Injuries and illness of athletes at the Tokyo 2020 Olympic and Paralympic summer games visiting outside facilities.

This study aimed to identify the reasons for transferring athletes to local medical facilities during the Olympic and Paralympic Games. Data on 567 injuries and other illnesses of athletes treated at the on-site clinics were collected from the Tokyo 2020 Organizing Committee. Of these, 84 athletes who required outpatient care during the Games were registered for this survey. During the Olympic and Paralympic Games, 66 (8.3/1 000) and 18 (7.2/1 000) athletes, respectively, consulted external medical facilities. In the Olympic Games, the reasons for these visits included 48 cases (72.7%) of injuries, 13 (19.7%) cases of illnesses, and 5 (7.6%) cases of heat stroke illness (HSI). Of these patients, 56 (84.9%) were treated as outpatients and 10 (15.1%) were hospitalized, while three of these patients required hospitalization for > 7 days. On the other hand, in the Paralympics Games, there were 7 (38.8%) cases of injuries, 9 (50.0%) other illnesses, 1 (5.6%) case of HSI, and 1 (5.6%) other cases, of which 11 (61.1%) were treated as outpatients and 7 (38.9%) were hospitalized, but none was hospitalized for > 7 days. Injuries accounted for 70% of the total cases at the 2021 Olympic Games, but only three (0.05%) were severe cases that required hospitalization for more than 1 week. In contrast, in the Paralympic Games, other illnesses accounted for approximately half of the total cases. This study provides details on the extent of injuries and other illnesses that were transferred to outside facilities, which has not been documented in previous games.

Exploring the Potential of CarbonCool® in Rapid Prehospital Cooling for Severe Heat Stroke.

OBJECTIVE: Heat stroke is a life-threatening condition that is characterized by body temperatures above 40 °C and central nervous system dysfunction. Immediate cooling is imperative to prevent irreversible cellular damage and improve patient outcomes. Here, we report two cases of heat stroke that highlight the use of a novel cooling suit (CarbonCool®) as a rapid cooling intervention administered in the prehospital setting, primarily focusing on patients with classic heat stroke. METHODS: This study was a retrospective review of two cases involving older patients with severe classic heat stroke, wherein CarbonCool® was used. The device was deployed at the scene of the incidents, throughout transport, and into the emergency department setting, allowing for continuous cooling and medical intervention as needed. The effectiveness of the cooling device was assessed based on the rate of temperature reduction and overall clinical outcomes of the patients. RESULTS: In both cases, CarbonCool® facilitated a rapid reduction in body temperature, aligning with the crucial requirement of immediate cooling for the management of heat stroke. The first case involved a comatose 90-year-old woman whose body temperature decreased from 42.0 to 35.8 °C within 60 min. The second case involved a comatose 70-year-old man who experienced a decrease in body temperature from 41.2 to 36.6 °C over 196 min. CarbonCool® allowed for the execution of concurrent resuscitative procedures and was compatible with various imaging modalities (including computed tomographic scan), allowing for continuous application from the scene to the intensive care unit. Moreover, both patients showed marked improvements in consciousness and were stabilized without the need for more invasive cooling procedures that are typically employed in hospital settings for such cases. Both patients were discharged without any disabilities. CONCLUSION: We present an innovative approach to prehospital care for patients with heat stroke through the use of CarbonCool®, highlighting its efficacy for rapid cooling and its potential impact on patient outcomes. However, further studies are warranted to fully confirm the efficacy of the system.

Crush syndrome: a review for prehospital providers and emergency clinicians.

