Spatiotemporal Mapping of Hole Nucleation and Growth during Block Copolymer Terracing with High-Speed Atomic Force Microscopy

As a platform for investigating two-dimensional phase separation, we track the structural evolution of block copolymer thin films during thermal annealing with environmentally controlled atomic force microscopy (AFM). Upon thermal annealing, block copolymer films with incommensurate thickness separate into a terraced morphology decorated with holes. With in situ imaging at 200 °C, we follow the continuous progression of terrace formation in a single region of a cylinder-forming poly(styrene-block-methyl methacrylate) thin film, beginning with the disordered morphology on an unpatterned silicon substrate and continuing through nucleation and coarsening stages. Topographic AFM imaging with nanoscale resolution simultaneously captures ensemble hole growth statistics while locally tracking polymer diffusion through measurements of the film thickness. At early times, we observe homogeneous hole nucleation and isotropic growth, with kinetics following the predictions of classical nucleation theory. At later times, however, we find anomalous hole growth which arises due to the combination of Ostwald ripening and coalescence mechanisms. In each case, our real-space observations highlight the importance of hole interactions for determining coarsening kinetics, mediated either through the interconnected phase for Ostwald ripening or through binary collision events for coalescence.

Inflation of residually stressed Fung-type membrane models of arteries

Elastic arteries are idealised as being incompressible orthotropic nonlinearly elastic cylinders. They are further idealised as being membranes in order to analyse the effect of the experimentally observed pre-stressing of arterial tissue on inflation. The pre-stress is modelled here using the opening-angle method. It is shown that there can be multiple unloaded states of arterial segments of Fung materials, suggesting the corresponding set of material parameters will not yield reliable predictions of arterial stress in three dimensions as there is no experimental evidence to support this non-uniqueness. It is also shown that the circumferential pre-strain has a simple magnifying scaling effect on the pressure-radial strain relation and on the axial force needed to maintain the membrane length during inflation; the effect of the axial pre-strain is more nuanced.

Controlling the Morphology of Dynamic Thia-Michael Networks to Target Pressure-Sensitive and Hot Melt Adhesives

A series of multistage (pressure-sensitive/hot melt) adhesives utilizing dynamic thia-Michael bonding motifs are reported. The benzalcyanoacetate Michael acceptors used in this work undergo bond exchange under ambient conditions without external catalysis, facilitating pressure-sensitive adhesion. A key feature of this system is the dynamic reaction-induced phase separation that lends reinforcement to the otherwise weakly bonded materials, enabling weak, repeatable pressure-sensitive adhesion under ambient conditions and strong adhesion when processed as a hot melt adhesive. By using different pairs of benzalcyanoacetate cross-linking units, the phase separation characteristics of the adhesives can be directly manipulated, allowing for a tailored adhesive response.

The residually stressed unloaded state of arteries: Membrane and thin cylinder approximations

A solution is obtained for incompressible non-linearly elastic membranes that describes the bending of a cylindrical sector to form a perfect cylinder for a wide class of materials that includes isotropic materials and orthotropic materials reinforced by two families of mechanically equivalent fibres that are wound helically about the axial direction. Despite the relative simplicity of the physical problem, the solution of the corresponding boundary value problem for thick cylinders requires a numerical solution for even the simplest models. It is shown, however, that the thin shell solution provides an excellent approximation to the solution of the problem for cylindrical sectors whose thicknesses are an order of magnitude greater than that assumed for membranes. The approximate stress distribution in such thin shells is obtained. In these residually stressed cylinders, the radial stress is approximately zero but the hoop and axial stresses are finite. Estimates of the residual stresses in the unloaded state are obtained. A closed-form solution for the bending moment necessary to effect the deformation is also obtained.

The effect of fiber-matrix interaction on the Poynting effect for torsion of fibrous soft biomaterials

The response of fibrous soft tissues undergoing torsional deformations is a topic of considerable current interest. Such deformations are common in ligaments and tendons and are also of particular interest in cardiac mechanics. A well-known context where such issues arise is in understanding the mechanical response of papillary muscles of the heart. Thus the classical torsion problem for solid or hollow cylinders composed of rubber-like materials has received renewed recent attention in the context of anisotropic materials. Here we consider the torsion of a solid circular cylinder composed of a transversely isotropic incompressible fiber-reinforced hyperelastic material. The focus of the work is on examining the effect of fiber-matrix interaction on the axial stress response with emphasis on the Poynting effect. The classic Poynting effect for isotropic rubber-like materials where torsion induces elongation of the cylinder is shown to be significantly different for the transversely isotropic models considered here. For sufficiently small total angles of twist, well within the range of physiological response, a reverse-Poynting effect is shown to hold where the cylinder tends to shorten on twisting while for larger angles of twist, the usual positive Poynting effect occurs. It is shown that the influence of the fiber-matrix interaction is to enhance the reverse Poynting effect. The results are illustrated using experimental data of other authors for skeletal muscles and for brain white matter.

Reaction of NO2 with Groups IV and VI Transition Metal Oxide Clusters

The addition of NO₂ to Group IV (MO₂)_n and Group VI (MO₃)_n (n = 1-3) nanoclusters was studied using both density functional theory (DFT) and coupled cluster theory (CCSD(T)). The structures and overall binding energetics were predicted for Lewis acid-base addition without transfer of spin (a physisorption-type process) and the formation of either cluster-ONO (HONO-like or bidentate bonding) or NO₃^- formation where for both the spin is transferred to the metal oxide clusters (a chemisorption-type process). Only chemisorption of NO₂ is predicted to be thermodynamically allowed at temperatures ≥298 K for Group IV (MO₂)_n clusters with the formation of surface chemisorbed NO₂ being by far the most energetically favorable. The ligand binding energies (LBEs) for physisorption and chemisorption on the TiO₂ nanoclusters are consistent with computational studies of the bulk solids. Chemisorption is only predicted to occur for (CrO₃)_n clusters in the form of a terminal nitrate containing species whereas the larger chemisorbed nitrate structures for (MoO₃)_n and (WO₃)_n were found to be metastable and unlikely to form in any appreciable amount at temperatures of 298 K and higher. NO₂ is predicted to only be capable of physisorbing to (MoO₃)_n and (WO₃)_n at lower temperatures and therefore unlikely to bind NO₂ at temperatures ≥298 K. Correlations between the (MO₃)_nNO₂ ligand bond energies and the chemical properties of the parent (MO₃)_n clusters (Lewis acidity, ionization potentials, excitation energies, and M = O/M-O bond strengths) are described.

