Page 680 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 55: Status Asthmaticus 499

Observation for 60 minutes after the last β-agonist dose helps ensure in the most severely obstructed patients who would be receiving higher
stability prior to discharge. Written medication instructions and an doses of β-agonists, drug delivery is most impaired resulting in minimal
asthma action plan should be provided. In general, patients should be systemic absorption and effect. In one study, albuterol delivered by MDI
discharged on oral corticosteroids. Inhaled corticosteroids (ICSs) should with spacer to a total dose of 1600 μg over 90 minutes was not associated
77
be continued (or even initiated) in the ED and follow-up appointments with increased cardiovascular morbidity in well-oxygenated patients.
should be made. After the first hour, dosing depends on clinical response and side effects.
Patients with severe airflow obstruction demonstrating a poor response Long-acting β-agonists (LABAs) are not recommended for treat-
to initial therapy and patients who deteriorate despite therapy should ment of acute asthma, although limited data do show that formoterol
be admitted to an ICU. Other indications for ICU admission include (which has quick onset of action) is effective and safe in this setting.
respiratory arrest, altered mental status, hypercapnia, arrhythmias, acute Combination therapy with a LABA and an ICS may be initiated or con-
78
coronary syndrome, and need for frequent inhaler treatments. tinued in hospitalized patients receiving rescue therapy, and may be
https://kat.cr/user/tahir99/
An incomplete response to treatment is defined as the persistence of required to achieve adequate outpatient control and decrease the risk of
mild wheezing or dyspnea and a PEFR or FEV between 50% and 69% future exacerbations.
1
of predicted. Patients in this group should be assessed individually, Subcutaneous β-agonists are not recommended unless the patient is
1
and while selected low-risk patients may be safely discharged from the unable to comply with inhaled therapy (such as those with an altered
ED, others require ongoing treatment in either the ED or the medi- mental status or impending cardiopulmonary arrest). They are no more
cal ward. Extended ED evaluation allows for assessment of the initial effective in the initial management of acutely ill asthmatics and are
response to systemic corticosteroids, and for those who are discharged associated with greater toxicity. 79-81 However, subcutaneous epinephrine
home decreases the risk of relapse and return to the ED. If the patient may benefit some patients not responding to several hours of an inhaled
34
demonstrates a good response to treatment over that period of time and β-agonist. Known cardiac disease and age >40 years are relative
82
close follow-up can be arranged, discharge home may be appropriate. contraindications to parenteral therapy. Intravenous infusions of
83
Again, these patients have better outcomes if they receive a course of β-agonists are not recommended because they are more toxic and less
oral steroids. Patients who continue to have an incomplete response efficacious than inhaled treatments. 84-88
69
should be admitted to a medical ward. Admission is also recommended Approximately two-thirds of patients respond to inhaled albuterol in a
when there is a harmful home environment or medical noncompliance. convincing dose-dependent fashion, generally allowing discharge home
from the ED. In these patients, 1.2 to 2.4 mg albuterol delivered by
89
THERAPY PRIOR TO INTUBATION MDI and spacer or 5 to 7.5 mg by nebulizer in the first hour is effective.
■ PHARMACOTHERAPY presumably because airway inflammation and mucus plugging adversely
In the remaining one-third of patients albuterol has minimal effect,
β-Agonists: Inhaled short-acting β-agonists (SABAs) are the cornerstone affects the dose response relationship.
