The apparent diet of predators and biases due to different handling times of their prey.

In order to estimate the true diet of predators, the prey of a number of predators is recorded at one time. Such sampling underestimates the true diet during a period of time. Where handling times of different types of prey are very different, these estimates will be biased, because prey that take a relatively long time to be eaten will be overestimated. We examined a rocky intertidal predatorprey system and demonstrated the existence of such bias. A number of hypothetical correlates of the bias were also investigated. As anticipated, variations in handling times were a major factor, but neither taxonomic affinity nor absolute size of the prey could predict the degree of underestimation in the true diet for any given type of prey. A previously described correction for this type of bias was tested, but found to be unsatisfactory. We suggest that it was too insensitive to variability in handling times.A simple computer model incorporating differences among prey in their handling times was also unable to predict the bias, but did indicate that non-random selection of prey was occurring.We concluded that where such biases are likely to occur, information on the handling times of different prey and/or accurate estimates of the true diets of the predators are essential for the predatory interaction to be interpreted properly. These results were discussed in relation to published accounts of diets of predators in rocky intertidal habitats. Many studies have not presented data on handling times of prey in the field, and the magnitude and importance of potential biases in these studies are therefore difficult to assess.

Variations in the electrocardiograms of young adults: are revised criteria for thrombolysis needed?

OBJECTIVE: The evaluation of chest pain in young adults has changed with the recognition of cocaine-induced myocardial ischemia. The high frequency of abnormal electrocardiograms (56-84%) in the cocaine-user population is largely due to "normal" electrocardiographic variants (early repolarization). The authors sought to determine the frequency of these "normal" variants in a young population, and whether these findings can be confused with acute ischemia. METHODS: A prospective convenience sample of subjects aged 18 to 35 without known heart disease was interviewed and had 12-lead electrocardiographic tracings performed. An emergency physician (physician 1) and a cardiologist (physician 2) read the tracings while blinded to patient history, age, and race. When the physicians disagreed, another physician adjudicated the diagnosis. RESULTS: Four hundred fourteen subjects (127 black, 175 Hispanic, and 112 Caucasian) were enrolled. Overall, 154 tracings (37%) were normal, 245 (59%) were abnormal but nondiagnostic for ischemia, and 15 (4%) were consistent with ischemia. Frequencies of repolarization "abnormalities" as determined by physicians 1 and 2, respectively, were: blacks, 32%, 51%; Hispanics, 26%, 35%; Caucasians, 17%, 27%; chi-squared, p = 0.02 and 0.0004. Patients with ischemic electrocardiograms according to physician 1 had a high frequency of repolarization "abnormalities" according to physician 2, and vice versa (100%, 61%). Electrocardiographic criteria for thrombolytic use per physician 2 were present in 31 patients (7%): blacks, 9%; Hispanics, 10%; and Caucasians, 2%; chi-squared, p = 0.03.

Cocaine-associated chest pain: one-year follow-up.

OBJECTIVE: To determine the one-year mortality and incidence of myocardial infarction (MI) post-hospital discharge or ED release for patients with cocaine-associated chest pain. METHODS: A prospective, observational study of an inception cohort of consecutive patients who presented to one of four municipal hospital EDs with cocaine-associated chest pain. Patients were followed for one year from the end of the enrollment period. Main outcome parameters were the one-year actuarial survival and the frequency of nonfatal MI. RESULTS: Mortality data were available for all 203 patients at a mean of 408 days. Additional clinical information was available for 185 patients (91%). There were six deaths (one-year actuarial survival 98%; 95% CI, 95-100%); none from MI. Nonfatal MI occurred in two patients (1%; 95% CI, 0-2%). Continued cocaine use was common (60%; 95% CI, 52-68%) and was associated with recurrent chest pain (75% vs 31%, p < 0.0001). No MI or death was reported for patients who claimed to have ceased cocaine use. CONCLUSIONS: Patients who presented with cocaine-associated chest pain commonly continued to use cocaine after discharge. Urgent evaluation of coronary anatomy or cardiac stress tests may not be necessary for patients for whom MI is ruled out and who do not have recurrent potentially ischemic pain. The subsequent risk for MI and death in this group appears to be low. Intervention strategies should emphasize cessation of cocaine use.

Prospective multicenter evaluation of cocaine-associated chest pain. Cocaine Associated Chest Pain (COCHPA) Study Group.

