Thromboprophylaxis in lower limb immobilisation after injury (TiLLI).

Venous thromboembolic disease is a major global cause of morbidity and mortality. An estimated 10 million episodes are diagnosed yearly; over half of these episodes are provoked by hospital admission/procedures and result in significant loss of disability adjusted life years. Temporary lower limb immobilisation after injury is a significant contributor to the overall burden of venous thromboembolism (VTE). Existing evidence suggests that pharmacological prophylaxis could reduce overall VTE event rates in these patients, but the proportional reduction of symptomatic events remains unclear. Recent studies have used different pharmacological agents, dosing regimens and outcome measures. Consequently, there is wide variation in thromboprophylaxis strategies, and international guidelines continue to offer conflicting advice for clinicians. In this review, we provide a summary of recent evidence assessing both the clinical and cost effectiveness of thromboprophylaxis in patients with temporary immobilisation after injury. We also examine the evidence supporting stratified thromboprophylaxis and the validity of widely used risk assessment methods.

Significant reduction in hospital-acquired thrombosis: impact of national risk assessment and real-time feedback.

OBJECTIVE: Since 2010, National Health Service hospitals in England have been incentivised to risk assess for Venous Thromboembolism (VTE) in all adult patients admitted, using a national tool. We studied the impact of this, together with local real-time reporting of VTE events to senior clinicians, on cases of hospital-acquired thrombosis (HAT) diagnosed, since 2010. METHODS: This was an observational cohort study reviewing all cases of VTE diagnosed between January 2010 and December 2016 in a single teaching hospital. These were matched against the number of patients admitted to produce crude incidence rates per thousand admissions. Similarly, all cases associated with inadequate thromboprophylaxis (TP) measures were documented over the same period. RESULTS: By the end of 2010, with 70% compliance with VTE risk assessment, improving to 90% (the national target) early in 2011, there were 217 HAT events from 103 845 admissions. In 2016, there were 176 HAT events from 119 128 admissions, being a significant reduction, relative risk (RR) 0.718 (95% CI 0.589 to 0.875; p=0.001). In 2010, there were 50 of 217 HAT events associated with inadequate TP, falling to 7 of 176 in 2016, also a significant reduction, RR 0.140 (95% CI 0.065 to 0.300; p=0.0001). CONCLUSIONS: National guidance on VTE prevention and mandatory risk assessment linked to local real-time reporting of VTE events are associated with significant reductions both in total HAT events and those associated with inadequate TP.

Pulmonary involvement in patients with thrombotic thrombocytopenic purpura.

OBJECTIVES: To determine the frequency of pulmonary involvement in patients with thrombotic thrombocytopenic purpura (TTP). METHODS: The experience of the Oklahoma TTP-HUS (hemolytic-uremic syndrome) Registry, a population-based cohort of consecutive patients without selection or referral bias, 1995-2012, was analyzed. Evidence for pulmonary involvement in patients with TTP was also documented with a systematic review of published reports. RESULTS: Only one of 74 Registry patients with acquired severe ADAMTS13 deficiency (activity <10%) had clinically important pulmonary involvement (transient PaO2 , 42 mm Hg; arterial O2 saturation, 78%; normal chest X-ray). No clinically important pulmonary involvement occurred in the remaining 73 patients. The systematic review identified 144 articles with search terms for TTP and pulmonary involvement; seven, published 1978-2002, had evaluable individual patient data. Five articles described single patients; only one patient was documented to have severe acquired ADAMTS13 deficiency; in none of the five patients was pulmonary involvement clearly related to TTP. Two articles were case series of seven patients each; no patients had ADAMTS13 activity measured. Each of the 14 patients had potential etiologies other than TTP for pulmonary involvement. CONCLUSIONS: Only one of 74 patients in the Oklahoma Registry had clinically important pulmonary involvement. A systematic review of published reports documented no clear evidence for pulmonary involvement resulting from TTP. Clinically important pulmonary involvement may be rare in patients with TTP because (i) pulmonary microvasculature may be inherently resistant to the formation of platelet thrombi and (ii) pulmonary function can be maintained in spite of multiple microvascular thrombi.

Guideline on the investigation, management and prevention of venous thrombosis in children.

Venous thrombo-embolism (VTE) is increasingly recognized in paediatric practice. Few clinical trials have been performed in this area in children and management is largely extrapolated from adult practice where there is a considerable evidence base. This is likely to be unsatisfactory for a number of reasons. Firstly, there are significant differences in epidemiology and potential differences in the mechanisms for VTE in this age group. Secondly, many aspects of haemostasis are age-dependant, which has implications for the use of anticoagulants in the paediatric population. Thirdly, there are very limited data available on the safety and efficacy of anticoagulants to manage specific indications in paediatric practice, often with limited paediatric formulations available. In addition, children may survive for a prolonged period following these events so that long-term consequences may be highly significant in this age group. The aim of this guideline is to provide a rational basis for the investigation and management of children aged 1 month-16 years with VTE, including cerebral venous thrombosis (CVT). The guideline is targeted at healthcare professionals involved in the management of children and adolescents with VTE, particularly paediatric haematologists.