INTRODUCTION: Disasters and accidents have occurred with increasing frequency in recent years. Primary disasters have the potential to result in mass casualty events involving crush syndrome (CS) and other serious injuries. Prehospital providers and emergency clinicians stand on the front lines of these patients' evaluation and treatment. However, the bulk of our current knowledge, derived from historical data, has remained unchanged for over ten years. In addition, no evidence-based treatment has been established to date. OBJECTIVE: This narrative review aims to provide a focused overview of, and update on, CS for both prehospital providers and emergency clinicians. DISCUSSION: CS is a severe systemic manifestation of trauma and ischemia involving soft tissue, principally skeletal muscle, due to prolonged crushing of tissues. Among earthquake survivors, the reported incidence of CS is 2-15%, and mortality is reported to be up to 48%. Patients with CS can develop cardiac failure, kidney dysfunction, shock, systemic inflammation, and sepsis. In addition, late presentations include life-threatening systemic effects such as hypovolemic shock, hyperkalemia, metabolic acidosis, and disseminated intravascular coagulation. Immediately beginning treatment is the single most important factor in reducing the mortality of disaster-situation CS. In order to reduce complications from CS, early, aggressive resuscitation is recommended in prehospital settings, ideally even before extrication. However, in large-scale natural disasters, it is difficult to diagnose CS, and to reach and start treatments such as continuous administration of massive amounts of fluid, diuresis, and hemodialysis, on time. This may lead to delayed diagnosis of, and high on-site mortality from, CS. To overcome these challenges, new diagnostic and therapeutic modalities in the CS animal model have recently been advanced. CONCLUSIONS: Patient outcomes can be optimized by ensuring that prehospital providers and emergency clinicians maintain a comprehensive understanding of CS. The field is poised to undergo significant advances in coming years, given recent developments in what is considered possible both technologically and surgically; this only serves to further emphasize the importance of the field, and the need for ongoing research.

Reflection characteristics of a cavity-resonator-integrated guided-mode resonance mirror for a microdiameter Gaussian beam.

A guided-mode resonance mirror was designed for reflecting a vertically incident Gaussian beam of 3.6-µm beam waist to a backpropagating Gaussian beam. A grating coupler (GC) is integrated in a waveguide resonance cavity consisting of a pair of distributed Bragg reflectors (DBRs) on a reflection substrate. An incident free-space wave is coupled by the GC into the waveguide, and the guided wave is resonated in the waveguide cavity and coupled out by the same GC to a free-space wave simultaneously in resonance condition. The reflection phase can vary by 2π rad, according to wavelength in a wavelength band of resonance. The grating fill factors of the GC were apodized to have a Gaussian profile in its coupling strength and resultantly maximize a Gaussian reflectance defined by the power ratio of backpropagating Gaussian beam to the incident Gaussian beam. The fill factors of the DBR were also apodized in the boundary zone to the GC in order to avoid discontinuity in equivalent refractive index distribution and resultant scattering loss. Guided-mode resonance mirrors were fabricated and characterized. The Gaussian reflectance of the mirror with the grating apodization was measured to be 90%, higher by 10% than that of the mirror without apodization. It is also demonstrated that the reflection phase changes more than π rad within wavelength band of 1 nm. The fill factor apodization narrows the resonance band.

Incidence and factor analysis for the heat-related illness on the Tokyo 2020 Olympic and Paralympic Games.

