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ICD Code: 493. Asthma



ICD Code: 493. Article Review
Title: McFadden ER; "Acute Severe Asthma." American Journal of Respiratory and Critical Care Medicine; V.168; 2003; p740
      DEFINING SEVERITY: Asthma "severity" has not yet been quantified with great precision. Part of the difficulty is that, unlike other illness, asthma severity is not defined solely as the extent of impairment in organ function. Rather, the definition consists of an arbitrary combination of the signs and symptoms present and the intensity of the cardiorespiratory abnormalities observed.
      MEASURES OF SEVERITY: The incidence and prevalence of severe episodes of asthma are unknown and vary as a function of the definition employed. On the basis of the most recent information from the National Center for Health Statistics on the incidence of acute episodes and admissions, and assuming that hospitalization is a perfect surrogate, 4% of the attacks nationally and 21% of all episodes treated in urgent care centers would be considered severe. Intensive care admissions range from 2% to 20%, the presence of hypercarbia varies from 10% to 63%, and intubation and respiratory support fluctuates between 2% and 70%.
      RECOVERY AND PERSISTENCE: Most asthma attacks are short-lived and clear with removal of the offending agent, but outside of laboratory provocations, there are no systematic data on spontaneous recovery. There is no consistent relationship between the duration of an attack and the physiological changes that ensue, and patients with apparently similar degrees of impairment can recover at different rates. Such observations suggest that undefined qualitative or quantitative differences in pathophysiology may exist depending on the initiating event.
      The reason people develop persistent complaints that bring them to medical attention is not clear. One tends to think of the immediate development and progression of symptoms, but such events are relatively infrequent; in large cohorts, only 13% to 14% of people describe complaints that were less than 3 hours in duration. Instead, symptoms are often present for days to weeks and patients tend to seek resolution when their rescue medicines no longer work. Typically, there is a gradual increase in complaints and the use of rescue medications over 5 to 7 days before the attacks develop, followed by a more rapid rise in the immediate 2- to 3-day period.
      The pattern of recovery after acute decompensations is bimodal. The majority clear within 1 to 2 hours with protocol treatment. Termination after ad hoc regimens is considerably longer. Of those sent home after directed care, about 3% return to the emergency department (ED) within 24 hours because of relapses and 7% return within 1 week. In studies using noncare path ED regimens, recurrences over the next 1 to 2 weeks vary between 15% and 17%. There are no differences in relapses as a function of the speed of onset of symptoms.
      TREATMENT RESPONSE: About one-fifth to one-third of ED patients have poor short-term responses to albuterol and require admission to the hospital. The initial peak expiratory flow rate (PEFR) of one group was 32% of predicted and rose to 41% after large doses of bronchodilators and steroids. After receiving additional intravenous glucocorticoids, and nebulized ipratropium and albuterol every 2 hours for 12 hours in the hospital, the PEFR reached 53%. An additional 36 hours of intensive therapy was needed to reach 58% of expected. This slow pattern of resolution makes a compelling case for the need to develop better drugs and/or innovative therapeutic strategies for such individuals. Equally important, the heterogeneity of responses that exist readily points out the ease with which clinical trials can be unknowingly biased unless the participants are carefully stratified. We need to know more about what works best for the sickest patients.
      INTENSIVE CARE: One evaluation of medical intensive care unit (MICU) admissions and outcomes from 18 investigations published over the last quarter-century represented 112 years of observation in 2157 patients. In the studies, about 21 patients with asthma were admitted to the MICU per year. Excluding one of the studies, the number falls to 13 to 14 patients per year. Criteria for MICU care were rarely stated; intubation and ventilatory assistance was believed to be necessary in about one-third of admissions, but the range was extremely wide (3% to 70%). The considerations employed in making this decision were given in 40% of the publications and included exhaustion, progressive hypercapnia, unconsciousness, deterioration of mental status, cardiopulmonary arrest, or the clinical assessment of the attending physician. There was no uniformity apparent in their application. The frequency of intubation also varied considerably (range, fewer than 1 to 29 cases per year). Fatalities occurred in 2.7% of the total admissions and 8.1% of those intubated (range, 0% to 38%). Mechanical ventilation was associated with 267 complications (number per intubation, 1.3; range, 0% to 7%). Events included hypotension, pneumothorax, pneumomediastinum, atelectasis, nosocomial pneumonia, arrhythmias, sepsis, gastrointestinal bleeding, and cerebral anoxia. There were no apparent trends over time. Research is needed to determine why such variability in treatment and outcomes exists and whether it could be altered by the use of consensus criteria.
      RISK FACTORS: Morbidity and potential mortality increase in asthma with socioeconomic deprivation, ethnicity, urban dwelling, and comorbid issues such as drug abuse. In the year 2000, the ED visits and hospitalization rates were 125% and 220% higher, respectively, among black non-Hispanics compared with white non-Hispanics.
      MORTALITY: It is debatable whether the existence of asthma per se shortens longevity. The overall mortality statistics for the 20th century in the U.S. have been flat and the death rate has hovered at about 2.0 per 100,000. In the last part of the 20th century there was an upward trend and deaths rose from 1.3 to 1.9 per 100,000. Although this is a large percentage change, the absolute number is still quite small. The most recent statistics indicate that 5438 patients with asthma died out of 16 to 17 million individuals at risk. By way of comparison, the fatalities from heart disease over the same period were more than two orders of magnitude greater (729,974 deaths, or 194.6 per 100,000) and those for cancer were 99 times higher. About 5 times more people died from suicide than asthma.
      Death from acute episodes is uncommon and is reported in less than 0.1% of patients in large series. Surveys of fatalities suggest that the vast majority occur suddenly and at places such as home or work and imply that little time, or opportunity, exists to forestall the course. This is statistically true but somewhat misleading. Of the patients reported thus far, slightly less than one-half died in the hospital and in about 85% the duration of the final episode was 12 hours or more, giving more than ample opportunity for treatment. The quintessential phenotype of rapidly fatal disease is "catastrophic," "brittle," or "sudden asphyxic" asthma. This is a dramatic but rare happening. It is assumed that there are far more "near-fatal" episodes of asthma than deaths, but there are no data as to how many. Here, too, a lack of uniform diagnostic criteria impacts the statistics. Despite continuing investigative effort, the risk factors predicting fatal asthma have not yet been identified from the standpoint of specificity and selectivity.
      PROGNOSIS: Despite concerns about increasing mortality, most patients survive acute episodes. The 18 investigations cited earlier report a total of 67 deaths in 15,300 asthma attacks of sufficient severity to bring the patient to the hospital. The number of fatalities that occur in the ED is not known, but none were described in these 18 studies. About 0.11% of deaths occurred in general hospital wards and 2.4% in the MICU. Death rates rise with intubation. In addition to hospital fatalities, the articles list 32 additional deaths postdischarge. Included in this experience is a European investigation that recorded an in-hospital mortality of 16.5% followed by postdischarge fatalities of 10.1% in Year 1 and 22.6% by Year 3. The reasons for the poor prognosis in this group of patients are not known. However, such data clearly point out the need for ongoing long-term monitoring to prevent/control recurrences.

Search Criteria: Text - American Journal of Respiratory and Critical Care Medicine; V.168; 2003; p740