Investigating the role of instructional focus in incidental pattern learning.

The authors used a novel dual-component training procedure that combined a serial reaction time task and an artificial grammar learning task to investigate the role of instructional focus in incidental pattern learning. In Experiment 1, participants either memorized letter strings as a primary task and reacted to the stimuli locations as a secondary task or vice versa. In Experiment 2, participants were given the same dual-component stimuli but performed only one of the two training tasks. Instructional focus affected the amount of learning and the likelihood of acquiring explicit knowledge of the underlying pattern. However, the effect of instructional focus varied for the different types of stimuli. These results are discussed in terms of the role of focused attention in incidental learning.

The risk of spinal haematoma following neuraxial anaesthesia or lumbar puncture in thrombocytopenic individuals.

Neuraxial anaesthesia is increasingly performed in thrombocytopenic patients at the time of delivery of pregnancy. There is a lack of data regarding the optimum platelet count at which spinal procedures can be safely performed. Reports are often confounded by the presence of other risk factors for spinal haematomata, such as anticoagulants, antiplatelet agents and other acquired or congenital coagulopathies/platelet function defects or rapidly falling platelet counts. In the absence of these additional risk factors, a platelet count of 80 x 10(9)/l is a 'safe' count for placing an epidural or spinal anaesthetic and 40 x 10(9)/l is a 'safe' count for lumbar puncture. It is likely that lower platelet counts may also be safe but there is insufficient published evidence to make recommendations for lower levels at this stage. For patients with platelet counts of 50-80 x 10(9)/l requiring epidural or spinal anaesthesia and patients with a platelet count 20-40 x 10(9)/l requiring a lumbar puncture, an individual decision based on assessment of risks and benefits should be made.

Thromboprophylaxis in patients with lower limb immobilisation - review of current status.

The risk for venous thromboembolism (VTE) associated with lower limb immobilisation is unclear, owing to of a lack of evidence from studies in this patient group. However, six small, randomised control trials (RCTs), totalling 1536 patients, compared low molecular weight heparin (LMWH) with controls and showed a significant reduction in asymptomatic deep vein thrombosis (DVT) from 17.1% to 9.8%, with very low bleeding rates. This is likely to be an underestimate of the real risk reduction as most trials excluded high-risk patients from randomisation. There have been no other controlled trials in cast-immobilised patients using alternative prophylactic measures. Together with the RCTs, other cohort studies have identified risk factors that increase the risk for VTE in lower limb immobilisation. In summary, patients in lower limb cast (or brace) immobilisation should be risk assessed and those deemed high risk for VTE should receive prophylactic LMWH for at least the duration of cast immobilisation.

Expertise promotes facilitation on a collaborative memory task.

The effect of expertise on collaborative memory was examined by comparing expert pilots, novice pilots, and non-pilots. Participants were presented with aviation scenarios and asked to recall the scenarios alone or in collaboration with a fellow participant of the same expertise level. Performance in the collaborative condition was compared to nominal group conditions (i.e., pooled individual performance). Results suggest that expertise differentially impacts collaborative memory performance. Non-experts (non-pilots and novices) were relatively disrupted by collaboration, while experts showed a benefit of collaboration. Verbal protocol analyses identified mechanisms related to collaborative skill and domain knowledge that may underlie experts' collaborative success. Specifically, experts were more likely than non-experts to explicitly acknowledge partner contributions by repeating back previously made statements, as well as to further elaborate on concepts in those contributions. The findings are interpreted according to the retrieval strategy disruption theory of collaborative memory and theories of grounding in communication.

Comparing Multiple Paths to Mastery: What is Learned?

Contemporary theories of learning postulate one or at most a small number of different learning mechanisms. However, people are capable of mastering a given task through qualitatively different learning paths such as learning by instruction and learning by doing. We hypothesize that the knowledge acquired through such alternative paths differs with respect to the level of abstraction and the balance between declarative and procedural knowledge. In a laboratory experiment we investigated what was learned about patterned letter sequences via either direct instruction in the relevant patterns or practice in solving letter-sequence extrapolation problems. Results showed that both types of learning led to mastery of the target task as measured by accuracy performance. However, behavioral differences emerged in how participants applied their knowledge. Participants given instruction showed more variability in the types of strategies they used to articulate their knowledge as well as longer solution times for generating the action implications of that knowledge as compared to the participants given practice. Results are discussed regarding the implications for transfer, generalization, and procedural application. Learning theories that claim generality should be tested against cross-scenario phenomena, not just parametric variations of a single learning scenario.