On the tension-compression switch hypothesis in arterial mechanics

The tension-compression switch hypothesis for soft tissue proposes that when collagen fibres are compressed they do not contribute to the mechanical response which is then assumed to be the isotropic response of the extra-cellular matrix in which they are embedded. Such an assumption would seem reasonable. However, three difficulties with its use are discussed here. First it is shown that the admittedly scant experimental evidence available suggests that it does not have a completely sound physical basis. The possible paradoxical nature of the tension-compression switch has been previously identified by other authors. If the fibres are predicted to be in compression by an anisotropic model, then the resulting isotropic stretch of the fibres predicted by the tension-compression switch can be tensile. Thus the fibres can have a duality of being simultaneously tensile and compressive if the tension-compression switch is employed. This is illustrated here with a particular emphasis on the nature of the isotropic stretching of the fibres when compressed and the essential role of the linear theory when predicting the mechanical response for non-linear deformations of arterial tissue. Finally it is shown that use of the tension-compression switch can result in the failure of some models to predict the mechanical response in the material characterisation tests that were used to determine the values of their material constants. Thus some anisotropic models can have better predictive capability without the tension-compression switch.

Direct Imaging of Interfacial Fluctuations in Confined Block Copolymer with in Situ Slow-Scan-Disabled Atomic Force Microscopy

Using environmentally controlled, high-speed atomic force microscopy (AFM), we examine dynamic fluctuations of topographically confined poly(styrene-block-methyl methacrylate) (PS-b-PMMA) cylinders. During thermal annealing, fluctuations drive perturbations of the block copolymer (BCP) interface between polymer domains, leading to pattern roughness. Whereas previous investigations have examined roughness in room-temperature and kinetically quenched samples, we directly visualize the dynamics of PS/PMMA interfaces in real space and time at in situ temperatures above the glass transition temperature, T_g. Imaging under these experimentally challenging thermal annealing conditions is critical to understanding the inherent connection between thermal fluctuations and BCP pattern assembly. Through the use of slow-scan-disabled AFM, we dramatically improve the imaging time resolution for tracking polymer dynamics. Fluctuations increase in intensity with temperature and, at high temperatures, become spatially coherent across their confining potential. Additionally, we observe that topographic confinement suppresses fluctuations and correlations in the proximity of the guiding field. In situ imaging at annealing temperatures represents a significant step in capturing the dynamics of chain mobility at BCP interfaces.

Magic angles and fibre stretch in arterial tissue: Insights from the linear theory

This work is motivated by the current widespread interest in modelling the mechanical response of arterial tissue. A widely used approach within the context of anisotropic nonlinear elasticity is to use an orthotropic incompressible hyperelasticity model which, in general, involves a strain-energy density that depends on seven independent invariants. The complexity of such an approach in its full generality is daunting and so a number of simplifications have been introduced in the literature to facilitate analytical tractability. An extremely popular model of this type is where the strain energy involves only three invariants. While such models and their generalisations have been remarkably successful in capturing the main features of the mechanical response of arterial tissue, it is generally acknowledged that such simplified models must also have some drawbacks. In particular, it is intuitively clear that the correlation of such models with experiment will suffer limitations due to the restricted number of invariants considered. Our purpose here is to use the linearised theory for infinitesimal deformations to provide some guidelines for the development of a more robust nonlinear theory. The linearised theory for incompressible orthotropic materials is developed and involves six independent elastic constants. The general stress-strain law is inverted to provide an expression for the fibre stretch in terms of the stress. We examine the linearised response for simple tension in two mutually perpendicular directions corresponding to the axial and circumferential directions in the artery, obtaining an explicit expression for the fibre stretch in terms of the applied tension, fibre angle and linear elastic constants. The focus is then on determining the range of fibre orientation angles that ensure that the fibres are in tension in these simple tension tests. It is shown that the fibre stretch is positive for both simple tension tests if and only if the fibre angle is restricted to lie between two special angles called generalised magic angles. For the special case where the strain-energy function for the nonlinear model depends only on the three invariants I₁,I₄,I₆, it is shown that the corresponding linearised model, called the standard linear model (SLM), depends on three elastic constants and the fibre stretch is positive only in the small range of fibre angles between the classic magic angles 35.26° and 54.74°. However, when the two additional invariants I₅,I₇ are included in the nonlinear strain energy so that the corresponding linear model involves four elastic constants, it is shown that the domain of fibre angle for which the stretch is positive is much larger and that the fibre stretch is monotonic with respect to the fibre angle in this range.

Correction to 'An empirical measure of nonlinear strain for soft tissue indentation'

[This corrects the article DOI: 10.1098/rsos.170894.].

Poynting and reverse Poynting effects in soft materials

In 1909, J. H. Poynting conducted a series of experiments on metal wires and found that loaded wires lengthen when twisted. Thus to maintain a constant length in such experiments, a compressive axial force would need to be applied at the ends of the specimen. This is the classical (positive) Poynting effect. Another example of such an effect arises when a soft material specimen is being axially sheared or rotated between two platens. The necessity to apply a normal force in order to maintain the relative distance between the platens is also often referred to as a Poynting-type effect. Both effects are inherently nonlinear phenomena. In recent papers, experimental data on the Poynting effect in soft solids have been reported. The seminal paper by Janmey et al. describes shearing experiments on hydrogels, impregnated with scleroproteins such as collagen and fibrin. It was shown that positive and negative (reverse) Poynting effects could occur. In this and subsequent papers by several authors, the microstructure of reinforced biogels involving semi-flexible filaments embedded in a soft matrix was exploited to examine the character of the normal stresses. The purpose of the present paper is to describe and review an alternative approach using the macroscopic phenomenological theory of hyperelasticity based on nonlinear continuum mechanics. Our aim is to demonstrate that such a theory can be used in a very transparent way to predict the occurrence of both positive and negative Poynting effects in anisotropic soft fibrous materials. It will be seen that material anisotropy plays a key role in the analysis.

A randomized trial of a brief intervention for obesity in college students

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

•  Brief motivational interventions have been found to be efficacious for obesity in older adult populations. •  Brief motivational interventions including delivery of personalized feedback have been found to be efficacious for reducing college student drinking.

WHAT THIS STUDY ADDS

•  First study to test the efficacy of a one-session, brief motivational intervention for obesity among college students. •  One session brief motivational interventions may have an impact on the reduction of calorie-dense foods and beverages. •  A brief, one-session motivational interview with personalized feedback may not be an intensive enough intervention for obesity treatment among college students.

SUMMARY

Young adults are at an increased risk for weight gain as they begin college and this has implications for the onset of future health consequences. Brief motivational interventions (BMIs) have been found to be effective with college students for reducing risky health behaviours such as alcohol consumption, but have not been developed and tested with a primary goal of reducing obesity. BMIs have been developed and tested for the treatment of obesity and weight-related health behaviours (WRHB) in other populations, such as adults and adolescents, with promising results. The purpose of the following study was to develop and test the efficacy of a BMI for weight loss among overweight and obese college students. Seventy undergraduate students (85.7% female, 57.1% African-American) completed an assessment about WRHBs and then were randomized to either receive a single 60-min BMI plus a booster phone call or to assessment only. At 3 months post-intervention, effect sizes within the intervention group were twice as large as within the assessment-only group on reductions in high-calorie foods and beverages. However, there were no statistically significant differences between groups on body mass index or WRHBs. The one-session nature of the session might not have been enough to produce significant change in weight.

Obesity is associated with premature occurrence of acute myocardial infarction

BACKGROUND

The American Heart Association has classified obesity as a major modifiable risk factor for coronary artery disease, but its relationship with age at presentation with acute myocardial infarction (AMI) is poorly documented.

