Diagnostic accuracy of a bedside D-dimer assay and alveolar dead-space measurement for rapid exclusion of pulmonary embolism: a multicenter study.

CONTEXT: A previous study suggested that the combination of a normal D-dimer assay and normal alveolar dead-space fraction is a highly sensitive screening test for pulmonary embolism (PE). OBJECTIVE: To determine if the combination of a normal alveolar dead-space fraction (volume of alveolar dead space/tidal volume

Statistical methodology: VIII. Using confirmatory factor analysis (CFA) in emergency medicine research.

How many underlying characteristics (or factors) does a set of survey questions measure? When subjects answer a set of self-report questions, is it more appropriate to analyze the questions individually, to pool responses to all of the questions to form one global score, or to combine subsets of related questions to define multiple underlying factors? Factor analysis is the statistical method of choice for answering such questions. When researchers have no idea beforehand about what factors may underlie a set of questions, they use exploratory factor analysis to infer the best explanatory model from observed data "after the fact." If, on the other hand, researchers have a hypothesis beforehand about the underlying factors, then they can use confirmatory factor analysis (CFA) to evaluate how well this model explains the observed data and to compare the model's goodness-of-fit with that of other competing models. This article describes the basic rules and building blocks of CFA: what it is, how it works, and how researchers can use it. The authors begin by placing CFA in the context of a common research application-namely, assessing quality of medical outcome using a patient satisfaction survey. They then explain, within this research context, how CFA is used to evaluate the explanatory power of a factor model and to decide which model or models best represent the data. The information that must be specified in the analysis to estimate a CFA model is highlighted, and the statistical assumptions and limitations of this analysis are noted. Analyzing the responses of 1,614 emergency medical patients to a commonly-used "patient satisfaction" questionnaire, the authors demonstrate how to: 1) compare competing factor-models to find the best-fitting model; 2) modify models to improve their goodness-of-fit; 3) test hypotheses about relationships among the underlying factors; 4) examine mean differences in "factor scores"; and 5) refine an existing instrument into a more streamlined form that has fewer questions and better conceptual and statistical precision than the original instrument. Finally, the role of CFA in developing new instruments is discussed.

Data elements for emergency department systems, release 1.0 (DEEDS): a summary report. DEEDS Writing Committee.

Variations in the way that data are entered in ED record systems impede the use of ED records for direct patient care and deter their reuse for many other legitimate purposes. To foster more uniform ED data, the Centers for Disease Control and Prevention's (CDC) National Center for Injury Prevention and Control is coordinating a public-private partnership that has developed recommended specifications for many observations, actions, instructions, conclusions, and identifiers that are entered in ED records. The partnership's initial product. Data Elements for Emergency Department Systems, Release 1.0 (DEEDS), is intended for use by individuals and organizations responsible for ED record systems. If the recommended specifications are widely adopted, then problems--such as data incompatibility and high costs of collecting, linking, and using data--can be substantially reduced. The collaborative effort that led to DEEDS, Release 1.0 sets a precedent for future review and revision of the initial recommendations.

Data elements for emergency department systems, release 1.0 (DEEDS): a summary report. DEEDS Writing Committee.

Variations in the way that data are entered in emergency department record systems impede the use of ED records for direct patient care and deter their reuse for many other legitimate purposes. To foster more uniform ED data, the Centers for Disease Control and Prevention's National Center for Injury Prevention and Control is coordinating a public-private partnership that has developed recommended specifications for many observations, actions, instructions, conclusions, and identifiers that are entered in ED records. The partnership's initial product, Data Elements for Emergency Department Systems, Release 1.0 (DEEDS), is intended for use by individuals and organizations responsible for ED record systems. If the recommended specifications are widely adopted, then problems--such as data incompatibility and high costs of collecting, linking, and using data--can be substantially reduced. The collaborative effort that led to DEEDS, Release 1.0 sets a precedent for future review and revision of the initial recommendations.

Predicting patient satisfaction: a study of two emergency departments.

To identify perceptions that predict overall patient (dis)satisfaction with Emergency Department (ED) care, we studied responses to a survey mailed to all discharged patients over a 6-month period (Academic Hospital), and to a telephone interview of a random sample of discharged patients over a 1-year period (Community Hospital). The survey and interview both assessed overall satisfaction, as well as satisfaction with perceived waiting times, information delivery, and expressive quality of physicians, nurses, and staff. Data for 1176 patients (training sample) and 1101 patients (holdout sample) who rated overall satisfaction as either "very good" or "very poor" (Academic Hospital), and for 856 patients (training sample) and 431 patients (holdout sample) who rated overall satisfaction as either "excellent" or "poor" (Community Hospital), were retained for analysis. For both hospitals, nonlinear tree models efficiently achieved overall classification accuracy exceeding 98% in training analysis and 95% in holdout analysis (all p < .0001). The findings suggest that overall patient (dis)satisfaction with care received in the ED is nearly perfectly predictable on the basis of patient-rated expressive qualities of ED staff, particularly physicians and nurses. Interventions designed to reinforce positive (and extinguish negative) expressive health-care provider behaviors may cut the number of extremely dissatisfied patients in half.

