The more you have, the more you lose: Muscle mass changes in trauma patients with prolonged hospitalizations.

INTRODUCTION: Sarcopenia is a clinically relevant loss of muscle mass with implications of increased morbidity and mortality in adult trauma populations.  Our study aimed to evaluate loss of muscle mass change in adult trauma patients with prolonged hospital stays. METHODS: Retrospective analysis using institutional trauma registry to identify all adult trauma patients with hospital length of stay >14 days admitted to our Level 1 center between 2010 and 2017. All CT images were reviewed, and cross-sectional area (cm2) of the left psoas muscle was measured at the level of the third lumbar vertebral body to determine total psoas area (TPA) and Total Psoas Index (TPI) normalized for patient stature.  Sarcopenia was defined as a TPI on admission below gender specific thresholds of 5.45(cm2/m2) in men and 3.85(cm2/m2) in women.  TPA, TPI, and rates of change in TPI were then evaluated and compared between sarcopenic and non-sarcopenic adult trauma patients. RESULTS: There were 81 adult trauma patients who met inclusion criteria. The average change in TPA was -3.8 cm2 and TPI was -1.3 cm2. On admission, 23% (n = 19) of patients were sarcopenic while 77% (n = 62) were not. Non-sarcopenic patients had a significantly greater change in TPA (-4.9 vs. -0.31, p<0.0001), TPI (-1.7 vs. -0.13, p<0.0001), and rate of decrease in muscle mass (p = 0.0002). 37% of patients who were admitted with normal muscle mass developed sarcopenia during admission.  Older age was the only risk factor independently associated with developing sarcopenia (OR: 1.04, 95%CI 1.00-1.08, p = 0.045). CONCLUSION: Over a third of patients with normal muscle mass at admission subsequently developed sarcopenia with older age as the primary risk factor. Patients with normal muscle mass at admission had greater decreases in TPA and TPI, and accelerated rates of muscle mass loss compared to sarcopenic patients.

A national trauma data bank analysis of large animal-related injuries.

INTRODUCTION: Large animal-related injuries (LARI) are relatively uncommon, but, nevertheless, a public hazard. The objective of this study was to better understand LARI injury patterns and outcomes. MATERIALS AND METHODS: We performed a retrospective review of the 2016 National Trauma Data Bank and used ICD-10 codes to identify patients injured by a large animal. The primary outcome was severe injury pattern, while secondary outcomes included mortality, hospital length of stay, ICU admission, and mechanical ventilation usage. RESULTS: There were 6,662 LARI included in our analysis. Most LARI (66%) occurred while riding the animal, and the most common type of LARI was fall from horse (63%). The median ISS was 9 and the most severe injuries (AIS ≥ 3) were to the chest (19%), head (10%), and lower extremities (10%). The overall mortality was low at 0.8%. Compared to non-riders, riders sustained more severe injuries to the chest (21% vs. 16%, p<0.001) and spine (4% vs. 2%, p<0.001). Compared to motor vehicle collisions (MVC), riders sustained fewer severe injuries to the head (10% vs. 12%, p<0.001) and lower extremity (10% vs. 12%, p=0.01). Compared to auto-pedestrian accidents, non-riders sustained fewer severe injuries to the head (11% vs. 19%, p<0.001) and lower extremity (10% vs. 20%, p<0.001). CONCLUSION: Patients involved in a LARI are moderately injured with more complex injuries occurring in the chest, head, and lower extremities. Fall from horse was the most common LARI mechanism. Overall mortality was low. Compared to non-riders, riders were more likely to sustain severe injuries to the chest and spine. Severe injury patterns were similar when comparing riders to MVC and, given that most LARI are riding injuries, we recommend trauma teams approach LARI as they would an MVC.

Risk scoring models fail to predict pulmonary embolism in trauma patients.

BACKGROUND: We aimed to identify risk factors and risk scoring models to help identify post-traumatic pulmonary embolisms (PE). METHODS: We performed a retrospective review (2014-2019) of all adult trauma patients admitted to our Level I trauma center that received a CT pulmonary angiogram (CTPA) for a suspected PE. A systematic literature search found eleven risk scoring models, all of which were applied to these patients. Scores of patients with and without PE were compared. RESULTS: Of the 235 trauma patients that received CTPA, 31 (13%) showed a PE. No risk scoring model had both a sensitivity and specificity above 90%. The Wells Score had the highest area under the curve (0.65). After logistic regression, no risk scoring model variables were independently associated with PE. CONCLUSIONS: In trauma patients with clinically suspected PE, clinical variables and current risk scoring models do not adequately differentiate patients with and without PE.

