Mathematical modeling of the impact of recirculation on exchange kinetics in tandem extracorporeal membrane oxygenation and therapeutic plasma exchange

Vascular access connection configurations during tandem extracorporeal membrane oxygenation (ECMO) and therapeutic plasma exchange (TPE) may impact exchange kinetics. In these tandem procedures, typically the TPE inlet line is proximal to the TPE return line with respect to blood flow in the ECMO device, maximizing the opportunity for replacement fluid homogenization within the ECMO circuit. However, if TPE inlet and return line connections are switched, recirculation—a phenomenon in which replacement fluid leaving the TPE return line is prematurely drawn into the TPE inlet line prior to satisfactory homogenization within the ECMO circuit—will occur. Such recirculation could diminish TPE efficacy in patients on ECMO and mitigate therapeutic benefits. Using a mathematical model of recirculation in tandem ECMO and TPE, we demonstrate that the predicted impact of recirculation is negligible and vascular access connection positioning does not appear to be a point of clinical concern with regard to TPE kinetics.     

Author Index to Volume 10

A 67-yr-old woman presented to a free-standing medical center with respiratory distress of 1 day's duration. She was found on evaluation to have asthma associated with “dipping” the ends of polyurethane-coated wire into molten solder in the production, in her home, of components for the electronics industry. This process has been known to result in the evolution of isocyanates. The patient's sister had also developed cough and wheeze after she performed similar home piecework. Neither the manufacturer nor the distributors of the wire had provided a warning of its potential respiratory hazards. This episode emphasizes the importance of the occupational history, and of following-back thoroughly on cases of occupational disease. In addition, this episode reminds us that home pieceworkers are unlikely to have benefit of advice from industrial hygienists or others skilled in recognizing potentially hazardous situations.     

In vitro and in vivo evaluation of polymer hydrogels for hemorrhage control

In vitro and in vivo experimentation of various synthetic polymer hydrogels was conducted to establish some of the integral material properties that influence hemostasis. In vitro swelling experiments suggested that positive electrostatic charge was a key determinant of the ability of a polymer hydrogel to absorb physiological fluids, e.g. human plasma and blood. In vitro testing using unadulterated sheep blood suggested positive electrostatic charge and crosslink density were key determinants of the ability of a material to induce or enhance clot formation. Hydrogel formulations composed of higher amounts of positive electrostatic charge and lower crosslink density were able to effectively induce and enhance clot formation in the presence of a coagulation cascade activator. In vivo experimentation confirmed that hydrogels containing higher electrostatic charge and low crosslink density are more effective at fostering the formation of a robust hemostatic plug to control blood loss.     

A new functional data‐based biomarker for monitoring cardiovascular behavior

Cardiac safety assessment in drug development concerns the ventricular repolarization (represented by electrocardiogram (ECG) T‐wave) abnormalities of a cardiac cycle, which are widely believed to be linked with torsades de pointes, a potentially life‐threatening arrhythmia. The most often used biomarker for such abnormalities is the prolongation of the QT interval, which relies on the correct annotation of onset of QRS complex and offset of T‐wave on ECG. A new biomarker generated from a functional data‐based methodology is developed to quantify the T‐wave morphology changes from placebo to drug interventions. Comparisons of T‐wave‐form characters through a multivariate linear mixed model are made to assess cardiovascular risk of drugs. Data from a study with 60 subjects participating in a two‐period placebo‐controlled crossover trial with repeat ECGs obtained at baseline and 12 time points after interventions are used to illustrate this methodology; different types of wave form changes were characterized and motivated further investigation. Copyright © 2012 John Wiley & Sons, Ltd.     

Incarceration and Sexual Risk: Examining the Relationship Between Men’s Involvement in the Criminal Justice System and Risky Sexual Behavior

In this study, we used data from Add Health Waves II and III to compare men who had been incarcerated to those who had not, and examined whether incarceration was associated with increased numbers of sexual partners and increased odds of concurrent partnerships. We used multivariate regression and propensity-score matching to compare sexual behavior of Wave III male respondents who had been incarcerated with those who had not, and compared sexual behavior at Wave II to identify differences in sexual behavior prior to incarceration. Incarceration was associated with an increased rate of lifetime sexual partnership, but this was attenuated by substance use. Criminal justice involvement was associated with increased odds of having partners who report concurrent partnerships, but no further increase was seen with incarceration. There were no significant sexual behavior differences prior to incarceration. These results suggest that the criminal justice system and substance use may interact to shape sexual behavior.     

Size does matter: High volume breast surgeons accept smaller excision margins for wide local excision – A national survey of the surgical management of wide local excision margins in UK breast cancer patients

IntroductionOptimal margins for wide local excision (WLE) have not been clearly established. Larger margins lead to lower recurrence rates but at the expense of cosmetic appearance. NICE guidelines recommend a 2 mm margin for ductal carcinoma in-situ (DCIS), whilst the British Association of Surgical Oncology (BASO) recommend units develop local guidelines. There are presently no specific guidelines for invasive cancer. We surveyed members of the Association of Breast Surgeons (ABS) in order to establish current practice nationally. We hypothesised that larger units may accept narrower excision margins to the benefit of better cosmesis.Materials and methodsA postal questionnaire was sent to all ABS members in October 2010. This consisted of questions about the current practice of the surgeon and their unit. 481 questionnaires were posted in total, all questionnaires returned by April 2011 were analysed.ResultsQuestionnaire response rate was 60% (281). Surgeons operating on over 50 cancers per year accepted smaller margins than those operating on less than 50 (p < 0.02). Acceptable adequate anterior and radial margins ranged from 0 to 10 mm for DCIS and 0 to 5 mm for invasive cancer. A variety of approaches to re-excising anterior margins were reported.ConclusionsThis survey suggests that substantial variations exist in current practice with regard to the approach to WLE. Operator workload appears to influence what is deemed to be an acceptable margin. There is a need for standardised national and international guidelines.