Margaret Hsieh

Repeat Pediatric Visits to a General Emergency Department

Abstract Study objective: To determine the rate of repeat visits among children cared for in a general emergency department and associated demographic and clinical variables. Methods: We carried out a chart review of patients seen in the ED of a general hospital serving both inner-city and suburban populations. Our subjects were all children younger than 18 years seen in the study ED between July 1, 1992, and June 30, 1993 (N=4,276). Results: We found 291 repeat visits (defined as a subsequent visit within 14 days) in 245 children. Among the 242 repeat visits for related complaints, 200 were unanticipated and most without a clear medical need. Mantel-Haenszel adjusted odds ratios (MHORs) showed a significantly increased risk of repeat visit with public insurance (controlled for age: MHOR, 2.57, and 95% confidence interval [CI], 1.93 to 3.43; controlled for race: MHOR, 2.70, and 95% CI, 1.99 to 3.66) and age younger than 2 years (controlled for insurance: MHOR, 1.67, and 95% CI, 1.27 to 2.19; controlled for race: MHOR, 1.89, and 95% CI, 1.47 to 2.47). Conclusion: Repeat visits were more likely for respiratory diagnoses and less likely for minor trauma. Both visits and repeat visits were more likely in patients from poorer census tracts than in those from equidistant, more affluent ones. [Zimmerman DR, McCarten-Gibbs KA, DeNoble DH, Borger C, Fleming J, Hsieh M, Langer JC, Breckenridge MB: Repeat pediatric visits to a general emergency department. Ann Emerg Med November 1996;28:467-473.]

Hyponatremia in runners requiring on-site medical treatment at a single marathon

STUDY OBJECTIVE Literature reports indicate an increasing number of cases of hyponatremia in athletes participating in moderate endurance events such as standard marathons. In this study, we evaluated the incidence of hyponatremia in marathon finishers requiring medical treatment on-site and attempted to assess the contribution of fluid type ingested and nonsteroidal antiinflammatory drug (NSAID) use to the development of hyponatremia. METHODS We examined a prospective, convenience sample of runners requiring intravenous hydration at the final medical tent of a standard marathon course and a comparison group of finishers who did not require intravenous hydration. After giving informed consent, subjects had blood drawn and answered a questionnaire regarding fluid intake on the course and NSAID use before the race. Blood samples were analyzed on-site for serum sodium values as well as other hematologic parameters. RESULTS Fifty-one subjects requiring intravenous hydration as well as 11 subjects who did not were enrolled. Three subjects (5.6%; 95% CI, 0-11.9%; missing = 8) in the intravenous hydration group had serum sodium less than 130 mEq/L. None of the three runners suffered neurologic or pulmonary consequences and only one required overnight hospital admission for hydration. The small number of hyponatremic subjects precluded the analysis of the role of fluid type or NSAID use in the development of hyponatremia or the development of a model for prediction. CONCLUSION This study found a 5.6% incidence of hyponatremia in marathon runners requiring medical treatment.

The Prevalence and Factors Associated With QTc Prolongation Among Emergency Department Patients

STUDY OBJECTIVE Previous studies have suggested that QTc prolongation may lead to significant morbidity and mortality. The prevalence of QTc prolongation among emergency department (ED) patients is unknown. The purpose of this study is to determine the prevalence of QTc prolongation among ED patients. METHODS This was a retrospective review of ED and inpatient data for all patients with an ECG conducted for any reason at a tertiary care university ED during a 3-month period. QTc prolongation was defined as computer-generated QTc intervals greater than or equal to 450 ms for men and greater than or equal to 460 ms for women. RESULTS Of the 1,558 eligible cases, 544 patients had QTc prolongation (35%; 95% confidence interval [CI] 32% to 37%). The prevalence of QTc intervals greater than or equal to 500 ms was 8% (120/1,558; 95% CI 6% to 9%). The most common comorbidities were structural heart disease, renal failure, and stroke. Forty-four percent (239/544; 95% CI 40% to 48%) of patients with any degree of QTc prolongation were discharged from the ED. Furthermore, 23% (28/120; 95% CI 16% to 32%) of patients with QTc intervals greater than or equal to 500 ms were discharged from the ED, including 16 patients with QTc intervals greater than or equal to 500 ms and QRS durations less than 120 ms (16/60; 27%; 95% CI 16% to 40%). Five percent of the patients with QTc prolongation died in the ED or during hospitalization (27/544; 95% CI 3% to 7%); none had QTc prolongation or torsades de pointes listed as a cause of death. CONCLUSION QTc prolongation occurred frequently among ED patients who had an ECG study for any reason. Nearly half of all patients with QTc prolongation were discharged from the ED.

Learning patient-specific predictive models from clinical data

We introduce an algorithm for learning patient-specific models from clinical data to predict outcomes. Patient-specific models are influenced by the particular history, symptoms, laboratory results, and other features of the patient case at hand, in contrast to the commonly used population-wide models that are constructed to perform well on average on all future cases. The patient-specific algorithm uses Markov blanket (MB) models, carries out Bayesian model averaging over a set of models to predict the outcome for the patient case at hand, and employs a patient-specific heuristic to locate a set of suitable models to average over. We evaluate the utility of using a local structure representation for the conditional probability distributions in the MB models that captures additional independence relations among the variables compared to the typically used representation that captures only the global structure among the variables. In addition, we compare the performance of Bayesian model averaging to that of model selection. The patient-specific algorithm and its variants were evaluated on two clinical datasets for two outcomes. Our results provide support that the performance of an algorithm for learning patient-specific models can be improved by using a local structure representation for MB models and by performing Bayesian model averaging.