Does preoperative magnetic resonance imaging alter the surgical plan in patients with acute traumatic cervical spinal cord injury?

BACKGROUND: Whether magnetic resonance imaging (MRI) adds value to surgical planning for patients with acute traumatic cervical spinal cord injury (ATCSCI) remains controversial. In this study, we compared surgeons' operative planning decisions with and without preoperative MRI. We had two hypotheses: (1) the surgical plan for ATCSCI would not change substantially after the MRI and (2) intersurgeon agreement on the surgical plan would also not change substantially after the MRI. METHODS: We performed a vignette-based survey study that included a retrospective review of all adult trauma patients who presented to our American College of Surgeons-verified level 1 trauma center from 2010 to 2019 with signs of acute quadriplegia and underwent computed tomography (CT), MRI, and subsequent cervical spine surgery within 48 hours of admission. We abstracted patient demographics, admission physiology, and injury details. Patient clinical scenarios were presented to three spine surgeons, first with only the CT and then, a minimum of 2 weeks later, with both the CT and MRI. At each presentation, the surgeons identified their surgical plan, which included timing (none, <8, <24, >24 hours), approach (anterior, posterior, circumferential), and targeted vertebral levels. The outcomes were change in surgical plan and intersurgeon agreement. We used Fleiss' kappa (κ) to measure intersurgeon agreement. RESULTS: Twenty-nine patients met the criteria and were included. Ninety-three percent of the surgical plans were changed after the MRI. Intersurgeon agreement was "slight" to "fair" both before the MRI (timing, κ = 0.22; approach, κ = 0.35; levels, κ = 0.13) and after the MRI (timing, κ = 0.06; approach, κ = 0.27; levels, κ = 0.10). CONCLUSION: Surgical plans for ATCSCI changed substantially when the MRI was presented in addition to the CT; however, intersurgeon agreement regarding the surgical plan was low and not improved by the addition of the MRI. LEVEL OF EVIDENCE: Diagnostic, level II.

Desmopressin is a transfusion sparing option to reverse platelet dysfunction in patients with severe traumatic brain injury.

BACKGROUND: Platelet dysfunction (PD) is an independent predictor of mortality in patients with severe traumatic brain injury (sTBI). Platelet transfusions (PLTs) have been shown to be an effective treatment strategy to reverse platelet inhibition. Their use is contingent on availability and may be associated with increased cost and transfusion-related complications, making desmopressin (DDAVP) attractive. We hypothesized that DDAVP would correct PD similarly to PLTs in patients with sTBI. METHODS: This retrospective study evaluated all blunt trauma patients admitted to an urban, level 1 trauma center from July 2015 to October 2016 with sTBI (defined as head abbreviated injury scale [AIS] ≥3) and PD (defined as adenosine diphosphate [ADP] inhibition ≥60% on thromboelastography) and subsequently received treatment. Per our institutional practice, patients with sTBI and PD are transfused one unit of apheresis platelets to reverse inhibition. During a platelet shortage, we interchanged DDAVP for the initial treatment. Patients were classified as receiving DDAVP or PLT based on the initial treatment. RESULTS: A total of 57 patients were included (DDAVP, n = 23; PLT, n = 34). Patients who received DDAVP were more severely injured (injury severity score, 29 vs. 23; p = 0.045), but there was no difference in head AIS (4 vs. 4, p = 0.16). There was no difference between the two groups in admission platelet count (244 ± 68 × 10/µL vs. 265 ± 66 × 10/µL, p = 0.24) or other coagulation parameters such as prothrombin time, partial thromboplastin time, or international normalized ratio. Before treatment, both groups had similar ADP inhibition as measured by thromboelastography (ADP, 86% vs. 89%, p = 0.34). After treatment, both the DDAVP and PLT groups had similar correction of platelet ADP inhibition (p = 0.28). CONCLUSION: In patients with severe traumatic brain injury and PD, DDAVP may be an alternative to PLTs to correct PD. LEVEL OF EVIDENCE: Therapeutic, level IV.

Fatal crashes in the 5 years after recreational marijuana legalization in Colorado and Washington.

