New Transcranial Doppler (TCD) Waveform Shape Parameters: A Repeatability/Reproducibility Study

Introduction and Objective

Doppler ultrasound is used in nearly every medical discipline for the evaluation of blood flow. The cerebral circulation is of particular interest, but is difficult to interpret because of the complex hemodynamics of the brain's blood flow. However, advances in the field of transcranial Doppler (TCD) could have important clinical and cost-saving benefits. We describe the testing of a novel method for acquiring and analyzing TCD flow velocity waveforms, in conjunction with other physiologic data. We also evaluate the repeatability and reproducibility of the technique.

Methods

We used custom-designed waveform analysis software to calculate 16 new waveform shape parameters and indices. We present the repeatability and reproducibility results for the new waveform shape parameters, as well as traditional TCD measurements, during repeated vasomotor reactivity studies on five healthy subjects. A ranked score ( mean value of test 1 and 2/coefficient of repeatability) is used to evaluate each parameter. The scores are presented by category: Traditional TCD Measurements, Velocity Minima, Velocity Maxima, Acceleration/Deceleration, Miscellaneous measures (e.g. blood pressure, heart rate), Time Measurements, and Shape Indices. Higher scores indicate better reproducibility.

Results

The mean scores of all parameters for each testing segment were Baseline 4.60, Hypercapnia 4.34, and Hypocapnia 4.00; showing that Baseline measurements are more easily reproduced than measurements during an intervention, particularly Hypocapnia. Individual parameters with the best reproducibility over all three testing segments are: RI (Resistance Index) 19.02; Mean Resistance ( mean blood pressure/mean velocity) 10.64; Umin (end-diastolic velocity) 9.84; Umaxdias (velocity rise immediately after aortic valve closure) 9.83; and DuDtmax (systolic acceleration) 8.54. We discuss why some parameters are more reliable than others in TCD studies and how the cyclical variations in the cerebral circulation can affect reproducibility.

Conclusions

This new methodology allows for discrete measurements of Doppler waveforms and would have the ability to track subtle changes during physiological or pharmacological interventions. These advances may aid the interpretation of complex cerebral hemodynamics, and increase the utility of this non-invasive, low-cost technique.

An ovine hepatorenal fibrocystic model of a Meckel-like syndrome associated with dysmorphic primary cilia and TMEM67 mutations

Meckel syndrome (MKS) is an inherited autosomal recessive hepatorenal fibrocystic syndrome, caused by mutations in TMEM67, characterized by occipital encephalocoele, renal cysts, hepatic fibrosis, and polydactyly. Here we describe an ovine model of MKS, with kidney and liver abnormalities, without polydactyly or occipital encephalocoele. Homozygous missense p.(Ile681Asn; Ile687Ser) mutations identified in ovine TMEM67 were pathogenic in zebrafish phenotype rescue assays. Meckelin protein was expressed in affected and unaffected kidney epithelial cells by immunoblotting, and in primary cilia of lamb kidney cyst epithelial cells by immunofluorescence. In contrast to primary cilia of relatively consistent length and morphology in unaffected kidney cells, those of affected cyst-lining cells displayed a range of short and extremely long cilia, as well as abnormal morphologies, such as bulbous regions along the axoneme. Putative cilia fragments were also consistently located within the cyst luminal contents. The abnormal ciliary phenotype was further confirmed in cultured interstitial fibroblasts from affected kidneys. These primary cilia dysmorphologies and length control defects were significantly greater in affected cells compared to unaffected controls. In conclusion, we describe abnormalities involving primary cilia length and morphology in the first reported example of a large animal model of MKS, in which we have identified TMEM67 mutations.

Wave intensity analysis and its application to the coronary circulation

Wave intensity analysis (WIA) is a technique developed from the field of gas dynamics that is now being applied to assess cardiovascular physiology. It allows quantification of the forces acting to alter flow and pressure within a fluid system, and as such it is highly insightful in ascribing cause to dynamic blood pressure or velocity changes. When co-incident waves arrive at the same spatial location they exert either counteracting or summative effects on flow and pressure. WIA however allows waves of different origins to be measured uninfluenced by other simultaneously arriving waves. It therefore has found particular applicability within the coronary circulation where both proximal (aortic) and distal (myocardial) ends of the coronary artery can markedly influence blood flow. Using these concepts, a repeating pattern of 6 waves has been consistently identified within the coronary arteries, 3 originating proximally and 3 distally. Each has been associated with a particular part of the cardiac cycle. The most clinically relevant wave to date is the backward decompression wave, which causes the marked increase in coronary flow velocity observed at the start of the diastole. It has been proposed that this wave is generated by the elastic re-expansion of the intra-myocardial blood vessels that are compressed during systolic contraction. Particularly by quantifying this wave, WIA has been used to provide mechanistic and prognostic insight into a number of conditions including aortic stenosis, left ventricular hypertrophy, coronary artery disease and heart failure. It has proven itself to be highly sensitive and as such a number of novel research directions are encouraged where further insights would be beneficial.