Introduction: Among the 43 venues of Tokyo 2020 Olympic Games (OG) and 33 venues of Paralympic Games (PG) were held, the heat island effect was highly expected to cause heat-related illnesses in the outdoor venues with maximum temperatures exceeding 35°C. However, the actual number of heat-related illness cases during the competition was lower than that was initially expected, and it was unclear under what conditions or environment-related heat illnesses occurred among athletes. Object: To clarify the cause and factors contributing to the occurrence of heat-related illness among athletes participating in the Tokyo 2020 Olympic and Paralympic Games. Method: This retrospective descriptive study included 15 820 athletes from 206 countries. From 21 July 2021 to 8 August 2021 for the Olympics, and from 24 August 2021 to 5 September 2021 for the Paralympics. The number of heat-related illness cases at each venue, the incidence rate for each event, gender, home continent, as well as the type of competition, environmental factors (such as venue, time, location and wet-bulb globe temperature (WBGT)), treatment factor and the type of competition were analysed. Results: More number of heat-related illnesses among athletes occurred at the OG (n=110, 76.3%) than at the PG (n=36, 23.7%). A total of 100 cases (100%) at the OG and 31 cases (86.1%) at the PG occurred at the outdoors venues. In the OG, a total of 50 cases (57.9%) occurred during the competition of marathon running and race walking at Sapporo Odori Park. Six of those, were diagnosed with exertional heat illness and treated with cold water immersion (CWI) at OG and one case at PG. Another 20 cases occurred in athletics (track and field) competitions at Tokyo National Olympic Stadium. In total, 10 cases (10.0%) were diagnosed with severe heat illness in the OG and 3 cases (8.3%) in the PG. Ten cases were transferred to outside medical facilities for further treatment, but no case has been hospitalised due to severe condition. In the factor analysis, venue zone, outdoor game, high WBGT (<28°C) and endurance sports have been found to have a higher risk of moderate and severe heat-related illness (p<0.05). The incidence rate and severity could be attenuated by proper heat-related illness treatment (CWI, ice towel, cold IV transfusion and oral hydration) reduced the severity of the illness, providing summer hot environment sports. Conclusion: The Tokyo 2020 Olympic and Paralympic summer games were held. Contrary to expectations, we calculated that about 1 in 100 Olympic athletes suffered heat-related illness. We believe this was due to the risk reduction of heat-related illness, such as adequate prevention and proper treatment. Our experience in avoiding heat-related illness will provide valuable data for future Olympic summer Games.

Acute in-competition medical care at the Tokyo 2020 Olympics: a retrospective analysis.

OBJECTIVE: To analyse injuries and illnesses during the 2020 Tokyo Olympic Summer Games. METHODS: This retrospective descriptive study included 11 420 athletes from 206 National Olympic Committees and 312 883 non-athletes. Incidences of injuries and illnesses during the competition period from 21 July to 8 August 2021 were analysed. RESULTS: A total of 567 athletes (416 injuries, 51 non-heat-related illnesses and 100 heat-related illnesses) and 541 non-athletes (255 injuries, 161 non-heat-related illnesses and 125 heat-related illnesses) were treated at the competition venue clinic. Patient presentation and hospital transportation rates per 1000 athletes were 50 and 5.8, respectively. Marathons and race walking had the highest incidence of injury and illness overall (17.9%; n=66). The highest incidence of injury (per participant) was noted in boxing (13.8%; n=40), sport climbing (12.5%; n=5) and skateboarding (11.3%; n=9), excluding golf, with the highest incidence of minor injuries. Fewer infectious illnesses than previous Summer Olympics were reported among the participants. Of the 100 heat-related illnesses in athletes, 50 occurred in the marathon and race walking events. Only six individuals were transported to a hospital due to heat-related illness, and none required hospital admission. CONCLUSION: Injuries and heat-related illnesses were lower than expected at the 2020 Tokyo Olympic Summer Games. No catastrophic events occurred. Appropriate preparation including illness prevention protocols, and treatment and transport decisions at each venue by participating medical personnel may have contributed to these positive results.

Repeatable Actuations of Organic Single Crystal Fibers Driven by Thermosalient-Phase-Transition-Induced Buckling.

