Cellular production of a de novo membrane cytochrome.

Heme-containing integral membrane proteins are at the heart of many bioenergetic complexes and electron transport chains. The importance of these electron relay hubs across biology has inspired the design of de novo proteins that recreate their core features within robust, versatile, and tractable protein folds. To this end, we report here the computational design and in-cell production of a minimal diheme membrane cytochrome which successfully integrates into the cellular membrane of live bacteria. This synthetic construct emulates a four-helix bundle found in modern respiratory complexes but has no sequence homology to any polypeptide sequence found in nature. The two b-type hemes, which appear to be recruited from the endogenous heme pool, have distinct split redox potentials with values close to those of natural membrane-spanning cytochromes. The purified protein can engage in rapid biomimetic electron transport with small molecules, with other redox proteins, and with biologically relevant diffusive electron carriers. We thus report an artificial membrane metalloprotein with the potential to serve as a functional electron transfer module in both synthetic protocells and living systems.

An expandable, modular de novo protein platform for precision redox engineering.

The electron-conducting circuitry of life represents an as-yet untapped resource of exquisite, nanoscale biomolecular engineering. Here, we report the characterization and structure of a de novo diheme "maquette" protein, 4D2, which we subsequently use to create an expanded, modular platform for heme protein design. A well-folded monoheme variant was created by computational redesign, which was then utilized for the experimental validation of continuum electrostatic redox potential calculations. This demonstrates how fundamental biophysical properties can be predicted and fine-tuned. 4D2 was then extended into a tetraheme helical bundle, representing a 7 nm molecular wire. Despite a molecular weight of only 24 kDa, electron cryomicroscopy illustrated a remarkable level of detail, indicating the positioning of the secondary structure and the heme cofactors. This robust, expressible, highly thermostable and readily designable modular platform presents a valuable resource for redox protein design and the future construction of artificial electron-conducting circuitry.

Computational design of de novo bioenergetic membrane proteins.

The major energy-producing reactions of biochemistry occur at biological membranes. Computational protein design now provides the opportunity to elucidate the underlying principles of these processes and to construct bioenergetic pathways on our own terms. Here, we review recent achievements in this endeavour of 'synthetic bioenergetics', with a particular focus on new enabling tools that facilitate the computational design of biocompatible de novo integral membrane proteins. We use recent examples to showcase some of the key computational approaches in current use and highlight that the overall philosophy of 'surface-swapping' - the replacement of solvent-facing residues with amino acids bearing lipid-soluble hydrophobic sidechains - is a promising avenue in membrane protein design. We conclude by highlighting outstanding design challenges and the emerging role of AI in sequence design and structure ideation.

Surviving severe COVID-19: Interviews with patients, informal carers and health professionals.

BACKGROUND: The COVID-19 pandemic has been associated with an unprecedented number of critical care survivors. Their experiences through illness and recovery are likely to be complex, but little is known about how best to support them. AIM: This study aimed to explore experiences of illness and recovery from the perspective of survivors, their relatives and professionals involved in their care. STUDY DESIGN: In-depth qualitative interviews were conducted with three stakeholder groups during the first wave of the pandemic. A total of 23 participants (12 professionals, 6 survivors and 5 relatives) were recruited from 5 acute hospitals in England and interviewed by telephone or video call. Data analysis followed the principles of Reflexive Thematic Analysis. FINDINGS: Three themes were generated from their interview data: (1) Deteriorating fast-a downhill journey from symptom onset to critical care; (2) Facing a new virus in a hospital-a remote place; and (3) Returning home as a survivor, maintaining normality and recovering slowly. CONCLUSIONS: Our findings highlight challenges in accessing care and communication between patients, hospital staff and relatives. Following hospital discharge, patients adopted a reframed 'survivor identity' to cope with their experience of illness and slow recovery process. The concept of survivorship in this patient group may be beneficial to promote and explore further. RELEVANCE TO CLINICAL PRACTICE: All efforts should be made to continue to improve communication between patients, relatives and health professionals during critical care admissions, particularly while hospital visits are restricted. Adapting to life after critical illness may be more challenging while health services are restricted by the impacts of the pandemic. It may be beneficial to promote the concept of survivorship, following admission to critical care due to severe COVID-19.