of treatment of smooth muscle–mediated bronchoconstriction and should Ipratropium Bromide: Overall, the data suggest an advantage in maximal
be given immediately regardless of prior use (Table 55-1). Albuterol is bronchodilation response when ipratropium bromide and albuterol are
70
the most widely used SABA, but others are available including levalb- combined in the initial emergency treatment of asthma. 90-100 However,
uterol, bitolterol, and pirbuterol. Levalbuterol in one-half the milligram several studies that generally used small doses of ipratropium bromide
dose of albuterol provides comparable efficacy and safety by metered dose showed little or no benefit to this combination, 101-105 and the addition
inhaler (MDI), but has not been studied by continuous administration. 62 of ipratropium bromide has not been shown to provide further benefit
Guidelines recommend repetitive or continuous administration once the patient is hospitalized. 62
depending on clinical response and side effects. A common strategy Combination therapy is recommended for patients critically ill on
is to give albuterol 2.5 mg by nebulization every 20 minutes during first presentation or not responding quickly (eg, within 30 minutes)
the first hour of ED management. Continuous administration (at the to albuterol alone. The Expert Panel of the NIH recommends adding
62
same total dose) may be slightly superior to repetitive dosing in patients 0.5 mg of ipratropium bromide to 2.5 mg of albuterol by nebulizer every
with severe exacerbations, although there is little difference between 20 minutes for three doses, then as needed. Alternatively combination
these two strategies in most cases. 71-74 Albuterol can also be delivered of four to eight puffs of ipratropium bromide MDI and four to eight
effectively by MDI with a spacer; four to eight puffs of albuterol by MDI puffs of albuterol (or eight puffs of a combination albuterol/ipratropium
with spacer is equivalent to a 2.5-mg nebulizer treatment. 75,76 MDIs bromide inhaler) can be given every 20 minutes for the first 1 to 3 hours
with spacers are less expensive and faster, but handheld nebulizers as guided by clinical response and toxicity. 62
require less supervision and coordination. Fortunately, frequent doses Corticosteroids: Systemic corticosteroids should be administered quickly
of β-agonists are generally well tolerated. This may relate to the fact that
to patients not responding in an immediate, marked, and durable
manner to initial bronchodilator therapy, particularly since benefits
are not immediately evident. Indeed McFadden’s group demonstrated
TABLE 55-1 Drugs Used in the Initial Treatment of Acute Severe Asthma no differences in physiologic or clinical variables in the first 6 hours in
105
Albuterol: 2.5 mg by nebulization every 20 minutes or four to eight puffs by MDI with spacer every 38 patients receiving hydrocortisone. Rodrigo and Rodrigo similarly
20 minutes; for intubated patients titrate to physiologic effect. Alternative: levalbuterol (see text) showed that early administration of steroids did not improve spirometry
in the first 6 hours. However, Littenberg and Gluck demonstrated that
106
Epinephrine: 0.3 mL of a 1:1000 solution subcutaneously every 20 minutes × 3.
Terbutaline is favored in pregnancy when parenteral therapy is indicated. Use with caution methylprednisolone 125 mg IV on arrival decreased admission rates
compared to placebo, and Lin and colleagues demonstrated improved
107
in patients >age 40 and in the presence of cardiac disease
108
peak flows after 1 and 2 hours of methylprednisolone. A systematic
Ipratropium bromide: 0.5 mg combined with albuterol by nebulization every 20 minutes or analysis for the Cochrane Review demonstrated that corticosteroids
four to eight puffs by MDI with spacer combined with albuterol every 20 minutes within 1 hour of arrival in the ED reduced admissions. 109,110 Systemic
Corticosteroids: Methylprednisolone 40 mg IV every 12 hours or prednisone PO 40 mg every steroids reduce the number of relapses and the risk of death. 110-113 In
114
12 hours hospitalized patients, they speed the rate of improvement. Oral and
115
Magnesium sulfate: 2 g IV over 20 minutes, repeat in 20 minutes if clinically indicated (total intravenous routes are equally effective, but oral steroids should be
4 g unless hypomagnesemic) avoided if there is concern regarding the need for intubation.
There is no clear dose-response relationship to steroids in acute
Leukotriene modifiers: Consider montelukast 10 mg PO daily
asthma. 116,117 In one meta-analysis by Manser and colleagues, there was

section04.indd 499 1/23/2015 2:20:12 PM