Thromboelastography as a Predictor of Outcomes Following Liver Transplantation.

BACKGROUND: Thromboelastography (TEG) has been used perioperatively during liver transplantation (LT) to provide a real-time global hemostasis assessment for targeted blood product replacement. We aimed to analyze the relationship between post-LT TEG results and outcomes. METHODS: We retrospectively analyzed patients undergoing LT from November 2008 to December 2014 at Mayo Clinic Florida. All 441 single-organ 1st-time LT patients aged ≥18 years requiring post-LT intensive care unit management were included. TEG parameters including r time, k time, α angle, and maximum amplitude were measured regularly during the first 24 hours after LT. Outcomes included return to the operating room secondary to bleeding, length of hospitalization, survival, and early allograft dysfunction. RESULTS: A prolonged and/or lengthening r time, k time, and r+k time were all independently associated with increased length of hospitalization after LT. Increased maximum amplitude on the first post-LT TEG was associated with early allograft dysfunction. No notable associations of TEG parameters with survival or return to operating room were observed. CONCLUSIONS: The association of absolute and temporal TEG value changes with increased length of hospitalization and early allograft dysfunction suggests that TEG may have a role in identifying patients at high risk for these outcomes.

OC-04 - Tissue factor positive microvesicles activate platelets in vitro and in vivo and enhance thrombosis in mice.

INTRODUCTION: Cancer patients have a 4- to 7- fold increased risk of venous thromboembolism (VTE) compared with general population. Most tumor cells express tissue factor (TF) and constitutively release small membrane microvesicles called tumor microvesicles (TMVs). Clinical studies have shown that circulating MP-TF activity is associated with VTE in pancreatic cancer but not in other types of cancer. Thrombin is a potent platelet agonist and activates platelets via protease activated receptors (PARs). AIM: To determine the contribution of the TF+ TMV-thrombin-platelet pathway to cancer-associated thrombosis. MATERIALS AND METHODS: A human pancreatic adenocarcinoma cell line expressing high levels of TF (BxPc-3) was selected to study the effect of TF+ TMVs on platelet activation and thrombosis. RESULTS: TF+ TMVs induced platelet activation in vitro in a thrombin-dependent manner. The presence of orthotopically grown BxPc-3 tumors in mice was associated with increased levels of thrombin-antithrombin III complexes (TATc) and larger thrombi in an inferior vena cava stenosis model compared with control mice. Furthermore, injection of BxPc-3 TF+ TMVs into mice triggered platelet activation and enhanced venous thrombosis in a TF-dependent manner. Importantly, BxPc-3 TF+ TMV-enhanced thrombosis was reduced in Par4-deficient mice and wild-type mice treated with the platelet inhibitor clopidogrel, suggesting that platelet activation was required for the enhanced thrombosis. CONCLUSIONS: These studies suggest that platelet inhibitors may reduce thrombosis in cancer patients with elevated levels of TF+ TMVs.

Tissue factor-positive tumor microvesicles activate platelets and enhance thrombosis in mice.

UNLABELLED: ESSENTIALS: Cancer patients have a high rate of venous thrombosis (VT) but the underlying mechanisms are unknown. Tumor-derived, tissue factor-positive microvesicles in platelet activation in vitro and in vivo were studied. Tumor-derived, tissue factor-positive microvesicles enhanced VT in mice. Platelets may contribute to VT in some cancer patients, and this could be prevented with antiplatelet drugs. BACKGROUND: Cancer patients have an approximately 4-fold increased risk of venous thromboembolism (VTE) compared with the general population, and cancer patients with VTE have reduced survival. Tumor cells constitutively release small membrane vesicles called microvesicles (MVs) that may contribute to thrombosis in cancer patients. Clinical studies have shown that levels of circulating tumor-derived, tissue factor-positive (TF(+) ) MVs in pancreatic cancer patients are associated with VTE. Objectives We tested the hypothesis that TF(+) tumor-derived MVs (TMVs) activate platelets in vitro and in mice. MATERIALS AND METHODS: We selected two human pancreatic adenocarcinoma cell lines expressing high (BxPc-3) and low (L3.6pl) levels of TF as models to study the effect of TF(+) TMVs on platelets and thrombosis. RESULTS AND CONCLUSIONS: We found that both types of TF(+) TMVs activated human platelets and induced aggregation in vitro in a TF and thrombin-dependent manner. Further, injection of BxPc-3 TF(+) TMVs triggered platelet activation in vivo and enhanced thrombosis in two mouse models of venous thrombosis in a TF-dependent manner. Importantly, BxPc-3 TF(+) TMV-enhanced thrombosis was reduced in Par4-deficient mice and in wild-type mice treated with clopidogrel, suggesting that platelet activation was required for enhanced thrombosis. These studies suggest that TF(+) TMV-induced platelet activation contributes to thrombosis in cancer patients.