Magnetic resonance imaging of mean cell size in human breast tumors.

PURPOSE: Cell size is a fundamental characteristic of all tissues, and changes in cell size in cancer reflect tumor status and response to treatments, such as apoptosis and cell-cycle arrest. Unfortunately, cell size can currently be obtained only by pathological evaluation of tumor tissue samples obtained invasively. Previous imaging approaches are limited to preclinical MRI scanners or require relatively long acquisition times that are impractical for clinical imaging. There is a need to develop cell-size imaging for clinical applications. METHODS: We propose a clinically feasible IMPULSED (imaging microstructural parameters using limited spectrally edited diffusion) approach that can characterize mean cell sizes in solid tumors. We report the use of a combination of pulse sequences, using different gradient waveforms implemented on clinical MRI scanners and analytical equations based on these waveforms to analyze diffusion-weighted MRI signals and derive specific microstructural parameters such as cell size. We also describe comprehensive validations of this approach using computer simulations, cell experiments in vitro, and animal experiments in vivo and demonstrate applications in preoperative breast cancer patients. RESULTS: With fast acquisitions (~7 minutes), IMPULSED can provide high-resolution (1.3 mm in-plane) mapping of mean cell size of human tumors in vivo on clinical 3T MRI scanners. All validations suggest that IMPULSED provides accurate and reliable measurements of mean cell size. CONCLUSION: The proposed IMPULSED method can assess cell-size variations in tumors of breast cancer patients, which may have the potential to assess early response to neoadjuvant therapy.

Long-term functional outcomes in polytrauma: a fundamentally new approach is needed in prediction.

PURPOSE: Modern trauma care has reduced mortality but poor long-term outcomes with low follow-up rates are common with limited recommendations for improvements. The aim of this study was to describe the impact of severe injury on the health-related quality of life, specifically characterise the non-responder population and to identify modifiable predictors of poorer outcomes. METHODS: Five-year (2012-2016) prospective cohort study was performed at a level 1 trauma centre. Baseline Short-Form Health Survey (SF36) was collected at admission, and at 6 and 12 months postinjury together with demographics, injury mechanism and severity, psychosocial wellbeing, and return to work capacity. RESULTS: Of the 306 consecutive patients [age 52 ± 17 years, male 72%, ISS 21 (17, 29), mortality 5%], 195 (64%) completed questionnaires at baseline, and at 12 months. Preinjury physical health scores were above the general population (53.1 vs. 50.3, p < 0.001) and mental health component was consistent with the population norms (51.7 vs. 52.9, p = 0.065). One year following injury, both physical health (13.2, 95% CI 14.8, 11.6) and mental health scores (6.0, 95% CI 8.1, 3.8) were significantly below age- and sex-adjusted preinjury baselines. Non-responders had similar ISS but with a lower admission GCS, and were more likely to be younger, and without comorbidities, employment, or university education. CONCLUSION: Contrary to their better than population norm preinjury health status, polytrauma patients remain functionally impaired at least 1 year after injury. The identified high risk for non-responding group needs more focused efforts for follow-up. A fundamentally different approach is required in polytrauma research which identify modifiable predictors of poor long-term outcomes.

Computational modelling of diatom silicic acid transporters predicts a conserved fold with implications for their function and evolution.

Diatoms are an important group of algae that can produce intricate silicified cell walls (frustules). The complex process of silicification involves a set of enigmatic integral membrane proteins that are thought to actively transport the soluble precursor of biosilica, dissolved silicic acid. Full-length silicic acid transporters are found widely across the diatoms while homologous shorter proteins have now been identified in a range of other organisms. It has been suggested that modern silicic acid transporters arose from the union of such partial sequences. Here, we present a computational study of the silicic acid transporters and related transporter-like sequences to help understand the structure, function and evolution of this class of membrane protein. The AlphaFold software predicts that all of the protein sequences studied here share a common fold in the membrane domain which is entirely different from the predicted folds of non-homologous silicic acid transporters from plants. Substrate docking reveals how conserved polar residues could interact with silicic acid at a central solvent-accessible binding site, consistent with an alternating access mechanism of transport. The structural conservation between these proteins supports a model where modern silicon transporters evolved from smaller ancestral proteins by gene fusion.

