Airway 7: Status Asthmaticus Portal
Asthma is a chronic, inflammatory disease characterized by reversible airflow obstruction. Status asthmaticus is severe progressive asthma unrelieved by usual asthmatic treatment (bronchodilator and anti-inflammatory drugs). Acute status asthmaticus may be triggered by multiple precipitants: environmental agents, medications, food and its additives, exercise, emotional stress, and others. Subacute exacerbations, frequently triggered by respiratory infection, may progress to status asthmaticus over a period of days.
Symptoms of an asthma attack include progressive dyspnea associated with wheezing and cough. A patient who presents with these symptoms and has a history of asthma is usually easy to diagnose. However, all that wheezes is not asthma. COPD, CHF, pulmonary embolism, croup, bronchiolitis, upper airway obstruction, pneumonia, bronchitis, allergic reactions, and other conditions may also present with the same symptoms. History is important for evaluating the exacerbation in the context of patients and their disease(s) and for immediate treatment purposes. Prior intubation/mechanical ventilation, chest tube insertion, ICU admission, and winter worsening are important risk factors for severe disease.1 Other risk factors include comorbidity, recent ED care, psychosocial problems, poor compliance/follow-up, chronic glucocorticoid use, and two or more hospitalizations in the past year.2 Symptoms and signs of significant asthmatic exacerbation include:
- Anxiety
- Ineffectiveness of bronchodilators to relieve dyspnea
- Patient too short of breath to complete a sentence in one breath
- Tachypnea, prolonged expiratory phase, use of accessory muscles of respiration (intercostals and sternocleidomastoids)
- Tachycardia
- Pulsus paradoxus (Defined as the exaggeration of the normal variation in the pulse volume, and thus the BP, with respiration becoming weaker with inspiration and stronger with expiration. This occurs because of the marked increase in pleural pressure swings generated by the inspiratory muscle effort required to facilitate air exchange.)
Particularly Ominous Signs
- Agitation
- Heart rate > 110 bpm
- Respiratory rate > 25 breaths per minute
- Paradoxical breathing pattern (inward movement of lower thoracic and abdominal wall musculature during inspiration); exaggerated use of accessory muscles
- Paradoxical pulse > 25 mm Hg (not always ominous; operator dependent; place in context)
- Diaphoresis
- Pulse oximetry: SaO2 < 90% (PEDS: in pediatric patients, this value is associated with high rates of admission)3
- Feeble respiratory efforts
- Silent chest—critical sign of severe respiratory distress (much less wheezing due to poor air movement)
- Cyanosis—critical sign of severe respiratory distress
Exhaustion, confusion, coma—Signs of impending cardiorespiratory arrest
- Bradycardia
- Hypotension
Diagnostic Tests
Tests can be useful in determining the treatment and disposition of some asthma patients in the context of the episode. Test selection is largely determined by the history and physical.
Pulmonary Function Tests (PFTs): The FEV1 (forced expiratory volume in the first second) and/or the PEFR (peak expiratory flow rate) are commonly tested by spirometry in the emergency setting. Using either test, a pretreatment value of less than 50% of that predicted indicates severe obstruction.4 Despite national guidelines for use of these tests in the management of asthma in the ED, there is considerable controversy over their utility in this setting.5 Keep chart(s) for predicted flows for sex/height/age readily available in the ED.6
Chest X-ray is not a routine evaluative tool for asthma in the emergency setting but is useful in evaluating additional or competing diagnoses (CHF, pneumonia, COPD, pneumothorax, etc.), some of which may be life threatening and require immediate attention.
Routine Lab Evaluation is not indicated for asthmatic exacerbations. Various tests for coexisting disease management may be useful. Hypokalemia may result from high-dose beta 2 agonist therapy, respiratory alkalosis, dehydration, and corticosteroid therapy. Corticosteroids may cause hyperglycemia.
Cardiac Monitoring, ECGs: These are not indicated for the asthmatic exacerbation; however, they are useful in the context of coexisting cardiac disease and/or dysfunction. Pulmonary disease patterns that can resolve with treatment of asthma include right ventricular strain, nonspecific ST-T changes, and right atrial enlargement.