HYPOTHESIS

The study was undertaken to evaluate the impact of obesity on age at presentation, and on in-hospital morbidity and mortality in patients with AMI.

METHODS

Our analysis includes a consecutive series of 906 Olmsted County patients (mean age 67.7 years, 51% male) admitted with AMI to the Mayo Clinic Coronary Care Unit (CCU). The patients were entered into the Mayo CCU Database, a prospective registry of data pertaining to patients admitted to the Mayo Clinic CCU with AMI. Age at AMI occurrence and in-hospital morbidity and mortality were noted.

RESULTS

Obese patients (body mass index [BMI] >30) with AMI were significantly younger than patients with AMI in the overweight (BMI 25-30) and normal-weight (BMI < 30) groups (62.3+/-13.1 vs. 66.9+/-13.2 and 72.9+/-13.4, respectively. p < 0.001). Obesity and overweight status were associated with male gender, diabetes mellitus, hypercholesterolemia, and smoking history; however, after multivariate adjustment for these risk factors, excess weight and premature AMI remained significantly associated. Compared with normal-weight patients, overweight patients presenting with AMI were 3.6 years younger (p < 0.001, confidence interval [CI] 1.9-5.4) and obese patients 8.2 years younger (p < 0.001, Cl 6.2-10.1). No significant increase in in-hospital morbidity and mortality was seen.

CONCLUSION

In this population-based study, overweight and obese status are independently associated with the premature occurrence of AMI, but not with an increased incidence of in-hospital complications.

Is simulation based medicine training the future of clinical medicine?

The training of physician in the art and science of clinical medicine presents several challenges that are well suited to simulation based medical education (SBME). Modern patient centered medical education seeks to provide comprehensive "hands-on" clinical exposure for physicians in training, while simultaneously providing maximum individual patient comfort and safety. The ethical conundrum is obvious: direct patient contact is needed in order to educate the best clinical physicians and surgeons, but patients have an expectation to be treated and have surgery performed only by highly trained healthcare personnel. This is the kernel of the "medical educators dilemma". Simulation based medical education can partially solve "the medical educators dilemma" by providing realistic medical education in a safe, error tolerant environment with convenience and advantages over conventional "bedside" training but is it real medicine or make believe!

A new simplified immediate prognostic risk score for patients with acute myocardial infarction

BACKGROUND

Immediate risk stratification of patients with myocardial infarction in the emergency department (ED) at the time of initial presentation is important for their optimal emergency treatment. Current risk scores for predicting mortality following acute myocardial infarction (AMI) are potentially flawed, having been derived from clinical trials with highly selective patient enrollment and requiring data not readily available in the ED. These scores may not accurately represent the spectrum of patients in clinical practice and may lead to inappropriate decision making.

METHODS

This study cohort included 1212 consecutive patients with AMI who were admitted to the Mayo Clinic coronary care unit between 1988 and 2000. A risk score model was developed for predicting 30 day mortality using parameters available at initial hospital presentation in the ED. The model was developed on patients from the first era (training set--before 1997) and validated on patients in the second era (validation set-during or after 1997).

RESULTS

The risk score included age, sex, systolic blood pressure, admission serum creatinine, extent of ST segment depression, QRS duration, Killip class, and infarct location. The predictive ability of the model in the validation set was strong (c = 0.78).

CONCLUSION

The Mayo risk score for 30 day mortality showed excellent predictive capacity in a population based cohort of patients with a wide range of risk profiles. The present results suggest that even amidst changing patient profiles, treatment, and disease definitions, the Mayo model is useful for 30 day risk assessment following AMI.

Kinetics of NO and NO2 Evolution from Illuminated Frozen Nitrate Solutions

The release of NO and NO2 from frozen aqueous NaNO3 irradiated at 313 nm was studied using time-resolved spectroscopic techniques. The kinetic behavior of NO and NO2 signals during on-and-off illumination cycles confirms that NO2 is a primary photoproduct evolving from the outermost ice layers and reveals that NO is a secondary species generated deeper in the ice, whence it eventually emerges due to its inertness and larger diffusivity. NO is shown to be more weakly held than NO2 by ice in thermal desorption experiments on preirradiated samples. The partial control of gaseous emissions by mass transfer, and hence by the morphology and metamorphisms of polycrystalline ice, is established by (1) the nonmonotonic temperature dependence of NO and NO2 signals upon stepwise warming under continuous illumination, (2) the fact that the NO, NO2 or NOx (NOx identical with NO + NO2) amounts released in bright thermograms performed under various heating ramps fail to scale with photon dose, due to irreversible losses in the adsorbed state. Because present NO/NO2 ratios are up to 10-fold smaller than those determined over sunlit snowpacks, we infer that the immediate precursors to NO mostly absorb at lambda > lambda(max) (NO3-) approximately 302 nm.

Photochemical Production and Release of Gaseous NO2from Nitrate-Doped Water Ice

Temperature-programmed NO2 emissions from frozen aqueous NaNO3 solutions irradiated at 313 nm were monitored as function of nitrate concentration and heating rate, H, above -30 degrees C. Emissions increase nonmonotonically with temperature, displaying transitions suggestive of underlying metamorphic transformations. Thus, NO2 emissions surge at ca. -8 degrees C in frozen [NO3-] > 200 microM samples warmed at H = 0.70 degrees C min(-1) under continuous irradiation, and also in the dark from samples that had been photolyzed at -30 degrees C. The amounts of NO2 released in individual thermograms, SigmaN, increase less than linearly with [NO3-] or the duration of experiments, revealing the significant loss of photogenerated NO2. The actual SigmaN proportional, variant [NO3-]1/2 dependence (at constant H) is consistent with NO2 hydrolysis: 2NO2 + H2O --> NO3- + NO2- + 2H+, overtaking NO2 desorption, even below the eutectic point (-18 degrees C for aqueous NaNO3). The increasingly larger NO2 losses detected in longer experiments (at constant [NO3-]) are ascribed to secondary photolysis of trapped NO2. The relevance of present results to the interpretation of polar NO2 measurements is briefly analyzed.

Unrecognized peripartum cardiomyopathy in Haitian women

OBJECTIVE

Haitian women have a high relative incidence of clinical presentation with peripartum cardiomyopathy (PPCM): an incidence estimated at one case per three hundred live births, a ten-fold occurrence compared to American women. Our objective has been to test the hypothesis that some Haitian women may have a forme fruste of PPCM while still without clinical symptoms.

METHOD

A preliminary case-control study was conducted at the Hospital Albert Schweitzer (HAS), Deschapelles, Haiti, in which 25 apparently healthy postpartum women, without cardiovascular symptoms and with a normal cardiovascular clinical examination, were selected from a consecutive list of obstetrical deliveries and screened by echocardiography for left ventricular dysfunction.

RESULT

Four out of 25 patients (16%) had asymptomatic left ventricular dysfunction that subsequently evolved towards either improvement or deterioration. Supporting evidence for the existence of asymptomatic left ventricular dysfunction or forme fruste PPCM is presented. A hypothetical schema of the pathophysiology of PPCM explains how a latent phase of variable duration may exist prior to onset of detectable clinical heart failure.

