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Journal club: Assessment of the acute asthmatic
The Literature of Emergency
Medicine
Journal Club: Assessment of the Acute Asthmatic HOWARD A. WERMAN,
MD, FRANK BIRINYI, MD, DOUGLAS A. RUND, MD
Ohio State University Use of peak expiratory flow rates to eliminate unnecessary arterial
blood gases in acute asthma.
Martin TG, Elenbaas RM, Pingleton SH. Ann Emer Med 1982;11:70-73.
Dr. Birinyi: This study tried to address two specific questions. First, the authors attempted to establish the relationship between the peak expiratory flow rate (PEFR) and arterial blood gas (ABG) measurements in asthmatic patients 15-39 years of age. The authors also considered the use of PEFR as a screening tool to identify asthmatics in whom ABG results would be severely abnormal. A prospective study was conducted in asthmatics presenting with an acute episode of airway obstruction. Prior to the initiation of therapy, an arterial blood gas sample was drawn and a peak expiratory flow rate was determined for each patient. The peak flow rate was then normalized for age, sex, and height and expressed as a percentage of normal value. This value was compared with the pH, PC,, and PO,, which were determined by blood gas analysis. The authors found small but statistically significant Pearson coefficients for the graphs of PEFR against pH, PcoZ, and Po,. When only asthmatics with PEFR values < 40% of normal were considered, these relationships became stronger. Most importantly, no asthmatic with a PEFR value of more than 25% of normal had a pH < 7.35 or a P,,, < 45 mm Hg. Only two patients with PEFR value > 25% of normal were found to be hypoxic (Po, < 60 mm Hg). The authors conclude that the PEFR can be used as a screening tool to determine which patients should have ABG measurements made. This study can be criticized for a number of reasons. Selection bias may be introduced because of the time period of the study. Patients were enrolled only during the months of August and September. This may have led to the inclusion of a large percentage of patients in whom an allergic component played a major role in
Address reprint requests to Dr. Rund: Division of Emergency Medicine, Rhodes Hall, University Hospitals, 450 W. 10th Avenue, Columbus, OH 43210-1228.
College
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their asthmatic attacks. This is important because these patients tend to have less severe disease, and their episodes of asthma are more easily reversed. Because the sample is skewed towards less severe disease, the true relationship between PEFR and ABG derangements may be obscured. This is compounded by the fact that although there are 89 observations in the study, this actually reflects only 51 patients. Finally, although some demographic data are presented on these patients, some important data are omitted. Information such as steroid use, previous hospitalizations for asthma, other asthmatic medications, and the presence of fever were not mentioned in the discussion. Thus, the ability to compare these data with other populations of asthmatics is limited. Dr. Thomas Bullock: Although the authors of this article are correct in stating that arterial blood gases are the most reliable measure of gas exchange, the major derangement in acute asthmatic attacks appears to be airway obstruction. The question thus becomes one of which is a better method of assessing the severity of an acute attack (PEFR or ABGs). This issue is never addressed in this study. From the tone of the article, it seems that the authors think that ABG measurements are an accurate method of determining the severity of asthma. This has been disputed by other studies. Arterial blood gases and pulmonary function testing in acute bronchial asthma: Predicting patient outcomes. Nowak RM, Tomlanovich MC, Sarkar DD, Kvale PA, An-
derson JA. JAMA 1983;249:2043-2046. Dr. Taylor: This study was undertaken to assess the value of pre-treatment and post-treatment arterial blood gas and pulmonary function tests in predicting the outcome of acute asthmatic attacks. The authors also attempted to establish guidelines for pulmonary function tests that would eliminate unnecessary arterial blood gas determinations. Asthmatics 16-40 years old who visited the emergency department (when one of the investigators was present) were enrolled in the study. Peak expiratory flow rate and forced expiratory volume in one second 89
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(FEV,) were measured, and arterial blood gas samples were drawn. After therapy with terbutaline (0.25 mg subcutaneously) and in some cases aminophylline (5.6 mg/kg), the measurements were repeated. Further therapy was administered, and the patient was either admitted to the hospital or discharged, depending on the clinical course. Discharged patients were contacted after 48 hours. Those patients who experienced continued difficulty with their asthma or who were seen in an emergency department during this time were considered to have relapsed. Thus, three groups of patients were defined: admitted patients, patients who were discharged and subsequently relapsed and those who were discharged without further difficulty. The authors found a mean age of 25.1 years among their patients and a mean duration of treatment of 4.8 hours. Among the pre-treatment values for the arterial blood gases and pulmonary function tests, no significant difference was found between the pH, Pco2, and Po, for the three groups. On the other hand, pulmonary function tests were able to distinguish the admitted patients and the patients who experienced relapse from the successfully treated group. The same findings were seen for post-treatment values in which the predictive value of pulmonary function tests was confirmed. Similarly to the previous study, there was a poor coorelation between the normalized FEV, values and the Po,. Also, the Po, and PcoZ measurements were not well correlated with the absolute FEV,. Finally, the authors found that a PEFR < 30% of predicted normal value and a FEV, < 25% of predicted normal value identified all cases of hypercarbia and hypoxia. The study is important in that it confirms the findings of the previous paper. These authors confirm that there is a poor correlation between pulmonary function testing and arterial blood gas determinations for acute asthmatic episodes. As an example, the authors point out that in a significant number of cases hypoxia worsened despite an improvement in pulmonary function measurements. Additionally, these authors found threshold values for pulmonary function measurements that identified all cases of hypoxia and hypercarbia in asthmatic patients. Specifically, once the patient had an FEV, above 1 1 or a PEFR above 200 l/ min, blood gas analysis was unnecessary. More importantly, these authors described the utility of arterial blood gas measurements and pulmonary function tests in predicting patient outcomes. The findings of this study demonstrate that pulmonary function tests are useful in separating those patients who will require admission or experience a relapse following discharge from those patients who will be successfully treated in the emergency department. Arterial blood gas measurements were not useful in this regard. 90
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Dr. Rund: Although the study is important in demonstrating the importance of pulmonary function tests in the assessment of the severity of asthma, there are several flaws. As in the previous study, the demographic data for the study population are scant. This again limits the comparison of this study population with the population seen by other emergency physicians. Additionally, the treatment in each case was not uniform for the study population. Initially, each asthmatic received terbutaline (0.25 mg subcataneously), but beyond that, there was no standardization of therapy. The mean duration of therapy of 4.8 hours is significantly less than that reported in other studies. The contribution of these factors to the differences among the three groups is unknown. Another point that will be reiterated in many of the subsequent studies is the subjective nature of the admission criteria. In most cases, clinical criteria were used. This is ambiguous, as the exact criteria are not specified. Also, numerous studies have documented the failure of clinical parameters such as wheezing, dypsnea, and tachypnea in reflecting the severity of asthma. The authors also indicate that in some cases, the FEV, was used to decide whether the patient was to be admitted. Obviously. this introduces bias in the results, as the factor under study is actually used to separate the three groups. Failure of peak expiratory flow rate to predict hospital admission in acute asthma. Martin TG, Elenbaas RM, Pingleton SH. Ann Emerg Med 1982;11:466-470.