Arterial Blood Gases: While pulse oximetry has rendered ABGs unnecessary in the vast majority of asthma presentations, measurements can be useful to evaluate the ventilation/acid-base status of the patient with prolonged/severe status asthmaticus, altered mental status, shock, impending cardio-respiratory arrest, or on the ventilator. In these settings, ABGs may help to refine the patient’s physiologic status. Tachypneic patients should be “blowing off” (lowering) their CO2. Near normal levels in this setting indicate a tiring patient with low reserves and impending failure; high levels of CO2 signify ventilatory failure. With this caveat in mind, the following table may be helpful in incorporating ABG values into clinical decision-making.
Stages of Asthma based on ABG readings:
Stage I—Patient is in the early stages of asthma and has normal ABGs.
Stage II—Patient has progressive increase in dyspnea and anxiety. This causes hyperventilation, which results in respiratory alkalosis and hypocapnia.
Stage III (crossover)—The patient's respiratory muscles are beginning to fatigue, and airway obstruction progresses. The blood pH and PCO2 return to normal as a pseudo-normalization. This is the first time that hypoxemia is seen.
Stage IV (respiratory failure)—The patient shows progressive respiratory deterioration with the development of respiratory acidosis, hypercapnia, and severe hypoxemia. (If the patient falls into either Stage III or Stage IV blood gas determination levels, the patient has severe asthma, and hospitalization is required.)
Figure: Arterial Blood Gases/Stages of Asthma
| Stage of Asthma |
pH | PCO2 | PO2 | Percentage of normal lung function (FEV1 or PEFR) |
| I | Normal | Normal | Normal | 70% to 100% |
| II | Increased | Decreased | Normal | 50% to 70% |
| III (Crossover) | Normal | Normal | Decreased | 25% to 50% |
| IV (Respiratory failure) | Decreased | Increased | Greatly decreased |
<25% |
Classification of Severity
While severity scales based on ABGs have been in use for some time, more recent literature has de-emphasized this approach. One reason for this, in addition to the availability of pulse oximetry, is that PFTs can predict hypercarbia and respiratory acidosis fairly reliably.7 Thus, patients with a PEFR > 25% predicted would be expected to have a pCO2 < 45 and a pH > 7.35.8
Several major guidelines utilize a combination of presenting clinical features, PFTs, and response to treatment in order to gauge the severity of the exacerbation
The Global Initiative for Asthma (GINA) classifies asthma exacerbations as follows9:
Moderate Exacerbation:
PEFR 60% to 80% predicted
Use of accessory muscles
Severe Exacerbation:
PEFR < 60% predicted
History of risk factors for near fatal asthma
Chest retraction
No improvement after initial treatment
The Expert Panel of the National Heart, Lung and Blood Institute uses PEFR for initial classification of severity10:
Mild Exacerbation
PEFR > 40% predicted
Moderate Exacerbation:
PEFR < 40% predicted
Actual or impending respiratory failure
Patients are then re-categorized according to response to initial treatment
For the most part, clinical features, PFTs, and ABGs tend to trend together,11 and the most practical approach, given current technology, would appear to base severity assessment primarily on clinical features, initial PFTs and pulse oximetry, and response to first-line treatment.12
Therapeutic Interventions
By definition, status asthmaticus is a severe episode of (usually) reversible airway obstruction. The goal of treatment is to ensure oxygenation, reverse airway obstruction, and reduce airway inflammation. The critical management task facing the provider is to determine if this severe attack is stable or unstable, as acute management changes on this decision. Conditions can change rapidly; greater vigilance than usual needs to be paid to interventions and their effects. Anticipation and advanced planning for these difficult cases are key for successful outcomes. While expert guidelines such as the NIH are not necessarily evidence based and asthma index scores are no better than clinical judgment in predicting outcomes,13,14 hospitals that use asthma guidelines may be more likely to engage in quality improvement in managing this important disease condition. A brief overview of therapies and discussion of stable and unstable management follows.