CONCLUSION

Screening Haitian women during the last month of pregnancy or in the early postpartum period may help to detect asymptomatic left ventricular dysfunction. Early detection and treatment of PPCM in a known high risk population could lead to improvements in maternal and fetal mortality and morbidity.

Strong predictive value of TIMI risk score analysis for in-hospital and long-term survival of patients with right ventricular infarction

BACKGROUND

While right ventricular myocardial infarction is associated with increased in-hospital morbidity and mortality, prognostic risk factors for in-hospital and long-term mortality are poorly defined.

OBJECTIVES

To evaluate the prognostic value of TIMI (Thrombolysis in Myocardial Infarction) risk score analysis in patients with right ventricular myocardial infarction (RVI).

DESIGN

Retrospective analysis of a community population.

SETTING

Mayo Clinic Coronary Care Unit.

PATIENTS

One hundred and two patients with RVI from 580 consecutive patients from Rochester, Minnesota admitted to the Coronary Care Unit with acute inferior or lateral wall myocardial infarction from January 1988 through March 1998.

MEASUREMENT

Combined TIMI risk score analysis with in-hospital and long-term mortality.

RESULTS

In-hospital morbidity (RVI: 54.9% vs non-RVI: 22.2%; P<0.001) and mortality (RVI: 21.6% vs non-RVI: 6.9%;P <0.001) were increased in patients with RVI. The TIMI risk score predicted risk (per one point increase in TIMI score) for in-hospital mortality (OR 1.23, 95% CI 1.02-1.51, P=0.037) and long-term mortality (OR 1.57, 95% CI 1.25-1.96, P<0.001). Patients with RVI whose TIMI risk score was >or=4 had significantly worse long-term survival compared to those patients with RVI and TIMI score <4 (P=0.006).

CONCLUSIONS

In-hospital morbidity and mortality, and long-term mortality are increased by right ventricular infarction and can be accurately predicted by the initial TIMI risk score.

Relative efficacy of a brief motivational intervention for college student drinkers

The authors evaluated the efficacy of Brief Alcohol Screening and Intervention for College Students (BASICS - L. A. Dimeff, J. S. Baer, D. R. Kivlahan, & G. A. Marlatt, 1999), a single session of drinking-related feedback intended to reduce heavy drinking and related harm. College student drinkers (N = 99) were assigned to BASICS, an educational intervention, or an assessment-only control group. At 3 months postintervention. there were no overall significant group differences, but heavier drinking BASICS participants showed greater reductions in weekly alcohol consumption and binge drinking than did heavier drinking control and education participants. At 9 months, heavier drinking BASICS participants again showed the largest effect sizes. BASICS participants evaluated the intervention more favorably than did education participants. This study suggests that BASICS may be more efficacious than educational interventions for heavier drinking college students.

Relative efficacy of a brief motivational intervention for college student drinkers

The authors evaluated the efficacy of Brief Alcohol Screening and Intervention for College Students (BASICS - L. A. Dimeff, J. S. Baer, D. R. Kivlahan, & G. A. Marlatt, 1999), a single session of drinking-related feedback intended to reduce heavy drinking and related harm. College student drinkers (N = 99) were assigned to BASICS, an educational intervention, or an assessment-only control group. At 3 months postintervention. there were no overall significant group differences, but heavier drinking BASICS participants showed greater reductions in weekly alcohol consumption and binge drinking than did heavier drinking control and education participants. At 9 months, heavier drinking BASICS participants again showed the largest effect sizes. BASICS participants evaluated the intervention more favorably than did education participants. This study suggests that BASICS may be more efficacious than educational interventions for heavier drinking college students.

Effect of concomitant or very early statin administration on in-hospital mortality and reinfarction in patients with acute myocardial infarction

In a retrospective analysis, 66 patients identified as having received a statin drug within 24 hours of admission for acute myocardial infarction were matched 3:1 with a control group of 198 patients not treated with a statin agent. End points of in-hospital mortality and in-hospital reinfarction were significantly lower in the statin-treated group, pointing to a benefit from very early statin treatment in acute myocardial infarction.

[Ca(2+)](i) signaling in renal arterial smooth muscle cells of pregnant rat is enhanced during inhibition of NOS

Vascular resistance and arterial pressure are reduced during normal pregnancy, but dangerously elevated during pregnancy-induced hypertension (PIH), and changes in nitric oxide (NO) synthesis have been hypothesized as one potential cause. In support of this hypothesis, chronic inhibition of NO synthesis in pregnant rats has been shown to cause significant increases in renal vascular resistance and hypertension; however, the cellular mechanisms involved are unclear. We tested the hypothesis that the pregnancy-associated changes in renal vascular resistance reflect changes in contractility and intracellular Ca(2+) concentration ([Ca(2+)](i)) of renal arterial smooth muscle. Smooth muscle cells were isolated from renal interlobular arteries of virgin and pregnant Sprague-Dawley rats untreated or treated with the NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME; 4 mg. kg(-1). day(-1) for 5 days), then loaded with fura 2. In cells of virgin rats incubated in Hanks' solution (1 mM Ca(2+)), the basal [Ca(2+)](i) was 86 +/- 6 nM. Phenylephrine (Phe, 10(-5) M) caused a transient increase in [Ca(2+)](i) to 417 +/- 11 nM and maintained an increase to 183 +/- 8 nM and 32 +/- 3% cell contraction. Membrane depolarization by 51 mM KCl, which stimulates Ca(2+) entry from the extracellular space, caused maintained increase in [Ca(2+)](i) to 292 +/- 12 nM and 31 +/- 2% contraction. The maintained Phe- and KCl-induced [Ca(2+)](i) and contractions were reduced in pregnant rats but significantly enhanced in pregnant rats treated with L-NAME. Phe- and KCl-induced contraction and [Ca(2+)](i) were not significantly different between untreated and L-NAME-treated virgin rats or between untreated and L-NAME + L-arginine treated pregnant rats. In Ca(2+)-free Hanks', application of Phe or caffeine (10 mM), to stimulate Ca(2+) release from the intracellular stores, caused a transient increase in [Ca(2+)](i) and a small cell contraction that were not significantly different among the different groups. Thus renal interlobular smooth muscle of normal pregnant rats exhibits reduction in [Ca(2+)](i) signaling that involves Ca(2+) entry from the extracellular space but not Ca(2+) release from the intracellular stores. The reduced renal smooth muscle cell contraction and [Ca(2+)](i) in pregnant rats may explain the decreased renal vascular resistance associated with normal pregnancy, whereas the enhanced cell contraction and [Ca(2+)](i) during inhibition of NO synthesis in pregnant rats may, in part, explain the increased renal vascular resistance associated with PIH.