Novel mouse hemostasis model for real-time determination of bleeding time and hemostatic plug composition.

INTRODUCTION: Hemostasis is a rapid response by the body to stop bleeding at sites of vessel injury. Both platelets and fibrin are important for the formation of a hemostatic plug. Mice have been used to uncover the molecular mechanisms that regulate the activation of platelets and coagulation under physiologic conditions. However, measurements of hemostasis in mice are quite variable, and current methods do not quantify platelet adhesion or fibrin formation at the site of injury. METHODS: We describe a novel hemostasis model that uses intravital fluorescence microscopy to quantify platelet adhesion, fibrin formation and time to hemostatic plug formation in real time. Repeated vessel injuries of ~ 50-100 µm in diameter were induced with laser ablation technology in the saphenous vein of mice. RESULTS: Hemostasis in this model was strongly impaired in mice deficient in glycoprotein Ibα or talin-1, which are important regulators of platelet adhesiveness. In contrast, the time to hemostatic plug formation was only minimally affected in mice deficient in the extrinsic tissue factor (TF(low)) or the intrinsic factor IX coagulation pathways, even though platelet adhesion was significantly reduced. A partial reduction in platelet adhesiveness obtained with clopidogrel led to instability within the hemostatic plug, especially when combined with impaired coagulation in TF(low) mice. CONCLUSIONS: In summary, we present a novel, highly sensitive method to quantify hemostatic plug formation in mice. On the basis of its sensitivity to platelet adhesion defects and its real-time imaging capability, we propose this model as an ideal tool with which to study the efficacy and safety of antiplatelet agents.

The fibrinogen γA/γ' isoform does not promote acute arterial thrombosis in mice.

BACKGROUND: Elevated plasma fibrinogen is associated with arterial thrombosis in humans and promotes thrombosis in mice by increasing fibrin formation and thrombus fibrin content. Fibrinogen is composed of six polypeptide chains: (Aα, Bß, and γ)2. Alternative splicing of the γ chain leads to a dominant form (γA/γA) and a minor species (γA/γ'). Epidemiological studies have detected elevated γA/γ' fibrinogen in patients with arterial thrombosis, suggesting that this isoform promotes thrombosis. However, in vitro data show that γA/γ' is anticoagulant due to its ability to sequester thrombin and suggest its expression is upregulated in response to inflammatory processes. OBJECTIVE: To determine whether γA/γ' fibrinogen is prothrombotic in vivo. METHODS: We separated γA/γA and γA/γ' fibrinogen from human plasma-purified fibrinogen and determined the effects on in vitro plasma clot formation and on in vivo thrombus formation and circulating thrombin-antithrombin complexes in mice. RESULTS AND CONCLUSIONS: Both γA/γA and γA/γ' fibrinogen were cleaved by murine and human thrombin and were incorporated into murine and human clots. When γA/γA or γA/γ' was spiked into plasma, γA/γA increased the fibrin formation rate to a greater extent than γA/γ'. In mice, compared to controls, γA/γA infusion shortened the time to carotid artery occlusion, whereas γA/γ' infusion did not. Additionally, γA/γ' infusion led to lower levels of plasma thrombin-antithrombin complexes following arterial injury, whereas γA/γA infusion did not. These data suggest that γA/γ' binds thrombin in vivo and decreases prothrombotic activity. Together, these findings indicate that elevated levels of γA/γA fibrinogen promote arterial thrombosis in vivo, whereas γA/γ' does not.