Enhanced activated charcoal delivery through small-bore tubing.

Activated charcoal is often given through small-bore tubing for pediatric patients or in attempts to bypass the stomach in patients who are vomiting. The viscosity makes activated charcoal difficult to administer through small-bore tubing. This in vitro study examined several interventions to facilitate flow of aqueous suspension activated charcoal through the small-bore tubing. Aqueous suspension activated charcoal with or without sorbitol had similar flow rates. Precoating the tubing with mineral oil gave only minimal increases in flow rate. A 10% dilution decreased the time to administer 240 ccs of aqueous suspension activated charcoal by 2/3. An additional 10% dilution reduced the time to administer the same dose a further 50%. Minimal dilution of aqueous suspension activated charcoal with tap water greatly increased flow rate through small-bore tubes.

Failure of N-acetylcysteine to reduce alpha amanitin toxicity.

Acetaminophen undergoes toxic conversion in the liver to a free-radical intermediary which binds to glutathione. N-Acetylcysteine acts as a glutathione precursor when natural stores are depleted, and is an effective antidote for acetaminophen overdose. Mushrooms containing amatoxins (such as Amanita phalloides) may undergo similar toxic conversion. However, in our amatoxin-poisoned mouse model, N-acetylcysteine (1.2 g kg-1) produced no change in survival or hepatic enzyme elevation compared to control animals. We conclude that N-acetylcysteine has no clinical role in the treatment of Amanita phalloides ingestion.

Dextromethorphan poisoning reversed by naloxone.

Dextromethorphan, a common ingredient in cough syrups, has rarely been described to cause toxicity. The authors describe an unusual case of a known asthmatic presenting with somnolence, who appeared to be in end-stage respiratory failure. Her partial response to routine naloxone, 1 mg, was surprising. However, additional naloxone was required to completely normalize the patient's mental status. The authors suggest naloxone be administered in doses of 0.4 mg or more intravenously in suspected dextromethorphan overdose.

Effects of alternate routes of epinephrine delivery in experimental bradycardia-hypotension.

The magnitude and rapidity of response to epinephrine given by various routes were evaluated using a new model of bradycardia and hypotension. In ten animals, left ventricular (LV) injection of 10 micrograms/kg of epinephrine was superior to right ventricular (RV) injection in regard to time to attain a 20% increase in heart rate (HR), a 10% increase in mean arterial pressure (MAP) and time to reach peak MAP, although the peak MAP itself did not significantly differ. Similar results occurred with a 15 micrograms/kg dose. Aortic injection in seven of the animals resulted in a much longer time to target HR, an equal time to target MAP and a longer time to peak MAP compared to LV injection. LV injection of epinephrine results in a significantly more rapid onset of action than RV injection in the bradycardic, hypotensive animal. Epinephrine's beneficial effect appears to be derived from its vasoconstrictive, chronotropic and inotropic properties.

Failure of cimetidine to affect phalloidin toxicity.

Phalloidin, a toxin of the mushroom Amanita phalloides, was felt to act as a pro-toxin, converted by hepatic microsomal mixed function oxidase enzymes. Therefore, pretreatment with cimetidine, a potent P450 cytochrome system inhibitor, might be expected to prevent the toxic conversion. In our mouse animal model of phalloidin exposure, pretreatment with 120 mg cimetidine/kg ip failed to improve survival compared to placebo pretreatment. Moreover, cimetidine pretreatment decreased survival (p less than 0.03). These results support an alternate mechanism for phalloidin toxicity, ie, that the toxic effects are related to the interaction of phalloidin with F-actin.

Long-term continuous monitoring of intraocular pressure in conscious primates.

A technique for chronic implantation of a device for long-term continuous, quantitative monitoring of intraocular pressure (IOP) in experimental animals is presented. The methodology employed is straight forward and should be easily duplicated for experimental investigations where such monitoring might be useful. Continuous IOP data recorded from the device implanted in a conscious adult rhesus monkey are compared with continuous IOP data reported by other investigators.