Status asthmaticus is severe and persistent asthma that does not respond to conventional therapy. The attacks can last longer than 24 hours. Infection, anxiety, nebulizer abuse, dehydration, in-creased adrenergic blockage, and nonspecific irritants may con-tribute to these episodes. An acute episode may be precipitated by hypersensitivity to aspirin.
The basic characteristics of asthma (constriction of the bronchi-olar smooth muscle, swelling of the bronchial mucosa, and thick-ened secretions) decrease the diameter of the bronchi and are apparent in status asthmaticus. A ventilation–perfusion abnor-mality results in hypoxemia and respiratory alkalosis initially, fol-lowed by respiratory acidosis. There is a reduced PaO2 and an initial respiratory alkalosis, with a decreased PaCO2 and an in-creased pH. As status asthmaticus worsens, the PaCO2 increases and the pH falls, reflecting respiratory acidosis.
The clinical manifestations are the same as those seen in severe asthma: labored breathing, prolonged exhalation, engorged neck veins, and wheezing. However, the extent of wheezing does not indicate the severity of the attack. As the obstruction worsens, the wheezing may disappear, and this is frequently a sign of impend-ing respiratory failure.
Pulmonary function studies are the most accurate means of as-sessing acute airway obstruction. Arterial blood gas measure-ments are obtained if the patient cannot perform pulmonary function maneuvers because of severe obstruction or fatigue, or if the patient does not respond to treatment. Respiratory alkalosis (low PaCO2) is the most common finding in patients with asthma. A rising PaCO2 (to normal levels or levels indicating respiratory acidosis) frequently is a danger sign of impending respiratory failure.
In the emergency setting, the patient is treated initially with a short-acting beta-adrenergic agonist and corticosteroids. The patient usually requires supplemental oxygen and intravenous flu-ids for hydration. Oxygen therapy is initiated to treat dyspnea, central cyanosis, and hypoxemia. Humidified oxygen by either Venturi mask or nasal catheter is administered. The flow is based on pulse oximetry or arterial blood gas values. The PaO2 is maintained at 65 to 85 mm Hg. Sedative medications are con-traindicated. If there is no response to repeated treatments, hos-pitalization is required. Other criteria indicating the need for hospitalization include poor pulmonary function test results and deteriorating blood gas levels (respiratory acidosis), which may indicate that the patient is tiring and will require mechanical ven-tilation. Although most patients do not need mechanical ventila-tion, it is used for patients in respiratory failure, for those who tire and are too fatigued by the attempt to breathe, or for those whose conditions do not respond to initial treatment.
Death from asthma is associated with several risk factors, including the following:
· Past history of sudden and severe exacerbations
· Prior endotracheal intubation for asthma
· Prior admission to the intensive care unit for an asthma exacerbation
· Two or more hospitalizations for asthma within the past year
· Three or more emergency care visits for asthma in the past year
· Excessive use of short-acting beta-adrenergic inhalers (more than two canisters per month)
· Recent withdrawal from systemic corticosteroids
· Comorbidity of cardiovascular disease or COPD
· Psychiatric disease
· Low socioeconomic status
· Urban residence (Expert Panel Report II, 1997)
The nurse constantly monitors the patient for the first 12 to 24 hours, or until status asthmaticus is under control. The nurse also assesses the patient’s skin turgor to identify signs of dehy-dration. Fluid intake is essential to combat dehydration, to loosen secretions, and to facilitate expectoration. The nurse administers intravenous fluids as prescribed, up to 3 to 4 L/day, unless con-traindicated. The patient’s energy needs to be conserved, and the room should be quiet and free of respiratory irritants, including flowers, tobacco smoke, perfumes, or odors of cleaning agents. A nonallergenic pillow should be used.
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