Differential phosphorylation of myosin light chain (Thr)18 and (Ser)19 and functional implications in platelets.

BACKGROUND: Myosin IIA is an essential platelet contractile protein that is regulated by phosphorylation of its regulatory light chain (MLC) on residues (Thr)18 and (Ser)19 via the myosin light chain kinase (MLCK). OBJECTIVE: The present study was carried out to elucidate the mechanisms regulating MLC (Ser)19 and (Thr)18 phosphorylation and the functional consequence of each phosphorylation event in platelets. RESULTS: Induction of 2MeSADP-induced shape change occurs within 5s along with robust phosphorylation of MLC (Ser)19 with minimal phosphorylation of MLC (Thr)18. Selective activation of G(12/13) produces both slow shape change and comparably slow MLC (Thr)18 and (Ser)19 phosphorylation. Stimulation with agonists that trigger ATP secretion caused rapid MLC (Ser)19 phosphorylation while MLC (Thr)18 phosphorylation was coincident with secretion. Platelets treated with p160(ROCK) inhibitor Y-27632 exhibited a partial inhibition in secretion and had a substantial inhibition in MLC (Thr)18 phosphorylation without effecting MLC (Ser)19 phosphorylation. These data suggest that phosphorylation of MLC (Ser)19 is downstream of Gq/Ca(2+) -dependent mechanisms and sufficient for shape change, whereas MLC (Thr)18 phosphorylation is substantially downstream of G(12/13) -regulated Rho kinase pathways and necessary, probably in concert with MLC (Ser)19 phosphorylation, for full contractile activity leading to dense granule secretion. Overall, we suggest that the amplitude of the platelet contractile response is differentially regulated by a least two different signaling pathways, which lead to different phosphorylation patterns of the myosin light chain, and this mechanism results in a graded response rather than a simple on/off switch.

Factors related to severe untreated tooth decay in rural adolescents: a case-control study for public health planning.

OBJECTIVES: In this case-control study of rural adolescents we identified factors to discriminate those who have high levels of tooth decay and receive treatment from those with similar levels who receive no treatment. METHODS: The sample was drawn from all 12-20-year-olds (n = 439) in a rural high school in Washington State, U.S. The criterion for being included was 5 or more decayed, missing or filled teeth. The questionnaire included structure, history, cognition and expectation variables based on a model by Grembowski, Andersen and Chen. RESULTS: No structural variable was related to the dependent variable. Two of 10 history variables were related: perceived poor own dental health and perceived poor mother's dental health. Four of eight cognition variables were also predictive: negative beliefs about the dentist, not planning to go to a dentist even if having severe problems, not being in any club or playing on a sports team and not having a best friend. No relationship was found for the expectation variable 'usual source of care'. CONCLUSIONS: These data are consistent with the hypothesis that untreated tooth decay is associated with avoidance of care and point to the importance of history and cognition variables in planning efforts to improve oral health of rural adolescents.

Recruiting phobic research subjects: effectiveness and cost.

Efficiently enrolling subjects is one of the most important and difficult aspects of a clinical trial. This prospective study evaluated strategies used in the recruitment of 144 dental injection phobics for a clinical trial evaluating the effectiveness of combining alprazolam with exposure therapy. Three types of recruitment strategies were evaluated: paid advertising, free publicity, and professional referral. Sixty-three percent of subjects were enrolled using paid advertising (the majority of them from bus advertisements [27.0%], posters on the University of Washington campus [20.1%], and newspaper advertisements [13.2%]). Free publicity (eg, television coverage, word of mouth) yielded 18.8% of enrolled subjects and professionaL referrals 14.6% of subjects. The average cost (1996 dollars) of enrolling 1 subject was $79. Bus and poster advertising attracted more initial contacts and yielded the greatest enrollment.

Psychiatric diagnoses among self-referred dental injection phobics.

In order to determine the psychiatric characteristics of people with dental injection phobia. 118 dental injection phobics were systematically assessed using a structured clinical interview and a written questionnaire. Fifty-four percent of subjects had a current Axis I diagnosis other than dental injection phobia, mainly anxiety, mood or adjustment disorder, and 68.6% of subjects had an additional lifetime Axis I diagnosis. Subjects with additional current Axis I diagnoses reported higher dental anxiety, greater severity of injection fear cognitions, and poorer relationships with dental professionals, than did subjects without any or with past Axis I diagnoses. Further investigation is needed to explore the treatment possibilities for patients with and without additional current diagnoses.