The outcomes of the most severe polytrauma patients: a systematic review of the use of high ISS cutoffs for performance measurement.

BACKGROUND: This systematic review aimed to describe the outcomes of the most severely injured polytrauma patients and identify the consistent Injury Severity Score based definition of utilised for their definition. This could provide a global standard for trauma system benchmarking. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist was applied to this review. We searched Medline, Embase, Cochrane Reviews, CINAHL, CENTRAL from inception until July 2022. Case reports were excluded. Studies in all languages that reported the outcomes of adult and paediatric patients with an ISS 40 and above were included. Abstracts were screened by two authors and ties adjudicated by the senior author. RESULTS: 7500 abstracts were screened after excluding 13 duplicates. 56 Full texts were reviewed and 37 were excluded. Reported ISS groups varied widely between the years 1986 and 2022. ISS groups reported ranged from 40-75 up to 51-75. Mortality varied between 27 and 100%. The numbers of patients in the highest ISS group ranged between 15 and 1451. CONCLUSIONS: There are very few critically injured patients reported during the last 48 years. The most critically injured polytrauma patients still have at least a 50% risk of death. There is no consistent inclusion and exclusion criteria for this high-risk cohort. The current approach to reporting is not suitable for monitoring the epidemiology and outcomes of the critically injured polytrauma patients. LEVEL OF EVIDENCE: Level 4-systematic review of level 4 studies.

Experimental demonstration of diffusion limitations on resolution and SNR in MR microscopy.

PURPOSE: MR microscopy is in principle capable of producing images at cellular resolution (<10 µm), but various factors limit the quality achieved in practice. A recognized limit on the signal to noise ratio and spatial resolution is the dephasing of transverse magnetization caused by diffusion of spins in strong gradients. Such effects may be reduced by using phase encoding instead of frequency encoding read-out gradients. However, experimental demonstration of the quantitative benefits of phase encoding are lacking, and the exact conditions in which it is preferred are not clearly established. We quantify the conditions where phase encoding outperforms a readout gradient with emphasis on the detrimental effects of diffusion on SNR and resolution. METHODS: A 15.2 T Bruker MRI scanner, with 1 T/m gradients, and micro solenoid RF coils < 1 mm in diameter, were used to quantify diffusion effects on resolution and the signal to noise ratio of frequency and phase encoded acquisitions. Frequency and phase encoding's spatial resolution and SNR per square root time were calculated and measured for images at the diffusion limited resolution. The point spread function was calculated and measured for phase and frequency encoding using additional constant time phase gradients with voxels 3-15 µm in dimension. RESULTS: The effect of diffusion during the readout gradient on SNR was experimentally demonstrated. The achieved resolutions of frequency and phase encoded acquisitions were measured via the point-spread-function and shown to be lower than the nominal resolution. SNR per square root time and actual resolution were calculated for a wide range of maximum gradient amplitudes, diffusion coefficients, and relaxation properties. The results provide a practical guide on how to choose between phase encoding and a conventional readout. Images of excised rat spinal cord at 10 µm × 10 µm in-plane resolution demonstrate phase encoding's benefits in the form of higher measured resolution and higher SNR than the same image acquired with a conventional readout. CONCLUSION: We provide guidelines to determine the extent to which phase encoding outperforms frequency encoding in SNR and resolution given a wide range of voxel sizes, sample, and hardware properties.

Cost-effectiveness of confirmatory techniques for the placement of lumbar pedicle screws.