Dr. Howard Bernstein: The authors of this prospective study attempted to assess the value of PEFR measurements as predictors of the need for hospitalization in acute asthmatic attacks. Asthmatics between the ages of 15 and 39 years who were experiencing acute attacks were enrolled in the study. The PEFR was measured prior to therapy. and treatment was initiated according to a standard protocol that included epinephrine, aminophylline, isoetharine, and corticosteroids where necessary. A second PEFR measurement was made after the first epinephrine treatment. The results of these measurements were blinded from the physician or nurse making these determinations. Patients were admitted to the hospital if 1) pre-treatment arterial blood gas measurements showed a pH < 7.20. a PC02 > 45 mm Hg, or a Pao, < 50 mm Hg; 2) dyspnea or wheezing was not improved by therapy; 3) complications such as pneumonia, pneumothorax, or pulmonary infiltrates were seen on chest radiograph; or 4) the patient visited the emergency department three times within a seven-day period. The PEFR before and after the first epinephrine dose, as well as the change in PEFR, were analyzed to determine the ability of
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these parameters to predict the need for hospitalization. The results were based on 86 visits by 51 patients. Only 10.5% of the patient visits resulted in hospital admissions. The authors found a statistically significant difference in the initial PEFR, post-treatment PEFR, and the change in PEFR after therapy between the admitted and discharged patients. They indicate, however, that despite this difference, there was too much overlap between these measurements to be clinically useful. The authors did find that no admitted patient had an initial PEFR > 30% of normal value or a change in PEFR of less than 20%. Additionally, the authors compared the data for patients who were discharged without further problems with that of patients who were seen within 48 hours. No statistically significant difference was seen between these two groups. The authors conclude that the single measurement of PEFR before or after treatment with epinephrine or measurement of the change in PEFR are neither sensitive nor specific enough to screen patients who will eventually require hospital admission. Those patients with a PEFR > 30% of normal value initially or a change in PEFR of more than 20% after therapy will not require hospital admission. There are several problems with this study. We have already commented on the lack of demographic data presented, limiting the ability to generalize the results of the study. In addition, the reader is not informed as to who is making the determination of clinical improvement. The level of training of individuals assessing the clinical status of the patients is an important piece of information that is not clearly presented in this study. Additionally, the time period over which the study was conducted could introduce some bias into the patient selection. It should also be pointed out that some patients were seen who had previously been treated by the authors. Although a second visit is not specifically listed as a criteria for admission, it is more likely that these patients would be admitted after their second visit. This again introduces some bias into the study results, as derangements in their pulmonary-function studies may not accurately reflect their being included in the admission group. Dr. Wet-man: Regarding the admission criteria cited
in this study, the results of the prior two studies have demonstrated that the correlation between arterial blood gas measurements and pulmonary-function tests is very poor. Thus, PEFR measurements would not be expected to predict which patients would be admitted on the basis of arterial blood gas measurements. In considering the patient with complications such as pneumonia or pneumothorax, I am unaware of any evidence that suggests that pulmonary-function tests
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are useful in predicting the need for admission of these patients. The fourth criteria of three emergency department visits in seven days was excluded from the analysis. Thus, the only valid criteria that are assessed in this study are the very subjective measures of improvement in dyspnea and reduction in wheezing. We have already discussed the validity of such criteria in predicting patient outcome. Dr. Rund: This last point raises a crucial issue regarding such studies on asthmatic patients in an emergency department. The question must be raised as to whether the use of clinical parameters such as dyspnea and wheezing represent the best criteria for determining the need for hospital admission. These criteria were utilized in this and the previous study. However, considering that the pathophysiology of asthma involves large and small airway obstruction, it would appear that assessment of FEV, or PEFR would be the best index of the need for hospitalization in the asthmatic. After all, these objective measures most accurately reflect the severity of the obstructive process. In other studies, the degree of dyspnea and the severity of wheezing have not been shown to correlate with the severity of asthma. In addition, small changes in these pulmonary parameters have been shown to result in dramatic improvements in clinical signs and symptoms of asthma. Thus, improvement in dyspnea or wheezing may not correlate with objective improvement in the acute asthmatic attack. Therefore, the reader must question the conclusions of any study that uses only subjective clinical criteria to define the need for hospitalization. Emergency room assessment and treatment of patients with acute asthma: Adequacy of conventional therapy. Kelsen SC, Kelsen DP, Fleegler BF, Jones RC, Rodman T. Am J Med 1978:64:622-628. Dr. Eric Davis: The authors of this article attempted to assess the adequacy of emergency department treatment for acute asthmatic attacks. Specifically, the authors intended to determine the improvement in airway obstruction measured spirometrically, the short-term outcome for these patients, and the relationship of subsequent clinical course to the degree of residual obstruction. Uncomplicated asthmatic patients who were experiencing an acute exacerbation were included in the study. Prior to therapy, a history, physical examination, and laboratory collection were performed. The laboratory data included an FEV, and arterial blood gases. Subsequent therapy included subcutaneous epinephrine, aminophylline, aerosolized bronchodilators, oxygen, and hydration according to a specified treatment protocol. Patients were assessed at one, three, and six hours after initiation of treatment and were admitted if they failed to meet the clinical criteria de91
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fined by the authors. These criteria included improvement in dyspnea, unlabored breathing, and marked reduction in wheezing. The authors studied 127 emergency department visits for 102 patients. Of the patient visits, 14.6% eventually resulted in hospitalization. A significant difference was seen between the admitted and discharged patients in the FEV, measurements. For the discharged group, the mean FEV, was 1.767 -+- 94 ml which was only 57% of the predicted normal value. Of this group, 26% experienced a relapse, which was defined as a visit to the emergency department for further care, and 6% of these patients required hospitalization. Although there was no significant difference in FEV, measurements between the group that was discharged without complications and the group that experienced a relapse, a significant difference existed in the FEV, measurements at the end of treatment. In particular, an increase in the FEV, measurement of less than 400 ml after therapy was shown to be highly predictive of relapse when compared with increases of more than 400 ml. Further analysis revealed that this difference could be explained by the greater duration of therapy in the group without complications. The average duration of therapy was 3.5 hours as compared with 1.5 hours in the group that eventually experienced a clinical relapse. In trying to correlate the physical findings and historical information to the severity of asthma, the authors were only able to find a relationship for pulsus paradoxicus and sternomastoid muscle retraction with severe disease. However, even in cases involving severe obstruction, these signs were generally absent. Arterial blood gas measurements again correlated poorly with the severity as assessed by spirometry. These authors conclude that clinical signs and symptoms are poor predictors of the patients’ ability to be discharged from the emergency department without complications. When this information alone is used to assess the response to therapy, the mean FEV, indicates. that airway function of discharged patients is still markedly abnormal at only 57% of the predicted normal value. Using this criterion, a significant number of patients were found to require a return visit for treatment of their asthma within ten days. In this study, the duration of therapy appeared to be the major factor in preventing a relapse in discharged patients. These authors are to be commended for their recognition of pulmonary function tests as an important endpoint in the assessment of the severity of asthma. However, there are some important flaws in the study design. First, the clinical decisions appear to have been made by a variety of observers, most of them in their first year of medical training. In addition, there is no description of the method of measuring the FEV, 92
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values. Were three measurements made? Was the best of these measurements used, or were they averaged? Was the patient upright or sitting? Finally, it is not stated that the observers were blinded to the results of the FEV, measurements. This is important, because if the observers were not blinded, it is possible that the results of these determinations could have influenced the decision to admit asthmatic patients. Dr. Kerldel Kidwell: The authors of this article have made an important conclusion regarding the assessment of the asthmatic patient. They point to the importance of spirometric measurements as the crucial endpoint in evaluating the response to therapy. This article clearly shows how in using clinical signs and symptoms alone as means of assessing the patient. asthmatics may be discharged from the emergency department with severe residual pulmonary dysfunction. This increases the risk of relapse in these patients. These authors have also shown that the major factor in determining the chance of relapse in an asthmatic patient appears to be the length of time that the patient receives treatment. In their series, there was a twohour difference in the mean duration of treatment for patients discharged without complications as compared with those who required further emergency department visits. Clearly, some of this difference could be explained by the different threshold that various physicians have for discharging patients with acute asthmatic episodes. However, it also points to the importance of an adequate period of intensive medical management for episodes of acute asthma in preventing further exacerbation. Dr. Rund: Many of the studies of the assessment of asthmatic patients in the emergency department have attempted to identify patients who will suffer a relapse of their disease and require further therapy. For an emergency physician, identification of these patients is considered crucial. As suggested by this article, relapses may be preventable with more prolonged initial therapy. From a risk-management perspective, patients who are discharged after being treated in the emergency department eventually to require further therapy are of special concern to the emergency physician. First, it must be realized that this population of patients can never be completely identified. This is because there are a number of factors that are unrelated to the pulmonary-function status of the patient after therapy that contribute to relapse of the disease. These factors include a return to environmental conditions known to provoke attacks and noncompliance with prescribed treatment. In addition, further information is needed regarding the clinical outcomes of this group of patients. In this study, the initial group of patients studied had an admission rate of 14.6%. Some patients had respiratory
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failure, and one death was recorded., In contrast, the relapse group had an admission rate of only 6%. No deaths were recorded, and no patients had respiratory failure. Thus, among the patients seen in this study, the vast majority who required a second emergency department visit were discharged after further therapy; no significant complications were seen. In this case, the risks of initially discharging a patient who will require a second emergency department visit must be weighed against the risk of unnecessarily hospitalizing these patients when first seen. Dr. Werman: Little information is provided by the authors on how follow-up of these patients was conducted. The percentage of patients for whom followup was accurately determined for the ten-day period is not mentioned. This is important, because without very careful follow-up procedures, it is possible that a serious complication or death may have been missed if other institutions checked.
