Balancing Hemostasis With Thrombosis: A Challenging Case of Pregnancy With a Mechanical Mitral Valve.

A 32-year-old pregnant woman with a mechanical mitral valve was admitted with vaginal bleeding and was found to have placenta previa. During her hospital stay, she developed acute valvular thrombosis. She underwent an emergency cesarean section followed by successful mechanical valve replacement.

Heart rate as an early predictor of severe cardiomyopathy and increased mortality in peripartum cardiomyopathy.

BACKGROUND: Delays in diagnosis of peripartum cardiomyopathy (PPCM) are common and are associated with worse outcomes; however, few studies have addressed methods for improving early detection. HYPOTHESIS: We hypothesized that easily accessible data (heart rate [HR] and electrocardiograms [ECGs]) could identify women with more severe PPCM and at increased risk of adverse outcomes. METHODS: Clinical data, including HR and ECG, from patients diagnosed with PPCM between January 1998 and July 2016 at our institution were collected and analyzed. Linear and logistic regression were used to analyze the relationship between HR at diagnosis and the left ventricular ejection fraction (LVEF) at diagnosis. Outcomes included overall mortality, recovery status, and major adverse cardiac events. RESULTS: Among 82 patients meeting inclusion criteria, the overall mean LVEF at diagnosis was 26 ± 11.1%. Sinus tachycardia (HR > 100) was present in a total of 50 patients (60.9%) at the time of diagnosis. In linear regression, HR significantly predicted lower LVEF (F = 30.00, p < .0001). With age-adjusted logistic regression, elevated HR at diagnosis was associated with a fivefold higher risk of overall mortality when initial HR was >110 beats per minute (adjusted odds ratio 5.35, confidence interval 1.23-23.28), p = .025). CONCLUSION: In this study, sinus tachycardia in women with PPCM was associated with lower LVEF at the time of diagnosis. Tachycardia in the peripartum period should raise concern for cardiomyopathy and may be an early indicator of adverse prognosis.

Severe asthma and death in a worker using methylene diphenyl diisocyanate MDI asthma death.

Diisocyanates are well-recognized to cause occupational asthma, yet diisocyanate asthma can be challenging to diagnose and differentiate from asthma induced by other allergens. The present study assesses the potential contribution of methylene diphenyl diisocyanate (MDI) to a workplace fatality. Examination of medical records, tissue, and blood from the deceased worker were undertaken. Formalin-fixed paraffin-embedded lung tissue sections were assessed through histologic and immunochemical stains. Serum MDI-specific IgE and IgG, and total IgE, were measured by enzyme-linked immunosorbent assays and/or Western blot. Information about potential chemical exposures and industrial processes in the workplace were provided by the employer and through interviews with co-workers. Review of the worker's medical records, occupational history, and autopsy findings were consistent with severe asthma as the cause of death, and ruled out cardiac disease, pulmonary embolism, or stroke. Lung pathology revealed hallmarks of asthma including smooth muscle hypertrophy, eosinophilia, basement membrane thickening, and mucus plugging of bronchioles. Immunochemical staining for MDI was positive in the thickened basement membrane of inflamed airways. MDI-specific serum IgE and IgG were significantly elevated and demonstrated specificity for MDI versus other diisocyanates, however, total serum IgE was normal (24 IU/ml). The workplace had recently introduced MDI into the foundry as part of a new process, but MDI air levels had not been measured. Respirators were not required. In summary, post-mortem findings support the diagnosis of diisocyanate asthma and a severe asthma attack at work as the cause of death in a foundry worker.

A cluster of hypersensitivity pneumonitis associated with exposure to metalworking fluids.