Colorado and Washington legalized recreational marijuana in 2012, but the effects of legalization on motor vehicle crashes remains unknown. Using Fatality Analysis Reporting System data, we performed difference-in-differences (DD) analyses comparing changes in fatal crash rates in Washington, Colorado and nine control states with stable anti-marijuana laws or medical marijuana laws over the five years before and after recreational marijuana legalization. In separate analyses, we evaluated fatal crash rates before and after commercial marijuana dispensaries began operating in 2014. In the five years after legalization, fatal crash rates increased more in Colorado and Washington than would be expected had they continued to parallel crash rates in the control states (+1.2 crashes/billion vehicle miles traveled, CI: -0.6 to 2.1, p = 0.087), but not significantly so. The effect was more pronounced and statistically significant after the opening of commercial dispensaries (+1.8 crashes/billion vehicle miles traveled, CI: +0.4 to +3.7, p = 0.020). These data provide evidence of the need for policy strategies to mitigate increasing crash risks as more states legalize recreational marijuana.

Goal-directed platelet transfusions correct platelet dysfunction and may improve survival in patients with severe traumatic brain injury.

BACKGROUND: Platelet dysfunction, defined as adenosine diphosphate inhibition greater than 60% on thromboelastogram, is an independent predictor of increased mortality in patients with severe traumatic brain injury (TBI). We changed our practice to transfuse platelets for all patients with severe TBI and platelet dysfunction. We hypothesized that platelet transfusions would correct platelet dysfunction and improve mortality in patients with severe TBI. METHODS: This retrospective review included adult trauma patients admitted to our Level I trauma center from July 2015 to October 2016 with severe TBI (head Abbreviated Injury Scale score ≥ 3) who presented with platelet dysfunction and subsequently received a platelet transfusion. Serial thromboelastograms were obtained to characterize the impact of platelet transfusion on clot strength. Subsequently, the platelet transfusion group was compared to a group of historical controls with severe TBI patients and platelet dysfunction who did not receive platelet transfusion. RESULTS: A total of 35 patients with severe TBI presented with platelet dysfunction. Following platelet transfusion clot strength improved as represented by decreased K time, increased α angle, maximum amplitude, and G-value, as well as correction of adenosine diphosphate inhibition. When comparing to 51 historic controls with severe TBI and platelet dysfunction, the 35 study patients who received a platelet transfusion had a lower mortality (9% vs. 35%; p = 0.005). In stepwise logistic regression, platelet transfusion was independently associated with decreased mortality (odds ratio, 0.23; 95% confidence interval, 0.06-0.92; p = 0.038). CONCLUSION: In patients with severe TBI and platelet dysfunction, platelet transfusions correct platelet inhibition and may be associated with decreased mortality. LEVEL OF EVIDENCE: Therapeutic, level II.

Mild to Moderate to Severe: What Drives the Severity of ARDS in Trauma Patients?

Acute respiratory distress syndrome (ARDS) is a complex inflammatory process with multifactorial etiologies. Risk factors for its development have been extensively studied, but factors associated with worsening severity of disease, as defined by the Berlin criteria, are poorly understood. A retrospective chart and trauma registry review identified trauma patients in our surgical intensive care unit who developed ARDS, defined according to the Berlin definition, between 2010 and 2015. The primary outcome was development of mild, moderate, or severe ARDS. A logistic regression model identified risk factors associated with developing ARDS and with worsening severity of disease. Of 2704 total patients, 432 (16%) developed ARDS. Of those, 100 (23%) were categorized as mild, 176 (41%) as moderate, and 156 (36%) as severe. Two thousand two hundred and seventy-two patients who did not develop ARDS served as controls. Male gender, blunt trauma, severe head and chest injuries, and red blood cell as well as total blood product transfusions are independent risk factors associated with ARDS. Worsening severity of disease is associated with severe chest trauma and volume of plasma transfusion. Novel findings in our study include the association between plasma transfusions and specifically severe chest trauma with worsening severity of ARDS in trauma patients.

Is It safe? Nonoperative management of blunt splenic injuries in geriatric trauma patients.