Gender-specific reduction in contractility and [Ca(2+)](i) in vascular smooth muscle cells of female rat

The hypothesis that vascular protection in females and its absence in males reflects gender differences in [Ca(2+)](i) and Ca(2+) mobilization mechanisms of vascular smooth muscle contraction was tested in fura 2-loaded aortic smooth muscle cells isolated from intact and gonadectomized male and female Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. In WKY cells incubated in Hanks' solution (1 mM Ca(2+)), the resting length and [Ca(2+)](i) were significantly different in intact males (64.5 +/- 1.2 microm and 83 +/- 3 nM) than in intact females (76.5 +/- 1.5 microm and 64 +/- 7 nM). In intact male WKY, phenylephrine (Phe, 10(-5) M) caused transient increase in [Ca(2+)](i) to 428 +/- 13 nM followed by maintained increase to 201 +/- 8 nM and 32% cell contraction. In intact female WKY, the Phe-induced [Ca(2+)](i) transient was not significantly different, but the maintained [Ca(2+)](i) (159 +/- 7 nM) and cell contraction (26%) were significantly less than in intact male WKY. In Ca(2+)-free (2 mM EGTA) Hanks', Phe and caffeine (10 mM) caused transient increases in [Ca(2+)](i) and contraction that were not significantly different between males and females. Membrane depolarization by 51 mM KCl caused 31% cell contraction and increased [Ca(2+)](i) to 259 +/- 9 nM in intact male WKY, which were significantly greater than a 24% contraction and 214 +/- 8 nM [Ca(2+)](i) in intact female WKY. Maintained Phe- and KCl-stimulated cell contraction and [Ca(2+)](i) were significantly greater in SHR than WKY in all groups of rats. Reduction in cell contraction and [Ca(2+)](i) in intact females compared with intact males was significantly greater in SHR ( approximately 30%) than WKY ( approximately 20%). No significant differences in cell contraction or [Ca(2+)](i) were observed between castrated males, ovariectomized (OVX) females, and intact males, or between OVX females with 17beta-estradiol implants and intact females. Exogenous application of 17beta-estradiol (10(-8) M) to cells from OVX females caused greater reduction in Phe- and KCl-induced contraction and [Ca(2+)](i) in SHR than WKY. Thus the basal, maintained Phe- and depolarization-induced [Ca(2+)](i) and contraction of vascular smooth muscle triggered by Ca(2+) entry from the extracellular space exhibit differences depending on gender and the presence or absence of female gonads. Cell contraction and [Ca(2+)](i) due to Ca(2+) release from the intracellular stores are not affected by gender or gonadectomy. Gender-specific reduction in contractility and [Ca(2+)](i) in vascular smooth muscle of female rats is greater in SHR than WKY rats.

Decreased [Ca(2+)](i) during inhibition of coronary smooth muscle contraction by 17beta-estradiol, progesterone, and testosterone

The clinical observation that coronary heart disease is more common in men and postmenopausal women than in premenopausal women has suggested cardiovascular protective effects of female sex hormones including hormone-mediated coronary vasodilation. We investigated whether the sex hormones induced coronary relaxation is due to a decrease in [Ca(2+)](i) as measured in single coronary smooth muscle cells isolated from gonadectomized male and female pigs. In the presence of external Ca(2+), prostaglandin F(2alpha) (PGF(2alpha); 10(-5) M) and membrane depolarization by 51 mM KCl caused significant cell contraction and maintained increase in [Ca(2+)](i) to 297 +/- 4 and 341 +/- 20 nM, respectively. At 10(-9) to 6 x 10(-7) M, 17beta-estradiol, progesterone, and testosterone caused inhibition of PGF(2alpha)- and KCl-induced contraction and [Ca(2+)](i) with 17beta-estradiol being most effective. 17alpha-Estradiol did not affect PGF(2alpha)-induced contraction, and the inhibition of PGF(2alpha) contraction by 17beta-estradiol, progesterone, or testosterone was abolished by tamoxifen and ICI 182, 780, RU-486, or flutamide, respectively. 17beta-Estradiol caused similar inhibition of PGF(2alpha)- and KCl-induced contraction and [Ca(2+)](i). Progesterone and testosterone caused greater inhibition of PGF(2alpha)-induced cell contraction and [Ca(2+)](i) compared with the KCl responses. In Ca(2+)-free (2 mM EGTA) solution, caffeine (10 mM) and carbachol (10(-5) M), which activate Ca(2+) release from intracellular stores, caused small cell contraction and transiently increased [Ca(2+)](i) to 256 +/- 53 and 262 +/- 32 nM, respectively. Sex hormones did not significantly affect caffeine- or carbachol-induced contraction or [Ca(2+)](i). Thus, 17beta-estradiol, progesterone, and testosterone cause relaxation of coronary smooth muscle cells and decrease [Ca(2+)](i) mainly by inhibiting Ca(2+) entry from extracellular space but not Ca(2+) release from intracellular stores. The differences in potency of sex hormones in reducing cell contraction and [Ca(2+)](i) suggest differences in the sensitivity of the PGF(2alpha)- and depolarization-activated Ca(2+) entry pathways to inhibition by sex hormones.

Gender differences in Ca(2+) entry mechanisms of vasoconstriction in Wistar-Kyoto and spontaneously hypertensive rats

We investigated whether putative vascular protection against hypertension in females reflects differences in the Ca(2+) mobilization mechanisms of vasoconstriction depending on the gender and the status of the gonads. Active stress and (45)Ca(2+) influx were measured in aortic strips isolated from intact and gonadectomized male and female Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). In aortic strips of intact male WKY incubated in normal Krebs' solution (2.5 mmol/L Ca(2+)), both phenylephrine (10(-5) mol/L) and membrane depolarization by 96 mmol/L KCl caused significant increases in active stress and (45)Ca(2+) influx. In intact female WKY, the phenylephrine- and KCl-induced stress and (45)Ca(2+) influx were significantly reduced. In Ca(2+)-free (2 mmol/L EGTA) Krebs' solution, stimulation of aortic strips with phenylephrine or caffeine (25 mmol/L) to induce Ca(2+) release from intracellular stores caused a transient increase in stress that was not significantly different between males and females. In SHR, the phenylephrine- and KCl-induced stress and (45)Ca(2+) influx were significantly greater than those in WKY in all groups of rats. The reduction in stress and Ca(2+) entry in intact females compared with intact males was greater in SHR than in WKY. The contractile responses and Ca(2+) entry in castrated male and ovariectomized female WKY or SHR were not significantly different from the respective responses in intact males. The contractile responses and Ca(2+) entry in ovariectomized female WKY or SHR with 17beta-estradiol implant were not significantly different from the respective responses in intact females. Thus, the phenylephrine- and depolarization-induced vascular reactivity and Ca(2+) entry in vascular smooth muscle are dependent on gender and on the presence or absence of functional female gonads. Ca(2+) release from intracellular stores is not affected by gender or gonadectomy. The gender-specific changes in vascular reactivity and Ca(2+) entry are augmented in hypertension.

Circumferential hymen elasticity. A marker of physiologic maturity

OBJECTIVE

To study the relationship between anatomic changes in the peripubertal female and sex hormonal maturation.

STUDY DESIGN

Medical records were reviewed on virginal females whose first gynecologic examination occurred between ages 9 and 20 and who were examined at least twice by the same gynecologist. Speculum sizes at each visit were surrogate measures of circumferential hymenal elasticity, the anatomic change of interest.