Treatment of dental fears: pharmacology or psychology?

Fear of dental treatment constitutes one of the major obstacles to receiving dental treatment, in both the UK and the USA. Treatment for such fear can be pharmacological or psychological, or a combination of both. In this article the aetiology, diagnosis and treatment of dental fear will be described and the treatment methods compared.

Dental fear among university employees: implications for dental education.

We surveyed 350 University of Washington permanent employees chosen randomly from among both faculty and staff. The aim was to determine the extent and nature of dental anxiety in the university population potentially available for teaching clinics. In addition, the relationship of fears to self-reported dental health, utilization of dental care, and other general and mental health issues was examined. Dental anxiety was prevalent in this population; 13 percent of subjects reported high dental fear. In contrast to respondents with lower dental fear, subjects with clinically significant fear reported poorer perceived dental health, a longer interval since their last dental appointment, a higher frequency of past fear behaviors, more physical symptoms during last dental injection, and higher percentage of symptoms of anxiety and depression. Dental anxiety was not associated with poorer perceived general health or a longer interval since the last dental injection. University employees are a rich source of potential teaching patients for achieving curricular requirements for managing anxious patients. Student clinicians need guidance to be able to recognize fearful patients; they also need instruction about psychiatric conditions like anxiety and depression in order to be able to better manage and prevent dropouts in their patient roster.

CARL: a LabVIEW 3 computer program for conducting exposure therapy for the treatment of dental injection fear.

This paper describes CARL (Computer Assisted Relaxation Learning), a computerized, exposure-based therapy program for the treatment of dental injection fear. The CARL program operates primarily in two different modes; in vitro, which presents a video-taped exposure hierarchy, and in vivo, which presents scripts for a dentist or hygienist to use while working with a subject. Two additional modes are used to train subjects to use the program and to administer behavioral assessment tests. The program contains five different modules, which function to register a subject, train subjects to use physical and cognitive relaxation techniques, deliver an exposure hierarchy, question subjects about the helpfulness of each of the therapy components, and test for memory effects of anxiolytic medication. Nine subjects have completed the CARL therapy program and 1-yr follow-up as participants in a placebo-controlled clinical trial examining the effects of alprazolam on exposure therapy for dental injection phobia. All nine subjects were able to receive two dental injections, and all reduced their general fear of dental injections. Initial results therefore indicate that the CARL program successfully reduces dental injection fear.

Dental fear among university students: implications for pharmacological research.

University students are often subjects in randomized clinical trials involving anxiolytic and analgesic medications used during clinical dental and medical procedures. The purpose of this study was to describe a typical university student population available for research by using data from a mail survey. Subjects were 350 students chosen randomly from all enrolled, full-time, traditional students on the main campus at the University of Washington in Seattle, WA. The aim was to determine the extent and nature of dental anxiety in this population. In addition, the relationships between subject willingness to receive dental injections and general and mental health and medical avoidance and medical fears were examined. The Dental Anxiety Scale (DAS) was used to measure dental anxiety. Dental anxiety was prevalent in this population; 19% of students reported high rates of dental fear. Thirteen percent of students had never had a dental injection. Students with no experience with dental injections were more reluctant than those with experience to receive an injection if one were needed. DAS scores were correlated with injection reluctance. Students who were reluctant to go ahead with a dental injection also reported poorer general and mental health than those who were less reluctant. These students also reported higher medical avoidance and medical anxiety scores. University students provide a rich source of potential subjects for clinical research. The student population, like the community at large, contains people with high levels of dental and medical fear.

Amnestic and anxiolytic effects of alprazolam in oral surgery patients.

