Asthma Management Handbook

Continuing treatment and considering additional treatment

Recommendations

If response to initial inhaled salbutamol is incomplete or poor, consider adding ipratropium bromide (if not used initially) or other add-on treatments. Continuing salbutamol as needed.

Note: Ipratropium bromide is recommended in combination with salbutamol in the initial treatment of patients with severe or life-threatening acute asthma.

Table. Add-on treatment options for acute asthma Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/61

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to named source(s):

  • Kirkland et al. 20171
  • Pollock et al. 20172
  • Castro-Rodriguez et al. 20153
  • Vézina et al. 20144
  • Griffiths et al. 20135

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For adults with severe or life-threatening acute asthma, or with poor response to repeated maximal doses of other bronchodilators, consider adding intravenous magnesium sulfate.

Give magnesium sulfate 10 mmol (2.5 g) diluted in a compatible solution as a single infusion over 20 minutes.

  • Intravenous magnesium sulfate may be associated with hypotension.

Table. How to administer intravenous magnesium sulfate Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/95

How this recommendation was developed

Evidence-based recommendation

Based on literature search and formulated by multidisciplinary working group

Key evidence considered:

  • Green 20166
  • Kew et al. 20147

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For children with severe or life-threatening acute asthma, or with poor response to repeated maximal doses of other bronchodilators, consider adding intravenous magnesium sulfate.

Give magnesium sulfate 0.1–0.2 mmol/kg (maximum 10 mmol) (25–50 mg/kg to maximum of 2 g) diluted in a compatible solution as a single infusion over 20 minutes.

Do not use intravenous magnesium sulfate in children younger than 2 years.

  • Intravenous magnesium sulfate may be associated with hypotension 

Table. How to administer intravenous magnesium sulfate Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/95

How this recommendation was developed

Evidence-based recommendation

Based on literature search and formulated by multidisciplinary working group.

Key evidence considered:

  • Griffiths et al. 20168
  • Irazuzta & Chiriboga 20179

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In emergency department or critical care units (e.g. intensive care unit, high-dependency unit), IV salbutamol  can be considered for patients with life-threatening acute asthma that has not responded to continuous nebulised salbutamol, after considering other add-on treatment options.

Monitor blood electrolytes, heart rate and acid/base balance (blood lactate).

Note: Follow your hospital/organisation’s protocols for dosage and delivery or use doses in the table.

  • Salbutamol toxicity (e.g. tachycardia, tachypnoea, metabolic acidosis, hypokalaemia) may occur with either the inhaled or IV route of administration. Risk may be increased when the inhaled and IV routes are used concomitantly.
  • The initial dose of salbutamol should be reduced for older adults. Dose reduction may be needed for people with impaired renal function. Impaired liver function may result in accumulation of unmetabolised salbutamol. Refer to TGA-approved product information.

Table. Add-on treatment options for acute asthma Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/61

 
How this recommendation was developed

Evidence-based recommendation

Based on literature search and formulated by multidisciplinary working group

Key evidence considered:

  • Starkey et al. 201410
  • Travers et al. 201211

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In critical care units (e.g. emergency department, intensive care unit, high-dependency unit), IV aminophylline or can be considered for patients with life-threatening acute asthma that has not responded to continuous nebulised salbutamol, after considering other add-on treatment options.

Monitor blood electrolytes, heart rate and acid/base balance (blood lactate).

Monitor serum theophylline concentration and titrate to maintain within therapeutic range to avoid toxicity (refer local protocols).

Note: Follow your hospital/organisation’s protocols for dosage and delivery or use doses in the table. Target blood levels differ between laboratories.

  • IV aminophylline is associated with nausea and vomiting.

Table. Add-on treatment options for acute asthma Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/61

How this recommendation was developed

Evidence-based recommendation

Based on literature search and formulated by multidisciplinary working group.

Key evidence considered:

  • Cooney et al. 201612
  • Singhi et al. 201413
  • Travers et al. 201214
  • Nair et al.  201215
  • Yung & South. 199816

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Adrenaline can be used for a patient with life-threatening acute asthma if there is no response to other bronchodilators and condition is rapidly deteriorating.

IM via needle and syringe

For adults or children, use (1:1000) and give 0.01 mg per kg up to 0.5 mg per dose (0.5 mL). Repeat every 3–5 minutes if needed.