RESULTS

Mean ages at the two visits for the 35 patients were 14.6 and 16.7 years, respectively, with substantial overlap in ages between visits. Average Tanner breast and pubic hair stages and speculum sizes were greater at the second visit (P < .001). At first visit, age, Tanner breast and pubic hair stages, and time elapsed from menarche, thelarche and pubarche correlated positively with larger speculum sizes (P < .10). Change in speculum size between visits was associated with younger age and lower Tanner pubic hair stages at first visit and with increases between visits in age, body mass index and Tanner pubic hair stages. Larger changes were associated with shorter elapsed time between the first visit and menarche, thelarche and pubarche.

CONCLUSION

Circumferential hymenal elasticity increases during adolescence. This anatomic change, the surrogate measure of which is specula diameter, can be used along with Tanner staging as a measure of physiologic maturity in adolescent women.

Endothelialized biological heart valve prostheses in the non-human primate model

OBJECTIVE

The main disadvantage of implanted cardiac valve bioprostheses remains primarily tissue failure due to calcification. Coating of bioprostheses with viable autologous endothelial cells may delay or even eliminate tissue calcification and subsequent cardiac dysfunction.

METHODS

Glutaraldehyde-preserved Hancock bioprostheses (n = 5), pretreated with glutamic acid (8%) and cryopreserved allografts (n = 5) were lined, using endothelial cells harvested from the external jugular vein. Coated specimens were cultivated for 9 days in Medium 199 supplemented with 20% fetal calf serum and basic fibroblast growth factor. Endothelialized grafts were anastomosed into the descending thoracal aorta of adult Chacma baboons. Untreated valve bioprostheses (n = 4) served as controls. Forty days after implantation the prostheses were examined morphologically and immunohistochemically.

RESULTS

After implantation endothelialized prostheses showed a positive Factor VIII related antigen reaction by immunohistochemistry on all valve surfaces. Scanning electron microscopy showed confluently lined leaflets with transplanted endothelial cells and displayed cobblestone morphology on all coated allografts. In contrast, the surface of pretreated xenograft valves revealed uncoated areas with platelet and leucocyte aggregates. No endothelium was observed on the leaflets of untreated controls 40 days after implantation.

CONCLUSION

In vitro endothelialization of cardiac valve bioprostheses with autologous endothelial cells is possible. The newly created endothelium is shear stress resistant and the antithrombotic as well as the antiaggregatory capacity of the transplanted cells were retained. Lining with autologous endothelial cells could improve the durability and clinical outcome of biological valve prostheses.

Predictive model to identify trauma patients with blood alcohol concentrations > or = 50 mg/dl

OBJECTIVE

To develop a simple model for identification of trauma patients who are likely to have a blood alcohol concentration > or = 50 mg/dL (BAC + 50).

METHODS

Demographic, clinical, and BAC data were collected from the clinical trauma registry and toxicology data base at a Level I trauma center. Logistic regression was used to analyze data from 11,206 patients to develop a predictive model, which was validated using a subsequent cohort of 3,523 patients.

RESULTS

In the model development cohort, alcohol was detected in the blood of 3,180 BAC-tested patients (28.7%), of whom 91.2% had a BAC + 50 status. Preliminary analysis revealed associations between a BAC + 50 status and sex, age, race, injury type (intentional vs. unintentional), and time of injury (night vs. day and weekend vs. weekday). A predictive model using four attributes (sex and injury type) identified patients at low, medium, and high risk for being BAC + 50. The model was validated using the second group of patients.

CONCLUSION

Injured patients with a high probability of being alcohol positive can be identified using a simple scoring system based on readily available demographic and clinical information.

High concentrations of active plasminogen activator inhibitor-1 in porcine coronary artery thrombi

Addition of exogenous plasminogen activator inhibitor-1 (PAI-1) to fibrin clots inhibits fibrinolysis in vivo. However, it is unknown whether the localized concentrations of active PAI-1 necessary to produce this antifibrinolytic effect can be recruited to acute arterial thrombi by endogenous mechanisms. We measured PAI-1 activity and antigen in porcine coronary artery thrombi that formed in response to acute vascular injury. Mean PAI-1 activity in thrombi (n = 5) was 36 +/- 5.1 micrograms/mL, which is > 2000 times its concentration in normal porcine plasma. The presence of markedly elevated concentrations of active PAI-1 in thrombi was confirmed by an immunoactivity assay and by demonstrating formation of sodium dodecyl sulfate-stable complexes after addition of 125I-urokinase to thrombus extracts. Comparative analysis of PAI-1 antigen by Western blotting and urokinase inhibition assay suggested that approximately one third of thrombus-associated PAI-1 was active. Histological examination of coronary thrombi revealed that they consisted predominantly of dense aggregates of platelets with interspersed islands of fibrin, which closely resemble the histological appearance of thrombi in patients with myocardial infarction and unstable angina pectoris. Washed porcine platelets prepared from peripheral blood contained sufficient PAI-1 antigen and activity to account for the concentrations observed in coronary artery thrombi. However, the specific activity of human platelet PAI-1 was lower than that of porcine platelet PAI-1 (2% versus 50% active, respectively), and human platelets inhibited in vitro fibrinolysis to a lesser extent than did porcine platelets. These results indicate that active PAI-1 accumulates in porcine coronary artery thrombi in concentrations markedly higher than those present in plasma and that PAI-1 may be an important determinant of the known resistance of platelet-rich thrombi to lysis by tissue-type plasminogen activator. These studies also underscore the importance of considering possible species differences in protein function when comparing animal models of thrombosis to acute coronary thrombosis in humans.

A new pressure ulcer risk assessment scale for individuals with spinal cord injury

Each year, one-fourth of the 200,000 individuals with spinal cord injury in the United States develop pressure ulcers. No method currently exists, however, to accurately identify which of these individuals are at increased risk for development of pressure ulcers. We studied 219 spinal cord-injured patients, seen at a Veterans Affairs Medical Center, during a 6-yr period. Our goal was to develop a pressure ulcer risk assessment scale, specifically for persons with SCI. Each risk factor had to meet four criteria: (1) statistical association with pressure ulcer development; (2) biologically plausible mechanism; (3) literature support; (4) improved prediction. Among the 219 spinal cord-injured patients evaluated, 176 (80.4 percent) had a history of one or more pressure ulcers. Fifteen risk factors met the four criteria for inclusion into the risk assessment scale. They were as follows: restricted activity level, degree of immobility, complete spinal cord injury, urinary disease, impaired cognitive function, diabetes, cigarette smoking, residence in a nursing home or hospital, hypoalbuminemia, and anemia. Compared with the more general scales available, for quantifying the risk of pressure ulcer development, preliminary results suggest that this new scale is a significant improvement for the spinal cord-disabled.

