Arterial Collapse during Thrombectomy for Stroke: Clinical Evidence and Experimental Findings in Human Brains and In Vivo Models.

BACKGROUND AND PURPOSE: Aspiration thrombectomy has become a preferred approach to recanalize large-vessel occlusion in stroke with a growing trend toward using larger-bore catheters and stronger vacuum pumps. However, the mechanical response of the delicate cerebral arteries to aspiration force has not been evaluated. Here, we provide preclinical and clinical evidence of intracranial arterial collapse in aspiration thrombectomy. MATERIALS AND METHODS: We presented a clinical case of arterial collapse with previously implanted flow diverters. We then evaluated the effect of vacuum with conventional aspiration catheters (with and without stent retrievers) in a rabbit model (n = 3) using fluoroscopy and intravascular optical coherence tomography. Then, in a validated human cadaveric brain model, we conducted 168 tests of direct aspiration thrombectomy following an experimental design modifying the catheter inner diameter (0.064 inch, 0.068 inch, and 0.070 inch), cerebral perfusion pressures (mean around 60 and 90 mm Hg), and anterior-versus-posterior circulation. Arterial wall response was recorded and graded via direct transluminal observation. RESULTS: Arterial collapse was observed in both the patient and preclinical experimental models. In the human brain model, arterial collapse was observed in 98% of cases in the M2 and in all the cases with complete proximal flow arrest. A larger bore size of the aspiration catheter, a lower cerebral perfusion pressure, and the posterior circulation in comparison with the anterior circulation were associated with a higher probability of arterial collapse. CONCLUSIONS: Arterial collapse does occur during aspiration thrombectomy and is more likely to happen with larger catheters, lower perfusion pressure, and smaller arteries.

Reducing AB plasma utilisation through the AB plasma appropriateness index.

OBJECTIVES: We hypothesised that there was inappropriate group AB plasma used in our hospital, identifiable by a novel key quality indicator (KQI) and mitigable through massive transfusion protocol (MTP) modification. BACKGROUND: Group AB plasma is a scarce resource strained by increasing usage worldwide when used as universal donor plasma in non-group AB patients. To reduce inappropriate use and to promote benchmarking to the best practice, we developed the AB plasma appropriateness index (ABAI). ABAI is the ratio of AB plasma transfused to group AB or unknown blood group patients to all AB plasma utilised, where values closer to 1 are better. METHODS: Data collected included AB plasma disposition by blood group, indications for transfusion, total blood utilisation, patient clinical characteristics and outcomes. ABAI during a 12-month period was retrospectively assessed, which led to implementation of pre-thawed group A plasma instead of group AB plasma for trauma patients starting in July 2017. RESULTS: The ABAI retrospectively showed inappropriate use in non-group AB patients in our hospital, the majority used to avoid expiry after thaw. When comparing 1-year pre- and post-implementation periods, ABAI improved from 0·464 to 0·900 (P < 0·0001). After exclusion of therapeutic plasma exchange, ABAI still improved (0·486-0·720, P < 0·0001). No differences in the length of stay or mortality associated in 32 patients receiving group A plasma for emergency release were observed. CONCLUSION: The ABAI is a novel KQI to indicate inappropriate AB plasma usage for quality improvement. This led to thawed A plasma use for MTPs, reducing inappropriate AB plasma usage.

Vox Sanguinis International Forum on the use of prehospital blood products and pharmaceuticals in the treatment of patients with traumatic haemorrhage.

While specific practices and transported blood products vary around the world, most of the respondents in this International Forum transported at least one blood product for the transfusion to bleeding patients en route to the hospital. The most commonly carried product was RBCs, while the use of whole blood will likely increase given the recent reports of its successful use in the civilian setting, and because of the change in the AABB's Standards regulating its use. It will be interesting to see if plasma use in the prehospital setting becomes more widely used given today's enhanced appreciated of the coagulopathy of trauma and plasma's beneficial effect in reversing it, and if blood products are transported to the scene of injury by more vehicles, that is, not just predominantly in helicopters. It was not surprising that TXA is being widely administered as close to the time of injury as possible given its potential benefit in these patients. This International Forum highlights the importance of focusing attention on prehospital transfusion management with a need to further high­quality research in this area to guide optimal resuscitation strategies.