BACKGROUND: Workers exposed to metalworking fluids (MWF) can develop respiratory illnesses including hypersensitivity pneumonitis (HP). These respiratory manifestations are likely due to microbial contamination of aerosolized MWF. This paper reports a cluster of HP and respiratory symptoms at a manufacturing plant where MWF and workplace air were contaminated with bacterial endotoxin despite frequent negative bacterial cultures of MWF. METHODS: A pulmonologist assessed and treated three workers with respiratory symptoms. The Occupational Safety and Health Administration (OSHA) inspected the plant. OSHA's investigation included bacterial culture of MWF, measurement of endotoxin concentrations in MWF and workplace air, review of the employer's fluid management program, and distribution of a cross-sectional symptom questionnaire. RESULTS: Three workers had biopsy-confirmed HP. In addition, 30.8% of questionnaire respondents reported work-related respiratory symptoms. OSHA detected endotoxin levels as high as 92,000 endotoxin units (EU)/ml in MWF and 3200 EU/m3 in air. Endotoxin concentrations and risk of MWF inhalation were highest near an unenclosed multistation computer numerical control machine. A contractor had tested this machine's MWF for bacterial growth weekly during the preceding three years, and most (96.0%) of those tests were negative. CONCLUSIONS: Contaminated MWF can cause severe occupational lung disease even if microorganisms do not grow in fluid cultures. Endotoxin testing can increase the sensitivity of detection of microbial contamination. However, employers should not rely solely upon MWF testing data to protect workers. Medical surveillance and meticulous source control, such as engineering controls to suppress MWF mist and prevent its inhalation, can reduce the likelihood of respiratory disease.

Noise and Occupational Medicine: Common Practice Problems.

: Noise-induced hearing loss (NIHL) represents the second most common occupational disease in the United States. Although the Occupational Safety and Health Administration (OSHA) has promulgated an occupational noise exposure standard and associated recordkeeping requirements, OSHA inspections increasingly document practices that violate both the noise standard and recordkeeping regulation. This article describes five deviations from good clinical practices masking the true societal costs of NIHL, leading to missed prevention opportunities, and creating burdens for individuals and society. These include attributing NIHL to nonoccupational sources, exculpating the workplace because of audiogram patterns without careful documentation, ignoring symptoms or physical examination findings, and simply denying work-relatedness, leading to employers inappropriately lining out cases from the OSHA 300 log. The practices identified by OSHA suggest that many individuals are not following widely recognized and accepted practices when administering hearing conservation programs.

Predicting Mechanical Ventilation and Mortality: Early and Late Indicators in Steven-Johnson Syndrome and Toxic Epidermal Necrolysis.

Steven-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are characterized by loss of the epidermis, often accompanied by sloughing of the oral mucosa and airway, which may be associated with the need for mechanical ventilation. We retrospectively examined our SJS and TEN population for factors predictive of the need for mechanical ventilation and mortality. Over more than a 7-year period, 74 subjects of ≥18 years old with biopsy-confirmed SJS-TEN were identified. Variables within the first 3 days of admission and throughout the entire hospital stay were analyzed for their value in predicting the need for mechanical ventilation and mortality. Predictive variables were examined using univariate and multivariate logistic regression analyses. Of our 74 subjects, 28 (37.8%) required mechanical ventilation and 11 (13.9%) died, all of whom were intubated. Patients requiring ventilation had a significantly higher %TBSA loss of epidermis on admission and progressive epidermal loss after admission. On multivariate analysis, acute kidney injury within the first 3 days of admission and fewer days from symptom onset to admission were statistically significant in predicting need for mechanical ventilation. In addition, the early need for mechanical ventilation, early serum bicarbonate <20 mm/L, and older age were all associated with higher mortality on multivariate analysis. In conclusion, the need for mechanical ventilation in adult TEN subjects is associated with higher mortality. This is the first time that mechanical ventilation has been specifically examined in the recent U.S. SJS and TEN population. The early recognition of patients at risk for ventilation may help guide management, especially in those patients admitted early after symptom development with acute kidney injury and extensive, progressing epidermal loss.

Not All Drugs Are Created Equal: The Importance of Causative Agent in Toxic Epidermal Necrolysis.

Toxic epidermal necrolysis (TEN), Steven-Johnson Syndrome (SJS), and SJS/TEN overlap make up a spectrum of severe mucocutaneous disease that is an adverse reaction to a large number of medications and various infectious agents. Little is known about the differences in acute course of illness depending on the inciting agent, which prompted the authors to further explore their experience with TEN. In a retrospective analysis, 88 patients ≥18 years old were identified with biopsy-confirmed TEN and a variety of variables were analyzed. The authors evaluated for differences in presentation and hospital course between drug class and medication half-life using Kruskal-Wallis for continuous variables and χ or Fisher's exact test for categorical variables. Those subjects with the inciting agent of allopurinol had 100% incidence of acute kidney injury (AKI), significantly higher than other drug classes with antibiotics having the second highest incidence at 14%. Medications with a half-life of <6 hours were also associated with a higher incidence of AKI. Acutely there are significant clinical differences in TEN patients depending on the drug class and medication half-life of the inciting agent. Allopurinol, drugs with a short half-life, and a diagnosis of TEN were all associated with greater incidence of AKI. This is the first time that the relationship between clinical course and inciting agent has been examined in a United States population.