Thermosalient crystals are molecular solids that exhibit explosive motions, such as sudden breaks and jumps, due to temperature-induced structural phase transitions between two polymorphs. Therefore, the development of molecular actuators with superior speed and power by deriving mechanical work from explosive motion is a fascinating concept. However, thermosalient transitions often cause crystal disintegration, which hampers repeatable phase transitions between the polymorphs. Here, it is reported that single crystal nano/microfibers of 1, 2, 4, 5-tetrabromobenzene (TBB), whose bulk crystals exhibit thermosalient behavior at ≈40 °C, can repeatedly transform between the low and high temperature polymorphs without disintegration. The structural tolerance against phase transition is attributed to the high flexibility of the nano/microfibers. It is observed that a structure consisting of a TBB fiber with both ends pinned to the substrate repeatedly buckles and straightens when the temperature is varied between 30 and 40 °C. It is demonstrated that buckling can lead to large displacement actuation as compared to a simple length change of the fiber. Moreover, the force generated by the buckling fiber is estimated and it is found that it can generate a force large enough to flick an object ≈104 times heavier than the fiber itself into the air against gravity.

Development of a Gait Rehabilitation Robot Using an Exoskeleton and Functional Electrical Stimulation: Validation in a Pseudo-paraplegic Model.

OBJECTIVE: We have developed a robot for gait rehabilitation of paraplegics for use in combination with functional electrical stimulation (FES). The purpose of this study was to verify whether the robot-derived torque can be reduced by using FES in a healthy-person pseudo-paraplegic model. METHODS: Nine healthy participants (22-36 years old) participated in this study. The robot exoskeleton was designed based on the hip-knee-ankle-foot orthosis for paraplegia. Participants walked on a treadmill using a rehabilitation lift to support their weight. The bilateral quadriceps femoris and hamstrings were stimulated using FES. The participants walked both with and without FES, and two walking speeds, 0.8 and 1.2 km/h, were used. Participants walked for 1 min in each of the four conditions: (a) 0.8 km/h without FES, (b) 0.8 km/h with FES, (c) 1.2 km/h without FES, and (d) 1.2 km/h with FES. The required robot torques in these conditions were compared for each hip and knee joint. The maximum torque was compared using one-way analysis of variance to determine whether there was a difference in the amount of assist torque for each gait cycle. RESULTS: Walking with the exoskeleton robot in combination with FES significantly reduced the torque in hip and knee joints, except for the right hip during extension. CONCLUSIONS: In the healthy-participant pseudo-paraplegic model, walking with FES showed a reduction in the robot-derived torque at both the hip and knee joints. Our rehabilitation robot combined with FES has the potential to assist paraplegics with various degrees of muscle weakness and thereby provide effective rehabilitation.

Immunoglobulin a suppresses B cell receptor-mediated activation of mouse B cells with differential inhibition of signaling molecules.

CONTEXT: We previously reported that monoclonal mouse immunoglobulin (Ig) A, OA-4, attenuates sensitization in mice by suppressing B cell activation. OBJECTIVE: Here, it is demonstrated for the first time that mouse IgA inhibits mouse B cell activation in vitro under natural conditions (i.e. in the absence of chemical, physical, and genetic modifications of IgA and B cells). MATERIALS AND METHODS: Mouse splenocytes were stimulated with anti-B cell receptor (BCR) antibody or lipopolysaccharide (LPS) in the presence or absence of OA-4. Splenic B cell proliferation and the activation of several intracellular signaling molecules were measured. RESULTS: Anti-BCR antibody-induced proliferation was markedly inhibited by OA-4 or the commercially available mouse IgA S107, whereas LPS-induced proliferation was weakly attenuated by a high concentration of OA-4. Moreover, OA-4 markedly decreased the anti-BCR antibody-induced phosphorylation of p44/42 mitogen-activated protein kinase (ERK) and CD22 and decreased phosphorylated phospholipase (PLC) γ2 and intracellular Ca2+ levels moderately, whereas protein kinase B (Akt) phosphorylation was not affected by OA-4. The MAPK/ERK kinase-ERK and phosphoinositide 3-kinase-Akt pathways were found to play a role in the proliferation of splenocytes induced by anti-BCR antibody based on experiments with their inhibitors. In contrast to that in splenic B cells, ERK phosphorylation induced by anti-BCR antibody in A20 cells was not inhibited by OA-4. The modulatory effects of IgA were different among the cell types and signaling pathways. CONCLUSION: IgA is a potential immunoregulatory drug utilizing new mechanisms that affect splenic B cells but not A20 lymphomas.

