Heparin resistance in severe thermal injury:a prospective cohort study

Background:Low molecular-weight heparin(LMWH)is routinely administered to burn patients for thromboprophylaxis.Some studies have reported heparin resistance,yet the mechanism(s)and prevalence have not been systematically studied.We hypothesized that nucleosomes,composed of histone structures with associated DNA released from injured tissue and activated immune cells in the form of neutrophil extracellular traps(NETs or NETosis),neutralize LMWH resulting in suboptimal anticoagulation,assessed by reduction in anti-factor Xa activity.Methods:Blood was sampled from>15%total body surface area(TBSA)burn patients receiving LMWH on days 5,10 and 14.Peak anti-factor Xa(AFXa)activity,anti-thrombin(ATIII)activity,cellfree DNA(cfDNA)levels and nucleosome levels were measured.Mixed effects regression was adjusted for multiple confounders,including injury severity and ATIII activity,and was used to test the association between nucleosomes and AFXa.Results:A total of 30 patients with severe burns were included.Mean TBSA 43%(SD 17).Twentythree(77%)patients were affected by heparin resistance(defined by AFXa activity<0.2 IU/mL).Mean peak AFXa activity across samples was 0.18 IU/mL(SD 0.11).Mean ATIII was 81.9%activity(SD 20.4).Samples taken at higher LWMH doses were found to have significantly increased AFXa activity,though the effect was not observed at all doses,at 8000 IU no samples were heparin resistant.Nucleosome levels were negatively correlated with AFXa(r=−0.29,p=0.050)consistent with the hypothesis.The final model,with peak AFXa as the response variable,was adjusted for nucleosome levels(p=0.0453),ATIII activity(p=0.0053),LMWH dose pre-sample(p=0.0049),drug given(enoxaparin or tinzaparin)(p=0.03),and other confounders including severity of injury,age,gender,time point of sample.Conclusions:Heparin resistance is a prevalent issue in severe burns.Nucleosome levels were increased post-burn,and showed an inverse association with AFXa consistent with the hypothesis that they may interfere with the anticoagulant effect of heparin in vivo and contribute to heparin resistance.Accurate monitoring of AFXa activity with appropriate therapy escalation plans are recommended with dose adjustment following severe burn injury.

Dehydroepiandrosterone:a potential therapeutic agent in the treatment and rehabilitation of the traumatically injured patient

Severe injuries are the major cause of death in those aged under 40,mainly due to road traffic collisions.Endocrine,metabolic and immune pathways respond to limit the tissue damage sustained and initiate wound healing,repair and regeneration mechanisms.However,depending on age and sex,the response to injury and patient prognosis differ significantly.Glucocorticoids are catabolic and immunosuppressive and are produced as part of the stress response to injury leading to an intra-adrenal shift in steroid biosynthesis at the expense of the anabolic and immune enhancing steroid hormone dehydroepiandrosterone(DHEA)and its sulphated metabolite dehydroepiandrosterone sulphate(DHEAS).The balance of these steroids after injury appears to influence outcomes in injured humans,with high cortisol:DHEAS ratio associated with increased morbidity and mortality.Animal models of trauma,sepsis,wound healing,neuroprotection and burns have all shown a reduction in proinflammatory cytokines,improved survival and increased resistance to pathological challenges with DHEA supplementation.Human supplementation studies,which have focused on post-menopausal females,older adults,or adrenal insufficiency have shown that restoring the cortisol:DHEAS ratio improves wound healing,mood,bone remodelling and psychological well-being.Currently,there are no DHEA or DHEAS supplementation studies in trauma patients,but we review here the evidence for this potential therapeutic agent in the treatment and rehabilitation of the severely injured patient.

The diagnostic and prognostic value of systems biology research in major traumatic and thermal injury: a review

As secondary complications remain a significant cause of morbidity and mortality amongst hospitalised trauma patients,the need to develop novel approaches by which to identify patients at risk of adverse outcome is becoming increasingly important.Centred on the idea that patients who experience"poor"outcome post trauma elicit a response to injury that is distinct from those who experience"good"outcome,tailored therapeutics is an emerging concept aimed at improving current treatment regimens by promoting patient-specific therapies.Making use of recent advancements in the fields of genomics,proteomics and metabolomics,numerous groups have undertaken a systems-based approach to analysing the acute immune and inflammatory response to major traumatic and thermal injury in an attempt to uncover a single or combination of biomarkers that can identify patients at risk of adverse outcome.Early results are encouraging,with all three approaches capable of discriminating patients with"good"outcome from those who develop nosocomial infections,sepsis and multiple organ failure,with differences apparent in blood samples acquired as early as 2 h post injury.In particular,genomic data is proving to be highly informative,identifying patients at risk of"poor"outcome with a higher degree of sensitivity and specificity than statistical models built upon data obtained from existing anatomical and physiological scoring systems.Here,focussing predominantly upon human-based research,we provide an overview of the findings of studies that have investigated the immune and inflammatory response to major traumatic and thermal injury at the genomic,protein and metabolite level,and consider both the diagnostic and prognostic potential of these approaches.

Traumatic injury is associated with reduced deoxyribonuclease activity and dysregulation of the actin scavenging system

Background:Traumatic injury is associated with increased concentrations of cell-free DNA(cfDNA)in the circulation,which contribute to post-injury complications.The endonuclease deoxyribonuclease 1(DNase-1)is responsible for removing 90%of circulating cfDNA.Recently,DNase activity was reported to be significantly reduced following major non-traumatic brain injury(TBI),but the processes responsible were not investigated.Moreover,it is not known how quickly following injury DNase activity is reduced and whether this also occurs after TBI.Methods:At 3 post-injury time points(≤1,4–12 and 48–72 hours),blood samples were obtained from 155 adult trauma patients that had sustained an isolated TBI(n=21),TBI with accompanying extracranial injury(TBI^(+))(n=53)or an extracranial injury only(ECI)(n=81).In addition to measuring cfDNA levels and the activity and expression of DNase,circulating concentrations of monomeric globular action(G-actin),an inhibitor of DNase-1,and the actin scavenging proteins gelsolin(GSN)and vitamin D binding protein(VDBP)were determined and values compared to a cohort of healthy controls.Results:Significantly elevated concentrations of plasma cfDNA were seen in TBI,TBI^(+)and ECI patients at all study time points when compared to healthy controls.cfDNA levels were significantly higher at≤1 hour post-injury in ECI patients who subsequently developed multiple organ dysfunction syndrome when compared to those who did not.Plasma DNase-1 protein was significantly elevated in all patient groups at all sampling time points.In contrast,DNase enzyme activity was significantly reduced,with this impaired function evident in TBI^(+)patients within minutes of injury.Circulating concentrations of G-actin were elevated in all patient cohorts in the immediate aftermath of injury and this was accompanied by a significant reduction in the levels of GSN and VDBP.Conclusions:The post-traumatic increase in circulating cfDNA that occurs following extracranial trauma and TBI is accompanied by reduced DNase activity.We propose that,secondary to reduced GSN and VDBP levels,elevated circulating concentrations of G-actin underlie the post-injury reduction in DNase activity.Reducing circulating cfDNA levels via therapeutic restoration of DNase-1 activity may improve clinical outcomes post-injury.