Established Therapies
- Oxygen. Liberal use is indicated without worry of toxicity in the short term. The goal is to keep saturation> than 90% (some sources recommend 92%)15 and/or arterial PO2 greater than 60 mm Hg.* Some guidelines recommend minimum saturations of 95% for children9 and pregnant women.10
- Beta adrenergic agonist agents. Inhalational/aerosal agents are the mainstay of asthma therapy. They relax bronchial smooth muscles. In the ED, these are given either by metered-dose inhalers (MDI) with spacers on an intermittent basis or by nebulization (intermittently or continuously). Either way has been shown to be therapeutically equivalent in multiple studies.16 Due to larger particle size and loss of medication from continuous flow, drug delivery by nebulizer is actually less efficient than by inhaler with spacer.17 Thus, 4 to 8 puffs of a 90 μg/puff albuterol inhaler are the recommended alternative to 2.5 to 5 mg of albuterol by nebulizer.12 However, effective use of the inhaler requires good technique, which may be difficult to achieve in severe attacks. There is also the perception that nebulization provides more uninterrupted access to the drug than does the inhaler. Patient and provider preference dictates choice of modality.
Albuterol is the most commonly used beta agonist. Formoterol, a long-acting beta agonist, also has a rapid enough onset of action to be useful in acute exacerbations, but experience with this agent has been much less than with albuterol. Pharmacologically, there is reason to believe that levalbuterol (Xopenex) would be more effective than albuterol with fewer side effects. However, clinical studies have failed to confirm this,18 and levalbuterol is more expensive.19
Albuterol:
- Intermittent MDI dosage for adults/PEDS: 2 spaced puffs every 5 minutes for 30 minutes or 4 to 8 puffs every 20 minutes.
- Intermittent nebulizer dosage for adults: albuterol 2.5 to 5 mg (0.5 to 1 cc of a 0.5% solution) in 2 to 3 cc NS every 20 minutes.
- Intermittent nebulizer dosage for PEDS: albuterol 0.15 mg/kg/dose (minimum of 1.25 mg/dose, up to 5 mg) in 2 to 3 cc NS every 20 minutes.
These doses can be repeated every 20 to 30 minutes if needed to a total of 3 doses.
For continuous treatment, see Continuous Albuterol Nebulization.
- Glucocorticoids. Effective agents that probably work by reducing inflammation and restoring beta-adrenergic responsiveness. Early use in an emergency setting results in fewer admissions and relapses.20 Effects are seen as early as 4 hours. Glucocorticoids may be used effectively via oral, IV, or IM routes.
- Adult: prednisone 40 to 60 mg PO, or methylprednisolone 60 to 125 mg IV/IM. PEDS: prednisone 1 to 2 mg/kg PO or methylprednisolone 1 to 2 mg/kg IV/IM. Repeat either one every 6 to 8 h.
- Anticholinergics. Ipratropium is an effective inhaled agent that works by reducing vagally mediated bronchospasm. Ipratropium works synergistically with the previously listed agents and is delivered by MDI with spacer or by nebulization. (It may be combined in the same holding chamber with albuterol.) The combination of inhaled ipratropium to an inhaled beta adrenergic agonist has been found to significantly improve PEFR and FEV1.21
- Dose: 0.5 mg by nebulization; PEDS: 0.5 mg if > 12 years, 0.25 mg if < 12 years; may repeat every 20 minutes if needed to a total of 3 doses. Peaks in 1 to 2 h.
Optional Therapies (established but second-line)
- Injectable adrenergic agents:
Epinephrine is a non-selective beta and alpha agonist and is effective in those instances where aerosolized agents aren’t readily available. Epinephrine may be given to geriatric patients with no history of recent angina or MI without precipitating dysrhythmias.13
- Dose: adults 0.3 to 0.5 mg of 1:1000 solution. PEDS: 0.01 mg/kg (up to 0.3 mg) of 1:1000 solution. Given SQ, the dose may be repeated as needed every 20 minutes for a total of 3 doses.
Terbutaline is a beta agonist that may, like epinephrine, be used SQ if other treatment modalities are unavailable, or a second- or third-line therapy in patients responding poorly to treatment.
- Dose: Adults 0.25 mg of the 1 mg/mL solution. PEDS: 0.01 mg/kg (up to 0.25 mg). Given SQ, the dose may be repeated as needed every 20 minutes for a total of 3 doses.
