STATUS ASTHMATICUS
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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