OBJECT: There is considerable variation in the use of adjunctive technologies to confirm pedicle screw placement. Although there is literature to support the use of both neurophysiological monitoring and isocentric fluoroscopy to confirm pedicle screw positioning, there are no studies examining the cost-effectiveness of these technologies. This study compares the cost-effectiveness and efficacy of isocentric O-arm fluoroscopy, neurophysiological monitoring, and postoperative CT scanning after multilevel instrumented fusion for degenerative lumbar disease. METHODS: Retrospective data were collected from 4 spine surgeons who used 3 different strategies for monitoring of pedicle screw placement in multilevel lumbar degenerative disease. A decision analysis model was developed to analyze costs and outcomes of the 3 different monitoring strategies. A total of 448 surgeries performed between 2005 and 2010 were included, with 4 cases requiring repeat operation for malpositioned screws. A sample of 64 of these patients was chosen for structured interviews in which the EuroQol-5D questionnaire was used. Expected costs and quality-adjusted life years were calculated based on the incidence of repeat operation and its negative effect on quality of life and costs. RESULTS: The decision analysis model demonstrated that the O-arm monitoring strategy is significantly (p < 0.001) less costly than the strategy of postoperative CT scanning following intraoperative uniplanar fluoroscopy, which in turn is significantly (p < 0.001) less costly than neurophysiological monitoring. The differences in effectiveness of the different monitoring strategies are not significant (p = 0.92). CONCLUSIONS: Use of the O-arm for confirming pedicle screw placement is the least costly and therefore most cost-effective strategy of the 3 techniques analyzed.

The most critically injured polytrauma patient mortality: should it be a measurement of trauma system performance?

PURPOSE: The risk of death after traumatic injury in developed trauma systems is at an all-time low. Among 'major trauma' patients (injury severity score, ISS > 15), the risk of dying is less than 10%. This group contains critical polytrauma patients (ISS 50-75), with high risks of death. We hypothesized that the reduction in trauma mortality was driven by reduction in moderate injury severity and that death from critical polytrauma remained persistently high. METHODS: A 20-year retrospective analysis ending December 2021 of a Level-1 trauma center's registry was performed on all trauma patients admitted with ISS > 15. Patients' demographics, injury severity and outcomes were collected. Multivariate logistic regression analysis was performed. Mortality was examined for the entire study group and separately for the subset of critical polytrauma patients (ISS 50-75). RESULTS: A total of 8462 severely injured (ISS > 15) trauma patients were identified during the 20-year period. Of these 238 (2.8%) were critical polytrauma patients (ISS 50-75). ISS > 15 mortality decreased from 11.3 to 9.4% over the study period (Adjusted OR 0.98, 0.97-0.99). ISS 50-75 mortality did not change significantly (46.2-60.0%), adjusted OR 0.96, 0.92-1.00). CONCLUSION: The improvement in trauma mortality over the past 20 years has not been experienced equally. The ISS50-75 critical polytrauma mortality is a practical group to capture. It could be a group for deeper study and reporting to drive improvement.

Bench to bore ramifications of inter-subject head differences on RF shimming and specific absorption rates at 7T.

PURPOSE: This study shows how inter-subject variation over a dataset of 72 head models results in specific absorption rate (SAR) and B1+ field homogeneity differences using common shim scenarios. METHODS: MR-CT datasets were used to segment 71 head models into 10 tissue compartments. These head models were affixed to the shoulders and neck of the virtual family Duke model and placed within an 8 channel transmit surface-loop array to simulate the electromagnetic fields of a 7T imaging experiment. Radio frequency (RF) shimming using the Gerchberg-Saxton algorithm and Circularly Polarized shim weights over the entire brain and select slices of each model was simulated. Various SAR metrics and B1+ maps were calculated to demonstrate the contribution of head variation to transmit inhomogeneity and SAR variability. RESULTS: With varying head geometries the loading for each transmit loop changes as evidenced by changes in S-parameters. The varying shim conditions and head geometries are shown to affect excitation uniformity, spatial distributions of local SAR, and SAR averaging over different pulse sequences. The Gerchberg-Saxton RF shimming algorithm outperforms circularly polarized shimming for all head models. Peak local SAR within the coil most often occurs nearest the coil on the periphery of the body. Shim conditions vary the spatial distribution of SAR. CONCLUSION: The work gives further support to the need for fast and more subject specific SAR calculations to maintain safety. Local SAR10g is shown to vary spatially given shim conditions, subject geometry and composition, and position within the coil.

Trends in polytrauma incidence among major trauma admissions.