Recommendations for Treatment of Hyponatraemia at Endurance Events

This review focuses on possible pathophysiology of exercise-associated hyponatraemia and its implication on evaluation and treatment of collapsed athletes during endurance events. Rehydration guidelines and field care have traditionally been based on the belief that endurance events create a state of significant fluid deficit in athletes, which must be corrected by liberal hydration. Beliefs in the necessity of liberal hydration may have contributed to cases of hyponatraemia. Assumptions that fluid loss accounts for the entire weight loss during exercise and that fluid ingestion is the only source of water gain during exercise may lead to an overestimation of the degree of volume depletion and the amount of fluid needed for replacement.Increasing evidence suggests that hyponatraemic athletes are fluid overloaded; ingestion of large amount of hypotonic fluid in combination with inappropriate or inadequate physiological responses leads to excessive retention of free fluid. Risk factors include hot weather, female sex, slower finishing time, and possibly the use of nonsteroidal anti-inflammatory medications. Symptoms of hyponatraemia can be subtle and can mimic those of other exercise-related illnesses, thereby complicating its diagnosis and leading to possible inappropriate treatment. Most athletes who collapse at the finish line experience exercise-associated collapse, a benign and transient form of postural hypotension that can be treated simply by continued ambulation after finishing or elevation of legs while in a supine position for those who cannot walk.Care providers should consider the use of intravenous hydration with normal saline carefully since it is not needed by most collapsed athletes and may worsen the condition of patients with unsuspected hyponatraemia. Historic information and clinical signs of volume depletion should be elicited prior to its use. Most hyponatraemic athletes will recover uneventfully with careful observation while awaiting spontaneous diuresis. Use of hypertonic saline should be reserved for patients with severe symptoms. Moderate consumption of carbohydrate-electrolyte solution during exercise may allow the maintenance of adequate hydration and the prevention of hyponatraemia.

Differences in initial severity of illness between black and white emergency department patients hospitalized with heart failure.

BACKGROUND Black patients hospitalized for heart failure have better reported short-term survival than white patients for unknown reasons. We sought to determine if initial severity of illness differed between black and white emergency department (ED) patients hospitalized for heart failure. METHODS We analyzed 1,408 black and 7,260 white randomly selected patients in one state hospitalized from an ED during 2003 and 2004 and with a discharge diagnosis of heart failure. We used three validated clinical prediction rules to estimate severity of illness on admission. RESULTS Black patients were younger than white patients (65.8 +/- 14.8 vs 77.4 +/- 11.5 years, P < .01) and were assigned to lower risk classes by all 3 prediction rules more frequently than white patients (P < .01). The odds ratio (95% CI) for classification of black versus white patients into the lowest risk class within the three rules ranged from 1.16 (1.00-1.33) to 4.30 (3.75-4.94). After adjusting for hospital clustering, the odds ratio (95% CI) for black versus white patient hospital death and complications was 0.75 (0.60-0.95) and, for 30-day death, was 0.34 (0.27-0.48). CONCLUSIONS Black ED patients hospitalized with heart failure are younger, less severely ill on admission and less likely to experience short-term fatal and nonfatal outcomes than white patients. Our findings suggest a varying opportunity between black and white patients when considering alternative initial treatment strategies and sites of care.

Derivation of Clinical Predictors of Failed Rescue Shock During Out-of-Hospital Ventricular Fibrillation

Background. Failed rescue shocks have been shown to decrease the likelihood of survival in the treatment of out-of-hospital ventricular fibrillation (VF). Avoidance of failed shocks may improve survival. Objective. We sought to derive clinical predictors that could be used by emergency medical services (EMS) personnel to identify a subset of VF patients whose first rescue shock is likely to fail, making them candidates for a cardiopulmonary resuscitation (CPR)-first strategy. Methods. After gaining institutional review board approval from all three institutions, we merged data from Los Angeles, Pittsburgh, andRoyal Oak into a new cardiac arrest database. We used classification andregression tree (CART) analyses to build the model. We defined a failed first rescue shock as one in which there was no return of spontaneous circulation (ROSC); the postshock electrocardiographic (ECG) rhythm was VF, pulseless electrical activity (PEA), or asystole; or subsequent shocks were delivered (indicating that the first shock had failed). Results. The database contains 5,046 cases, of which 1,777 (35%) had VF as the initial ECG rhythm. Sufficient data were present for 748 cases. Using unwitnessed collapse, a response time of >6 minutes, andabsence of bystander CPR (BCPR) on EMS arrival as predictors, 35 of 35 (100%, 95% confidence interval [CI] 100–91.4%) cases had failed first rescue shocks. Second shock failure was predicted in 162 of 164 (99%) cases. Conclusions. Unwitnessed collapse, response time >6 minutes, andabsence of BCPR may be useful in predicting which VF patients are likely to have failed first shocks andwould thereby benefit from a CPR-first strategy. Stacked rescue shocks most often fail, andthis outcome can also be predicted.