Background:Necrotizing soft-tissue infections (NSTI) caused by Clostridium spp. are rare. High rates of amputation and mortality are reported, but knowledge on clinical characteristics and outcome is largely based on retrospective cohorts. The role of Clostridium spp. as part of polymicrobial NSTI is also unclear. Method:We identified all clostridial cases from the INFECT cohort, a prospective study including patients with confirmed NSTI admitted to 5 Scandinavian referral hospitals over a 4-year period. Selected parameters were compared to a control group of nonclostridial polymicrobial infections. Additionally, we analyzed polymicrobial infections with clostridial species. Results:Ten cases of clostridial NSTIs were identified, evenly divided between cases caused by Clostridium perfringens and Clostridium septicum. Immunodeficiency (4/10) and penetrating trauma (3/10) were significantly more frequent compared to polymicrobial controls. Clostridial NSTI was also associated with extremity involvement (10/10) and severe pain (7/9). Radiological evidence of gas (4/7) did not distinguish clostridial from polymicrobial infections. Two patients underwent amputation, and 2 others died within 30 days. The cohort also included seven polymicrobial NSTIs with Clostridium spp., with higher rates of both comorbidity (7/7) and 30-day mortality (4/7). Conclusions:Clostridial NSTIs were associated with extremity infection, immunodeficiency, and penetrating trauma. The cases demonstrate a wide spectrum of severity. In polymicrobial NSTIs involving Clostridium spp., the mortality was particularly high, but the pathogenetic role of clostridia in these infections is unclear.

Hyperbaric oxygen (HBO2) treatment is regularly used as adjuvant treatment in patients with necrotizing soft tissue infections (NSTI). Several observational studies have suggested an association between hyperbaric oxygen (HBO2) treatment and improved survival in patients with necrotizing soft tissue infections (NSTIs); however, the evidence remains inconclusive. Most patients with NSTI are severely ill, having sepsis or septic shock, and requiring mechanical ventilation and inotropic support in an intensive care unit (ICU). Although recent data suggest that the beneficial effect of HBO2 may be largest in the most severely ill, not all patients may receive it due to hemodynamic instability, pressure chamber capabilities, and availability, thereby potentially introducing selection bias. From January 2013 until June 2017, we conducted a multicenter, prospective, consecutive, observational study (The INFECT study, ClinicalTrials.gov number; NCT01790698) enrolling NSTI patients at five clinical centers delivering HBO2 to NSTI patients in an ICU setting in Denmark, Norway, and Sweden. A total of 409 consecutive patients with necrotizing soft tissue infections were prospectively enrolled in the study, of whom 402 (98.3

Streptococcus pyogenes (group A streptococci; GAS) is the main causative pathogen of monomicrobial necrotizing soft tissue infections (NSTIs). To resist immuno-clearance, GAS adapt their genetic information and/or phenotype to the surrounding environment. Hyper-virulent streptococcal pyrogenic exotoxin B (SpeB) negative variants caused by covRS mutations are enriched during infection. A key driving force for this process is the bacterial Sda1 DNase. Bacterial infiltration, immune cell influx, tissue necrosis and inflammation in patient´s biopsies were determined using immunohistochemistry. SpeB secretion and activity by GAS post infections or challenges with reactive agents were determined via Western blot or casein agar and proteolytic activity assays, respectively. Proteome of GAS single colonies and neutrophil secretome were profiled, using mass spectrometry. Here, we identify another strategy resulting in SpeB-negative variants, namely reversible abrogation of SpeB secretion triggered by neutrophil effector molecules. Analysis of NSTI patient tissue biopsies revealed that tissue inflammation, neutrophil influx, and degranulation positively correlate with increasing frequency of SpeB-negative GAS clones. Using single colony proteomics, we show that GAS isolated directly from tissue express but do not secrete SpeB. Once the tissue pressure is lifted, GAS regain SpeB secreting function. Neutrophils were identified as the main immune cells responsible for the observed phenotype. Subsequent analyses identified hydrogen peroxide and hypochlorous acid as reactive agents driving this phenotypic GAS adaptation to the tissue environment. SpeB-negative GAS show improved survival within neutrophils and induce increased degranulation. Our findings provide new information about GAS fitness and heterogeneity in the soft tissue milieu and provide new potential targets for therapeutic intervention in NSTIs.