and the coroner’s
office were not
An index predicting relapse and need for hospitalization in patients with acute bronchial asthma. Fischl MA, Pitchenik A, Gardner LB. N Engl J Med 1981;305:783-789. Dr. Murk Smith: In response to the long treatment times for acutely asthmatic patients treated in the emergency department and to the high rate of relapse in these patients, the authors of this article have attempted to develop a predictive index that could be used to determine the need for admission among acute asthmatics early in the course of therapy. Using this index early in the course of therapy could potentially prevent prolonged stays in the emergency department. This index might also be applied to determine patients at risk for a relapse of their asthma. Asthmatics ages 15-45 years were included in the study. Prior to therapy, a brief history, physical examination, and laboratory tests were performed by the house officer. Laboratory data included an arterial blood gas sample and PEFR measurement. Patients were then treated according to a standard protocol that included subcutaneous epinephrine, terbutaline, aeroxolized isoetharine, aminophylline, hydrocortisone, and intravenous hydration. Further assessments were made by the house officer hourly. A disposition was made after 8-12 hours of therapy. Patients were discharged if they were no longer dyspneic, their wheezing was resolved, and accessory muscle retractions were absent. Follow-up data were obtained on all discharged patients except for ten patients. These patients were excluded from analysis. Once the data were collected, they were analyzed to determine which elements of the history, physical examination, and laboratory data were useful in predicting the need for admission and the risk of relapse. Finally, a predictive index was developed by deter-
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mining the cutoff point for each factor that mathematically maximized the predictive value for ihe significant variables. A total of 205 patients were studied. Of these, 22% were initially admitted and 20% were discharged and returned for further therapy. During subsequent emergency department visits, the average duration of therapy was longer than in the initial visit, and 83% of the patients required admission. Seven of the 14 factors analyzed were found statistically to significantly predict patient outcome. No single factor was consistently predictive of admission or relapse. A multifactorial predictor index was developed using the seven factors that were determined previously. A score of “0” or “1” was assigned to each variable. These variables included a pulse rate > 1201 min, a respiratory rate > 30/min, pulsus paradoxicus > 18mm Hg, PEFR < 120 l/min, moderate to severe dyspnea, moderate to severe accesory muscle use, and moderate to severe wheezing. A statistically significant difference was seen between the relapse and admitted groups when compared with the successfully treated group of initial presentation. When the index was applied to the relapse and admitted groups, more than 95% had scores of 4 or greater. This was true for only 3% of the successfully treated group. Although a statistically significant difference was found between the relapse and admitted groups when compared with the successfully treated group at one hour of therapy, there was significant overlap of the predictive index scores. Therefore, the predictive index applied at one hour was not considered useful. The authors concluded that application of the predictive index prior to therapy could be a potentially useful tool to determine the need for hospitalization and the risk of relapse in acute asthmatic episodes. Because no single factor, including PEFR, was predic’tive of relapse or admission, a multivariate approach was needed. The authors of this study have taken an interesting approach towards the assessment of the acute asthmatic. There is no question that the development of a predictive index that could be applied during the early stages of treatment and would accurately determine the need for hospitalization would be quite useful. This study addresses an important issue that has not been mentioned in our previous discussions. The duration of therapy for many asthmatics in the studies described has been as long as 12 hours. In most emergency departments, allowing a patient to occupy a bed for this period of time is not only impractical in terms of patient flow, but is also quite costly. In some cases, it may be less expensive to hospitalize these patients for a day. An early predictive index would eliminate these lengthy visits. In reviewing this study, one sees many potential 93
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problems. The first problem lies in the number of observers who are involved in assessing the patients. This study utilizes medical house officers. This presents at least two problems. Because of the usual rotating schedule of house officers, a large number of physicians are making observations and disposition determinations over the course of the study. In fact, the authors point out that 30% of the 205 patients were seen by at least two physicians during their emergency department visit. In addition, the level of training is not clearly stated in the paper. There would be a greater confidence in the medical judgements of senior-level house officers than in those of interns. This study also uses very subjective discharge criteria that include improvement of dyspnea and wheezing, which have not been shown to correlate with the severity of asthma. It was clear that historical and physical examination data were recorded according to a written protocol. Although this does insure more complete records, it also introduces a potential bias into the study. It is known that the behavior of both subjects and observers is influenced by the knowledge that they are participating in a study. Finally, it must be stated that this study includes data from the initial patient visits. Thus, the predictive index cannot be assumed to apply to the visits of patients experiencing a relapse. Dr. Kidwell: With regard to this last point, it is important that these studies should specifically exclude return visits for relapsed patients. In this study, the admission rate for relapsed patients is 83%. This contrasts sharply with the admission rate of 6% reported in the last study discussed. This can be interpreted to imply a tremendous bias at this institution to admit patients who return to the emergency department after recent treatment for acute bronchial asthma. The threshold for considering these patients as clinically improved appears to be much higher in these relapsed patients. One can see how these patients, if utilized to develop a predictive index, would invalidate the results of the study. It is also interesting that these authors found a weak but statistically significant association between arterial blood gas measurements and PEFR determinations. This was not seen in other studies that we have discussed. This study showed a statistically significant difference in the severity of arterial blood gas derangements between the admitted and relapsed groups. This is in contradistinction to the findings of Nowak et al that were discussed previously. Despite the findings of other studies, these authors recommend the use of arterial blood gas measurements in the treatment of acute asthmatic attacks. Dr. Nuncy Trhfik: One must be leary of the results of this study, because it is concluded that a predictive index as determined at initial presentation is more reliable than one determined an hour after treatment.
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This goes against the clinical experience of many emergency physicians who have successfully treated and discharged many asthmatics from the emergency department that initially presented with a severe asthmatic attack. By the same token, there are other asthmatics who present with only moderate distress but do not improve clinically or spirometrically with treatment. Thus, intuition alone tells us that the validity of a pre-treatment index is questionable. In addition, one must consider the findings of both Kelsen et al and Nowak et al, which showed that the major factor in determining the patient outcome was the reversibility of the asthmatic attack. Both studies concluded that some measures of the patient status determined after initiation of therapy were necessary to predict the need for hospital admission. The authors of this study should have been concerned about the validity of their results when they did not reflect the findings of other authors.
Performance of an index predicting the response of patients with acute bronchial asthma to intensive emergency department treatment. Rose CC, Murphy JG, Schwartz JS.