Ring-closing reaction in diarylethene captured by femtosecond electron crystallography.

The photoinduced ring-closing reaction in diarylethene, which serves as a model system for understanding reactive crossings through conical intersections, was directly observed with atomic resolution using femtosecond electron diffraction. Complementary ab initio calculations were also performed. Immediately following photoexcitation, subpicosecond structural changes associated with the formation of an open-ring excited-state intermediate were resolved. The key motion is the rotation of the thiophene rings, which significantly decreases the distance between the reactive carbon atoms prior to ring closing. Subsequently, on the few picosecond time scale, localized torsional motions of the carbon atoms lead to the formation of the closed-ring photoproduct. These direct observations of the molecular motions driving an organic chemical reaction were only made possible through the development of an ultrabright electron source to capture the atomic motions within the limited number of sampling frames and the low data acquisition rate dictated by the intrinsically poor thermal conductivity and limited photoreversibility of organic materials.

Mapping molecular motions leading to charge delocalization with ultrabright electrons.

Ultrafast processes can now be studied with the combined atomic spatial resolution of diffraction methods and the temporal resolution of femtosecond optical spectroscopy by using femtosecond pulses of electrons or hard X-rays as structural probes. However, it is challenging to apply these methods to organic materials, which have weak scattering centres, thermal lability, and poor heat conduction. These characteristics mean that the source needs to be extremely bright to enable us to obtain high-quality diffraction data before cumulative heating effects from the laser excitation either degrade the sample or mask the structural dynamics. Here we show that a recently developed, ultrabright femtosecond electron source makes it possible to monitor the molecular motions in the organic salt (EDO-TTF)2PF6 as it undergoes its photo-induced insulator-to-metal phase transition. After the ultrafast laser excitation, we record time-delayed diffraction patterns that allow us to identify hundreds of Bragg reflections with which to map the structural evolution of the system. The data and supporting model calculations indicate the formation of a transient intermediate structure in the early stage of charge delocalization (less than five picoseconds), and reveal that the molecular motions driving its formation are distinct from those that, assisted by thermal relaxation, convert the system into a metallic state on the hundred-picosecond timescale. These findings establish the potential of ultrabright femtosecond electron sources for probing the primary processes governing structural dynamics with atomic resolution in labile systems relevant to chemistry and biology.

Full characterization of RF compressed femtosecond electron pulses using ponderomotive scattering.

High bunch charge, femtosecond, electron pulses were generated using a 95 kV electron gun with an S-band RF rebunching cavity. Laser ponderomotive scattering in a counter-propagating beam geometry is shown to provide high sensitivity with the prerequisite spatial and temporal resolution to fully characterize, in situ, both the temporal profile of the electron pulses and RF time timing jitter. With the current beam parameters, we determined a temporal Instrument Response Function (IRF) of 430 fs FWHM. The overall performance of our system is illustrated through the high-quality diffraction data obtained for the measurement of the electron-phonon relaxation dynamics for Si (001).

Femtosecond dynamics of the ring closing process of diarylethene: a case study of electrocyclic reactions in photochromic single crystals.

The cyclization reaction of the photochromic diarylethene derivative 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)perfluorocyclopentene was studied in its single crystal phase with femtosecond transient absorption spectroscopy. The transient absorption measurements were performed with a robust acquisition scheme that explicitly exploits the photoreversibility of the molecular system and monitors the reversibility conditions. The crystalline system demonstrated 3 × 10(4) repeatable cycles before significant degradation was observed. Immediately following photoexcitation, the excited state absorption associated with the open-ring conformation undergoes a large spectral shift with a time constant of approximately 200 fs. Following this evolution on the excited state potential energy surface, the ring closure occurs with a time constant of 5.3 ps, which is significantly slower than previously reported measurements for similar derivatives in the solution phase. Time resolved electron diffraction studies were used to further demonstrate the assignment of the transient absorption dynamics to the ring closing reaction. The mechanistic details of the ring closing are discussed in the context of prior computational work along with a vibrational mode analysis using density functional theory to give some insight into the primary motions involved in the ring closing reaction.