Additional Options
- Magnesium sulfate given
intravenously is efficacious in at least some patients with severe
asthma (not indicated in moderate cases).22,23,24,25 Magnesium
has a
rapid onset of action and is cleared rapidly. While clinical trials
have shown magnesium to be safe, some experts recommend that the
patient be watched for potential magnesium side effects, such as
decreased deep tendon reflexes, decreased respiratory rate, decreased
renal output, nausea, vomiting, and hypertension. Careful monitoring of
BP and serum magnesium
levels is
recommended if using continued infusion.
- Dose: 2 g IV over 20 minutes; follow with infusion of 2 g/h as needed. PEDS: 25 mg/kg IV to a maximum dose of 2 g.
Heliox (a mixture of 80% helium and 20% oxygen) works by lowering airway resistance and respiratory work. Its role in asthma continues to evolve; it may be useful in patients with respiratory acidosis and failed conventional therapy.
Intravenous terbutaline has been used with success in some emergency settings. However, clinical trials have not consistently found it to improve outcomes,26 and adverse effects can be limiting.27
Non-Invasive Ventilation, Intubation, and Mechanical Ventilation of Patients with Asthma
Small studies23 of BiPAP use in selected cases of asthma show the treatment is promising. This may be an adjunct in treatment if the team is familiar with its use. (Vol III—AIR5 Noninvasive Ventilatory Support)
Many physicians believe that the decision to intubate the asthmatic patient is made on clinical grounds, and don’t rely on any set criteria to do so. Obvious scenarios where patients need intubation include coma and respiratory arrest; other indications for intubation include worsening scenarios/parameters (such as progressive respiratory acidosis [increased PCO2], progressive hypoxia [decreased PO2], declining alertness, increasing agitation), especially in the context of vigorous therapy. Intubating an asthmatic patient is a demanding intervention. Oral intubation is preferred (larger diameter tube, no nasal bleeding), and RSI is the method of choice. Consider the use of ketamine as the induction agent of RSI, as it causes bronchial smooth muscle relaxation. With intubation and mechanical ventilation, the state of air-trapping/airflow obstruction is associated with large tidal volumes and auto-PEEP/increased residual volumes. This increases the risk for barotrauma and its deadly sequelae, tension pneumothorax. To monitor this dynamic hyperinflation condition, an indirect measurement is used called the plateau pressure (Pplat), which reflects alveolar pressure. (This is the airway pressure measured after a 0.5 second pause at the end of inspiration.) A ventilator technique termed permissive hypercapnia (also called controlled hypoventilation) is used to keep the Pplat less than 30 cm H2O. This consists of a prolonged expiratory phase, a reduced respiratory rate, and rapid flow rates. Initial ventilator settings consist of 100% O2, assist control mode, respiratory rate of 8 to 10, no PEEP, a tidal volume of 6 to 8 mL/min, and and inspiratory flow of 80 to 100 L/min.24 If Pplat is greater than 30 cm H2O, minute ventilation (respiratory rate x tidal volume) is lowered. This relative hypoventilation results in hypercapnia (and respiratory acidosis), but PaO2 levels are able to be maintained and mortality is reduced.28,29 To maintain patient comfort and tolerance with this ventilatory support, heavy sedation and neuromuscular blockade is usually required. ABGs are monitored to keep pH > 7.15 (with the use of IV bicarbonate if necessary). Severe metabolic acidosis, severe hypoxemia, and severe hypertension are relative contraindications to using this ventilator technique. Inhaled medications are continued on schedule while patients are on the ventilator.
Not to be Considered in Emergency Therapy
- Routine use of theophylline is not recommended in emergency management of asthma. Some studies have demonstrated a modest improvement in pulmonary function when intravenous theophylline is added to nebulized albuterol30; however, the evidence is lacking to recommend its use for routine asthma therapy much less in the emergency setting.31
- Continuous ketamine has not been shown to be useful (except as a sedative for intubation).
- Antihistamines and mucolytics are not used.
- Avoid sedatives, tranquilizers, narcotics in non-intubation management of severe asthma.
- Avoid non-indicated hydration measures.
- Avoid inhalational lidocaine if using RSI, which can cause bronchoconstriction.
Assessing Response to Treatment
-
Obtain PFTs after therapy is started and every 15 to 30 minutes in the acute phase of management; evaluate data in the context of the patient’s condition.