Penetrating cardiac injury repaired under "intentional cardiac arrest" with adenosine triphosphate.

BACKGROUND: Repairing a cardiac injury with beating heart is sometimes difficult and is associated with increased risks of complications. Here we report a case of cardiac injury repaired with administration of adenosine triphosphate (ATP). CASE PRESENTATION: A 46-year-old man was stabbed in his chest with a knife and transferred to our hospital. He was hemodynamically unstable, and echocardiography showed pericardial effusion. Emergency thoracotomy revealed a full-thickness injury in the right ventricle next to the coronary artery. He went into cardiac arrest and was resuscitated with adrenaline administration. We tried to suture immediately, but it was difficult because of tachycardia. After administering 20 mg of ATP (80 mg in total over 15 min), bradycardia was induced that led to "intentional cardiac arrest" after which suturing was performed. He was discharged on the 13th day without complications. CONCLUSION: Cases of penetrating cardiac injury repaired using ATP are rare. Administration of ATP may be a useful option while repairing cardiac injuries.

Phase-transition-induced jumping, bending, and wriggling of single crystal nanofibers of coronene.

For decades, it has been reported that some organic crystals suddenly crack, break, or jump when they are heated from room temperature. Recently, such crystals have been intensively studied both in fundamental science and for high-speed mechanical device applications. According to these studies, the sudden crystal motions have been attributed to structural phase transitions induced by heating. Stress created by the phase transition is released through the sudden and rapid motion of the crystals. Here we report that single crystal nanofibers of coronene exhibit a new type of ultrafast motion when they are cooled from room temperature and subsequently heated to room temperature. The nanofibers make centimeter-scale jumps accompanied by surprisingly unique behaviors such as sharp bending and wriggling. We found that the motions are caused by a significantly fast structural phase transition between two polymorphs of coronene. A theoretical investigation revealed that the sudden force generated by the phase transition together with the nanoscale dimensions and elastic properties create dynamical instability in the nanofibers that results in the motions. Our finding demonstrates the novel mechanism that leads to ultrafast, large deformation of organic crystals.

Diagnosis and Surgical Treatment of Thoracic Dorsal Arachnoid Web: A Report of Two Cases.

INTRODUCTION: An arachnoid web (AW) is a relatively rare disease and shows clinical symptoms and radiological findings similar to those of an arachnoid cyst (AC) or spinal cord herniation (SCH). Since the operative procedures for an AW are generally different from those intrathecal disorders, correct preoperative differential diagnosis is important. The purposes of this study were to report the usefulness of magnetic resonance imaging (MRI) and computed tomography (CT) myelography for diagnosing AW and to show the histological findings and clinical results. Case Description. Two patients, a 79-year-old man and a 43-year-old woman, are presented. The primary diagnoses were AC with ossification of the ligamentum flavum and epidural hematoma, respectively, in previous hospitals. They were finally diagnosed by the characteristic MRI and CT myelogram finding called the "scalpel sign." Histological findings showed epithelial cells and fibrous tissue derived from arachnoid tissues and microcalcifications. After surgery, the scalpel sign has vanished, and aggravation of their symptoms was prevented. CONCLUSION: An AW is refractory, but early detection by MRI and CT myelography and early treatment improve outcomes after surgery.

Division of functional roles for termite gut protists revealed by single-cell transcriptomes.