Variability in disease severity caused by a microbial pathogen is impacted by each infection representing a unique combination of host and pathogen genomes. Here, we show that the outcome of invasive Streptococcus pyogenes infection is regulated by an interplay between human STING genotype and bacterial NADase activity. S. pyogenes -derived c-di-AMP diffuses via streptolysin O pores into macrophages where it activates STING and the ensuing type I IFN response. However, the enzymatic activity of the NADase variants expressed by invasive strains suppresses STING-mediated type I IFN production. Analysis of patients with necrotizing S. pyogenes soft tissue infection indicates that a STING genotype associated with reduced c-di-AMP-binding capacity combined with high bacterial NADase activity promotes a ‘perfect storm’ manifested in poor outcome, whereas proficient and uninhibited STING-mediated type I IFN production correlates with protection against host-detrimental inflammation. These results reveal an immune-regulating function for bacterial NADase and provide insight regarding the host-pathogen genotype interplay underlying invasive infection and interindividual disease variability.

BACKGROUND:Necrotizing soft-tissue infections (NSTI) are life-threatening conditions often caused by β-hemolytic streptococci, group A Streptococcus (GAS) in particular. Optimal treatment is contentious. The INFECT cohort includes the largest set of prospectively enrolled streptococcal NSTI cases to date.METHODS:From the INFECT cohort of 409 adults admitted with NSTI to 5 clinical centers in Scandinavia, patients culture-positive for GAS or Streptococcus dysgalactiae (SD) were selected. Risk factors were identified by comparison with a cohort of nonnecrotizing streptococcal cellulitis. The impact of baseline factors and treatment on 90-day mortality was explored using Lasso regression. Whole-genome sequencing of bacterial isolates was used for emm typing and virulence gene profiling.RESULTS:The 126 GAS NSTI cases and 27 cases caused by SD constituted 31% and 7% of the whole NSTI cohort, respectively. When comparing to nonnecrotizing streptococcal cellulitis, streptococcal NSTI was associated to blunt trauma, absence of preexisting skin lesions, and a lower body mass index. Septic shock was significantly more frequent in GAS (65%) compared to SD (41%) and polymicrobial, nonstreptococcal NSTI (46%). Age, male sex, septic shock, and no administration of intravenous immunoglobulin (IVIG) were among factors associated with 90-day mortality. Predominant emm types were emm1, emm3, and emm28 in GAS and stG62647 in SD.CONCLUSIONS:Streptococcal NSTI was associated with several risk factors, including blunt trauma. Septic shock was more frequent in NSTI caused by GAS than in cases due to SD. Factors associated with mortality in GAS NSTI included age, septic shock, and no administration of IVIG.

BACKGROUND Necrotizing soft-tissue infections (NSTIs) are rapidly progressing infections frequently complicated by septic shock and associated with high mortality. Early diagnosis is critical for patient outcome, but challenging due to vague initial symptoms. Here, we identified predictive biomarkers for NSTI clinical phenotypes and outcomes using a prospective multicenter NSTI patient cohort. METHODS Luminex multiplex assays were used to assess 36 soluble factors in plasma from NSTI patients with positive microbiological cultures (n = 251 and n = 60 in the discovery and validation cohorts, respectively). Control groups for comparative analyses included surgical controls (n = 20), non-NSTI controls (i.e., suspected NSTI with no necrosis detected upon exploratory surgery, n = 20), and sepsis patients (n = 24). RESULTS Thrombomodulin was identified as a unique biomarker for detection of NSTI (AUC, 0.95). A distinct profile discriminating mono- (type II) versus polymicrobial (type I) NSTI types was identified based on differential expression of IL-2, IL-10, IL-22, CXCL10, Fas-ligand, and MMP9 (AUC >0.7). While each NSTI type displayed a distinct array of biomarkers predicting septic shock, granulocyte CSF (G-CSF), S100A8, and IL-6 were shared by both types (AUC >0.78). Finally, differential connectivity analysis revealed distinctive networks associated with specific clinical phenotypes. CONCLUSIONS This study identifies predictive biomarkers for NSTI clinical phenotypes of potential value for diagnostic, prognostic, and therapeutic approaches in NSTIs. TRIAL REGISTRATION ClinicalTrials.gov NCT01790698. FUNDING Center for Innovative Medicine (CIMED); Region Stockholm; Swedish Research Council; European Union; Vinnova; Innovation Fund Denmark; Research Council of Norway; Netherlands Organisation for Health Research and Development; DLR Federal Ministry of Education and Research; and Swedish Children’s Cancer Foundation.