-
Values < 40% of predicted indicates poor response. Aggressive inhalational therapy is indicated (continuous nebulizers of beta agonists along with multiple-dose ipratropium). Consider using magnesium IV, heliox, BiPAP. Reassess the need for intubation. ABGs may provide helpful information. Start admission process (ICU, unless more treatment is anticipated in the ED).
-
Values between 40% and 70% indicate an incomplete response. Continue therapy and assessment, whether in the ED or hospital. Sustained incomplete responses may pose dispositional problems. Consider a wide variety of information, not just medical, in making discharge decision. Relapses happen.
-
Values > 70% in the context of sustained response (at least over several hours), no symptoms, and a normal physical exam indicates good response. Consider all elements of a patient’s situation when planning discharge. For the asthmatic component of the ED visit, all discharged patients generally get:
- intense (“on demand”) beta agonist therapy (always with spacers),
- 5 to 10 day course of non-tapered corticosteroids, and
- close follow-up.
Unstable Status Asthmaticus
Unstable asthma is diagnosed by rapid assessment and clinical judgment. Among other considerations are factors such as cyanosis, hypotension, bradycardia, severe exhaustion, confusion, coma, feeble respiratory efforts, impending arrest, and worsening parameters despite vigorous treatment. The situation demands intense multimodal management with immediately available emergency airway equipment. While preparing for intubation, give O2, continuous inhaled beta agonists (or epinephrine SQ if there is any delay in therapy), multiple-dose ipratropium, magnesium IV, and corticosteroids IV.
- If improvement occurs rapidly and intubation is not imminent, continue treatments while evaluation proceeds. A baseline pulmonary function test may be performed at this time and repeated every 15 to 30 minutes.
- If there is no improvement, proceed with airway management. (If immediately available and familiar to the user, BiPAP may buy some time or provide a bridge to improvement in selected patients). (Vol III—AIR1 Rapid Sequence Intubation, AIR4 Ventilatory Management, AIR5 Noninvasive Ventilatory Support)
- Consider Heliox treatment if available. (Vol III—AIR3 Heliox Treatment)
- Continue treatment while searching for and managing comorbidities. Constantly reassess the patient for effects of all interventions.
- Management of a worsening condition despite maximizing the previous modalities is facilitated by serial ABGs; place arterial line if possible. Involve consultants early. Think ahead to possible anesthetic agents and/or nitric oxide (NO) if available. Arrange ICU admission.
Comments and Caveats
- Start or continue all patients with severe asthma on systemic corticosteroids. The use of inhaled steroids in the setting of status asthmaticus is controversial at best. One study found an additive effect from the addition of inhaled steroids to oral steroids in acute asthma.32 Other studies suggest that inhaled steroids are similarly effective to oral steroids alone in acute asthma patients who can be discharged from the ED.33,34 Nevertheless, in patients with a severe asthma attack, the use of systemic steroids (PO, IM, or IV) is preferred.
- Don’t delay treatment once in the ED.
- Be prepared to have to insert chest tubes in mechanically ventilated patients. Pneumothoraces happen.
- Do not under-treat pregnant asthmatics, especially with corticosteroids. Management is similar except for epinephrine SQ, which constricts the arterial supply to the uterus and therefore is not used.
- Geriatric patients with asthma often have coexisting disease. (Fortunately, COPD treatment is similar to asthmatic therapy.) New onset wheezing may be CHF. Also, geriatric patients are more susceptible to medication side effects and interactions.
- PEDS: Pediatric therapy is similar to adult therapy. Hydration status in children is important. The younger the child, the more important the hydration status. Treat dehydration. It is reasonable to x-ray children who are wheezing for the first time in order to rule out manifestation of other diseases; otherwise, use clinical judgment for x-rays (as in adult management).
- Educate patients on use of spacers with their MDIs; always use one with ED MDI therapy.