Restenosis, reocclusion and adverse cardiovascular events after successful balloon angioplasty of occluded versus nonoccluded coronary arteries. Results from the Multicenter American Research Trial With Cilazapril After Angioplasty to Prevent Transluminal Coronary Obstruction and Restenosis (MARCATOR)

OBJECTIVES

This study sought to compare the frequency of restenosis, reocclusion and adverse cardiovascular events after angioplasty of occluded versus nonoccluded coronary arteries.

BACKGROUND

Angioplasty of chronically occluded coronary arteries is believed to be associated with a higher frequency of restenosis and reocclusion than angioplasty of subtotal stenoses. Whether this leads to adverse cardiovascular events is unknown.

METHODS

The Multicenter American Research Trial With Cilazapril After Angioplasty to Prevent Restenosis (MARCATOR) was a placebo-controlled trial with angiographic follow-up to determine the effect of the angiotensin-converting enzyme inhibitor cilazapril on the frequency of restenosis. In this trial, restenosis was defined as 1) angiographic reduction of minimal lumen diameter > or = 0.72 mm between angioplasty and the follow-up visit; and 2) > 50% diameter stenosis on the follow-up angiogram. We identified 139 patients with successful angioplasty of a coronary occlusion (Group 1) and compared the frequency of restenosis, reocclusion and adverse cardiovascular events with that in 1,295 patients with successful angioplasty of a subtotal stenosis (Group 2).

RESULTS

Restenosis occurred in 36 patients with occluded arteries (29%) versus 264 with nonoccluded arteries (23%, p = 0.177) by definition 1 and in 62 patients with occluded arteries (49%) versus 478 with nonoccluded arteries (42%, p = 0.119) by definition 2. Occlusion was present in 24 Group 1 patients (19%) compared with 74 Group 2 patients (7%) (p < 0.001). During the 6 month follow-up period, two Group 1 patients (1.4%) and six Group 2 patients (0.5%) died; no Group 1 patients and 10 Group 2 patients (0.8%) developed severe congestive heart failure; nonfatal myocardial infarction occurred in 4 Group 1 patients (2.9%) and 31 Group 2 patients (2.4%); repeat coronary angioplasty or bypass surgery was performed in 29 Group 1 patients (21%) and 232 Group 2 patients (18%); and angina was present in 18 Group 1 and 163 Group 2 patients (13% for both). Eighty-six Group 1 patients (62%) and 853 Group 2 patients (66%) remained free of these adverse events during the 6-month follow-up period (p = 0.513).

CONCLUSIONS

The frequency of restenosis was slightly but not significantly greater after successful angioplasty of an occluded artery than after angioplasty of a subtotal stenosis. Although reocclusion was more frequent, occurring in 19% of patients, the net clinical benefit of angioplasty in such patients was similar to that in patients with subtotal stenoses over the 6-month follow-up period.

Multivariate models for predicting survival of patients with trauma from low falls: the impact of gender and pre-existing conditions

OBJECTIVE

To determine if pre-existing conditions significantly improve the ability of current (TRISS and ASCOT) methods for predicting survival of patients with trauma from low falls.

DESIGN

Retrospective analysis using logistic regression models to identify significant independent predictors of survival.

SETTING

Eight hospitals affiliated with New York Medical College.

PATIENTS

A total of 1906 patients with trauma from low falls who were admitted to the eight hospitals between July 1987 and June 1989.

MAIN RESULTS

Gender and several pre-existing conditions significantly improved the ability of age and the physiologic and anatomic variables contained in the TRISS and ASCOT methodologies to predict survival for trauma patients suffering from low falls, with males experiencing a lower probability of survival. Odds of survival for patients with these pre-existing conditions ranged from 0.18 to 0.59 times the odds of survival for similar patients without the pre-existing conditions when the TRISS variables were used, and from 0.23 to 0.56 times the odds for similar patients when ASCOT variables were used. Furthermore, some substantial differences were found when hospital performance was assessed with and without the benefit of pre-existing conditions.

CONCLUSIONS

Pre-existing conditions and male gender are significantly related to survival of patients with trauma from low falls, and should be included along with age and the various physiologic and anatomic measures currently being used to predict survival for those patients.

New developments in infective endocarditis

Endocarditis as seen today differs significantly from that outlined by Sir William Osler in his famous Gulstonian lectures in 1885. The median age of the patients has increased; the spectrum of predisposing cardiac lesions has changed; more cases are due to unusual organisms, including gram-negative bacteria and fungi; and more cases present acutely and the classic findings of late endocarditis are seldom seen. Endocarditis was untreatable and uniformly fatal in 1885. Although continued advances in medical and surgical therapy have significantly increased survival, the recent appearance of multiresistant organisms in some cases is reminiscent of the Osler era. Recent advances in the diagnosis and management of endocarditis include the identification of a specific Staphylococcus aureus receptor protein on endothelial cells, better imaging of the cardiac structures using transesophageal echocardiography, improvement in clinical diagnostic criteria and surgical techniques, and the use of outpatient oral antibiotics for penicillin-sensitive streptococcal endocarditis.

Validation of TRISS and ASCOT using a non-MTOS trauma registry

OBJECTIVES

To validate the Trauma and Injury Severity Score (TRISS) and A Severity Characterization of Trauma (ASCOT) models for patients with blunt injuries using an independent trauma registry, and to develop new TRISS and ASCOT models for types of patients with blunt injuries and examine their fit.

DESIGN

Retrospective analysis of clinical data from the Institute for Trauma and Emergency Care (ITEC).

MATERIALS AND METHODS

Statistical models were developed using TRISS and ASCOT variables applied to ITEC data for patients with blunt injuries. These models were compared to Major Trauma Outcome Study (MTOS) models with regard to the resulting coefficients and hospital quality assessments. Also, separate models were developed for different groups of blunt injuries, and these models were compared with one another and tested for adequacy of fit.

MEASUREMENTS AND MAIN RESULTS

ASCOT performed acceptably well when new coefficients were derived using ITEC data, but TRISS did not. Although the models developed from MTOS and from ITEC coefficients generally yielded similar hospital quality assessments, there were some notable exceptions. Some TRISS and ASCOT variables were not significantly related to survival for some subgroups of blunt injuries, and neither the TRISS nor the ASCOT model was an adequate predictor of survival for patients suffering from low falls.

CONCLUSIONS

New TRISS and ASCOT coefficients should be derived if survival for patients with blunt injuries is to be predicted accurately in independent trauma registries. Also, it may be wise to consider developing separate models for subgroups of patients, particularly if hospitals in the registry have different mixes of patient types.