PURPOSE: Polytrauma is increasingly recognized as a disease beyond anatomical injuries. Due to population growth, centralization, and slow uptake of preventive measures, major trauma presentations in most trauma systems show a slow but steady increase. The proportional contribution of polytrauma patients to this increase is unknown. METHODS: A 13-year retrospective analysis ending 31/12/2021 of all major trauma admissions (ISS > 15) to a level-1 trauma center were included. Polytrauma was classified using the Newcastle definition. Linear regression analysis was used to compare the rates of patient presentation over time. Logistic regression was used to measure for change in proportion of polytrauma. Data are presented as median (IQR), with odds ratios and 95% confidence intervals as appropriate. RESULTS: 5897 (age: 49 ± 43 years, sex: 71.3% male, ISS: 20 ± 9, mortality: 10.7%) major trauma presentations were included, 1,616 (27%) were polytrauma (age: 45 ± 37 years, 72.0% male, ISS: 29 ± 14, mortality: 12.7%). Major trauma presentations increased significantly over the study period (+ 8 patients per year (3-14), p < 0.01), aged significantly (0.42 years/year (0.25-0.59, p < 0.001). The number of polytrauma presentations per year did not change significantly (+ 1 patients/year (- 1 to 4, p > 0.2). Overall unadjusted mortality did not change (OR 0.99 (0.97-1.02). Polytrauma mortality fell significantly (OR 0.96 (0.92-0.99)) over the study period. CONCLUSIONS: Polytrauma patients represent about 25% of the major trauma admissions, with higher injury severity, static incidence and higher but improving mortality in comparison to all major trauma patients. Separate reporting and focused research on this group are warranted as monitoring the entire major trauma cohort does not identify these specifics of this high acuity subgroup.

Using Smartwatches to Observe Changes in Activity During Recovery From Critical Illness Following COVID-19 Critical Care Admission: 1-Year, Multicenter Observational Study.

BACKGROUND: As a sequela of the COVID-19 pandemic, a large cohort of critical illness survivors have had to recover in the context of ongoing societal restrictions. OBJECTIVE: We aimed to use smartwatches (Fitbit Charge 3; Fitbit LLC) to assess changes in the step counts and heart rates of critical care survivors following hospital admission with COVID-19, use these devices within a remote multidisciplinary team (MDT) setting to support patient recovery, and report on our experiences with this. METHODS: We conducted a prospective, multicenter observational trial in 8 UK critical care units. A total of 50 participants with moderate or severe lung injury resulting from confirmed COVID-19 were recruited at discharge from critical care and given a smartwatch (Fitbit Charge 3) between April and June 2020. The data collected included step counts and daily resting heart rates. A subgroup of the overall cohort at one site-the MDT site (n=19)-had their smartwatch data used to inform a regular MDT meeting. A patient feedback questionnaire and direct feedback from the MDT were used to report our experience. Participants who did not upload smartwatch data were excluded from analysis. RESULTS: Of the 50 participants recruited, 35 (70%) used and uploaded data from their smartwatch during the 1-year period. At the MDT site, 74% (14/19) of smartwatch users uploaded smartwatch data, whereas 68% (21/31) of smartwatch users at the control sites uploaded smartwatch data. For the overall cohort, we recorded an increase in mean step count from 4359 (SD 3488) steps per day in the first month following discharge to 7914 (SD 4146) steps per day at 1 year (P=.003). The mean resting heart rate decreased from 79 (SD 7) beats per minute in the first month to 69 (SD 4) beats per minute at 1 year following discharge (P<.001). The MDT subgroup's mean step count increased more than that of the control group (176% increase vs 42% increase, respectively; +5474 steps vs +2181 steps, respectively; P=.04) over 1 year. Further, 71% (10/14) of smartwatch users at the MDT site and 48% (10/21) of those at the control sites strongly agreed that their Fitbit motivated them to recover, and 86% (12/14) and 48% (10/21), respectively, strongly agreed that they aimed to increase their activity levels over time. CONCLUSIONS: This is the first study to use smartwatch data to report on the 1-year recovery of patients who survived a COVID-19 critical illness. This is also the first study to report on smartwatch use within a post-critical care MDT. Future work could explore the role of smartwatches as part of a randomized controlled trial to assess clinical and economic effectiveness. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.12968/ijtr.2020.0102.

Small-residue packing motifs modulate the structure and function of a minimal de novo membrane protein.

