Use of automated external defibrillators by a U.S. airline

BACKGROUND: Passengers who have ventricular fibrillation aboard commercial aircraft rarely survive, owing to the delay in obtaining emergency care and defibrillation. METHODS: In 1997, a major U.S. airline began equipping its aircraft with automated external defibrillators. Flight attendants were trained in the use of the defibrillator and applied the device when passengers had a lack of consciousness, pulse, or respiration. The automated external defibrillator was also used as a monitor for other medical emergencies, generally at the direction of a passenger who was a physician. The electrocardiogram that was obtained during each use of the device was analyzed by two arrhythmia specialists for appropriateness of use. We analyzed data on all 200 instances in which the defibrillators were used between June 1, 1997, and July 15, 1999. RESULTS: Automated external defibrillators were used for 200 patients (191 on the aircraft and 9 in the terminal), including 99 with documented loss of consciousness. Electrocardiographic data were available for 185 patients. The administration of shock was advised in all 14 patients who had electrocardiographically documented ventricular fibrillation, and no shock was advised in the remaining patients (sensitivity and specificity of the defibrillator in identifying ventricular fibrillation, 100 percent). The first shock successfully defibrillated the heart in 13 patients (defibrillation was withheld in 1 case at the family's request). The rate of survival to discharge from the hospital after shock with the automated external defibrillator was 40 percent. A total of 36 patients either died or were resuscitated after cardiac arrest. No complications arose from use of the automated external defibrillator as a monitor in conscious passengers. CONCLUSIONS: The use of the automated external defibrillator aboard commercial aircraft is effective, with an excellent rate of survival to discharge from the hospital after conversion of ventricular fibrillation. There are not likely to be complications when the device is used as a monitor in the absence of ventricular fibrillation.     

Cost effectiveness of early discharge after uncomplicated acute myocardial infarction

BACKGROUND: Reducing the length of hospitalizations can reduce short-term costs, but there are few data on the long-term clinical and economic consequences of early discharge. METHODS: Using data from the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO-1) trial, we identified 22,361 patients with acute myocardial infarction who had an uncomplicated course for 72 hours after thrombolysis. Then, using a decision-analytic model, we examined the cost effectiveness of an additional day of hospitalization in this group. We defined incremental survival attributable to another day of monitored hospitalization, using Kaplan-Meier estimates to determine the rate of resuscitation after cardiac arrest between 72 and 96 hours. Lifetime survival curves for each group in the decision-analytic model were estimated from empirical one-year survival data from GUSTO-1. The costs of key hospital resources (e.g., room and monitoring) were derived from data in the GUSTO-1 cost-effectiveness analysis. RESULTS: Of the patients with an uncomplicated course within 72 hours after thrombolysis, 16 had ventricular arrhythmias during the next 24 hours; 13 of these patients (81 percent) survived for at least 24 hours. On average, another 0.006 year of life per patient could be saved by keeping patients with an uncomplicated course in the hospital another day. At a cost of $624 for hospital and physicians' services, extending the hospital stay by another day would cost $105,629 per year of life saved. In sensitivity analyses, it was found that a fourth day of hospitalization would be economically attractive only if its cost could be reduced by more than 50 percent or if a high-risk subgroup could be identified in which the estimated survival benefit would be doubled. CONCLUSIONS: Hospitalization of patients with uncomplicated myocardial infarction beyond three days after thrombolysis is economically unattractive by conventional standards.     

Modelling multiple laser pulses for port wine stain treatment

Many port wine stains (PWS) are still resistant to pulsed dye laser treatment. However, anecdotal information suggests that multiple-pulse laser irradiation improves patient outcome. Our aims in this note are to explain the underlying mechanism and estimate the possible thermal effects of multiple pulses in vascular structures typical of PWS. Based on linear response theory, the linear combination of two thermal contributions is responsible for the total increase in temperature in laser irradiated blood vessels: direct light absorption by blood and direct bilateral thermal heat conduction from adjacent blood vessels. The latter contribution to the increase in temperature in the targeted vessel can be significant, particularly if some adjacent vessels are in close proximity, such as in cases of optical shielding of the targeted vessel, or if the vessels are relatively distant but many in number. We present evidence that multiple-pulse laser irradiation targets blood vessels that are optically shielded by other vessels. Therefore, it may be a means of enhancing PWS therapy for lesions that fail to respond to single-pulse dye laser treatment.     

Intrinsic dynamics in neuronal networks. I. Theory

Many networks in the mammalian nervous system remain active in the absence of stimuli. This activity falls into two main patterns: steady firing at low rates and rhythmic bursting. How are these firing patterns generated? Specifically, how do dynamic interactions between excitatory and inhibitory neurons produce these firing patterns, and how do networks switch from one firing pattern to the other? We investigated these questions theoretically by examining the intrinsic dynamics of large networks of neurons. Using both a semianalytic model based on mean firing rate dynamics and simulations with large neuronal networks, we found that the dynamics, and thus the firing patterns, are controlled largely by one parameter, the fraction of endogenously active cells. When no endogenously active cells are present, networks are either silent or fire at a high rate; as the number of endogenously active cells increases, there is a transition to bursting; and, with a further increase, there is a second transition to steady firing at a low rate. A secondary role is played by network connectivity, which determines whether activity occurs at a constant mean firing rate or oscillates around that mean. These conclusions require only conventional assumptions: excitatory input to a neuron increases its firing rate, inhibitory input decreases it, and neurons exhibit spike-frequency adaptation. These conclusions also lead to two experimentally testable predictions: 1) isolated networks that fire at low rates must contain endogenously active cells and 2) a reduction in the fraction of endogenously active cells in such networks must lead to bursting.     