BACKGROUND: Because of increased failure rates of nonoperative management (NOM) of blunt splenic injuries (BSI) in the geriatric population, dogma dictated that this management was unacceptable. Recently, there has been an increased use of this treatment strategy in the geriatric population. However, published data assessing the safety of NOM of BSI in this population is conflicting, and well-powered multicenter data are lacking. METHODS: We performed a retrospective analysis of data from the National Trauma Data Bank (NTDB) from 2014 and identified young (age < 65) and geriatric (age ≥ 65) patients with a BSI. Patients who underwent splenectomy within 6 hours of admission were excluded from the analysis. Outcomes were failure of NOM and mortality. RESULTS: We identified 18,917 total patients with a BSI, 2,240 (12%) geriatric patients and 16,677 (88%) young patients. Geriatric patients failed NOM more often than younger patients (6% vs. 4%, p < 0.0001). On logistic regression analysis, Injury Severity Score of 16 or higher was the only independent risk factor associated with failure of NOM in geriatric patients (odds ratio, 2.778; confidence interval, 1.769-4.363; p < 0.0001). There was no difference in mortality in geriatric patients who had successful vs. failed NOM (11% vs. 15%; p = 0.22). Independent risk factors for mortality in geriatric patients included admission hypotension, Injury Severity Score of 16 or higher, Glasgow Coma Scale score of 8 or less, and cardiac disease. However, failure of NOM was not independently associated with mortality (odds ratio, 1.429; confidence interval, 0.776-2.625; p = 0.25). CONCLUSION: Compared with younger patients, geriatric patients had a higher but comparable rate of failed NOM of BSI, and failure rates are lower than previously reported. Failure of NOM in geriatric patients is not an independent risk factor for mortality. Based on our results, NOM of BSI in geriatric patients is safe. LEVEL OF EVIDENCE: Therapeutic, level IV.

Crash Fatality Rates After Recreational Marijuana Legalization in Washington and Colorado.

OBJECTIVES: To evaluate motor vehicle crash fatality rates in the first 2 states with recreational marijuana legalization and compare them with motor vehicle crash fatality rates in similar states without recreational marijuana legalization. METHODS: We used the US Fatality Analysis Reporting System to determine the annual numbers of motor vehicle crash fatalities between 2009 and 2015 in Washington, Colorado, and 8 control states. We compared year-over-year changes in motor vehicle crash fatality rates (per billion vehicle miles traveled) before and after recreational marijuana legalization with a difference-in-differences approach that controlled for underlying time trends and state-specific population, economic, and traffic characteristics. RESULTS: Pre-recreational marijuana legalization annual changes in motor vehicle crash fatality rates for Washington and Colorado were similar to those for the control states. Post-recreational marijuana legalization changes in motor vehicle crash fatality rates for Washington and Colorado also did not significantly differ from those for the control states (adjusted difference-in-differences coefficient = +0.2 fatalities/billion vehicle miles traveled; 95% confidence interval = -0.4, +0.9). CONCLUSIONS: Three years after recreational marijuana legalization, changes in motor vehicle crash fatality rates for Washington and Colorado were not statistically different from those in similar states without recreational marijuana legalization. Future studies over a longer time remain warranted.

Thromboelastogram does not detect pre-injury anticoagulation in acute trauma patients.

PURPOSE: Thromboelastography (TEG) has been recommended to characterize post-traumatic coagulopathy, yet no study has evaluated the impact of pre-injury anticoagulation (AC) on TEG variables. We hypothesized patients on pre-injury AC have a greater incidence of coagulopathy on TEG compared to those without AC. METHODS: This retrospective chart review evaluated all trauma patients admitted to an urban, level one trauma center from February 2011 to September 2014 who received a TEG within the first 24h. Patients were classified as receiving pre-injury AC or no AC if their documented medications prior to admission included warfarin, dabigatran, or anti-Xa (aXa) inhibitors (apixaban or rivaroxaban). The presence of coagulopathy on TEG or conventional assays was defined by exceeding local laboratory reference standards. RESULTS: A total of 54 patients were included (AC, n=27 [warfarin n=13, dabigatran n=6, aXa inhibitor n=8] vs. no AC, n=27). Baseline characteristics were similar between groups, including age (72±13years vs. 72±15; p=0.85), male gender (70% vs. 74%; p=0.76) and blunt mechanism of injury (100% vs. 100%; p=1). There was no difference in the number of patients determined to have coagulopathy on TEG (no AC 11% vs. AC 15%; p=0.99). Conventional tests, including the international normalized ratio (INR) and activated partial thromboplastin time (aPTT), identified coagulopathy in a high proportion of anti-coagulated patients (no AC 22% vs. AC 85%; p<0.01). CONCLUSION: TEG has limited clinical utility to evaluate the presence of pre-injury AC. Traditional markers of drug induced coagulopathy should guide reversal decisions.