Intensive care unit (ICU) patients develop stress induced insulin resistance causing hyperglycemia, large glucose variability and hypoglycemia. These glucose metrics have all been associated with increased rates of morbidity and mortality. The only way to achieve safe glucose control at a lower glucose range (e.g., 4.4-6.6 mmol/L) will be through use of an autonomous closed loop glucose control system (artificial pancreas). Our goal with the present study was to assess the safety and performance of an artificial pancreas system, composed of the EIRUS (Maquet Critical Care AB) continuous glucose monitor (CGM) and novel artificial intelligence-based glucose control software, in a swine model using unannounced hypo- and hyperglycemia challenges. Fourteen piglets (6 control, 8 treated) underwent sequential unannounced hypoglycemic and hyperglycemic challenges with 3 IU of NovoRapid and a glucose infusion at 17 mg/kg/min over the course of 5 h. In the Control animals an experienced ICU physician used every 30-min blood glucose values to maintain control to a range of 4.4-9 mmol/L. In the Treated group the artificial pancreas system attempted to maintain blood glucose control to a range of 4.4-6.6 mmol/L. Five of six Control animals and none of eight Treated animals experienced severe hypoglycemia (< 2.22 mmol/L). The area under the curve 3.5 mmol/L was 28.9 (21.1-54.2) for Control and 4.8 (3.1-5.2) for the Treated animals. The total percent time within tight glucose control range, 4.4-6.6 mmol/L, was 32.8% (32.4-47.1) for Controls and 55.4% (52.9-59.4) for Treated (p < 0.034). Data are median and quartiles. The artificial pancreas system abolished severe hypoglycemia and outperformed the experienced ICU physician in avoiding clinically significant hypoglycemic excursions.

PURPOSE:Necrotising soft-tissue infections (NSTI) are characterised by necrosis, fast progression, and high rates of morbidity and mortality, but our knowledge is primarily derived from small prospective studies and retrospective studies.METHODS:We performed an international, multicentre, prospective cohort study of adults with NSTI describing patient's characteristics and associations between baseline variables and microbiological findings, amputation, and 90-day mortality.RESULTS:We included 409 patients with NSTI; 402 were admitted to the ICU. Cardiovascular disease [169 patients (41%)] and diabetes [98 (24%)] were the most common comorbidities; 122 patients (30%) had no comorbidity. Before surgery, bruising of the skin [210 patients (51%)] and pain requiring opioids [172 (42%)] were common. The sites most commonly affected were the abdomen/ano-genital area [140 patients (34%)] and lower extremities [126 (31%)]. Monomicrobial infection was seen in 179 patients (44%). NSTI of the upper or lower extremities was associated with monomicrobial group A streptococcus (GAS) infection, and NSTI located to the abdomen/ano-genital area was associated with polymicrobial infection. Septic shock [202 patients (50%)] and acute kidney injury [82 (20%)] were common. Amputation occurred in 22% of patients with NSTI of an extremity and was associated with higher lactate level. All-cause 90-day mortality was 18% (95% CI 14-22); age and higher lactate levels were associated with increased mortality and GAS aetiology with decreased mortality.CONCLUSIONS:Patients with NSTI were heterogeneous regarding co-morbidities, initial symptoms, infectious localisation, and microbiological findings. Higher age and lactate levels were associated with increased mortality, and GAS infection with decreased mortality.