Donor deferral policies for men who have sex with men: past, present and future.

We review the history and evolution of blood donor criteria for men who have sex with men (MSM). Deferral policies in many jurisdictions, including Australia, New Zealand, Canada, the United States, Brazil and many western European countries are based on a period of abstinence from MSM, often of 12 months duration. Several countries (Italy, Spain and Portugal) defer donors based on sexual behaviours considered to be at high risk, regardless of whether the partner is same sex or opposite sex. Compliance is a key determinant in the efficacy of any deferral policy. We summarize research themes and strategies discussed at a January 2017 meeting held in Toronto, Canada, to provide an evidence basis for future policy changes.

Audit of provincial IVIG Request Forms and efficacy documentation in four Ontario tertiary care centres.

OBJECTIVE: Retrospective audit of IVIG Request Forms in four Ontario tertiary care centres: to determine the case mix of new IVIG requests, to authenticate information provided, and to determine documentation of clinical efficacy. AIMS: To understand contributors to increases in IVIG utilisation and to determine whether IVIG is being used and monitored appropriately. INTRODUCTION: Intravenous immunoglobulin (IVIG) use in Canada is high compared with other developed countries. We performed a retrospective audit of new IVIG Request Forms across four tertiary care centres in Ontario, one with an active surveillance programme, to determine the case mix, authenticate information provided and assess documentation of efficacy. METHODS: Consecutive adult patients with a first-time IVIG request in 2014 were included. The ordering physician specialty, form completeness, documentation of diagnostic criteria for the medical condition and indication for IVIG use and documentation of efficacy were assessed by form and chart review. RESULTS: Of 178 patients, the most common indications for IVIG were immune thrombocytopenia (24.2%) and secondary immune deficiency (20.2%). The most frequent prescribers were haematologists (37.6%) and neurologists (10.7%). Other conditions not listed on the form represented 24.2% of cases, with most not indicated in current guidelines. A total of 32.6% of cases overall lacked verification of diagnostic criteria and 51.7% lacked verification for IVIG utilisation criteria, with the number of cases meeting criteria based on documentation being higher at the active surveillance site (P = 0.005). A total of 19.1% of cases had a discrepancy between the indication written on the form and the documented clinical diagnosis. A total of 18.7% of clinic notes following IVIG had no mention of efficacy. CONCLUSION: Our audit demonstrates a lack of compliance with IVIG Request Form requirements, a lack of documentation of diagnostic criteria and efficacy, and suggests inappropriate use of IVIG. Current implementation of the form may not be sufficient as a strategy for improving appropriate IVIG use.

Which creatinine-based estimated glomerular filtration rate equation best predicts all-cause mortality in Chinese subjects with type 2 diabetes?

AIM: In Chinese, ethnicity-based and/or diabetes specific modifications of the Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations have been developed for determining estimated glomerular filtrate rate (eGFR). This study aimed to compare the performance of five different creatinine-based eGFR equations in predicting all-cause mortality among Chinese subjects with type 2 diabetes (T2DM). METHODS: A total of 6739 Chinese subjects with T2DM were included. Their eGFR was calculated using the MDRD, CKD-EPI, their respective modified equations for Chinese, and the diabetes specific CKD-EPI Chinese T2DM equations. Multiple Cox regression analysis was used to evaluate the associations of eGFR with all-cause mortality. C-statistics, net reclassification index (NRI) and integrated discrimination index (IDI) were applied to assess the discrimination and reclassification of each eGFR equation in predicting mortality outcome. RESULTS: Over a follow-up of 5.7years, the incidence of all-cause mortality was 12.9% (N=867). The CKD-EPI equation discriminated all-cause mortality better than the MDRD equation (C-statistics: 0.714 vs. 0.689, p<0.0001), and Chinese modification of their respective equations did not improve discrimination. Among the five eGFR equations evaluated, the CKD-EPI Chinese T2DM equation provided the best discrimination in predicting all-cause mortality among Chinese subjects with T2DM, and was the only equation providing a significantly positive NRI and IDI relative to the CKD-EPI equation. CONCLUSIONS: Among Chinese subjects with T2DM, our findings suggested that the CKD-EPI Chinese T2DM equation best predicted all-cause mortality, and relative to the CKD-EPI equation, conferred improved discrimination and reclassification.

