A spacer is a chamber that keeps the nebulized drug

in suspension to allow a more reliable delivery of the bea

agonist to the lungs. Bronchodilation from MDI beta-2

agonists is equivalent to that achieved by nebulization.

Parenteral beta agonists include terbutaline 0.25 mg or

epinephrine 0.3 mg subcutaneously and can be useful in a

life-threatening exacerbation. Avoid in patients with a history of ischemic heart disease.

Corticosteroids. Steroids suppress inflammation,

increase the responsiveness of beta-2 adrenergic receptors

in the airway smooth muscle, and decrease the recruitment and activation of inflammatory cells. They are indicated in moderate to severe exacerbations, patients who

fail to respond to initial beta-2 agonist therapy, patients

who are on chronic steroids, and for patients who meet

the criteria for hospitalization. The clinical effect of corticosteroids is not seen immediately, as the peak effect

occurs within 6 to 12 hours. Oral or IV routes may be used

as both have equal bioavailability. Prednisone 60 mg orally

or methylprednisolone (Solu-Medrol) 125 mg IV are

equivalent doses. Aerosolized corticosteroids are important in chronic treatment and prevention of relapse in

asthmatic patients, but they do not play a role in the treatment of acute exacerbations.

Anticholinergic agents. Ipratropium bromide 0.5 mg

via nebulizer can be used in conjunction with beta -2 agonist therapy for moderate to severe asthma exacerbations.

It competitively antagonizes acetylcholine and subsequently decreases cyclic guanosine monophosphate, causing bronchodilation. The onset of action is 20 minutes,

with a peak effect within 1-6 hours.

Other treatments. Magnesium sulfate (MgSO 4) 2 g N

over 20 minutes is given for severe asthma exacerbations

and works by causing relaxation of smooth muscle.

Antibiotics should be given for evidence of pneumonia.

Methylxanthines (Theophylline) is not recommended in

the emergency setting. Heliox is a helium-oxygen (80:20

or 70:30) mixture that has a lower density compared with

room air, which allows it to travel through narrow air passages in a more laminar fashion instead of causing turbulence. This allows increased delivery of oxygen or

bronchodilator medications to the alveoli, thereby decreasing the work of breathing.

ASTHMA

Noninvasive positive pressure ventilation (NPPV) may

be used in patients with significant work of breathing and

early fatigue. Although its use in COPD and CHF patients

has been well established, the use of NPPV in acute

asthma needs further evidence to determine the optimal

recommendations.

Intubation with mechanical ventilation may be required

for severe acute asthma due to fatigue, persistent hypoxia,

worsening hypercarbia, or altered mentation. Ketarnine

(2 mg/kg) should be used as the induction agent because it

causes bronchodilation. The goal is to maintain adequate

oxygenation until the patient responds to therapies and

mechanical ventilation can be withdrawn. However, dur ­

ing mechanical ventilation patients can develop high lung

pressures because they are unable to expire a full breathe.

This can lead to barotrauma, pneumothorax, or hypotension. Several strategies can be used to prevent these complications. Using the largest endotracheal tube possible will

decrease airway resistance, and ventilator settings should

be set to allow for increases in the expiration time to prevent air trapping. This is done by using a low respiratory

rate (permissive hypercarbia) and low tidal volumes

(5-7 mL!kg). However, if all other therapies fail, intuba ­

tion is necessary.

DISPOSITION

� Admission

The decision to admit is based on the combination of

patient symptoms, physical examination findings,

responses to treatment, 02 saturation, PEFR/FEV1 measurements, and the patient's social limitations to medical

care. ICU admission should be considered in patients with

severe exacerbations and poor response to treatment

judged by altered mentation or continued respiratory distress. Patients who require continuous albuterol, noninvasive ventilation, or intubation should be admitted to the

ICU. Floor admission is considered for patients with continued symptoms and a PEFR/FEV1 that remains <70% of

predicted despite treatment.

� Discharge

It is acceptable to discharge patients without respiratory

distress or hypoxia, who have good aeration and dimin ­

ished wheezing, with a sustained response after the final

albuterol treatment. The goal of the FEV1 or PEFR should

be >70% predicted before discharge. Discharged patients

should be sent home with an inhaler and spacer and

should be instructed on their proper use. Proper technique

for use of the MDI is to remove the cap and shake; exhale

completely; place mouth on end of spacer; depress inhaler

so that 1 puff is delivered into the spacer; start inspiration

of medicine from spacer; continue slow, deep inspiration;

hold breath 5-10 seconds; and wait 20 seconds between

each puff.

CHAPTER 21

A steroid burst should also be used in patients who

had a moderate to severe exacerbation, but who improved

enough to go home. This includes a 5 - to 1 0-day course

of prednisone at 40-60 mg per day to keep the inflammatory effects of asthma under control. Patients should also

have peak flow meters with instructions on a home

asthma action plan detailing when to return to the ED

based on their symptoms and PEFR. In addition, patients

should be given instructions to avoid asthma triggers ( eg,