N Engl J Med 1984;310:573-577. Dr. Cheryl Lee: This study was done as a follow-up to the previous study. The authors attempted to determine the validity of the predictive index, which was applied in a prospective fashion. Asthmatics ages 1445 years who presented to the emergency department with an acute asthmatic attack were enrolled in the study. Historical information and physical examination data obtained were similar to those in the previous study. Laboratory information included arterial blood gas measurements, serum theophylline levels, leukocyte and differential counts, and a chest radiograph. Treatment was initiated according to the protocol of the previous article but was modified at the discretion of the treating physician. Patients were discharged when dyspnea, wheezing, and accesory muscle retractions were absent. Follow-up of patients was done by telephone ten days after the initial visit. Relapse was defined as a return visit to the emergency department or an unscheduled visit to a physician’s office. The data were analyzed to determine whether any difference existed among any of the outcome groups with respect to the predictive index. The data were also examined to determine the degree of association of the variables of the predictive index and other information with the clinical outcome. A total of 107 visits for 86 patients were included in the analysis. Of these patients, 72% were female, 91% were black, and 44% had a history of steroid use. The distribution of patients in the admitted (14%), relapsed (21%), and successfully treated groups (65%) were similar to those in the previous studies discussed. The major finding of the study was that when a cutoff of
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greater than or equal to 4 for the predictive index was used, as suggested in the previous report, the specificity was 0.71, the sensitivity was 0.40, and the positive predictive value was 0.43. The index performed better on the subset of patients who presented with a productive cough and fever or who used steroids on the day of the emergency department visit. Two variables, steroid use and theophylline use on the day of the visit, were more highly predictive of clinical outcome than any factors used in the predictive index. The authors conclude that while the defined predictive index did correlate with the need for hospitalization, the association was not strong enough to be clinically useful. Although there were many criticisms of the previous article, one must be careful not to reject the findings of that study on the basis of this report alone, because there are many important differences between the two reports. One important difference lies in the patient population. Unfortunately, as was previously stated, the demographic data are not well presented in the prior study, so no valid comparison can be made. Such information as steroid use, outpatient medications, duration of symptoms, and recent previous attacks would be important information used to compare the two patient populations. Another difference is that the authors of this article included 21 patients who had returned to the emergency department following an earlier visit. As was mentioned in our previous discussion, the first article addressed only initial visits for acute asthma. Finally, in the article by Fischl, a strict treatment protocol was specified in the care of the acute episode. In the present series, the treatment could be modified at the discretion of the treating physician. One could argue that in this series, the clinical outcomes of hospitalization and relapse might reflect inadequate therapy rather than the patients’ initial clinical presentation as in the Fischl study. Dr. Bullock: One of the major criticisms of the previous study was the concern about the reproducibility of observations for subjective variables as dyspnea, wheezing, and accessory muscle use. The results of this study demonstrate the legitimacy of this concern. When multiple observations were made in this study on these three subjective variables, no statistically significant differences were found among the three outcome groups. Dr. Rund: We have previously discussed the significance of the group of patients who “relapse” and require a subsequent visit to the emergency department. One notable difference between this study and the previous study is the rate of admission for relapsed patients. In this study, 14% of relapsed patients required hospital admission. This is consistent with the findings of Kelsen and contrasts with the 83% rate in the previous study. One of these patients required admission to the intensive care unit. Thus, significant
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complications are possible in the relapsed group, and these patients should be approached with caution. On the other hand, careful examination reveals that the PEFR and the medications prescribed were not different for the patients who were successfully discharged and those who experienced a relapse of their disease. This implies that other factors, such as noncompliance with medication or return to precipitating allergen, may have been important in causing a relapse. From this perspective, relapse may have been unavoidable in these patients. Dr. Smith: Although it is tempting to ignore the results of the Fischl study based on the findings of this last study, one must recognize some value in the original study. If one considers the seven criteria used to determine the index, one realizes that all of these parameters are used by clinicians to assess the asthmatic patient in the emergency department. However, unlike the index, most of us do not place equal importance on each of these parameters. Personally, as suggested in several initial studies, I place a great deal of reliance on spirometric measurements such as the PEFR in assessing these patients. (These values should be normalized for height and age using the table provided by the manufacturer. This allows more accurate assessment of individual patients). Additionally, I include other factors in my personal ‘index’ such as steroid dependence, use of bronchodilators on the day of the emergency visit, history of recent attacks, and presence or absence of fever. All of these factor are a part of my decision to admit or discharge an asthmatic patient . Dr. Rund: In reviewing all of these studies, we have identified several important flaws in the study design that are present in many of these studies. The most important dilemma is the inexact nature of the outcome criteria used in most of these studies. Usually, the study endpoint was admission or discharge of the asthmatic patient. Unfortunately, the criteria for discharge most often included the absence of wheezing, the lack of accessory muscle retractions, and improvement in the patient’s dyspnea. The problem lies not only in the subjective nature of these criteria but also in the fact that these clinical parameters have not been shown to correlate with the severity of asthma. Sternocleidomastoid retractions, although more indicative of severe asthma, were still absent in the majority of significant episodes of asthma in the Kelsen study. The fact that the most accurate measure of severity in these cases is pulmonary function is a dilemma. In most of these studies, this was the parameter being studied and, thus, it could not be included as an endpoint of therapy. Dr. Werman: Several other points concerning the design of these studies should also be mentioned. Many of the studies, which were conducted in teaching institutions, had several residents and interns administering therapy, making decisions on disposi-
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tion, and recording clinical observations. This introduces two concerns. First, one might argue that at this level of training, decisions on admission and discharge may not be valid based solely on the inexperience of the observer. Observations on the severity of subjective parameters such as wheezing, accessory muscle use, and dyspnea are likewise suspect. Additionally, even if the level of experience was excluded, the fact that so many persons were making observations in the studies makes the results highly variable. In the Fischl study, as many as 30% of the patients had at least two physicians administering the therapy during the course of their visit to the emergency department. Dr. Davis: The importance of including complete demographic information in the results section of the study was also stressed several times in the discussion. This enables the reader to generalize the results of the study to the group of patients typically seen in the reader’s practice. In addition, in several of these studies, it enabled us to identify factors that may have affected the study results. For studies on asthmatic patients, these data should include age, sex, current medications, history of previous attacks, need for prior hospitalization for asthma, current medications, use of steroids in the past or at present, intrinsic or extrinsic causes, and length of the present attack. One other point mentioned that makes these studies difficult to compare was the variability in the treatment protocols and the duration of therapy. As suggested in the Kelsen article, the length of treatment is a major determinant of the prognosis for an asthmatic patient. Thus, some studies may be criticized for an inadequate or incomplete period of treatment for the study participants. Dr. Trhlik: The findings of these studies apply to a very specific population, pure asthmatics ages 15-45 years. Two important populations have not been included in our discussions. First are pediatric patients with asthma. Because asthma is primarily a disease of childhood, these discussions are not applicable to the majority of asthmatics. As these patients are less likely to be cooperative in performing pulmonary function tests, a greater reliance on clinical variables is needed in assessing pediatric patients. Patients with a large bronchospastic component of their chronic obstructive pulmonary disease have also not been discussed. This consititutes a large number of patients seen in our emergency department. The role of arterial blood gas measurement and pulmonary function testing has yet to be elucidated in these patients. One of the factors that I place a great emphasis on is the use of steroids in asthmatic patients. To me, this indicates a patient with significant disease, and my threshold for admitting these patients is low. Another 96
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parameter that I consider is the speech pattern in these individuals. If there is any derangement such as whispering or frequent pauses because the patient needs to “catch his breath,” I am very likely to admit these patients unless they respond dramatically. Having been trained in the care of asthmatics several years ago, I personally still rely on arterial blood gas analysis in these individuals. I consider the pattent’s P,,, in making clinical decisions. A Pco, of 40 mm Hg or more in a patient that is experiencing severe bronchospasm also lowers the admission threshold I use. Dr. Kidwell: I have found from personal experience and from studies such as those cited that the PEFR is the most useful means of following the course in an acute asthmatic episode. I consider a PEFR of less than 200 l/min to indicate a severe attack. I also restrict arterial blood gas samples to patients with PEFR of less than 100 Urnin. These are rough guidelines, and as Dr. Smith pointed out, to be more accurate, these values should be normalized for the age and height of the patient. In making a final disposition, I use many of the parameters of the Fischl index, as well as some other criteria that have already been discussed. Again, I consider the results of the patient’s pulmonary-function testing as the most important factor. Generally, a PEFR of more than 300 I/min or at least a doubling of the initial PEFR from when*the patient first presented is preferable. I also use the patient’s subjective assessment of the acute attack in making a final decision. While a subjective feeling of improvement does not always assure me that the asthma has improved, I am more cautious with patients who still feel dyspneic after therapy. Dr. Bullock: I have also found that 1 rely more heavily on the results of pulmonary-function tests to monitor the course of acute asthmatic episodes seen in the emergency department. I have also reserved the use of arterial blood gas determinations for those patients who do not improve after intensive therapy. As an emergency physician, I remain concerned about the group likely to relapse after treatment for asthma. I think that we can conclude from these discussions that more work is needed to define this group of patients better. Certainly, some of the discussions have enabled me to identify several risk factors for treatment failure. A careful history must be obtained from patients regarding precipating factors for asthmatic attacks. If these can be identified, care must be taken not to discharge the patient to the same environment that caused the original symptoms. In addition, clear instructions must be given to the patient regarding any discharge medications. The physician must be certain that the patient understands exactly how the medications are to be taken, as well as the potential side effects.