Alpha-helical integral membrane proteins contain conserved sequence motifs that are known to be important in helix packing. These motifs are a promising starting point for the construction of artificial proteins, but their potential has not yet been fully explored. Here, we study the impact of introducing a common natural helix packing motif to the transmembrane domain of a genetically-encoded and structurally dynamic de novo membrane protein. The resulting construct is an artificial four-helix bundle with lipophilic regions that are defined only by the amino acids L, G, S, A and W. This minimal proto-protein could be recombinantly expressed by diverse prokaryotic and eukaryotic hosts and was found to co-sediment with cellular membranes. The protein could be extracted and purified in surfactant micelles and was monodisperse and stable in vitro, with sufficient structural definition to support the rapid binding of a heme cofactor. The reduction in conformational diversity imposed by this design also enhances the nascent peroxidase activity of the protein-heme complex. Unexpectedly, strains of Escherichia coli expressing this artificial protein specifically accumulated zinc protoporphyrin IX, a rare cofactor that is not used by natural metalloenzymes. Our results demonstrate that simple sequence motifs can rigidify elementary membrane proteins, and that orthogonal artificial membrane proteins can influence the cofactor repertoire of a living cell. These findings have implications for rational protein design and synthetic biology.

Traumatic haemopneumothorax and 'whole-body' subcutaneous emphysema: successful use of a small-bore chest drain.

A 56-year-old man presented having had two falls at home. He had a background of multiple sclerosis. After his second fall, during which he had fallen onto the toilet injuring his right chest, he was brought into the emergency department reporting pleuritic chest discomfort. Immediately evident was extensive swelling from his forehead to his thighs, which on palpation was found to be subcutaneous emphysema. A chest X-ray showed a large right-sided pneumothorax for which a chest drain was inserted. A CT revealed extensive surgical emphysema, pneumomediastinum, pneumoperitoneum and gas within the spinal canal. It also showed right-sided rib fractures and associated haemothorax. He was managed conservatively with a 12-French (F), small-bore, chest drain and made a complete recovery without complication. This case challenges the widely held, but poorly evidenced, opinion that traumatic haemopneumothorax needs to be managed with a large-bore surgical chest drain.

Influence of the timing of internal fixation of femur fractures during shock resuscitation on remote organ damage.

BACKGROUND: Reamed intramedullary nailing is the gold standard for management of femur fractures. Nailing within 24 h is proven to reduce complications from ongoing bleeding, soft-tissue damage and pain. However, when combined with haemorrhagic shock, femur fracture and intramedullary nailing are associated with immune-mediated damage to remote organs. We studied whether delaying fracture fixation until resuscitation was succeeding would lead to a significant reduction in remote organ damage. METHODS: Twenty male rabbits underwent closed femur fracture, haemorrhagic shock, resuscitation and either immediate nailing (group: ImmFix, n = 9), delayed nailing (group: DelFix, n = 8) or just splinting (group: NoFix, n = 3). Haemorrhagic shock was maintained for 60 min. Resuscitation was with shed blood and Hartmann's solution. Animals were euthanized 8 h after fixation; the lungs and small bowel were scored histologically by two pathologists. RESULTS: Groups did not differ in weight, haemorrhage volume or magnitude of shock. At 8 h, there was no difference in end-organ damage between ImmFix and DelFix groups (11.3 ± 1.6 and 13.2 ± 1.6 versus 8.1 ± 1.3 and 12.9 ± 1.1, P = 0.26 between groups). However, the NoFix group had significantly greater end-organ damage when compared with the fixation at any time groups (17.3 ± 2.7 and 17.0 ± 3.3 versus 9.8 ± 1.1 and 13.1 ± 1, P = 0.01 between groups). CONCLUSION: In this laboratory model, we have demonstrated that timely femur fracture fixation outweighs the potential harmful effects of surgery performed during haemorrhagic shock with simultaneous resuscitation. We have failed to demonstrate a difference between immediate and delayed fixation during resuscitation.

Cell necrosis-independent sustained mitochondrial and nuclear DNA release following trauma surgery.