Controlling piezoelectric response in semiconductor quantum dots via impulsive charge localization.

By direct observation of coherent acoustic phonons, we demonstrate a novel extrinsic piezoelectric response in colloidal CdSe semiconductor quantum dots. This response is driven by the migration of charges to the surface of the quantum dot on a vibrationally impulsive time scale. Surface- and fluence-dependent studies reveal that the observed carrier capture based piezo response is controllable and is at least an order of magnitude larger than the intrinsic piezo response of wurtzite CdSe.

State-resolved manipulations of optical gain in semiconductor quantum dots: Size universality, gain tailoring, and surface effects.

Optical gain in strongly confined colloidal semiconductor quantum dots is measured using state resolved pump/probe spectroscopy. Though size tunable optical amplification has been previously reported for these materials, the influence of confinement enhanced multiexcitonic interactions has limited prior demonstrations to specific particle sizes or host media. Here we show that the influence of the interfering multiexcitonic interactions, and hence the development of optical gain, is dependent on the identity of the initially prescribed excitonic state. By maintaining a constant excitonic state in the size tunable electronic structure of these materials, we recover the predicted universal development of optical gain, reflected by size-independent occupation thresholds, and differential gains. In addition, we explicitly compare the influence of surface passivation on the development and lifetime of the optical gain. Furthermore, we introduce a general, state-resolved pumping scheme which enables control over the optical gain spectrum. The capacity to manipulate the optical gain spectra of these spherically confined systems is evident in both the measured stimulated emission and amplified spontaneous emission. We anticipate that state-resolved optical excitation will be a useful method of enabling the development and manipulation of optical gain in any quantized nanostructure.

Gain control in semiconductor quantum dots via state-resolved optical pumping.

Excitonic state-resolved optical pumping experiments were performed on strongly confined semiconductor quantum dots. We demonstrate for the first time that optical gain is dependent upon the initial excitonic state. By prescribing the specific multiexcitonic states which can create, block, and ultimately control optical gain spectra, we recover the theoretically predicted size independence, even in systems which previously showed zero gain. In addition, we show for the first time that stimulated emission in quantum dots can be controlled via specific multiexcitonic interactions.

State-resolved studies of biexcitons and surface trapping dynamics in semiconductor quantum dots.

Biexcitons in strongly confined, colloidal CdSe quantum dots were investigated with excitonic state selectivity combined with 10 fs temporal precision. Within the first 50 fs, the first excited state of the biexciton was observed. By 100 ps, mixed character biexcitons were observed, comprised of a core exciton and a surface trapped exciton. The size dependence of the biexciton binding energies is reported for these specific biexcitons. Analysis of the spectral signatures of each biexcitonic state yields a quantitative measure of enhanced excited state trapping rates at the surface of the quantum dots. By comparing the biexcitonic signals to the state-filling signals, we show that it is primarily the holes which are trapped at the interface on the 100 ps time scale.

Noise analysis and noise reduction methods in kilohertz pump-probe experiments.

We analyze sources of noise in kilohertz frequency pump/probe experiments and present a method for reducing experimental noise by identifying and filtering noisy shots. The power spectrum of instrumental noise shows high frequency, small amplitude modulations which cannot be averaged out. A histogram analysis shows that low frequency, large amplitude signals pose a serious obstacle to signal averaging for improved signal to noise. In kilohertz frequency pump/probe experiments, this low frequency noise typically arises from laser scatter due to bubbles, dust, and defects. We quantify the effectiveness in analyzing and rejecting these large amplitude signals which can produce a hindrance to the effectiveness of signal averaging.

Excision of a Dermatobia hominis larva from the heel of a South American traveler: a case report.

Although foot and ankle specialists are well versed in treating insect bites and foreign bodies, many physicians in the United States are unfamiliar with parasitic organisms that are common in other parts of the world. This article presents a case of a patient inoculated in the posterior heel with the larva of a Dermatobia hominis, or human bot fly. Excision of the larva provided a complete resolution of the patient's symptoms. Although the initial clinical presentation suggested a simple foreign body, the patient's recent travel history to Brazil shows that a thorough history is essential to establishing a complete list of differential diagnoses.