Medicine
Journal Club: Assessment of the Acute Asthmatic HOWARD A. WERMAN,
MD, FRANK BIRINYI, MD, DOUGLAS A. RUND, MD
Ohio State University Use of peak expiratory flow rates to eliminate unnecessary arterial
blood gases in acute asthma.
Martin TG, Elenbaas RM, Pingleton SH. Ann Emer Med 1982;11:70-73.
Dr. Birinyi: This study tried to address two specific questions. First, the authors attempted to establish the relationship between the peak expiratory flow rate (PEFR) and arterial blood gas (ABG) measurements in asthmatic patients 15-39 years of age. The authors also considered the use of PEFR as a screening tool to identify asthmatics in whom ABG results would be severely abnormal. A prospective study was conducted in asthmatics presenting with an acute episode of airway obstruction. Prior to the initiation of therapy, an arterial blood gas sample was drawn and a peak expiratory flow rate was determined for each patient. The peak flow rate was then normalized for age, sex, and height and expressed as a percentage of normal value. This value was compared with the pH, PC,, and PO,, which were determined by blood gas analysis. The authors found small but statistically significant Pearson coefficients for the graphs of PEFR against pH, PcoZ, and Po,. When only asthmatics with PEFR values < 40% of normal were considered, these relationships became stronger. Most importantly, no asthmatic with a PEFR value of more than 25% of normal had a pH < 7.35 or a P,,, < 45 mm Hg. Only two patients with PEFR value > 25% of normal were found to be hypoxic (Po, < 60 mm Hg). The authors conclude that the PEFR can be used as a screening tool to determine which patients should have ABG measurements made. This study can be criticized for a number of reasons. Selection bias may be introduced because of the time period of the study. Patients were enrolled only during the months of August and September. This may have led to the inclusion of a large percentage of patients in whom an allergic component played a major role in
Address reprint requests to Dr. Rund: Division of Emergency Medicine, Rhodes Hall, University Hospitals, 450 W. 10th Avenue, Columbus, OH 43210-1228.
College
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their asthmatic attacks. This is important because these patients tend to have less severe disease, and their episodes of asthma are more easily reversed. Because the sample is skewed towards less severe disease, the true relationship between PEFR and ABG derangements may be obscured. This is compounded by the fact that although there are 89 observations in the study, this actually reflects only 51 patients. Finally, although some demographic data are presented on these patients, some important data are omitted. Information such as steroid use, previous hospitalizations for asthma, other asthmatic medications, and the presence of fever were not mentioned in the discussion. Thus, the ability to compare these data with other populations of asthmatics is limited. Dr. Thomas Bullock: Although the authors of this article are correct in stating that arterial blood gases are the most reliable measure of gas exchange, the major derangement in acute asthmatic attacks appears to be airway obstruction. The question thus becomes one of which is a better method of assessing the severity of an acute attack (PEFR or ABGs). This issue is never addressed in this study. From the tone of the article, it seems that the authors think that ABG measurements are an accurate method of determining the severity of asthma. This has been disputed by other studies. Arterial blood gases and pulmonary function testing in acute bronchial asthma: Predicting patient outcomes. Nowak RM, Tomlanovich MC, Sarkar DD, Kvale PA, An-
derson JA. JAMA 1983;249:2043-2046. Dr. Taylor: This study was undertaken to assess the value of pre-treatment and post-treatment arterial blood gas and pulmonary function tests in predicting the outcome of acute asthmatic attacks. The authors also attempted to establish guidelines for pulmonary function tests that would eliminate unnecessary arterial blood gas determinations. Asthmatics 16-40 years old who visited the emergency department (when one of the investigators was present) were enrolled in the study. Peak expiratory flow rate and forced expiratory volume in one second 89
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(FEV,) were measured, and arterial blood gas samples were drawn. After therapy with terbutaline (0.25 mg subcutaneously) and in some cases aminophylline (5.6 mg/kg), the measurements were repeated. Further therapy was administered, and the patient was either admitted to the hospital or discharged, depending on the clinical course. Discharged patients were contacted after 48 hours. Those patients who experienced continued difficulty with their asthma or who were seen in an emergency department during this time were considered to have relapsed. Thus, three groups of patients were defined: admitted patients, patients who were discharged and subsequently relapsed and those who were discharged without further difficulty. The authors found a mean age of 25.1 years among their patients and a mean duration of treatment of 4.8 hours. Among the pre-treatment values for the arterial blood gases and pulmonary function tests, no significant difference was found between the pH, Pco2, and Po, for the three groups. On the other hand, pulmonary function tests were able to distinguish the admitted patients and the patients who experienced relapse from the successfully treated group. The same findings were seen for post-treatment values in which the predictive value of pulmonary function tests was confirmed. Similarly to the previous study, there was a poor coorelation between the normalized FEV, values and the Po,. Also, the Po, and PcoZ measurements were not well correlated with the absolute FEV,. Finally, the authors found that a PEFR < 30% of predicted normal value and a FEV, < 25% of predicted normal value identified all cases of hypercarbia and hypoxia. The study is important in that it confirms the findings of the previous paper. These authors confirm that there is a poor correlation between pulmonary function testing and arterial blood gas determinations for acute asthmatic episodes. As an example, the authors point out that in a significant number of cases hypoxia worsened despite an improvement in pulmonary function measurements. Additionally, these authors found threshold values for pulmonary function measurements that identified all cases of hypoxia and hypercarbia in asthmatic patients. Specifically, once the patient had an FEV, above 1 1 or a PEFR above 200 l/ min, blood gas analysis was unnecessary. More importantly, these authors described the utility of arterial blood gas measurements and pulmonary function tests in predicting patient outcomes. The findings of this study demonstrate that pulmonary function tests are useful in separating those patients who will require admission or experience a relapse following discharge from those patients who will be successfully treated in the emergency department. Arterial blood gas measurements were not useful in this regard. 90
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Dr. Rund: Although the study is important in demonstrating the importance of pulmonary function tests in the assessment of the severity of asthma, there are several flaws. As in the previous study, the demographic data for the study population are scant. This again limits the comparison of this study population with the population seen by other emergency physicians. Additionally, the treatment in each case was not uniform for the study population. Initially, each asthmatic received terbutaline (0.25 mg subcataneously), but beyond that, there was no standardization of therapy. The mean duration of therapy of 4.8 hours is significantly less than that reported in other studies. The contribution of these factors to the differences among the three groups is unknown. Another point that will be reiterated in many of the subsequent studies is the subjective nature of the admission criteria. In most cases, clinical criteria were used. This is ambiguous, as the exact criteria are not specified. Also, numerous studies have documented the failure of clinical parameters such as wheezing, dypsnea, and tachypnea in reflecting the severity of asthma. The authors also indicate that in some cases, the FEV, was used to decide whether the patient was to be admitted. Obviously. this introduces bias in the results, as the factor under study is actually used to separate the three groups. Failure of peak expiratory flow rate to predict hospital admission in acute asthma. Martin TG, Elenbaas RM, Pingleton SH. Ann Emerg Med 1982;11:466-470.