Thromboelastography Does Not Detect Preinjury Antiplatelet Therapy in Acute Trauma Patients.

Thromboelastography (TEG) with platelet mapping has been proposed as an assay to detect the presence of antiplatelet agents (APA), yet no study has evaluated TEG markers of platelet dysfunction in acute trauma patients stratified by the use of preinjury APA. We hypothesized that patients on preinjury APA would demonstrate prolonged TEG markers of platelet dysfunction compared with those not on preinjury APA. This retrospective review evaluated all trauma patients admitted to a Level I trauma center from February 2011 to April 2013 who received a TEG within the first 24 hours of admission. Patients were classified as receiving preinjury APA or no APA if their documented medications included either aspirin or adenosine diphosphate (ADP) antagonists, including clopidogrel, prasugrel, and ticagrelor. A total of 129 patients were included (APA, n = 35; no APA n = 94) in the study. The time from admission to the first TEG was similar (APA 175 ± 289 minutes versus no APA 216 ± 321 minutes, P = 0.5). There was no significant difference in TEG markers of platelet dysfunction, including per cent ADP inhibition (APA 61.7 ± 25.8% versus no APA 62.3 ± 28.8%; P = 0.91) or per cent arachidonic acid inhibition (APA 58.2 ± 31% versus no APA 53.8 ± 34%; P = 0.54). Both groups had similar proportion of severe platelet dysfunction, defined as ADP inhibition greater than 70 per cent (APA 40% versus no APA 40%; P = 0.8) and arachidonic acid inhibition greater than 70 per cent (APA 40% versus no APA 39%; P = 0.89). In conclusion, platelet dysfunction after major trauma is common. Therefore, TEG alone should not be used to evaluate for the presence of APA due to apparent lack of specificity.

Mass Casualty Incident Management Preparedness: A Survey of the American College of Surgeons Committee on Trauma.

Mass casualty incidents (MCIs) are events resulting in more injured patients than hospital systems can handle with standard protocols. Several studies have assessed hospital preparedness during MCIs. However, physicians and trauma surgeons need to be familiar with their hospital's MCI Plan. The purpose of this survey was to assess hospitals' and trauma surgeon's preparedness for MCIs. Online surveys were e-mailed to members of the American College of Surgeons committee on Trauma Ad Hoc Committee on Disaster and Mass Casualty Management before the March 2012 meeting. Eighty surveys were analyzed (of 258). About 76 per cent were American College of Surgeons Level I trauma centers, 18 per cent were Level II trauma centers. Fifty-seven per cent of Level I and 21 per cent of Level II trauma centers had experienced an MCI. A total of 98 per cent of respondents thought it was likely their hospital would see a future MCI. Severe weather storm was the most likely event (95%), followed by public transportation incident (86%), then explosion (85%). About 83 per cent of hospitals had mechanisms to request additional physician/surgeons, and 80 per cent reported plans for operative triage. The majority of trauma surgeons felt prepared for an MCI and believed an event was likely to occur in the future. The survey was limited by the highly select group of respondents and future surveys will be necessary.

Use of Magnetic Resonance Cholangiopancreatography in Clinical Practice: Not as Good as We Once Thought.

BACKGROUND: Magnetic resonance cholangiopancreatography (MRCP) is believed to be a useful tool to evaluate the biliary tree and pancreas for stones, tumors, or injuries to the ductile system. The purpose of this study was to compare the accuracy of MRCP to the gold standard, endoscopic retrograde cholangiopancreatography (ERCP), in our institution. STUDY DESIGN: We performed a retrospective review of all MRCP followed by ERCP (follow-on ERCP) at a single institution over a 6-year period. Exam findings from MRCP were compared with findings on the follow-on ERCP and compared. Studies were grouped into 2 main classifications: tests being performed for patients with suspected choledocholithiasis (stone disease) and tests being performed for concerns of malignant strictures or duct injuries (non-stone disease). RESULTS: A total of 81 patients had MRCPs and follow-on ERCPs in this time period. Thirty-six patients had positive findings on MRCP and ERCP for stones in the common duct system, and 14 patients had positive findings on MRCP and subsequent ERCP for masses and strictures of the common duct. Three patients had positive MRCP and ERCP findings for pancreatic duct abnormalities. The specificity and positive predictive value of MRCP were 94% and 98%, respectively. However, 13 of 28 patients had lesions identified on ERCP after a normal MRCP. The sensitivity and negative predictive value were 80% and 54%, respectively. CONCLUSIONS: Magnetic resonance cholangiopancreatography was not useful in the management algorithm of either stone or non-stone disease of the biliary tree or pancreas. It should be abandoned as a diagnostic tool for work-up of biliary duct pathology.