OBJECTIVE: To describe a large cohort of patients who had chest pain following cocaine use, and to determine the incidence of and clinical characteristics predictive for myocardial infarction in this group of patients. METHODS: A prospective observational cohort study of consecutive patients with cocaine-associated chest pain was conducted in six municipal hospital emergency departments (EDs). Demographic variables, drug abuse patterns, medical histories, chest pain characteristics, ECG results, and laboratory data were recorded. Myocardial infarction was the primary endpoint. RESULTS: Fourteen of 246 patients (5.7%; 95% confidence interval [CI], 2.7-8.7%) had myocardial infarction, as diagnosed by elevated CK-MB isoenzyme levels. There were two deaths (0.8%). The patients had a median age of 33 years. The majority were male (71.5%), non-white (83.3%), cigarette smokers (83.3%) who used cocaine regularly. Chest pain began a median of 60 minutes after cocaine use and persisted for a median of 120 minutes. Chest pain was most frequently described as substernal (71.3%) and pressure-like (46.7%). Shortness of breath (59.3%) and diaphoresis (38.6%) were common. There was no clinical difference between patients who had myocardial infarctions and those who did not. Twelve patients had arrhythmias and four had congestive heart failure. All cases requiring intervention were evident upon presentation. An ECG revealing ischemia or infarction had a sensitivity of 35.7% for predicting a myocardial infarction. The specificity, positive predictive value, and negative predictive value of the ECGs were 89.9%, 17.9%, and 95.8%, respectively. CONCLUSIONS: Myocardial infarction in patients who have cocaine-associated chest pain is not uncommon. No clinical parameter available to the physician can adequately identify patients at very low risk for myocardial infarction. Therefore, all patients with cocaine-associated chest pain should be evaluated for myocardial infarction.

Groin tissue necrosis requiring skin graft following parenteral abuse of buprenorphine tablets.

In May 2002 Buprenorphine (Subutex) was listed on the Australian Pharmaceutical Benefits Schedule for treatment in opioid dependence. In addition to broadening treatment options, buprenorphine has the advantage of an improved safety profile. The risk of overdose is lessened but other risks remain due to diversion. French experience reports widespread deviation of buprenorphine sublingual tablets to intravenous injection. We report a case of attempted parenteral administration of buprenorphine tablets. Stringent protocols for dispensing are appropriate.

"Abnormal" electrocardiograms in patients with cocaine-associated chest pain are due to "normal" variants.

"Abnormal" electrocardiograms are found in 56% to 84% of patients with cocaine-associated chest pain. This study was designed to assess whether these findings can be explained by "normal" variations in young patients' electrocardiograms. This cross-sectional study was conducted in a municipal hospital emergency department and walk-in clinic. History and results of an electrocardiogram for consecutive patients with cocaine-associated chest pain, aged 18 to 35 years, were compared to normal controls matched for age, race, and gender. Electrocardiograms underwent detailed analysis by two physicians blinded to both the study protocol and the hypothesis. Interphysician concordance for electrocardiographic diagnosis was substantial. There were 112 patients enrolled, 56 in each group. There was no significant difference found in the mean frequency of electrocardiographic diagnoses between the cocaine-associated chest pain patients and controls. The early repolarization variant was common. In conclusion, "normal" variations (J point and ST segment elevations) account for many of the "abnormal" electrocardiograms observed in young patients with cocaine-associated chest pain. Further study is needed to define the prevalence of these "normal" variations, and to determine if standard electrocardiographic criteria for thrombolysis apply to young patients.

Implications of 'supply-side' ecology for environmental assessment and management.

Recent work in marine ecology has reaffirmed an insight from fisheries science that knowledge about the production, dissemination and success of propagules can guide our management of populations and assemblages. Understanding the variable nature of recruitment relationships can both aid and hinder attempts at environmental monitoring, rehabilitation and innovative selection of marine reserves. The effects of human impacts in marine environments may be first manifest in alterations to recruitment, which also constitutes the only path by which many populations could recover.

Sewage and the biota on seashores: Assessment of impact in relation to natural variability.

The three largest sewage outfalls serving Sydney, New South Wales, Australia are to be moved several kilometres offshore in 1991-2. Changes in their environmental impact due to these moves are likely, but detection relies on a good understanding of the present impacts on the natural environment. Biological surveys in 1986-8 of rocky intertidal sites located directly at the present cliff outfalls have been compared to several (≥2) other shores some distance away (which serve as controls). This technique of multiple control sites is recommended as a way of including natural variability in the data set. By comparing the community structure at the point of impact to the range among control sites, it is theoretically possible to be more sure of whether purported impacts represent a response out of the ordinary. Effects detected in this way include gross reductions in species diversity, with complete dominace of rocky shore biota by ephemeral green algae and the absence of animals. Zonation disappears close to outfalls. These striking effects were, however, very localised. Denudation experiments suggested great recruitment and productivity of these algae, but the community as a whole is held at an early stage of succession. Such clear alterations attributable to sewage pollution suggests that this ecosystem would be a good indicator of any changes occurring once outfalls are moved offshore. Continued monitoring including multiple control sites is recommended.

Hyperkalemic ascending paralysis.