BACKGROUND: Mitochondrial DNA (mtDNA), a potent proinflammatory damage-associated molecular pattern, is released in large titers following trauma. The effect of trauma surgery on mtDNA concentration is unknown. We hypothesized that mtDNA and nuclear DNA (nDNA) levels would increase proportionately with the magnitude of surgery and both would then decrease rapidly. METHODS: In this prospective pilot, plasma was sampled from 35 trauma patients requiring orthopedic surgical intervention at six perioperative time points. Healthy control subjects (n = 20) were sampled. DNA was extracted, and the mtDNA and nDNA were assessed using quantitative polymerase chain reaction. Markers of cell necrosis were also assayed (creatine kinase, lactate dehydrogenase, and aspartate aminotransferase). RESULTS: The free plasma mtDNA and nDNA levels (ng/mL) were increased in trauma patients compared with healthy controls at all time points (mtDNA: preoperative period, 108 [46-284]; postoperative period, 96 [29-200]; 7 hours postoperatively, 88 [43-178]; 24 hours, 79 [36-172]; 3 days, 136 [65-263]; 5 days, 166 [101-434] [healthy controls, 11 (5-19)]) (nDNA: preoperative period, 52 [25-130]; postoperative period, 100 [35-208]; 7 hours postoperatively, 75 [36-139]; 24 hours postoperatively, 85 [47-133]; 3 days, 79 [48-117]; 5 days, 99 [41-154] [healthy controls, 29 (16-54)]). Elevated DNA levels did not correlate with markers of cellular necrosis. mtDNA was significantly elevated compared with nDNA at preoperative period (p = 0.003), 3 days (p = 0.003), and 5 days (p = 0.0014). Preoperative mtDNA levels were greater with shorter time from injury to surgery (p = 0.0085). Postoperative mtDNA level negatively correlated with intraoperative crystalloid infusion (p = 0.0017). Major pelvic surgery (vs. minor) was associated with greater mtDNA release 5 days postoperatively (p < 0.05). CONCLUSION: This pilot of heterogeneous orthopedic trauma patients showed that the release of mtDNA and nDNA is sustained for 5 days following orthopedic trauma surgery. Postoperative, circulating DNA is not associated with markers of tissue necrosis but is associated with surgical invasiveness and is inversely related to intraoperative fluid administration. Sustained elevation of mtDNA levels could be of inflammatory origin and may contribute to postinjury dysfunctional inflammation. LEVEL OF EVIDENCE: Prospective study, level III.

Patterns of CT use and surgical intervention in upper limb periarticular fractures at a level-1 trauma centre.

OBJECTIVES: The universal availability of CT scanners has led to lower thresholds for imaging despite significant financial costs and radiation exposure. We hypothesised that this recent trend has increased the use of CT for upper limb periarticular fractures and led to more frequent operative management. METHOD: A 5-year retrospective study (01/07/2005-30/06/2010) was performed on all adult patients with upper extremity periarticular fractures (OTA: 11, 13, 21 and 23) admitted to a level-1 trauma centre. Patients were identified from the institution's prospectively maintained OTA classification database. RESULTS: A total of 1734 upper extremity periarticular fractures were identified in 1651 patients. 65% (1132/1734) were operated on. 32% (557/1734) had CT imaging and 78% (431/557) of these had operative management. CT use for all fractures and ages showed no change (0.56%/year, p = 0.210, r(2) = 0.457). Operative intervention increased at a rate of 2.17%/year (p = 0.004, r(2) = 0.959). Within each fracture type, CT rates showed no change. Operative management of proximal humerus and distal radius fractures became more frequent (6.30%/year, p = 0.002, r(2) = 0.969 and 0.96%/year, p = 0.046, r(2) = 0.784 respectively). Fractures around the elbow showed no change. In patients younger than 55 years, only proximal humerus fractures had more frequent imaging (3.17%/year, p = 0.023, r(2) = 0.866). In patients over 55 the frequency of CT scanning did not increase, but they were more frequently operated on (4.09%/year, p = 0.012, r(2) = 0.907). In older patients the rate of surgical intervention increased in all but the distal humerus region, Proximal humerus (6.19%/year, p = 0.015, r(2) = 0.894), proximal forearm (4.57%/year, p = 0.007, r(2) = 0.931) and distal radius (2.70%/year, p = 0.002, r(2) = 0.871). CONCLUSION: During the examined 5-year period no increases of in CT imaging frequency were observed. The significantly increased number of operations among older patients is unlikely to be driven by imaging frequency.