Optimal Cut-Offs of Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) to Identify Dysglycemia and Type 2 Diabetes Mellitus: A 15-Year Prospective Study in Chinese.

BACKGROUND: The optimal reference range of homeostasis model assessment of insulin resistance (HOMA-IR) in normal Chinese population has not been clearly defined. Here we address this issue using the Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS), a prospective population-based cohort study with long-term follow-up. MATERIAL & METHODS: In this study, normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) were defined according to the 1998 World Health Organization criteria. Dysglycemia referred to IFG, IGT or T2DM. This study comprised two parts. Part one was a cross-sectional study involving 2,649 Hong Kong Chinese subjects, aged 25-74 years, at baseline CRISPS-1 (1995-1996). The optimal HOMA-IR cut-offs for dysglycemia and T2DM were determined by the receiver-operating characteristic (ROC) curve. Part two was a prospective study involving 872 subjects who had persistent NGT at CRISPS-4 (2010-2012) after 15 years of follow-up. RESULTS: At baseline, the optimal HOMA-IR cut-offs to identify dysglyceia and T2DM were 1.37 (AUC = 0.735; 95% confidence interval [CI] = 0.713-0.758; Sensitivity [Se] = 65.6%, Specificity [Sp] = 71.3%] and 1.97 (AUC = 0.807; 95% CI = 0.777-0.886; Se = 65.5%, Sp = 82.9%) respectively. These cut-offs, derived from the cross-sectional study at baseline, corresponded closely to the 75th (1.44) and 90th (2.03) percentiles, respectively, of the HOMA-IR reference range derived from the prospective study of subjects with persistent NGT. CONCLUSIONS: HOMA-IR cut-offs, of 1.4 and 2.0, which discriminated dysglycemia and T2DM respectively from NGT in Southern Chinese, can be usefully employed as references in clinical research involving the assessment of insulin resistance.

Evaluation of the appropriateness of frozen plasma usage after introduction of prothrombin complex concentrates: a retrospective study.

BACKGROUND: Prothrombin complex concentrates (PCCs) can be used instead of frozen plasma (FP) transfusion to reverse the effect of warfarin. Audits have demonstrated over usage of FP transfusions even before the introduction of PCC. The objective of this study was to determine the appropriateness of current FP transfusion practice in the current era since the introduction of PCCs. METHODS: A retrospective cohort study of consecutive patients receiving FP over 3 months was carried out. Each episode of FP use over a 24-h period was adjudicated independently by two reviewers as appropriate (consistent with Canadian/AABB guidelines), appropriate but inconsistent with guidelines or inappropriate. Discrepancies were resolved by a third reviewer. Use of FP to reverse warfarin was considered inappropriate. FP usage from previous years was assessed as baseline. RESULTS: During the study period, 111 FP transfusions were administered. 74.8% of FP usage occurred in the ICU. The proportion of FP transfusions that were deemed appropriate, inconsistent yet appropriate or inappropriate were 33/89 (37.1%), 16/89 (18.0%) and 40/89 (44.9%), respectively, when use of FP for therapeutic plasma exchange was excluded. The most common reasons for inappropriate use were the absence of bleeding with an increased INR or warfarin reversal. CONCLUSION: Our study is the first to audit FP transfusions in the post-PCC era in Canada. FP usage remains inappropriately high in INR prolongation without another indication or to reverse warfarin. Targeted interventions to reduce FP usage in the future should focus on the ICU and on education about warfarin reversal.

Different volumes of injectate using electrostimulator and blinded techniques for brachial plexus block in dogs.