Background Necrotizing soft tissue infections (NSTIs) caused by group A Streptococcus (GAS) and occasionally by Staphylococcus aureus (SA) frequently involve the deep fascia and often lead to muscle necrosis. Methods To assess the pathogenicity of GAS and S. aureus for muscles in comparison to keratinocytes, adhesion and invasion of NSTI-GAS and NSTI-SA isolates were assessed in these cells. Bloodstream infections (BSI-SA) and noninvasive coagulase-negative staphylococci (CNS) isolates were used as controls. Results NSTI-SA and BSI-SA exhibited stronger internalization into human keratinocytes and myoblasts than NSTI-GAS or CNS. S. aureus internalization reached over 30% in human myoblasts due to a higher percentage of infected myoblasts (>11%) as compared to keratinocytes (<3%). Higher cytotoxicity for myoblasts of NSTI-SA as compared to BSI-SA was attributed to higher levels of psmα and RNAIII transcripts in NSTI-SA. However, the 2 groups were not discriminated at the genomic level. The cellular basis of high internalization rate in myoblasts was attributed to higher expression of α5β1 integrin in myoblasts. Major contribution of FnbpAB-integrin α5β1 pathway to internalization was confirmed by isogenic mutants. Conclusions Our findings suggest a factor in NSTI-SA severity is the strong invasiveness of S. aureus in muscle cells, a property not shared by NSTI-GAS isolates.

Background: Despite seemingly functional coagulation, hemorrhagic lesion progression is a common and devastating condition following traumatic brain injury (TBI), stressing the need for new diagnostic techniques. Multiple electrode aggregometry (MEA) measures platelet function and could aid in coagulopathy assessment following TBI. The aims of this study were to evaluate MEA temporal dynamics, influence of concomitant therapy, and its capabilities to predict lesion progression and clinical outcome in a TBI cohort. Material and methods: Adult TBI patients in a neurointensive care unit that underwent MEA sampling were retrospectively included. MEA was sampled if the patient was treated with antiplatelet therapy, bled heavily during surgery, or had abnormal baseline coagulation values. We assessed platelet activation pathways involving the arachidonic acid receptor (ASPI), P2Y(12) receptor, and thrombin receptor (TRAP). ASPI was the primary focus of analysis. If several samples were obtained, they were included. Retrospective data were extracted from hospital charts. Outcome variables were radiologic hemorrhagic progression and Glasgow Outcome Scale assessed prospectively at 12 months posttrauma. MEA levels were compared between patients on antiplatelet therapy. Linear mixed effect models and uni-/multivariable regression models were used to study longitudinal dynamics, hemorrhagic progression and outcome, respectively. Results: In total, 178 patients were included (48% unfavorable outcome). ASPI levels increased from initially low values in a time-dependent fashion (p < 0.001). Patients on cyclooxygenase inhibitors demonstrated low ASPI levels (p < 0.001), while platelet transfusion increased them (p < 0.001). The first ASPI (p = 0.039) and TRAP (p = 0.009) were significant predictors of outcome, but not lesion progression, in univariate analyses. In multivariable analysis, MEA values were not independently correlated with outcome. Conclusion: A general longitudinal trend of MEA is identified in this TBI cohort, even in patients without known antiplatelet therapies. Values appear also affected by platelet inhibitory treatment and by platelet transfusions. While significant in univariate models to predict outcome, MEA values did not independently correlate to outcome or lesion progression in multivariable analyses. Further prospective studies to monitor coagulation in TBI patients are warranted, in particular the interpretation of pathological MEA values in patients without antiplatelet therapies.