Methamphetamine absorption by skin lipids: accumulated mass, partition coefficients, and the influence of fatty acids

Occupants of former methamphetamine laboratories, often residences, may experience increased exposure through the accumulation of the methamphetamine in the organic films that coat skin and indoor surfaces. The objectives of this study were to determine equilibrium partition coefficients of vapor-phase methamphetamine with artificial sebum (AS-1), artificial sebum without fatty acids (AS-2), and real skin surface films, herein called skin oils. Sebum and skin oil-coated filters were exposed to vapor-phase methamphetamine at concentrations ranging from 8 to 159 ppb, and samples were analyzed for exposure time periods from 2 h to 60 days. For a low vapor-phase methamphetamine concentration range of ~8-22 ppb, the equilibrium partition coefficient for AS-1 was 1500 ± 195 μg/g/ppb. For a high concentration range of 98-112 ppb, the partition coefficient was lower, 459 ± 80 μg/g/ppb, suggesting saturation of the available absorption capacity. The low partition coefficient for AS-2 (33 ± 6 μg/g/ppb) suggests that the fatty acids in AS-1 and skin oil are responsible for much high partition coefficients. We predict that the methamphetamine concentration in skin lipids coating indoor surfaces can exceed recommended surface remediation standards even for air concentrations well below 1 ppb.

A Mixed-Methods Evaluation of a Social Paediatrics Block Rotation for Paediatric Residents

BACKGROUND: Poverty and social injustice have a direct link to health outcomes and health care utilization, especially for children. Understanding the complexity of impact of social determinants on health is essential in providing effective, compassionate care to vulnerable populations. Currently, there is a paucity of literature on the impact of various models of advocacy curricula on pediatric residents and future involvement in advocacy. Social Pediatrics is an approach to child health that focuses on the child, in illness, and in health, within the context of their society, environment, school, and family.

OBJECTIVES: 1) To determine if a social pediatrics rotation greater enables residents to become involved in advocacy projects during their residency and interest for career. 2) To identify resident knowledge translation of the social determinants of health and their impact on the pediatric population. 3) To characterize the barriers and enablers, if any, for residents to engage in advocacy.

DESIGN/METHODS: The Social Pediatrics rotation was embedded in the second year of a postgraduate pediatric curriculum. Knowledge and attitudes of resident participants before and after the rotation was assessed with written tests and surveys. A qualitative descriptive study of community partners and resident perspectives was semi-structured interviews, thematic coding and analysis via an inductive-iterative approach.

RESULTS: 21 residents completed pre-and post- written knowledge tests, and 12 residents completed optional attitudinal surveys. Knowledge increased from 68% prior to rotation, to 80% (p < 0.001) following the rotation. All residents completing written surveys indicated increased likelihood of participating in social pediatrics and advocacy in practice following this rotation. Results from 6 resident and 5 community partner interviews included: enhanced knowledge of social determinants of health, residency curricula development with further mental health placements, future practice models involving vulnerable populations, multi-disciplinary learning opportunities, and advocacy projects both at the patient and community level. Community partners shared experiences of residents demonstrating enthusiasm and engagement in placements, some logistical challenges but value in experiences outside hospital environment, particularly in learning from multidisciplinary team.

CONCLUSION: Pediatric residents demonstrate increase in knowledge of social determinants of health and an increased interest in community advocacy initiatives and vulnerable populations following a block rotation in Social Pediatrics. Community partners valued engagement with pediat-ric residents, identifying key learning opportunities in these unique environments and report few barriers to continued involvement. Future directions include impact on advocacy work or career decisions, and multi-centre collaboration.

P18: MULTIPLE DIAGNOSIS OR CONTINUUM OF DISEASE: MULTICENTRIC CASTLEMAN'S DISEASE

Purpose of Study

Multicentric Castleman's disease (MCD) is a rare lymphoproliferative disorder characterized by peripheral lymphadenopathy (LAD), hepatosplenomegaly(HSM), and B symptoms. It is associated with HIV and HHV8 infection.

We report a case of young woman presented with B symptoms, workup suggestive of lupus but lymph node biopsy (BX) was consistent with MCD. Association of SLE with MCD is rare. We report this case to increase awareness of this potential diagnostic and therapeutic dilemma.

Methods Used

Patient is a 27 yr old black woman presented with malaise, fevers, cough, weight loss, arthralgia, alopecia, numbness of extremities and Raynaud's phenomenon. Patient had skin tightness around the mouth, telangiectasia, digital ulcers, HSM, pitting edema, diffuse LAD and moderate pericardial effusion.