To compare different volumes of injectate using electrostimulator (ES)-guided and blind brachial plexus blockade (BPB) techniques in dogs. Prospective, randomised, blinded study. Fifty-eight healthy adult purpose-bred beagle dogs. Animals were randomised into 4 groups based on the volume of methylene blue 0.1 per cent administered for BPB, three using ES technique: E1 (0.2 ml/kg, n=22), E2 (0.6 ml/kg, n=22), and E3 (1.0 ml/kg, n=14), and one using blinded technique B4 (1.0 ml/kg, n=14). After euthanasia, the axillary region was dissected and nerves identified by a blinded evaluator. Success was defined as 3/4 nerves stained, or presence of dye in the tissue immediately surrounding the plexus. There were no significant differences between groups when total nerve count, adjacent staining, success rate (92.8-100 per cent), or rate of haematoma were evaluated. The musculocutaneous nerve was significantly more targeted in B4 than E1 and E2, but not E3. Electrostimulator-guided BPB using lower volumes of injectate had similar success rate as the blinded technique using higher volume, thus, lower volumes can be used without compromising success. When an ES is not available, the blind technique with 1 ml/kg is also acceptable. However, when performing an ES-guided BPB, volumes as low as 0.2 ml/kg can be used. As volume is increased, the musculocutaneous nerve becomes more likely to be targeted.

Multi-modality gellan gum-based tissue-mimicking phantom with targeted mechanical, electrical, and thermal properties.

This study develops a new class of gellan gum-based tissue-mimicking phantom material and a model to predict and control the elastic modulus, thermal conductivity, and electrical conductivity by adjusting the mass fractions of gellan gum, propylene glycol, and sodium chloride, respectively. One of the advantages of gellan gum is its gelling efficiency allowing highly regulable mechanical properties (elastic modulus, toughness, etc). An experiment was performed on 16 gellan gum-based tissue-mimicking phantoms and a regression model was fit to quantitatively predict three material properties (elastic modulus, thermal conductivity, and electrical conductivity) based on the phantom material's composition. Based on these material properties and the regression model developed, tissue-mimicking phantoms of porcine spinal cord and liver were formulated. These gellan gum tissue-mimicking phantoms have the mechanical, thermal, and electrical properties approximately equivalent to those of the spinal cord and the liver.

Bioimpedance of soft tissue under compression.

In this paper compression-dependent bioimpedance measurements of porcine spleen tissue are presented. Using a Cole-Cole model, nonlinear compositional changes in extracellular and intracellular makeup; related to a loss of fluid from the tissue, are identified during compression. Bioimpedance measurements were made using a custom tetrapolar probe and bioimpedance circuitry. As the tissue is increasingly compressed up to 50%, both intracellular and extracellular resistances increase while bulk membrane capacitance decreases. Increasing compression to 80% results in an increase in intracellular resistance and bulk membrane capacitance while extracellular resistance decreases. Tissues compressed incrementally to 80% show a decreased extracellular resistance of 32%, an increased intracellular resistance of 107%, and an increased bulk membrane capacitance of 64% compared to their uncompressed values. Intracellular resistance exhibits double asymptotic curves when plotted against the peak tissue pressure during compression, possibly indicating two distinct phases of mechanical change in the tissue during compression. Based on these findings, differing theories as to what is happening at a cellular level during high tissue compression are discussed, including the possibility of cell rupture and mass exudation of cellular material.

Structural differences between soluble and membrane bound cytochrome P450s.

The superfamily of cytochrome P450s forms a large class of heme monooxygenases with more than 13,000 enzymes represented in organisms from all biological kingdoms. Despite impressive variability in sizes, sequences, location, and function, all cytochrome P450s from various organisms have very similar tertiary structures within the same fold. Here we show that systematic comparison of all available X-ray structures of cytochrome P450s reveals the presence of two distinct structural classes of cytochrome P450s. For all membrane bound enzymes, except the CYP51 family, the beta-domain and the A-propionate heme side chain are shifted towards the proximal side of the heme plane, which may result in an increase of the volume of the substrate binding pocket and an opening of a potential channel for the substrate access and/or product escape directly into the membrane. This structural feature is also observed in several soluble cytochrome P450s, such as CYP108, CYP151, and CYP158A2, which catalyze transformations of bulky substrates. Alternatively, both beta-domains and the A-propionate side chains in the soluble isozymes extend towards the distal site of the heme. This difference between the structures of soluble and membrane bound cytochrome P450s can be rationalized through the presence of several amino acid inserts in the latter class which are involved in direct interactions with the membrane, namely the F'- and G'-helices. Molecular dynamics using the most abundant human cytochrome P450, CYP3A4, incorporated into a model POPC bilayer reveals the facile conservation of a substrate access channel, directed into the membrane between the B-C loop and the beta domain, and the closure of the peripheral substrate access channel directed through the B-C loop. This is in contrast to the case when the same simulation is run in buffer, where no such channel closing occurs. Taken together, these results reveal a key structural difference between membrane bound and soluble cytochrome P450s with important functional implications induced by the lipid bilayer.