An experimental model of hemothorax autotransfusion: impact on coagulation.

BACKGROUND: Traumatic hemothorax (HTX) has been demonstrated to predictably contain low fibrinogen, low hematocrit, and low platelet counts. When analyzed on its own, shed HTX demonstrates coagulopathy. However, when mixed with normal pooled plasma (NPP) at physiologically relevant dilutions, HTX demonstrates accelerated coagulation. We hypothesize that when HTX is mixed with a patient's own plasma, the mixture will demonstrate hypercoagulability. The accelerated coagulation of this mixture would have important implications for the autotransfusion of HTX as a method of resuscitating a trauma patient. METHODS: Adult trauma patients from whom greater than 140 mL of HTX was evacuated within 1 hour of tube thoracostomy were included. HTX was sampled at 1 hour after evacuation, and a portion of the sample was centrifuged and stored as frozen plasma for later analysis. The remainder of the sample was analyzed (coagulation, hematology, electrolytes), and values were compared with concurrent venous values extracted via chart review. A citrate tube containing the patient's venous blood was additionally spun down and frozen for subsequent mixing study analysis. Coagulation was further evaluated by mixing serial dilutions of the previously frozen HTX with NPP. Additionally, the previously frozen HTX was mixed in serial dilutions with the previously frozen sample of patient plasma (PTP). RESULTS: Subjects (10) were enrolled based on inclusion criteria and collection of a discarded venous sample. In HTX samples analyzed alone, no thrombus was formed in any coagulation test (activated partial thromboplastin time [aPTT] > 180). The median aPTT value of PTP alone was 25.5. In 1-hour specimens mixed at a clinically relevant dilution of 1:4, HTX mixed with NPP had a mediana PTT value of 26.0, whereas HTX mixed with PTP had a median aPTT value of 21.7. Thus, the mixture of HTX + PTP demonstrated a statistically significantly lower aPTT than the mixture of HTX + NPP (P = 0.01). Additionally, the mixture of HTX and PTP shows a statistically significantly lower aPTT value than PTP alone (P = 0.03), indicating a hypercoagulable state. CONCLUSIONS: HTX demonstrates coagulopathy when analyzed independently, but is hypercoagulable when mixed with NPP or PTP. Furthermore, mixing studies show a statistically significantly lower aPTT when HTX is mixed with PTP versus HTX mixed with NPP. Thus, autotransfusion of HTX would likely produce a hypercoagulable state in vivo, and should not be used in place of other blood products to resuscitate a trauma patient. The autotransfusion of HTX may, however, be of use in a resource-limited environment where other blood products are not available.

A small amount can make a difference: a prospective human study of the paradoxical coagulation characteristics of hemothorax.

BACKGROUND: The evacuated hemothorax has been poorly described because it varies with time, it has been found to be incoagulable, and its potential effect on the coagulation cascade during autotransfusion is largely unknown. METHODS: This is a prospective descriptive study of adult patients with traumatic chest injury necessitating tube thoracostomy. Pleural and venous samples were analyzed for coagulation, hematology, and electrolytes at 1 to 4 hours after drainage. Pleural samples were also analyzed for their effect on the coagulation cascade via mixing studies. RESULTS: Thirty-four subjects were enrolled with a traumatic hemothorax. The following measured coagulation factors were significantly depleted compared with venous blood: international normalized ratio (>9 vs 1.1) (P < .001) and activated partial thromboplastin time (aPTT) (>180 vs 24.5 seconds) (P < .001). Mixing studies showed a dose-dependent increase in coagulation dilutions through 1:8 (P < .05). CONCLUSIONS: An evacuated hemothorax does not vary in composition significantly with time and is incoagulable alone. Mixing studies with hemothorax plasma increased coagulation, raising safety concerns.