Endothelialization of cardiac valve bioprostheses

The main disadvantage of implanted xenograft valves used in cardiac surgery is their poor clinical long-term result, due to early tissue degeneration. In order to improve the performance of such glutaraldehyde fixed bioprostheses, a biological coating with viable endothelial cells was suggested. Therefore, glutaraldehyde preserved bovine pericard patches, as well as commercially available xenograft valves, were lined using human venous endothelial cells or microvascular cells from the subcutaneous fat tissue. Before cells were transplanted into their new environment, grafts were treated with an amino acid solution in order to neutralize the cytotoxic effect of free aldehydes, and precoated with fibronectin-heparin and basic fibroblast growth factor (bFGF) or endothelial cell growth supplement (ECGS) in order to enhance cell proliferation. Coated specimens were kept in culture conditions for a further seven days. Proliferation of transplanted cells was verified by an increase of activation following 3H-thymidine incorporation, while the maintained metabolic cell activity was demonstrated via Prostacycline (PGI2) measurement. Morphology was evaluated by means of scanning electron microscopy (SEM). As evaluated by the beta-Counter, 7 ng/ml bFGF (288,727 +/- 39,668 counts on day 4) substantially enhanced cell proliferation after seeding, opposed to the stimulation with 30,000 ng/ml ECGS (91,924 +/- 1129 counts on day 4), (p < 0.001). The PGI2 release of transplanted cells was stimulated with 25 microM Na arachidonic acid by the factor 2.6 +/- 0.3 and inhibited with 5 mM acetylsalicylic acid by the factor 0.7 +/- 0.2 on day 4 when compared with the basic level.(ABSTRACT TRUNCATED AT 250 WORDS)

Dual response runs in prehospital trauma care

The effects of dual responses [Basic Life Support (BLS) and Advanced Life Support (ALS)] on the outcomes of trauma patients were evaluated. Outcomes included changes in physiologic measurements between the scene and the emergency department (ED), and survival to hospital discharge. Data for 2394 patients with penetrating, motor vehicle crash (MVC), or other blunt injuries were included. Changes in physiologic measurements (Revised Trauma Scores) between the prehospital and ED settings were positively associated with documented ALS or dual response care. Survival to hospital discharge among penetrating injury patients was negatively related to dual responses, whereas that among MVC patients was positively associated with dual responses. Parallel results were found for a subset of more severely injured patients. Future research should confirm and refine these results so that protocols for the appropriate use of dual response runs can be developed.

Basic life support versus advanced life support for injured patients with an injury severity score of 10 or more

To study the value of advanced life support (ALS) compared with basic life support (BLS) for penetrating and motor vehicle crash (MVC) patients, data were collected from eight hospitals over 24 months on 781 consecutive patients with Injury Severity Scores > or = 10 as well as on a subset of 219 hypotensive patients. Initial prehospital Revised Trauma Scores (RTSs) were compared with initial emergency department RTSs. Scene times, total prehospital times, and the use of a pneumatic antishock garment (PASG), intravenous fluids, and endotracheal intubation were also documented. A modified TRISS method was used to compare mortality rates. The MVC ALS patients showed improvement in mean RTSs between prehospital and the emergency department while MVC BLS patients did not. Mean changes in blood pressure (BP) and the percentage of patients with improved BP were significantly higher among patients who received ALS; ALS was associated with increased use of PASGs and IV fluids. There were no differences between groups with respect to observed versus predicted mortality. Similar results were found in the hypotensive subset of patients. No benefit from the use of ALS for trauma patients with total prehospital times of less than 35 minutes was documented.

Long-term outcome in patients undergoing surgical repair of tetralogy of Fallot

BACKGROUND

Although corrective surgery for tetralogy of Fallot has been available for more than 30 years, the occurrence of late sudden death in patients in whom surgery was apparently successful remains worrisome.

METHODS

We studied long-term survival among 163 patients who survived 30 days after complete repair of tetralogy of Fallot, examining follow-up hospital records and death certificates when relevant.

RESULTS

The overall 32-year actuarial survival rate among all patients who survived surgery was 86 percent, as compared with an expected rate of 96 percent in a control population matched for age and sex (P < 0.01). Thirty-year actuarial survival rates were calculated for the patient subgroups. The survival rates among patients less than 5 years old, 5 to 7 years old, and 8 to 11 years old were 90, 93, and 91 percent, respectively--slightly less than the expected rates (P < 0.001, P = 0.06, and P = 0.02). Among patients 12 years old or older at the time of surgery, the survival rate was 76 percent, as compared with an expected rate of 93 percent (P < 0.001). The performance of a palliative Blalock-Taussig shunt procedure before repair, unlike the performance of a Waterston or Potts shunt procedure, was not associated with reduced long-term survival, nor was the need for a trans-annular patch at the time of surgery. Independent predictors of long-term survival were older age at operation (P = 0.02) and a higher ratio of right ventricular to left ventricular systolic pressure after surgery (P = 0.008). Late sudden death from cardiac causes occurred in 10 patients during the 32-year period.

CONCLUSIONS

Among patients with surgically repaired tetralogy of Fallot, the rate of long-term survival after the postoperative period is excellent but remains lower than that in the general population. The risk of late sudden death is small.

Is 24-hour operating room staff absolutely necessary for level II trauma center designation?

Recent papers from established trauma centers reported average elapsed times from emergency department (ED) admission to the operating room (OR) of greater than 100 minutes for patients judged to be in immediate need of surgery. This study was undertaken to determine whether patients treated at an institution desiring level II trauma center designation in a geographic area with a low incidence of penetrating trauma suffered any adverse effects because of lack of a 24-hour in-house OR staff. Trauma registry data at The Stamford Hospital, a suburban community teaching hospital without OR nursing staff in-house at night, were reviewed and compared with data from three affiliated level I trauma centers and with established national standards using TRISS methodology. Of 659 major trauma patients, 86 (44 blunt, 42 penetrating) underwent surgery within 12 hours of admission. Patients' injuries were similar in severity to those seen at the affiliated trauma centers and to the Major Trauma Outcome Study population. Mortality rates were also similar. No statistically significant differences were seen in elapsed times from ED arrival to OR arrival even in the subgroup of patients with systolic blood pressure values of < or = 90 mm Hg. No unexpected adverse outcomes could be ascribed to the lack of 24-hour OR staffing in this setting. The estimated cost of providing additional OR staffing is $145,000 per year. Since times to the OR and outcomes were similar to those at level I centers, this expense may not be warranted.

A study of pneumatic antishock garments in severely hypotensive trauma patients

The effectiveness of a pneumatic antishock garment (PASG) on severely hypotensive trauma patients (BP < or = 50 mm Hg) was studied using two data sets. The first included data from eight hospitals collected over 4 1/2 years; the second included 2 years of data from an additional eight hospitals. Data were collected by trained nurse abstractors whose interrater reliability was extremely high for AIS and ISS scoring. One hundred forty-two patients had blood pressures < 50 mm Hg. The PASG patients had a higher survival rate than non-PASG patients (Pr = 0.055). The PASG appeared to have the most effect on patients with abdominal injuries since no patient with such an injury survived unless a PASG was applied. Controlling for severity using the TRISS method, z scores indicated that the survival rate in the PASG group was significantly higher than expected whereas that in the non-PASG group was similar to that predicted; the same pattern was found when blunt injury and penetrating injury patients were analyzed separately. Improvement in survival among PASG patients occurred despite an average scene time that was 4.7 minutes longer than that for non-PASG patients. No improvement in survival among PASG versus non-PASG patients with blood pressures of 50-70 mm Hg or in those with blood pressures of 90 mm Hg or less was found. We conclude that the use of PASG in severely hypotensive patients (BP < or = 50) should be considered medically acceptable pending randomized controlled studies.