Obesity and non-fatal motor vehicle crash injuries: sex difference effects.

BACKGROUND: Obesity and motor vehicle crash (MVC) injuries are two parallel epidemics in the United States. An important unanswered question is whether there are sex differences in the associations between the presence of obesity and non-fatal MVC injuries. OBJECTIVES: To further understand the association between obesity and non-fatal MVC injuries, particularly the sex differences in these relations. METHODS: We examined this question by analyzing data from the 2003 to 2007 National Automotive Sampling System Crashworthiness Data System (NASS CDS). A total of 10,962 drivers who were aged 18 years or older and who survived frontal collision crashes were eligible for the study. RESULTS: Male drivers experienced a lower rate of overall non-fatal MVC injuries than did female drivers (38.1 versus 52.2%), but experienced a higher rate of severe injuries (0.7 versus 0.2%). After adjusting for change in velocity (ΔV) during the crashes, obese male drivers showed a much higher risk (logistic coefficients of body mass index (BMI) for moderate, serious and severe injury are 0.0766, 0.1470 and 0.1792, respectively; all P<0.05) of non-fatal injuries than did non-obese male drivers and these risks increased with injury severity. Non-fatal injury risks were not found to be increased in obese female drivers. The association between obesity and risk of non-fatal injury was much stronger for male drivers than for female drivers. CONCLUSION: The higher risk of non-fatal MVC injuries in obese male drivers might result from their different body shape and fat distribution compared with obese female drivers. Our findings should be considered for obesity reduction, traffic safety evaluation and vehicle design for obese male drivers and provide testable hypotheses for future studies.

c-Myc and beta-catenin cooperate with loss of p53 to generate multiple members of the primitive neuroectodermal tumor family in mice.

Primitive neuroectodermal tumors (PNETs) are a family of primary malignant brain tumors that include medulloblastomas. Although genetic models of a subset of medulloblastomas are documented over the past decade, the molecular basis of other subclasses of PNET remains unclear. As elevated c-Myc expression, activation of Wnt/beta-catenin signaling and dysfunction of p53 are seen in human PNETs, we investigated what role these abnormalities have in the formation of PNETs. Incorporating these abnormalities, we generated supratentorial PNET (sPNET) in mice using somatic cell gene transfer. We show that sPNETs arise from GFAP-expressing cells by forced c-Myc expression combined with p53 inactivation. beta-catenin activation promotes tumor progression and induces divergent differentiation. These c-Myc+beta-catenin-induced PNETs are histologically similar to large cell/anaplastic medulloblastomas and can occur in both cerebrum and cerebellum. Furthermore, we have obtained one PNET with marked epithelial differentiation having histological resemblance to choroid plexus carcinoma in this series. Our results in mice suggest that sPNET with varied differentiation and large cell/anaplastic medulloblastomas may be two tumor groups with similar genetic foundations. These data provide insights into the biology and classification of human PNETs and suggest that multiple tumor types or variants can be generated from a fixed set of genetic abnormalities.

Association of autoantibodies with Ku and DNA repair proteins in connective tissue diseases.