Background: In neuromodulation therapies, hardware-related infections are a major challenge often leading to hardware removal. Objective: To investigate the role of adjuvant hyperbaric oxygen therapy (HBOT) in hardware-related infections. Methods: Fourteen hardware-related infection events in 12 consecutive patients between 2002 and 2015 were treated with antibiotics and adjuvant HBOT at the Karolinska University Hospital (Stockholm, Sweden). Two time-independent infection events related to hardware replacements occurred in 2 patients. Infection resolution and the need for hardware removal were assessed. Results: Twelve out of 14 events of hardware-related infection were successfully treated without hardware removal (86%). The 2 patients treated twice with HBOT on 2 time-independent occasions could retain their hardware in both cases. Hardware was removed following HBOT failure in 2 infection events, with long-term infection control achieved in all patients. Further, an intrathecal pump malfunction caused by HBOT at 2.8 bars was observed, leading to a change in the manufacturer’s guidelines. Conclusions: This study indicates a potential benefit of adjuvant HBOT in the treatment of hardware-related infections in neuromodulation, diminishing the need for hardware removal and treatment interruption. Prospective studies are warranted to establish the role of adjuvant HBOT in the treatment of hardware-related infections in neuromodulation.

Primary Objective: to Investigate the presence of circulating microparticles (MPs) of brain tissue origin In the systemic and cerebrovenous blood of patients with severe traumatic brain Injury (TBI).& para;& para;Research Design: Prospective observational study in 15 consecutive patients with severe isolated TBI.& para;& para;Methods and Procedures: We repeatedly measured concentrations of MPs expressing glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE) and aquaporin-4 (AQP4), in arterial and cerebrovenous blood at admittance to hospital and up to 72 hours after the injury.& para;& para;Main Outcomes and Results: Concentrations of MPs expressing GFAP and AQP4 were significantly higher In the TBI group compared with healthy controls: GFAP 2.0 [1.1-7.9] vs. 1.3 [1-2.1] x 10(6)/mL, p < 0.001; AQP4 0.1 [0.07-0.22] vs. 0.08 [0.06-0.11] x 10(6)/mL, p < 0.001 (median, range). No transcranial gradients were found. Levels of NSE-expressing MPs were also higher in the TBI group compared with healthy controls: 0.4 [0.25-2.1] vs. 0.26 [0.13-0.98] x 10(6)/mL, p < 0.05; however, regarding NSE-posItive non-platelet MPs, there were no differences between patients and controls.& para;& para;Conclusions: Patients with TBI have higher numbers of brain-derived MPs. Further studies are needed, however, to Identify specific and sensitive MP markers of brain Injury.

Early assessment of necrotising soft tissue infection (NSTI) is challenging. Analysis of inflammatory markers could provide important information about disease severity and guide decision making. For this purpose, we investigated the association between cytokine levels and the Laboratory Risk Indicator for Necrotising Fasciitis (LRINEC)-score, disease severity and mortality in NSTI patients. In 159 patients, plasma was analysed for IL-1β, IL-6, IL-10 and TNF-α upon admission. The severity of NSTI was assessed by SAPS, SOFA score, septic shock, microbial aetiology, renal replacement therapy and amputation. We found no significant difference in cytokine levels according to a LRINEC- score above or below 6 (IL-1β: 3.0 vs. 1.3; IL-6: 607 vs. 289; IL-10: 38.4 vs. 38.8; TNF-α: 15.1 vs. 7.8 pg/mL, P > 0.05). Patients with β-haemolytic streptococcal infection had higher level of particularly IL-6. There was no difference in mortality between patients with a LRINEC-score above or below 6. In the adjusted analysis assessing 30-day mortality, the association was strongest for IL-1β (OR 3.86 [95% CI, 1.43-10.40], P = 0.008) and IL-10 (4.80 [1.67-13.78], P = 0.004). In conclusion, we found no significant association between the LRINEC-score and cytokine levels on admission. IL-6 was consistently associated with disease severity, whereas IL-1β had the strongest association with 30-day mortality.