The microbiome in the hindgut of wood-feeding termites comprises various species of bacteria, archaea, and protists. This gut community is indispensable for the termite, which thrives solely on recalcitrant and nitrogen-poor wood. However, the difficulty in culturing these microorganisms has hindered our understanding of the function of each species in the gut. Although protists predominate in the termite gut microbiome and play a major role in wood digestion, very few culture-independent studies have explored the contribution of each species to digestion. Here, we report single-cell transcriptomes of four protists species comprising the protist population in worldwide pest Coptotermes formosanus. Comparative transcriptomic analysis revealed that the expression patterns of the genes involved in wood digestion were different among species, reinforcing their division of roles in wood degradation. Transcriptomes, together with enzyme assays, also suggested that one of the protists, Cononympha leidyi, actively degrades chitin and assimilates it into amino acids. We propose that C. leidyi contributes to nitrogen recycling and inhibiting infection from entomopathogenic fungi through chitin degradation. Two of the genes for chitin degradation were further revealed to be acquired via lateral gene transfer (LGT) implying the importance of LGT in the evolution of symbiosis. Our single-cell-based approach successfully characterized the function of each protist in termite hindgut and explained why the gut community includes multiple species.

Design considerations of grating couplers in directionally coupled waveguides.

The far-field pattern of an optical wave radiating from a grating coupler integrated in a directional coupler is discussed based on the coupled mode theory. It is shown that there are two types of intensity distributions with respect to the radiation angle. One type shows a simple single lobe, while the other has a deformed lobe or two lobes. Far-field patterns are discussed along with near-field patterns. They are determined by directional coupling strength as well as radiation decay strength. A parameter is introduced to indicate the type. The indicator is useful as a key parameter for device design.

Design of a narrowband retroreflector based on guided-mode resonance.

A narrowband retroreflector consisting of a grating coupler and a waveguide cavity integrated on a highly reflective substrate is proposed. A theoretical model based on coupled-mode theories is discussed to provide analytical expression of the reflection and transmission coefficients under oblique incidence. The retroreflector was designed with a 20-µm aperture for 1540-nm-wavelength operation and 8-deg-angle incidence. Finite-difference time-domain simulation showed a retroreflection spectrum with a bandwidth of 2 nm and a maximum retroreflectance of 85% and a minimum specular reflectance of 5%.

Emerging Atomic Energy Levels in Zero-Dimensional Silicon Quantum Dots.

Driven by the emergence of colloidal semiconductor quantum dots (QDs) of tunable emission wavelengths, characteristic of exciton absorption peaks, outstanding photostability and solution processability in device fabrication have become a key tool in the development of nanomedicine and optoelectronics. Diamond cubic crystalline silicon (Si) QDs, with a diameter larger than 2 nm, terminated with hydrogen atoms are known to exhibit bulk-inherited spin and valley properties. Herein, we demonstrate a newly discovered size region of Si QDs, in which a fast radiative recombination on the order of hundreds of picoseconds is responsible for photoluminescence (PL). Despite retaining a crystallographic structure like the bulk, controlling their diameters in the 1.1-1.7 nm range realizes the strong PL with continuous spectral tunability in the 530-580 nm window, the narrow spectral line widths without emission tails, and the fast relaxation of photogenerated carriers. In contrast, QDs with diameters greater than 1.8 nm display the decay times on the microsecond order as well as the previous Si QDs. In addition to the five-orders-of-magnitude variation in the PL decay time, a systematic study on the temperature dependence of PL properties suggests that the energy structure of the smaller QDs does not retain an indirect band gap character. It is discussed that a 1.7 nm diameter is critical to undergo changes in energy structure from bulky to molecular configurations.

Long-Term Outcomes of Endovascular Stenting for Blunt Renal Artery Injuries with Stenosis: A Report of Five Consecutive Cases.