OBJECTIVE: To analyse the autoimmune response to DNA damage response factors in systemic autoimmune rheumatic disease (SARD) patients and to determine their association with autoantibodies to Ku antigen. METHODS: We have screened the serum of 239 patients suffering from SARD, including systemic lupus erythematosus, systemic sclerosis and rheumatoid arthritis to detect the occurrence of autoantibodies to Ku and four other DNA damage response factors that form macromolecular complexes with Ku using an immunoprecipitation assay. RESULTS: We identified samples positive for autoantibodies to Ku (20.5%), DNA-dependent protein kinase catalytic subunit (DNA-PKcs, 8.4%) and poly(ADP-ribose) polymerase (5.9%), and report for the first time autoantibodies directed against two additional DNA repair proteins, Werner (6.3%) and Mre11 (9.6%). Remarkably, we found a striking correlation between the production of antibodies to Ku and the other four Ku-binding factors. Sixty-five percent of anti-Ku-positive sera were found to contain at least one of the four anti-DNA repair antibodies vs only 10% of the anti-Ku-negative sera. CONCLUSION: Our results suggest that the autoantibodies directed against Ku are elicited by macromolecular protein complexes containing Ku and the associated DNA damage proteins. The presence of autoantibodies directed against macromolecular complexes known to play roles in the DNA damage response provides evidence that B-cell responses to latent or persistent DNA damage may be present at the onset or during the development of autoimmunity in certain SARDs.

DNA-PK phosphorylation sites on Oct-1 promote cell survival following DNA damage.

Octamer transcription factor-1 (Oct-1) has recently been shown to function as a stress sensor that promotes cell survival subsequent to DNA damage. Here, we show that the survival signal imparted by Oct-1 following exposure to ionizing radiation (IR) is dependent upon DNA-dependent protein kinase (DNA-PK)-dependent phosphorylation of a cluster of 13 specific ser/thr residues within the N-terminal transcriptional regulatory domain of Oct-1. Although IR treatment did not affect the recruitment of Oct-1 to the histone H2B promoter, the recruitment of RNA polymerase II, TATA-binding protein and histone H4 acetylation were strongly reduced, consistent with a decrease in Oct-1 transcriptional regulatory potential following IR exposure. Ser/Thr-Ala substitution of 13 sites present in Oct-1 transcriptional regulatory domain eliminated Oct-1 phosphorylation subsequent to IR exposure. Further, these substitutions prevented Oct-1 from rescuing the survival of IR-treated Oct-1-/- murine embryonic fibroblasts, providing a direct link between DNA-PK-dependent phosphorylation and the contribution of Oct-1 to cell survival. These results implicate Oct-1 as a primary effector in a DNA-PK-dependent cell survival pathway that is activated by double-stranded DNA breaks.

Turbulent flow evaluation of the venous needle during hemodialysis.

Arteriovenous (AV) grafts and fistulas used for hemodialysis frequently develop intimal hyperplasia (IH) at the venous anastomosis of the graft, leading to flow-limiting stenosis, and ultimately to graft failure due to thrombosis. Although the high AV access blood flow has been implicated in the pathogenesis of graft stenosis, the potential role of needle turbulence during hemodialysis is relatively unexplored. High turbulent stresses from the needle jet that reach the venous anastomosis may contribute to endothelial denudation and vessel wall injury. This may trigger the molecular and cellular cascade involving platelet activation and IH, leading to eventual graft failure. In an in-vitro graft/needle model dye injection flow visualization was used for qualitative study of flow patterns, whereas laser Doppler velocimetry was used to compare the levels of turbulence at the venous anastomosis in the presence and absence of a venous needle jet. Considerably higher turbulence was observed downstream of the venous needle, in comparison to graft flow alone without the needle. While turbulent RMS remained around 0.1 m/s for the graft flow alone, turbulent RMS fluctuations downstream of the needle soared to 0.4-0.7 m/s at 2 cm from the tip of the needle and maintained values higher than 0.1 m/s up to 7-8 cm downstream. Turbulent intensities were 5-6 times greater in the presence of the needle, in comparison with graft flow alone. Since hemodialysis patients are exposed to needle turbulence for four hours three times a week, the role of post-venous needle turbulence may be important in the pathogenesis of AV graft complications. A better understanding of the role of needle turbulence in the mechanisms of AV graft failure may lead to improved design of AV grafts and venous needles associated with reduced turbulence, and to pharmacological interventions that attenuate IH and graft failure resulting from turbulence.