BACKGROUND:The INFECT project aims to advance our understanding of the pathophysiological mechanisms in necrotizing soft tissue infections (NSTIs). The INFECT observational study is part of the INFECT project with the aim of studying the clinical profile of patients with NSTIs and correlating these to patient-important outcomes. With this protocol and statistical analysis plan we describe the methods used to obtain data and the details of the planned analyses.METHODS:The INFECT study is a multicentre, prospective observational cohort study. Patients with NSTIs are enrolled in five Scandinavian hospitals, which are all referral centres for NSTIs. The primary outcomes are the descriptive variables of the patients. Secondary outcomes include identification of factors associated with 90-day mortality and amputation; associations between affected body part, maximum skin defect and Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score and 90-day mortality; 90-day mortality in patients with and without acute kidney injury (AKI) and LRINEC score of six and above or below six; and association between affected body part at arrival and microbiological findings. Exploratory outcomes include univariate analyses of baseline characteristics associations with 90-day mortality. The statistical analyses will be conducted in accordance with the predefined statistical analysis plan.CONCLUSION:Necrotizing soft tissue infections result in severe morbidity and mortality. The INFECT study will be the largest prospective study in patients with NSTIs to date and will provide important data for clinicians, researchers and policy makers on the characteristics and outcomes of these patients.

To provide retrospective, descriptive information on patients with cervical necrotizing fasciitis treated at a single center during the years 1998–2014, and to evaluate the outcome of a newly introduced treatment strategy. Retrospective analysis of clinical data obtained from medical records. Mortality, pre-morbidity, severity of illness, primary site of infection, type of bacteria, time parameters. The observed 3-month mortality was 6/59 (10 %). The most common initial foci of the infection were pharyngeal, dental or hypopharyngeal. The most common pathogen was Streptococcus milleri bacteria within the Streptococcus anginosus group (66 % of the cases). Using a combined treatment with early surgical debridement combined with hyperbaric oxygen treatment, it is possible to reduce the mortality rate among patients suffering from cervical necrotizing fasciitis, compared to the expected mortality rate and to previous historical reports. Data indicated that early onset of hyperbaric oxygen treatment may have a positive impact on survival rate, but no identifiable factor was found to prognosticate outcome.

Traumatic brain injury (TBI) is associated with a high mortality and severe long-term morbidity in survivors. TBI often affects previously healthy young persons, and represents one of the most common causes of death among younger patients. The outcome in general trauma patients has improved over the recent decades. Unfortunately, lesser improvements have been achieved in the treatment of TBI. The pathophysiology of TBI is complicated, and changes in the haemostatic system are important parts of the complex response that occurs following TBI. Development of socalled secondary brain injuries with bleeding complications follow the trauma and contributes to the adverse outcome. In the present thesis patients with severe isolated TBI were studied, with a focus on abnormalities in coagulation and platelet function. Cerebrovenous blood samples were collected repeatedly and compared to samples from the arterial circulation, in order to investigate the pathophysiological processes within the damaged brain. In agreement with previous studies, we observed that changes in the haemostatic system developed in hours to days following TBI. Intracerebral inflammation was also present in the TBI patients, which may modify coagulation responses to injury. Signs of “platelet dysfunction”, with a decreased platelet response to arachidonic acid, was observed in the patients, and over time a bleeding tendency developed. This “platelet dysfunction” was associated with bleeding complications. We also investigated circulating microparticles (MPs) released from platelets, endothelial cells and leukocytes using flow-cytometry. We found that activation of platelets took place when blood passed the injured brain, as there was a transcranial gradient in platelet MPs exposing the platelet activation marker P-selectin. We also found that endothelial derived MPs exposing tissue factor were generated in the injured brain and released into the circulation, whereas leukocyte derived MPs exposing tissue factor seemed to accumulate in the brain. In order to identify new brain specific markers of injury we assessed circulating MPs exposing antigens from brain tissue (from astrocytes and neurons) using flow cytometry. These MPs were higher in plasma from TBI patients compared to healthy controls, but there was a considerable variability between individuals, and also with-in the patients over time. More research is needed before MPs derived from brain tissue can be used as biomarkers in TBI. Monitoring of coagulation and platelet function in TBI may provide information regarding which patients that will develop bleeding complications and need hemostatic (procoagulant) treatment. Solid evidence that this improves patient outcome is, however, lacking at present. LIST OF SCIENTIFIC PAPERS I. “Coagulation abnormalities associated with severe isolated traumatic brain injury: cerebral arteriovenous differences in coagulation and inflammatory markers”, Nekludov M, Antovic J, Bredbacka S, Blombäck M., J.Neurotrauma, 2007, 24(1): 174−80 II. ”Platelet dysfunction in patients with severe traumatic brain injury”, Nekludov M, Bellander B-M, Blombäck M, Wallen H., J.Neurotrauma, 2007, 24 (11): 1699−706. III. "Formation of microparticles in the injured brain of patients with severe isolated traumatic brain Injury”, Nekludov M, Mobarrez F, Gryth D, Bellander B-M, Wallen H. J.Neurotrauma, 31:1927−33 IV. "Brain-derived microparticles in patients with severe isolated traumatic brain injury”, Nekludov M, Bellander B-M, Gryth D, Wallen H, Mobarrez F. Manuscript