Dr. Howard Bernstein: The authors of this prospective study attempted to assess the value of PEFR measurements as predictors of the need for hospitalization in acute asthmatic attacks. Asthmatics between the ages of 15 and 39 years who were experiencing acute attacks were enrolled in the study. The PEFR was measured prior to therapy. and treatment was initiated according to a standard protocol that included epinephrine, aminophylline, isoetharine, and corticosteroids where necessary. A second PEFR measurement was made after the first epinephrine treatment. The results of these measurements were blinded from the physician or nurse making these determinations. Patients were admitted to the hospital if 1) pre-treatment arterial blood gas measurements showed a pH < 7.20. a PC02 > 45 mm Hg, or a Pao, < 50 mm Hg; 2) dyspnea or wheezing was not improved by therapy; 3) complications such as pneumonia, pneumothorax, or pulmonary infiltrates were seen on chest radiograph; or 4) the patient visited the emergency department three times within a seven-day period. The PEFR before and after the first epinephrine dose, as well as the change in PEFR, were analyzed to determine the ability of
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these parameters to predict the need for hospitalization. The results were based on 86 visits by 51 patients. Only 10.5% of the patient visits resulted in hospital admissions. The authors found a statistically significant difference in the initial PEFR, post-treatment PEFR, and the change in PEFR after therapy between the admitted and discharged patients. They indicate, however, that despite this difference, there was too much overlap between these measurements to be clinically useful. The authors did find that no admitted patient had an initial PEFR > 30% of normal value or a change in PEFR of less than 20%. Additionally, the authors compared the data for patients who were discharged without further problems with that of patients who were seen within 48 hours. No statistically significant difference was seen between these two groups. The authors conclude that the single measurement of PEFR before or after treatment with epinephrine or measurement of the change in PEFR are neither sensitive nor specific enough to screen patients who will eventually require hospital admission. Those patients with a PEFR > 30% of normal value initially or a change in PEFR of more than 20% after therapy will not require hospital admission. There are several problems with this study. We have already commented on the lack of demographic data presented, limiting the ability to generalize the results of the study. In addition, the reader is not informed as to who is making the determination of clinical improvement. The level of training of individuals assessing the clinical status of the patients is an important piece of information that is not clearly presented in this study. Additionally, the time period over which the study was conducted could introduce some bias into the patient selection. It should also be pointed out that some patients were seen who had previously been treated by the authors. Although a second visit is not specifically listed as a criteria for admission, it is more likely that these patients would be admitted after their second visit. This again introduces some bias into the study results, as derangements in their pulmonary-function studies may not accurately reflect their being included in the admission group. Dr. Wet-man: Regarding the admission criteria cited
in this study, the results of the prior two studies have demonstrated that the correlation between arterial blood gas measurements and pulmonary-function tests is very poor. Thus, PEFR measurements would not be expected to predict which patients would be admitted on the basis of arterial blood gas measurements. In considering the patient with complications such as pneumonia or pneumothorax, I am unaware of any evidence that suggests that pulmonary-function tests
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are useful in predicting the need for admission of these patients. The fourth criteria of three emergency department visits in seven days was excluded from the analysis. Thus, the only valid criteria that are assessed in this study are the very subjective measures of improvement in dyspnea and reduction in wheezing. We have already discussed the validity of such criteria in predicting patient outcome. Dr. Rund: This last point raises a crucial issue regarding such studies on asthmatic patients in an emergency department. The question must be raised as to whether the use of clinical parameters such as dyspnea and wheezing represent the best criteria for determining the need for hospital admission. These criteria were utilized in this and the previous study. However, considering that the pathophysiology of asthma involves large and small airway obstruction, it would appear that assessment of FEV, or PEFR would be the best index of the need for hospitalization in the asthmatic. After all, these objective measures most accurately reflect the severity of the obstructive process. In other studies, the degree of dyspnea and the severity of wheezing have not been shown to correlate with the severity of asthma. In addition, small changes in these pulmonary parameters have been shown to result in dramatic improvements in clinical signs and symptoms of asthma. Thus, improvement in dyspnea or wheezing may not correlate with objective improvement in the acute asthmatic attack. Therefore, the reader must question the conclusions of any study that uses only subjective clinical criteria to define the need for hospitalization. Emergency room assessment and treatment of patients with acute asthma: Adequacy of conventional therapy. Kelsen SC, Kelsen DP, Fleegler BF, Jones RC, Rodman T. Am J Med 1978:64:622-628. Dr. Eric Davis: The authors of this article attempted to assess the adequacy of emergency department treatment for acute asthmatic attacks. Specifically, the authors intended to determine the improvement in airway obstruction measured spirometrically, the short-term outcome for these patients, and the relationship of subsequent clinical course to the degree of residual obstruction. Uncomplicated asthmatic patients who were experiencing an acute exacerbation were included in the study. Prior to therapy, a history, physical examination, and laboratory collection were performed. The laboratory data included an FEV, and arterial blood gases. Subsequent therapy included subcutaneous epinephrine, aminophylline, aerosolized bronchodilators, oxygen, and hydration according to a specified treatment protocol. Patients were assessed at one, three, and six hours after initiation of treatment and were admitted if they failed to meet the clinical criteria de91
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fined by the authors. These criteria included improvement in dyspnea, unlabored breathing, and marked reduction in wheezing. The authors studied 127 emergency department visits for 102 patients. Of the patient visits, 14.6% eventually resulted in hospitalization. A significant difference was seen between the admitted and discharged patients in the FEV, measurements. For the discharged group, the mean FEV, was 1.767 -+- 94 ml which was only 57% of the predicted normal value. Of this group, 26% experienced a relapse, which was defined as a visit to the emergency department for further care, and 6% of these patients required hospitalization. Although there was no significant difference in FEV, measurements between the group that was discharged without complications and the group that experienced a relapse, a significant difference existed in the FEV, measurements at the end of treatment. In particular, an increase in the FEV, measurement of less than 400 ml after therapy was shown to be highly predictive of relapse when compared with increases of more than 400 ml. Further analysis revealed that this difference could be explained by the greater duration of therapy in the group without complications. The average duration of therapy was 3.5 hours as compared with 1.5 hours in the group that eventually experienced a clinical relapse. In trying to correlate the physical findings and historical information to the severity of asthma, the authors were only able to find a relationship for pulsus paradoxicus and sternomastoid muscle retraction with severe disease. However, even in cases involving severe obstruction, these signs were generally absent. Arterial blood gas measurements again correlated poorly with the severity as assessed by spirometry. These authors conclude that clinical signs and symptoms are poor predictors of the patients’ ability to be discharged from the emergency department without complications. When this information alone is used to assess the response to therapy, the mean FEV, indicates. that airway function of discharged patients is still markedly abnormal at only 57% of the predicted normal value. Using this criterion, a significant number of patients were found to require a return visit for treatment of their asthma within ten days. In this study, the duration of therapy appeared to be the major factor in preventing a relapse in discharged patients. These authors are to be commended for their recognition of pulmonary function tests as an important endpoint in the assessment of the severity of asthma. However, there are some important flaws in the study design. First, the clinical decisions appear to have been made by a variety of observers, most of them in their first year of medical training. In addition, there is no description of the method of measuring the FEV, 92
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values. Were three measurements made? Was the best of these measurements used, or were they averaged? Was the patient upright or sitting? Finally, it is not stated that the observers were blinded to the results of the FEV, measurements. This is important, because if the observers were not blinded, it is possible that the results of these determinations could have influenced the decision to admit asthmatic patients. Dr. Kerldel Kidwell: The authors of this article have made an important conclusion regarding the assessment of the asthmatic patient. They point to the importance of spirometric measurements as the crucial endpoint in evaluating the response to therapy. This article clearly shows how in using clinical signs and symptoms alone as means of assessing the patient. asthmatics may be discharged from the emergency department with severe residual pulmonary dysfunction. This increases the risk of relapse in these patients. These authors have also shown that the major factor in determining the chance of relapse in an asthmatic patient appears to be the length of time that the patient receives treatment. In their series, there was a twohour difference in the mean duration of treatment for patients discharged without complications as compared with those who required further emergency department visits. Clearly, some of this difference could be explained by the different threshold that various physicians have for discharging patients with acute asthmatic episodes. However, it also points to the importance of an adequate period of intensive medical management for episodes of acute asthma in preventing further exacerbation. Dr. Rund: Many of the studies of the assessment of asthmatic patients in the emergency department have attempted to identify patients who will suffer a relapse of their disease and require further therapy. For an emergency physician, identification of these patients is considered crucial. As suggested by this article, relapses may be preventable with more prolonged initial therapy. From a risk-management perspective, patients who are discharged after being treated in the emergency department eventually to require further therapy are of special concern to the emergency physician. First, it must be realized that this population of patients can never be completely identified. This is because there are a number of factors that are unrelated to the pulmonary-function status of the patient after therapy that contribute to relapse of the disease. These factors include a return to environmental conditions known to provoke attacks and noncompliance with prescribed treatment. In addition, further information is needed regarding the clinical outcomes of this group of patients. In this study, the initial group of patients studied had an admission rate of 14.6%. Some patients had respiratory
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failure, and one death was recorded., In contrast, the relapse group had an admission rate of only 6%. No deaths were recorded, and no patients had respiratory failure. Thus, among the patients seen in this study, the vast majority who required a second emergency department visit were discharged after further therapy; no significant complications were seen. In this case, the risks of initially discharging a patient who will require a second emergency department visit must be weighed against the risk of unnecessarily hospitalizing these patients when first seen. Dr. Werman: Little information is provided by the authors on how follow-up of these patients was conducted. The percentage of patients for whom followup was accurately determined for the ten-day period is not mentioned. This is important, because without very careful follow-up procedures, it is possible that a serious complication or death may have been missed if other institutions checked.
