractures (OVCFs). In response to several shortcomings of BK, alternative methods have been introduced, among which is radiofrequency kyphoplasty (RFK). Biomechanical comparisons of BK and RFK are very sparse. The purpose of this study was to perform a biomechanical study in which BK and RFK are compared. METHODS: Each of the two study groups comprised six specimens prepared from two functional spinal units (FSUs) cut from fresh-frozen cadaveric spines (3 of T9-T11 and 3 of T12-L2). VCFs (A1.2 type) were created in the middle VB of each of the FSUs, with a height loss of 30% of the VB. After that, the specimens were subjected to cyclic compression-compression loading. The following parameters were determined: range of motion (ROM), height of the middle VB, augmentation time, cement interdigitation and cement distribution. Also, the cement layer, the trabecular bone in the augmented VB and the bone-cement interface were examined for cracks. All of these parameters were determined at various stages, namely in the intact middle VB and after its fracture, cement augmentation and subject to the cyclic loading protocol. RESULTS: Fractures caused a significant increase in median ROM and a significant reduction in the height of fractured VB. Cement augmentation significantly stabilized the fractures and led to partial height restoration. ROM and vertebral height, however, were not restored to the intact levels. Cyclic loading led to a further significant increase in ROM and a significant height reduction. There were no significant differences between BK and RFK in terms of any of these parameters. CONCLUSIONS: BK and RFK achieved similar results for fracture stabilization and restoration of the height of the fractured VB. RFK involved shorter cement augmentation time and less damage to the trabecular bone.

Efficacy of Hemostatic Agents in Humans With Rotational Thromboelastometry: An in-vitro Study.

OBJECTIVES: Hemorrhage is the leading cause of preventable death in military conflicts. Different types of hemostatic dressings have been compared in animal studies for their ability to control bleeding. However, the effects of hemostatic agents in animals may be different from those in humans. The aim of this study was to assess the efficacy of hemostatic dressings in human blood. METHODS: Clotting time, clot formation time, α-angle, maximum clot firmness, and lysis index of human blood incubated with QuikClot Gauze, Celox Gauze, QuikClot ACS+, and standard gauze, were compared using rotational thromboelastometry (ROTEM). Nonactivated, intrinsically activated, extrinsically activated, and fibrin-based ROTEM were used to elucidate different mechanisms of action of those dressings. RESULTS: QuikClot Gauze was the most efficacious hemostatic dressing, followed by Celox Gauze and standard gauze. QuikClot ACS+ was clearly outperformed. CONCLUSIONS: Modern hemostatic dressings such as QuikClot Gauze and Celox Gauze should be preferred to previous generations of hemostatic dressings, such as QuikClot ACS+. In vitro studies like ROTEM can provide valuable information about the mechanisms of action of hemostatic dressings. A combination of different mechanisms of action may increase the efficacy of hemostatic dressings.