Laboratory results consistent with hemolytic anemia with Hb 5.6 g/dl, direct coombs positive, elevated reticulocyte count, LDH and low haptoglobin. Initial RF, ANA, and all infectious work up including HIV were normal. She was transfused cautiously, with inconclusive LN and bone marrow Bx. Patient left hospital against medical advice.

She presented two days later with altered mental status (AMS) and hypotension. CT head and Lumbar puncture were negative. Hypotension responded to fluids, but no response in AMS. Repeat ANA, AntiSSB, AntiSm, AntiRNP, and Antihistone antibodies were positive. Patient met diagnostic criteria for SLE and was subsequently treated for lupus cerebritis with pulse steroids, with moderate improvement in mental status. Repeat LNBX revealed reactive lymphadenitis with features of MCD, HHV8 negative. Patient was treated with IL-6 inhibitor Siltuximab, with significant improvement in mental status.

Summary of Results

MCD is a rare angiolymphoproliferative disorder of unclear etiology. Most cases occur in middle aged men and are associated with immunosuppression where as SLE is common in women of child bearing age. Reported cases of MCD in association with SLE are common in immunocompetent young women. Our patient is a young woman, HIV/HHV8 negative with good response to Siltuximab, favoring MCD.

Conclusions

It is unclear whether this finding of MCD and SLE represents an overlap or a pure association. However, this phenomenon needs further investigation.

Prediction of Late Death or Disability at Age 5 Years Using a Count of 3 Neonatal Morbidities in Very Low Birth Weight Infants

OBJECTIVE

To evaluate bronchopulmonary dysplasia (BPD), serious brain injury, and severe retinopathy of prematurity (ROP) as predictors of poor long-term outcome in very low birth weight infants.

STUDY DESIGN

We examined the associations between counts of the 3 morbidities and long-term outcomes in 1514 of 1791 (85%) infants with birth weights of 500-1250 g who were enrolled in the Caffeine for Apnea of Prematurity trial from October 1999, to October 2004, had complete morbidity data, and were alive at 36 weeks postmenstrual age (PMA). BPD was defined as use of supplemental oxygen at 36 weeks PMA. Serious brain injury on cranial ultrasound included grade 3 and 4 hemorrhage, cystic periventricular leucomalacia, porencephalic cysts, or ventriculomegaly of any cause. Poor long-term outcome was death after 36 weeks PMA or survival to 5 years with 1 or more of the following disabilities: motor impairment, cognitive impairment, behavior problems, poor general health, deafness, and blindness.

RESULTS

BPD, serious brain injury, and severe ROP occurred in 43%, 13%, and 6% of the infants, respectively. Each of the 3 morbidities was similarly and independently correlated with poor 5-year outcome. Rates of death or disability (95% CI) in children with none, any 1, any 2, and all 3 morbidities were 11.2% (9.0%-13.7%), 22.9% (19.6%-26.5%), 43.9% (35.5%-52.6%), and 61.5% (40.6%-79.8%), respectively.

CONCLUSIONS

In very low birth weight infants who survive to 36 weeks PMA, a count of BPD, serious brain injury, and severe ROP predicts the risk of a late death or survival with disability at 5 years.

Accumulation of gas-phase methamphetamine on clothing, toy fabrics, and skin oil

To better understand methamphetamine exposure and risk for occupants of former residential clandestine methamphetamine laboratories, we measured the dynamic accumulation of methamphetamine in skin oil, cotton and polyester (PE) clothing, upholstery, and toy fabric (substrates) exposed to 15-30 ppb (91-183 μg/m(3)) neutral methamphetamine in air for up to 60 days. The average equilibrium partition coefficients at 30% RH, in units of μg of methamphetamine per gram of substrate per ppb, are 3.0 ± 0.2 for a PE baby blanket, 5.6 ± 3.5 for a PE fabric toy, 3.7 ± 0.2 for a PE shirt, 18.3 ± 8.0 for a PE/cotton upholstery fabric, and 1200 ± 570 in skin oil. The partition coefficients at 60% RH are 4.5 ± 0.4, 5.2 ± 2.1, 4.5 ± 0.6, 36.1 ± 3.6, and 1600 ± 1100 μg/(g ppb), respectively. There was no difference in the partition coefficient for a clean and skin-oil-soiled cotton shirt [15.3 ± 2.1 μg/(g ppb) @ 42 days]. Partition coefficients for skin oil may be sensitive to composition. 'Mouthing' of cloth is predicted to be the dominant exposure pathway [60 μg/(kg body weight*ppb)] for a toddler in former meth lab, and indoor air concentrations would have to be very low (0.001 ppb) to meet the recommended reference dose for children.

PRACTICAL IMPLICATIONS

Gas-phase methamphetamine transfers to and accumulates on clothing, toys and other fabrics significantly increases risk of ingestion of methamphetamine. Current remediation methods should consider measurement of postremediation gas-phase air concentrations of methamphetamine in addition to surface wipe samples.