and the coroner’s
office were not
An index predicting relapse and need for hospitalization in patients with acute bronchial asthma. Fischl MA, Pitchenik A, Gardner LB. N Engl J Med 1981;305:783-789. Dr. Murk Smith: In response to the long treatment times for acutely asthmatic patients treated in the emergency department and to the high rate of relapse in these patients, the authors of this article have attempted to develop a predictive index that could be used to determine the need for admission among acute asthmatics early in the course of therapy. Using this index early in the course of therapy could potentially prevent prolonged stays in the emergency department. This index might also be applied to determine patients at risk for a relapse of their asthma. Asthmatics ages 15-45 years were included in the study. Prior to therapy, a brief history, physical examination, and laboratory tests were performed by the house officer. Laboratory data included an arterial blood gas sample and PEFR measurement. Patients were then treated according to a standard protocol that included subcutaneous epinephrine, terbutaline, aeroxolized isoetharine, aminophylline, hydrocortisone, and intravenous hydration. Further assessments were made by the house officer hourly. A disposition was made after 8-12 hours of therapy. Patients were discharged if they were no longer dyspneic, their wheezing was resolved, and accessory muscle retractions were absent. Follow-up data were obtained on all discharged patients except for ten patients. These patients were excluded from analysis. Once the data were collected, they were analyzed to determine which elements of the history, physical examination, and laboratory data were useful in predicting the need for admission and the risk of relapse. Finally, a predictive index was developed by deter-
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mining the cutoff point for each factor that mathematically maximized the predictive value for ihe significant variables. A total of 205 patients were studied. Of these, 22% were initially admitted and 20% were discharged and returned for further therapy. During subsequent emergency department visits, the average duration of therapy was longer than in the initial visit, and 83% of the patients required admission. Seven of the 14 factors analyzed were found statistically to significantly predict patient outcome. No single factor was consistently predictive of admission or relapse. A multifactorial predictor index was developed using the seven factors that were determined previously. A score of “0” or “1” was assigned to each variable. These variables included a pulse rate > 1201 min, a respiratory rate > 30/min, pulsus paradoxicus > 18mm Hg, PEFR < 120 l/min, moderate to severe dyspnea, moderate to severe accesory muscle use, and moderate to severe wheezing. A statistically significant difference was seen between the relapse and admitted groups when compared with the successfully treated group of initial presentation. When the index was applied to the relapse and admitted groups, more than 95% had scores of 4 or greater. This was true for only 3% of the successfully treated group. Although a statistically significant difference was found between the relapse and admitted groups when compared with the successfully treated group at one hour of therapy, there was significant overlap of the predictive index scores. Therefore, the predictive index applied at one hour was not considered useful. The authors concluded that application of the predictive index prior to therapy could be a potentially useful tool to determine the need for hospitalization and the risk of relapse in acute asthmatic episodes. Because no single factor, including PEFR, was predic’tive of relapse or admission, a multivariate approach was needed. The authors of this study have taken an interesting approach towards the assessment of the acute asthmatic. There is no question that the development of a predictive index that could be applied during the early stages of treatment and would accurately determine the need for hospitalization would be quite useful. This study addresses an important issue that has not been mentioned in our previous discussions. The duration of therapy for many asthmatics in the studies described has been as long as 12 hours. In most emergency departments, allowing a patient to occupy a bed for this period of time is not only impractical in terms of patient flow, but is also quite costly. In some cases, it may be less expensive to hospitalize these patients for a day. An early predictive index would eliminate these lengthy visits. In reviewing this study, one sees many potential 93
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problems. The first problem lies in the number of observers who are involved in assessing the patients. This study utilizes medical house officers. This presents at least two problems. Because of the usual rotating schedule of house officers, a large number of physicians are making observations and disposition determinations over the course of the study. In fact, the authors point out that 30% of the 205 patients were seen by at least two physicians during their emergency department visit. In addition, the level of training is not clearly stated in the paper. There would be a greater confidence in the medical judgements of senior-level house officers than in those of interns. This study also uses very subjective discharge criteria that include improvement of dyspnea and wheezing, which have not been shown to correlate with the severity of asthma. It was clear that historical and physical examination data were recorded according to a written protocol. Although this does insure more complete records, it also introduces a potential bias into the study. It is known that the behavior of both subjects and observers is influenced by the knowledge that they are participating in a study. Finally, it must be stated that this study includes data from the initial patient visits. Thus, the predictive index cannot be assumed to apply to the visits of patients experiencing a relapse. Dr. Kidwell: With regard to this last point, it is important that these studies should specifically exclude return visits for relapsed patients. In this study, the admission rate for relapsed patients is 83%. This contrasts sharply with the admission rate of 6% reported in the last study discussed. This can be interpreted to imply a tremendous bias at this institution to admit patients who return to the emergency department after recent treatment for acute bronchial asthma. The threshold for considering these patients as clinically improved appears to be much higher in these relapsed patients. One can see how these patients, if utilized to develop a predictive index, would invalidate the results of the study. It is also interesting that these authors found a weak but statistically significant association between arterial blood gas measurements and PEFR determinations. This was not seen in other studies that we have discussed. This study showed a statistically significant difference in the severity of arterial blood gas derangements between the admitted and relapsed groups. This is in contradistinction to the findings of Nowak et al that were discussed previously. Despite the findings of other studies, these authors recommend the use of arterial blood gas measurements in the treatment of acute asthmatic attacks. Dr. Nuncy Trhfik: One must be leary of the results of this study, because it is concluded that a predictive index as determined at initial presentation is more reliable than one determined an hour after treatment.
1986
This goes against the clinical experience of many emergency physicians who have successfully treated and discharged many asthmatics from the emergency department that initially presented with a severe asthmatic attack. By the same token, there are other asthmatics who present with only moderate distress but do not improve clinically or spirometrically with treatment. Thus, intuition alone tells us that the validity of a pre-treatment index is questionable. In addition, one must consider the findings of both Kelsen et al and Nowak et al, which showed that the major factor in determining the patient outcome was the reversibility of the asthmatic attack. Both studies concluded that some measures of the patient status determined after initiation of therapy were necessary to predict the need for hospital admission. The authors of this study should have been concerned about the validity of their results when they did not reflect the findings of other authors.
Performance of an index predicting the response of patients with acute bronchial asthma to intensive emergency department treatment. Rose CC, Murphy JG, Schwartz JS.