Hyperbaric oxygen (HBO) therapy has been suggested a treatment option in order to reduce the development of secondary insults succeeding traumatic brain injury. This case report studied the course of a 23-year-old gentleman with a close range transhemispheric gunshot wound. The biochemical parameters, using a multi-modal monitoring in the neuro-intensive care unit, improved following HBO treatment.

The potential pathophysiological role of circulating microparticles (MPs) has been recognized in various conditions, such as cardiovascular and thrombotic diseases. Traumatic brain injury (TBI) has a complex pathophysiology that involves coagulopathy and inflammation. We investigated endothelial-, platelet-, and leukocyte-derived microparticles (EMPs, PMPs, and LMPs, respectively) in 16 patients with severe isolated TBI. Arterial and cerebrovenous samples were taken repeatedly, during 1-72 h after injury. Subpopulations of MPs, exposing tissue factor (TF) and P-selection, were also studied. MP counts in cerebrovenous samples, irrespective of cellular origin, were higher in TBI cases, compared to healthy controls (peak levels of EMPs were approximately 7 times higher, PMPs 1.4 times higher, and LMPs 2 times higher, respectively; p<0.001 for all). MP counts declined sharply from high levels shortly after the trauma toward slightly elevated levels 72 h later. EMPs and PMPs exposing TF, as well as PMPs exposing P-selection, showed a transcranial gradient with higher concentration in cerebrovenous, compared to arterial, samples. In contrast, LMPs exposing TF were higher in arterial samples, suggesting accumulation of LMPs in the brain. We conclude that the pattern of circulating MPs is altered after TBI. PMPs exposing P-selection and EMPs exposing TF seem to be generated in the injured brain, whereas LMPs exposing TF are accumulated. The pathophysiological significance of these changes in MP pattern in TBI should be further investigated. Including MPs exposing brain-specific antigens in the assessment of brain injury would give further information of origin and likely give additional information of the size of the injury, given that the MP phenotypes investigated in the present study are not brain-specific markers.

Supine subjects exposed to hypergravity show a marked arterial desaturation. Previous work from our laboratory has also shown a paradoxical reduction of lung perfusion in dependent lung regions in supine subjects exposed to hypergravity. We reasoned that the increased lung weight during hypergravity caused either direct compression of the blood vessels in the dependent lung tissue or that poor regional ventilation caused reduced perfusion through hypoxic pulmonary vasoconstriction (HPV). The objective of this study was to evaluate the importance of HPV through measurements of arterial oxygenation during exposure to hypergravity with normal and attenuated HPV. A further increased arterial desaturation during hypergravity with attenuated HPV would support the hypothesis that HPV contributes to the paradoxical redistribution of regional perfusion. In a two-phased randomized study we first exposed 12 healthy subjects to 5 G while supine during two single-blinded conditions; control and after 50 mg sildenafil p.o.. In a second phase, 12 supine subjects were exposed to 5 G during three single-blinded conditions; control, after 100 mg sildenafil p.o. and after inhalation of 10 μg iloprost. There was a substantial arterial desaturation by 5–30% units in all subjects with no or only minor differences between conditions. The results speak against HPV as a principal mechanism for the hypergravity-induced reduction of lung perfusion in dependent lung regions in supine humans.