PURPOSE: This study was designed to identify a dose of alprazolam that would reduce anxiety associated with oral surgery without causing accompanying memory impairment. PATIENTS AND METHODS: Thirty-six subjects in experiment 1 and 48 subjects in experiment 2 were pretested on a computerized memory battery to establish baseline performance. Subjects were then randomly assigned to receive placebo, 0.25 mg, or 0.75 mg oral alprazolam (experiment 1) or placebo, 0.25 mg, 0.50 mg, or 0.75 mg oral alprazolam (experiment 2). Forty-five minutes after the double-blind administration of alprazolam, subjects were given a second memory battery. The memory batteries tested story recall and recognition and word recall and recognition. Subjects in experiment 2 subsequently underwent oral surgery for the removal of one to four molars. The subjects completed anxiety questionnaires both before and after surgery. RESULTS: The 0.75-mg and 0.50-mg doses, but not the 0.25-mg dose, impaired word recall. The 0.75-mg dose also impaired story recall and recognition. The proportion of subjects reporting moderate to high anxiety during oral surgery decreased with increasing doses of alprazolam. Multiple regression indicated that the 0.75-mg alprazolam dose significantly decreased anxiety during oral surgery. The 0.25-mg and 0.50-mg doses also tended to reduce anxiety, but beta values for these doses did not reach significance. CONCLUSIONS: These findings indicate that alprazolam produces memory impairment at the dosages necessary to produce clinically significant anxiolysis during oral surgery.

Four dimensions of fear of dental injections.

In 1995, students and staff at the University of Washington were surveyed regarding avoidance of dental care and fear of dental injections. More than 25 percent of adults surveyed expressed at least one clinically significant fear of injections. Almost one in 20 respondents indicated avoiding, cancelling or not appearing for dental appointments because of fear of dental injections. Fear of dental injections consists of four dimensions. General fear of dental injections including pain of injection and of bodily injury from injection are the two most common dimensions of dental injection fear. Many people also express fears of acquired disease. Fear related to local anesthetic (such as side effects, inadequate anesthesia) is less frequent. Some respondents have fears that must be categorized using more than one of these dimensions. Understanding the nature of a patient's fear of injection may suggest strategies to address his or her concerns.

Development of a scale to measure the social and psychological effects of severe dental anxiety: social attributes of the Dental Anxiety Scale.

This paper describes the development of a scale designed to measure the extent to which severe dental anxiety or phobia affects patients' social wellbeing outside of the dental setting. Items initially selected on the basis of clinical experience were administered to two groups: 78 patients seeking help for severe anxiety and 88 patients attending the general clinic of a dental hospital. Items on the scale discriminated between these two groups and also between patients who were reluctant to attend even when experiencing symptoms and those who attend more regularly. Although the scale correlated moderately well with Corah's Dental Anxiety Scale, factor analysis indicated that its items assess the effects of severe anxiety on the two domains of psychological reactions and social inhibition as they occur as indirect effects of dental care. The scale could be included in assessments designed to measure the social and psychological effects of severe dental anxiety.

Assessing abuse and neglect and dental fear in women.

Little is known about how specific life stressors, such as sexual, physical and emotional abuse and neglect, might be factors in the establishment or maintenance of dental fears or might affect routine dental treatment. The authors collected data from 462 female members of a large urban health maintenance organization about their dental fear and histories of childhood and adult traumas. According to these data, a history of trauma appears to be significantly associated with elevated dental fear, although multiple factors play a major role in the establishment and maintenance of these phobias.

Frustrating patient visits.

OBJECTIVES: This study, part of a national mail survey of dentist malpractice liability claims, reports the reliability and validity of a new 22-item instrument measuring frustrating patient visits. METHODS: The items were subjected to factor analysis and subscales constructed. Reliability was assessed using Cronbach's alpha. Validity was assessed by comparing subscale scores to self-reports of satisfaction and liability claims. RESULTS: Factor analysis revealed four subscales representing unpleasant feelings, lack of communication, compliance, and practice organization (alpha = 0.60-0.86). Compliance was the most important factor. Subscale scores were related to satisfaction with practice and the proportion of patient visits in the practice that were frustrating to the dentist. Dentists who reported frustrating patient visits as quite typical of their practices were more likely to have had a malpractice liability claim within the last five years. CONCLUSION: This instrument may be of value in detecting patient-dentist communication difficulties that are the precursor to liability claims.