N Engl J Med 1984;310:573-577. Dr. Cheryl Lee: This study was done as a follow-up to the previous study. The authors attempted to determine the validity of the predictive index, which was applied in a prospective fashion. Asthmatics ages 1445 years who presented to the emergency department with an acute asthmatic attack were enrolled in the study. Historical information and physical examination data obtained were similar to those in the previous study. Laboratory information included arterial blood gas measurements, serum theophylline levels, leukocyte and differential counts, and a chest radiograph. Treatment was initiated according to the protocol of the previous article but was modified at the discretion of the treating physician. Patients were discharged when dyspnea, wheezing, and accesory muscle retractions were absent. Follow-up of patients was done by telephone ten days after the initial visit. Relapse was defined as a return visit to the emergency department or an unscheduled visit to a physician’s office. The data were analyzed to determine whether any difference existed among any of the outcome groups with respect to the predictive index. The data were also examined to determine the degree of association of the variables of the predictive index and other information with the clinical outcome. A total of 107 visits for 86 patients were included in the analysis. Of these patients, 72% were female, 91% were black, and 44% had a history of steroid use. The distribution of patients in the admitted (14%), relapsed (21%), and successfully treated groups (65%) were similar to those in the previous studies discussed. The major finding of the study was that when a cutoff of
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greater than or equal to 4 for the predictive index was used, as suggested in the previous report, the specificity was 0.71, the sensitivity was 0.40, and the positive predictive value was 0.43. The index performed better on the subset of patients who presented with a productive cough and fever or who used steroids on the day of the emergency department visit. Two variables, steroid use and theophylline use on the day of the visit, were more highly predictive of clinical outcome than any factors used in the predictive index. The authors conclude that while the defined predictive index did correlate with the need for hospitalization, the association was not strong enough to be clinically useful. Although there were many criticisms of the previous article, one must be careful not to reject the findings of that study on the basis of this report alone, because there are many important differences between the two reports. One important difference lies in the patient population. Unfortunately, as was previously stated, the demographic data are not well presented in the prior study, so no valid comparison can be made. Such information as steroid use, outpatient medications, duration of symptoms, and recent previous attacks would be important information used to compare the two patient populations. Another difference is that the authors of this article included 21 patients who had returned to the emergency department following an earlier visit. As was mentioned in our previous discussion, the first article addressed only initial visits for acute asthma. Finally, in the article by Fischl, a strict treatment protocol was specified in the care of the acute episode. In the present series, the treatment could be modified at the discretion of the treating physician. One could argue that in this series, the clinical outcomes of hospitalization and relapse might reflect inadequate therapy rather than the patients’ initial clinical presentation as in the Fischl study. Dr. Bullock: One of the major criticisms of the previous study was the concern about the reproducibility of observations for subjective variables as dyspnea, wheezing, and accessory muscle use. The results of this study demonstrate the legitimacy of this concern. When multiple observations were made in this study on these three subjective variables, no statistically significant differences were found among the three outcome groups. Dr. Rund: We have previously discussed the significance of the group of patients who “relapse” and require a subsequent visit to the emergency department. One notable difference between this study and the previous study is the rate of admission for relapsed patients. In this study, 14% of relapsed patients required hospital admission. This is consistent with the findings of Kelsen and contrasts with the 83% rate in the previous study. One of these patients required admission to the intensive care unit. Thus, significant
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complications are possible in the relapsed group, and these patients should be approached with caution. On the other hand, careful examination reveals that the PEFR and the medications prescribed were not different for the patients who were successfully discharged and those who experienced a relapse of their disease. This implies that other factors, such as noncompliance with medication or return to precipitating allergen, may have been important in causing a relapse. From this perspective, relapse may have been unavoidable in these patients. Dr. Smith: Although it is tempting to ignore the results of the Fischl study based on the findings of this last study, one must recognize some value in the original study. If one considers the seven criteria used to determine the index, one realizes that all of these parameters are used by clinicians to assess the asthmatic patient in the emergency department. However, unlike the index, most of us do not place equal importance on each of these parameters. Personally, as suggested in several initial studies, I place a great deal of reliance on spirometric measurements such as the PEFR in assessing these patients. (These values should be normalized for height and age using the table provided by the manufacturer. This allows more accurate assessment of individual patients). Additionally, I include other factors in my personal ‘index’ such as steroid dependence, use of bronchodilators on the day of the emergency visit, history of recent attacks, and presence or absence of fever. All of these factor are a part of my decision to admit or discharge an asthmatic patient . Dr. Rund: In reviewing all of these studies, we have identified several important flaws in the study design that are present in many of these studies. The most important dilemma is the inexact nature of the outcome criteria used in most of these studies. Usually, the study endpoint was admission or discharge of the asthmatic patient. Unfortunately, the criteria for discharge most often included the absence of wheezing, the lack of accessory muscle retractions, and improvement in the patient’s dyspnea. The problem lies not only in the subjective nature of these criteria but also in the fact that these clinical parameters have not been shown to correlate with the severity of asthma. Sternocleidomastoid retractions, although more indicative of severe asthma, were still absent in the majority of significant episodes of asthma in the Kelsen study. The fact that the most accurate measure of severity in these cases is pulmonary function is a dilemma. In most of these studies, this was the parameter being studied and, thus, it could not be included as an endpoint of therapy. Dr. Werman: Several other points concerning the design of these studies should also be mentioned. Many of the studies, which were conducted in teaching institutions, had several residents and interns administering therapy, making decisions on disposi-
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tion, and recording clinical observations. This introduces two concerns. First, one might argue that at this level of training, decisions on admission and discharge may not be valid based solely on the inexperience of the observer. Observations on the severity of subjective parameters such as wheezing, accessory muscle use, and dyspnea are likewise suspect. Additionally, even if the level of experience was excluded, the fact that so many persons were making observations in the studies makes the results highly variable. In the Fischl study, as many as 30% of the patients had at least two physicians administering the therapy during the course of their visit to the emergency department. Dr. Davis: The importance of including complete demographic information in the results section of the study was also stressed several times in the discussion. This enables the reader to generalize the results of the study to the group of patients typically seen in the reader’s practice. In addition, in several of these studies, it enabled us to identify factors that may have affected the study results. For studies on asthmatic patients, these data should include age, sex, current medications, history of previous attacks, need for prior hospitalization for asthma, current medications, use of steroids in the past or at present, intrinsic or extrinsic causes, and length of the present attack. One other point mentioned that makes these studies difficult to compare was the variability in the treatment protocols and the duration of therapy. As suggested in the Kelsen article, the length of treatment is a major determinant of the prognosis for an asthmatic patient. Thus, some studies may be criticized for an inadequate or incomplete period of treatment for the study participants. Dr. Trhlik: The findings of these studies apply to a very specific population, pure asthmatics ages 15-45 years. Two important populations have not been included in our discussions. First are pediatric patients with asthma. Because asthma is primarily a disease of childhood, these discussions are not applicable to the majority of asthmatics. As these patients are less likely to be cooperative in performing pulmonary function tests, a greater reliance on clinical variables is needed in assessing pediatric patients. Patients with a large bronchospastic component of their chronic obstructive pulmonary disease have also not been discussed. This consititutes a large number of patients seen in our emergency department. The role of arterial blood gas measurement and pulmonary function testing has yet to be elucidated in these patients. One of the factors that I place a great emphasis on is the use of steroids in asthmatic patients. To me, this indicates a patient with significant disease, and my threshold for admitting these patients is low. Another 96
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parameter that I consider is the speech pattern in these individuals. If there is any derangement such as whispering or frequent pauses because the patient needs to “catch his breath,” I am very likely to admit these patients unless they respond dramatically. Having been trained in the care of asthmatics several years ago, I personally still rely on arterial blood gas analysis in these individuals. I consider the pattent’s P,,, in making clinical decisions. A Pco, of 40 mm Hg or more in a patient that is experiencing severe bronchospasm also lowers the admission threshold I use. Dr. Kidwell: I have found from personal experience and from studies such as those cited that the PEFR is the most useful means of following the course in an acute asthmatic episode. I consider a PEFR of less than 200 l/min to indicate a severe attack. I also restrict arterial blood gas samples to patients with PEFR of less than 100 Urnin. These are rough guidelines, and as Dr. Smith pointed out, to be more accurate, these values should be normalized for the age and height of the patient. In making a final disposition, I use many of the parameters of the Fischl index, as well as some other criteria that have already been discussed. Again, I consider the results of the patient’s pulmonary-function testing as the most important factor. Generally, a PEFR of more than 300 I/min or at least a doubling of the initial PEFR from when*the patient first presented is preferable. I also use the patient’s subjective assessment of the acute attack in making a final decision. While a subjective feeling of improvement does not always assure me that the asthma has improved, I am more cautious with patients who still feel dyspneic after therapy. Dr. Bullock: I have also found that 1 rely more heavily on the results of pulmonary-function tests to monitor the course of acute asthmatic episodes seen in the emergency department. I have also reserved the use of arterial blood gas determinations for those patients who do not improve after intensive therapy. As an emergency physician, I remain concerned about the group likely to relapse after treatment for asthma. I think that we can conclude from these discussions that more work is needed to define this group of patients better. Certainly, some of the discussions have enabled me to identify several risk factors for treatment failure. A careful history must be obtained from patients regarding precipating factors for asthmatic attacks. If these can be identified, care must be taken not to discharge the patient to the same environment that caused the original symptoms. In addition, clear instructions must be given to the patient regarding any discharge medications. The physician must be certain that the patient understands exactly how the medications are to be taken, as well as the potential side effects.