Hyperkalemia is a life-threatening electrolyte disturbance. The clinical presentation is most commonly related to its effects on cardiac conductivity and contractility, although weakness and respiratory compromise may occur. We describe what we believe to be the first reported case of life-threatening hyperkalemia presenting as an ascending paralysis which was associated with standard-dose trimethoprim-sulfamethoxazole therapy. The patient had mild, underlying renal disease which predisposed him to develop hyperkalemia. This case underscores the need to use caution in prescribing trimethoprim to such patients.

Supply-side ecology and benthic marine assemblages.

Many marine invertebrates have a planktonic stage of their life history during which widespread dispersal and much mortality occur. The numbers surviving to recruit into habitats occupied by adults are therefore very variable in time and space. Models for the structure and dynamics of benthic assemblages tend to focus on processes causing death - often assuming consistent arrivals of recruits. Supply-side ecology is a newly fashionable term to describe recent interest in the long-realized consequences of variations in recruitment. Such variations have important influences on theory and empirical research in these assemblages.

The use of evidence-based medicine in the practice of consultant physicians. Results of a questionnaire survey.

BACKGROUND: Information is lacking about the extent to which Australasian physicians apply methods of evidence-based medicine (EBM) in routine practice. AIMS: To assess the frequency and predictors of use of EBM methods in a sample of consultant physicians in adult medicine. METHODS: Self-administered questionnaires were distributed to a convenience sample of 545 physicians from October 1998 to January 1999. RESULTS: One hundred and eleven questionnaires were returned (20% response rate). Ninety-eight (88%) respondents formulated five or less clinical questions per week; 69 (62%) undertook five or more evidence searches per week, the majority as MEDLINE searches involving therapeutic topics. Respondents identified insufficient time (74%), limited search skills (41%), and limited access to evidence (43%) as search impediments. In determining evidence quality, 37% frequently relied on global impressions, while 22% frequently applied explicit critical appraisal (p=0.008). Efficiency of literature searches was rated on average as good/very good by 18%, fair by 52% and poor by 30%. As a result of EBM, 47% frequently had confidence in pre-existing decisions increased, 39% gained improved knowledge, and 5% altered clinical decisions. Frequently encountered inhibitors to changing practice were personal conservatism (40%), organisational constraints (40%), and interdisciplinary tensions (39%). Perceived weaknesses of EBM included: limited applicability to individual patients (26%); evidence deficiencies (25%); and too time consuming (13%). In making EBM more attractive, one third requested reliable evidence sources at the point of care. CONCLUSIONS: The application of EBM to routine practice by physicians is constrained by deficient EBM skills, limited access to evidence, lack of time, and cognitive and environmental factors. Targeted education in EBM and systems that quickly deliver high-quality evidence at the point of care are needed in realising the full potential of EBM to improve care.

Organizing factors in the comprehension and recall of connected discourse.

This experiment is based on the theory that, in reading, one uses cues in order to activate an organizing system as an aid in reading the material. The variables introduced into the experiment include (1) the form of oragnization (meaningful, scrambled, and pseudo) and (2) the choice of material (descriptive, abstract, and technical). Having read a paragraph, subjects read a list of words including some from the paragraph and some not and were asked to check those words that they remembered as belonging to the paragraph. Accuracy is highest when subjects have been most successful in activating an appropriate organizing system.

Nitroglycerin in the treatment of cocaine associated chest pain--clinical safety and efficacy.

The optimal medical regimen for the treatment of cocaine associated myocardial ischemia has not been defined. While animal and human data demonstrate the risks of beta-adrenergic blockade, studies in the cardiac catheterization laboratory suggest a beneficial role of nitroglycerin. We performed a prospective multicenter observational study to evaluate the clinical safety and efficacy of nitroglycerin in the treatment of cocaine associated chest pain at six municipal hospital centers. Of 246 patients presenting with cocaine associated chest pain, 83 patients were treated with nitroglycerin at the discretion of the treating physician. Relief of chest pain and/or adverse hemodynamic outcome were the primary endpoints. Baseline comparisons of patients treated with nitroglycerin to those not treated with nitroglycerin found that the treated patients were at higher risk of ischemic heart disease. They were older (36 years vs 32 years, p = 0.0008), more likely to have an ischemic electrocardiogram (27% vs 4%, p < 0.0001), to be admitted (94% vs 40%, p < 0.0001), and to have a discharge diagnosis of ischemic heart disease (41% vs 9%, p < 0.0001). Nitroglycerin was beneficial in 41 patients (49%; 95% CI, 38-60%): 37 patients (45%) had relief or reduction in the severity of chest pain and 4 patients (5%) had other beneficial effects. Only one patient had an adverse outcome (transient hypotension in the setting of a right ventricular infarct). Nitroglycerin is safe and possibly effective in the treatment of cocaine associated chest pain.