Set Up Of Continuous Albuterol Delivery
| Policy | Continuous
albuterol aerosol therapy is a method of bronchodilator administration
for patients with severe acute wheezing due to reactive airways. The
equipment is set up at bedside to continuously deliver as little as 0.1
mg/kg/h of albuterol to a maximum of 0.5 mg/kg/h via face mask. This therapy will be ordered when intermittent nebulizer treatments do not improve the patient’s condition. Respiratory care staff will perform and record a clinical assessment as often as necessary. (Discuss with ordering physician.) |
| Objective | To provide continuous bronchodilator medication for patients with severe bronchospasm |
| Equipment | IV
med pump 3-way stopcock 18-gauge needle Hudson updraft nebulizer Primary IV pump tubing Normal saline bag mixed with appropriate meds (obtained in pharmacy) O2 flow meter 6-inch flex tubing Appropriate aerosol mask |
| Medication Procedure |
See flow sheet.
Chart continuous administration in nurses’ notes. Clinical assessment will be done on respiratory care flow sheet during continuous therapy. Use air flowmeter to drive nebulizer. If patient requires O2, use nasal cannula set at proper flow under aerosol mask. If patients’ O2 requirements cannot be met using nasal cannula, use O2 flowmeter to drive nebulizer, remove nasal cannula.  This is a Heart brand continuous medication nebulizer. Monitor every hour for approximately 30 cc/h output and proper setting of flowmeter at 10 LPM. Consult with respiratory therapy for proper equipment and set up. |
Albuterol-Continuous
Nebulization
(Maximum 0.5 mg/kg/hour)
| Child's Weight (kg) |
Age | Dose | Albuterol (5 mg/mL) |
Normal Saline |
Total |
| 5 to 10 kg | 23 wks to 1 y | 2.5 mg/h | 2 mL | 118 mL | 120 mL |
| 10.1 to 15 kg | 1 to 5 y | 5 mg/h | 4 mL | 116 mL | 120 mL |
| 15.1 to 20 kg | 1 to 5 y | 7.5 mg/h | 6 mL | 114 mL |
120 mL |
| 20.1 to 25 kg | 5 to 9 y | 10.0 mg/h | 8 mL | 112 mL | 120 mL |
| 25.1 to 30 kg | 5 to 9 y | 12.5 mg/h | 10 mL | 110 mL | 120 mL |
| >30 kg | 9 to 16 y | 15 mg/h | 12 mL | 108 mL | 120 mL |
Note: Each 120 mL of dilution is based on continuous nebulization of 30 mL/h over a 4-hour period at 10 L/min oxygen flow rate.
| Child's Weight (kg) |
Age | Dose | Albuterol (5 mgs/mL) |
Normal Saline | Total |
| 5 to 10 kg | 23 wks to 1 y | 2.5 mg/h | 2 mL | 94 mL | 96 mL |
| 10.1 to 15 kg | 1 to 5 y | 5 mg/h | 4 mL | 92 mL | 96 mL |
| 15.1 to 20 kg | 1 to 5 y | 7.5 mg/h | 6 mL | 90 mL | 96 mL |
| 20.1 to 25 kg | 5 to 9 y | 10 mg/h | 8 mL | 88 mL | 96 mL |
| 25.1 to 30 kg | 5 to 9 y | 12.5 mg/h | 10 mL | 86 mL | 96 mL |
| >30 kg | 9 to 16 y | 15 mg/h | 12 mL | 84 mL | 96 mL |
Note: Each 96 mL of dilution is based on continuous nebulization of 24 mL/h over a 4-hour period at 8 L/min oxygen flow rate.
| Child's Weight (kg) |
Age | Dose | Albuterol (5 mg/mL) |
Normal Saline |
Total |
| 5 to 10 kg | 23 wks to 1 y | 2.5 mg/h | 2 mL | 58 mL | 60 mL |
| 10.1 to 15 kg | 1 to 5 y | 5 mg/h | 4 mL | 56 mL | 60 mL |
| 15.1 to 20 kg | 1 to 5 y | 7.5 mg/h | 6 mL | 54 mL | 60 mL |
| 20.1 to 25 kg | 5 to 9 y | 10 mg/h | 8 mL | 52 mL | 60 mL |
| 25.1 to 30 kg | 5 to 9 y | 12.5 mg/h | 10 mL | 50 mL | 60 mL |
| >30 kg | 9 to 16 y | 15 mg/h | 12 mL | 48 mL | 60 mL |
Note: Each 60 mL of dilution is based on continuous nebulization of 15 mL/h over a 4-hour period at 5 L/min oxygen flow rate.
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