Dyspepsia is associated with CagA-positive Helicobacter pylori

OBJECTIVE: The role of Helicobacter pylori in nonulcer dyspepsia is controversial. Speculation has arisen that only strains of H. pylori carrying the CagA virulence factor are important in the development of dyspepsia. The objective of this study was to determine whether nonulcer dyspepsia correlated with CagA-positive H. pylori infection. METHODS: A total of 435 healthy blood donors and 102 general medicine clinic respondents completed the Bowel Disease Questionnaire and the PRIME-MD survey, a validated screen for common psychiatric disorders. Subjects were classified as cases of nonulcer dyspepsia if they reported pain in the upper abdomen more than six times in the previous year and denied a past or current history of peptic ulcer disease. Study participants were tested for IgG antibodies to H. pylori and the CagA protein. RESULTS: Clinic respondents were more likely than healthy blood donors to meet the case definition for nonulcer dyspepsia (34% vs 13%, p < 0.001), to be seropositive for H. pylori (54% vs 18%, p < 0.001), and to be CagA seropositive (41% vs 10%, p = 0.01). Logistic regression identified CagA seropositivity (p = 0.03), race (p = 0.001), and positive screens for depression (p = 0.007) or somatization (p < 0.001) as variables independently associated with nonulcer dyspepsia. CONCLUSION: Infection with a CagA-positive strain of H. pylori is associated with a clinical diagnosis of nonulcer dyspepsia. However, nonulcer dyspepsia was also strongly and independently associated with positive screens for depression or somatization disorder as well as with ethnicity. These potential sources of variance should be considered in the design of future studies evaluating nonulcer dyspepsia.     

Meniere's disease: An immune complex-mediated illness?

The cause of Menière's disease is unknown. Recent clinical research suggests that one etiology is immune-mediated damage to the inner ear. The diagnosis of autoimmune Menière's syndrome is largely based on history, response to steroids, or results of nonspecific laboratory tests such as serological studies. Polyethylene glycol (PEG) assay was used to determine levels of circulating immune complexes (CIC) in 30 patients with Menière's disease and 20 control subjects. Patients with Menière's disease had a statistically significant elevation of serum circulating immune complexes when compared to the control group. This suggests that CICs may be involved in the pathogenesis of Menière's disease, either as a direct cause of damage, or as a by-product of an underlying autoimmune abnormality. Therapeutic implications include use of plasmapheresis to remove the complexes or CIC monitoring to serve as a marker for treatment efficacy.     

Recognition of synthetic speech by hearing-impaired elderly listeners.

The Modified Rhyme Test (MRT), recorded using natural speech and two forms of synthetic speech, DECtalk and Votrax, was used to measure both open-set and closed-set speech-recognition performance. Performance of hearing-impaired elderly listeners was compared to two groups of young normal-hearing adults, one listening in quiet, and the other listening in a background of spectrally shaped noise designed to simulate the peripheral hearing loss of the elderly. Votrax synthetic speech yielded significant decrements in speech recognition compared to either natural or DECtalk synthetic speech for all three subject groups. There were no differences in performance between natural speech and DECtalk speech for the elderly hearing-impaired listeners or the young listeners with simulated hearing loss. The normal-hearing young adults listening in quiet out-performed both of the other groups, but there were no differences in performance between the young listeners with simulated hearing loss and the elderly hearing-impaired listeners. When the closed-set identification of synthetic speech was compared to its open-set recognition, the hearing-impaired elderly gained as much from the reduction in stimulus/response uncertainty as the two younger groups. Finally, among the elderly hearing-impaired listeners, speech-recognition performance was correlated negatively with hearing sensitivity, but scores were correlated positively among the different talker conditions. Those listeners with the greatest hearing loss had the most difficulty understanding speech and those having the most trouble understanding natural speech also had the greatest difficulty with synthetic speech.     

Blood pressure reactivity to exercise: stability, determinants, family aggregation, and prediction

Previous studies have shown blood pressure reactivity to exercise predicts future resting blood pressure. Subjects in this study were 206 healthy Mexican-American and Anglo-American families with fifth or sixth grade children. A total of 539 children (mean age = 12 years) and parents (mean age = 37 years) had complete data at baseline, and 79% were remeasured 48 months later. Blood pressure was measured during a submaximal cycle ergometer fitness test. Reactivity measures included systolic blood pressure at 70% of maximal heart rate (SBP70) and slope of the blood pressure-heart rate association during exercise (SLOPE). Stability of reactivity measures over 24 months varied from .22 to .63 (all p less than 0.001). Correlates of blood pressure reactivity in parents included resting heart rate, gender, age, and sodium intake. Correlates of reactivity in children included resting heart rate, body mass index, and age. Modest but significant levels of family aggregation of blood pressure reactivity were observed. In stepwise multiple regression analyses, SBP70 at baseline predicted resting blood pressure 48 months later in parents but not in children. The present results confirm previous studies indicating systolic blood pressure reactivity to exercise is a significant predictor of later resting blood pressure.     

Methylphenidate for depression in hospice practice: a case series

Psychostimulants such as methylphenidate have been used for depression in cancer patients. We report the successful use of methylphenidate to treat depression in 10 consecutive patients with advanced cancer. A rapid onset of effect was noted. Appetite, concentration, fatigue, and sedation also improved in some persons. No severe side effects were noted.