BACKGROUND: Renal artery stenting is performed for renal artery injuries to preserve renal function and prevent renovascular hypertension. However, its indications are controversial and its long-term prognosis remains unknown. Here, we evaluate the characteristics and long-term outcomes of renal artery stenting for blunt renal artery injuries at our institution. METHODS: We retrospectively reviewed patients with blunt renal artery injuries who had been treated with stenting over a 12-year period at our institution. Five patients (three men and two women) were included. RESULTS: Trauma resulted from falls in three patients and motor vehicle accidents in two. All patients had experienced multiple injuries (median injury severity score, 24 [range, 16-48]; median revised trauma score, 5.9672 [4.0936-7.8408]; and median probability of survival, 0.689 [0.533-0.980]). All renal artery injuries involved stenosis because of traumatic arterial dissection or intimal tear; no cases of total occlusion were observed. No complications due to the intervention itself were observed. Although two patients developed reversible acute renal failure, none required long-term hemodialysis. One patient with renovascular hypertension was treated with antihypertensive agents for a month and subsequently became normotensive without further medication. All patients underwent postoperative computed tomography, which revealed no stent occlusion or renal atrophy. Renal scintigraphy for three patients demonstrated preserved differential renal function. All five patients survived. CONCLUSIONS: Renal artery stenting for hemodynamically stable blunt renal artery injuries with stenosis is suggested to be safe and helps in avoiding long-term hemodialysis and renovascular hypertension.

The reductive aromatization of naphthalene diimide: a versatile platform for 2,7-diazapyrenes.

The reductive aromatization of naphthalene diimide provides tetrapivaloxy-2,7-diazapyrene, which serves as a versatile platform toward peripherally substituted 2,7-diazapyrenes. Time-resolved microwave conductivity measurements demonstrated that the intrinsic electron mobility of 2,7-diazapyrene is significantly higher than that of the corresponding pyrene.

Wavelength division multiplexer based on cavity-resonator-integrated guided-mode resonance filters for a compact multi-wavelength light source.

Cavity-resonator-integrated guided-mode resonance filters (CRIGF) consisting of a grating coupler in a waveguide resonator formed by two distributed Bragg reflectors of different reflectances can act as a wavelength-selective reflector and an input waveguide coupler for an incident free-space wave. Integration of CRIGFs in a waveguide is proposed to give an array of external mirrors and a wavelength division multiplexer for constructing a compact multi-wavelength light source. Four CRIGFs of 10-µm-size aperture with a wavelength spacing of 15 nm were designed and fabricated. The reflectance of 62% and output efficiency of higher than 18% were theoretically predicted. Multiplexing of four wavelengths was confirmed experimentally.

Initial inferior vena cava diameter predicts massive transfusion requirements in blunt trauma patients: A retrospective cohort study.

OBJECTIVES: The inferior vena cava (IVC) diameter is associated with shock and increased mortality in trauma patients. However, there are no reports examining the association between the IVC diameter and massive transfusion (MT) requirements in trauma patients. The aim of this study was to evaluate the association between IVC diameter and MT requirements in patients with blunt trauma. METHODS: We retrospectively reviewed all patients who were consecutively hospitalized with blunt trauma (Injury Severity Score [ISS] ≥16) between from November 1, 2011 to March 30, 2016. Univariate and multivariate analyzes were performed to identify the independent predictors of MT (defined as >10units of red cell concentrate transfusions within 24h of admission). Receiver operating characteristic curve and the area under the curve (AUC) were estimated. RESULTS: Of the 222 patients included in this study, MT occurred in 22.5% patients. On multiple regression analysis, IVC diameter [Odds ratio (OR), 0.88; 95% confidence interval (CI), 0.80-0.96; p<0.01], fibrin degradation product (FDP; OR, 1.01; 95% CI, 1.00-1.01; p<0.01), and fibrinogen level (OR, 0.99; 95% CI, 0.98-1.00; p<0.01) were strong predictors of MT. IVC diameter demonstrated moderate accuracy (AUC, 0.74; cutoff level, 13.0mm; sensitivity, 67%; specificity, 73%). Combined cutoff levels of FDP <80.5µg/ml, fibrinogen ≥165mg/dl, and IVC diameter ≥13mm could also determine how unnecessary a MT was with 100% accuracy. CONCLUSIONS: Initial IVC diameter is a predictor of MT in blunt trauma patients.