IM via auto-injector

Adult: 0.3 mg IM

Child >20 kg: 0.3 mg IM

Child 10–20 kg, 0.15 mg IM

Repeat dose after 5 minutes if required.

IV infusion

Adult, child, initially 0.1 microgram/kg/minute IV initially, then titrate according to response.

Slow IV injection

Adult: 50 micrograms (0.5 mL adrenaline 1:10 000) IV. Repeat according to response. Give IV infusion if repeated doses required.

Child: initial dose 1 microgram/kg (0.01 mL/kg adrenaline 1:10 000) IV. Titrate dose according to response.

  • Do not use adrenaline in place of salbutamol as initial bronchodilator.
  • IV administration can be considered if response to repeated IM doses and volume expansion is inadequate. IV adrenaline should only be given by health professionals experienced in its use and with continuous monitoring of ECG, pulse oximetry and BP. IV infusion is safer than slow bolus (used for imminent cardiac arrest).
  • Auto-injector doses are as recommended by the Australasian Society of Clinical Immunology and Allergy for the management of anaphylaxis. For some children they are higher than the doses recommended by the manufacturer.
How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

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Montelukast is not recommended for the management of acute asthma in adults or children in acute care settings.

How this recommendation was developed

Evidence-based recommendation

Based on literature search and formulated by multidisciplinary working group

Key evidence considered:

  • Wang et al. 201817
  • Zubairi et al 201318
  • Ramsay et al. 201119
  • Todi et al. 201020
  • Harmanci et al. 200621

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In adults and adolescents, non-invasive positive pressure ventilation can be considered if the patient is starting to tire or shows signs of respiratory failure.

  • Do not sedate patient
  • If no improvement, intubate and start mechanical ventilation
How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to named source(s):

  • Gupta et al. 201022
  • Soma et al. 200823
  • Brandão et al. 200924

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Intubate and start mechanical ventilation for patients with:

  • respiratory arrest
  • acute respiratory failure that has not responded to treatment
  • severe exhaustion suggesting impending respiratory arrest
  • inadequate response to non-invasive positive pressure ventilation.
How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

Last reviewed version 2.0

If respiratory distress or increased work of breathing does not respond to treatment, consider transfer to an intensive care unit.

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available).

Last reviewed version 2.0

In adults, admit patient to hospital if (any of):

  • hypoxia at presentation
  • FEV1 <60% predicted (or 50% of usual, if known) at 1-hour check
  • respiratory distress/increased work of breathing unresolved or unable to lie flat without dyspnoea 1–2 hours after presentation
  • a history of ICU admission for asthma
  • presentation for acute asthma within the past 4 weeks
  • frequent presentations for acute asthma (e.g. several over previous year)
  • high recent use of beta2 agonists
  • patient cannot be monitored adequately at home or cannot easily return to hospital if needed
  • other risk factors for adverse outcomes.

Table. Risk factors for adverse asthma outcomes in adults and adolescents Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/table/show/40

How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available), with particular reference to named source(s):

  • Wilson et al. 200325
  • Aldington & Beasley. 200726

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In children, admit patient to hospital if (any of):

  • hypoxia at presentation
  • respiratory distress/increased work of breathing unresolved 1–2 hours after presentation
  • a history of ICU admission for asthma
  • presentation for acute asthma within the past 4 weeks
  • frequent presentations for acute asthma (e.g. several over previous year)
  • high recent use of beta2 agonists
  • patient cannot be monitored adequately at home or cannot easily return to hospital if needed
  • food allergy
  • other risk factors for adverse outcomes.

Table. Risk factors for life-threatening asthma flare-ups in children

Asthma-related factors

Poor asthma control

Admission to hospital in preceding 12 months

History of intubation for acute asthma

Over-use of short-acting beta2 agonist reliever

Abnormal spirometry findings

Reversible expiratory airflow limitation on spirometry despite treatment

Poor adherence to preventer

Incorrect inhaler technique for preventer

Poor adherence to asthma action plan

Exposure to clinically relevant allergens

Exposure to tobacco smoke

Other clinical factors

Allergies to foods, insects, medicines

Obesity

Family-related factors

Frequent failure to attend consultations/lack of follow-up after an acute flare-up

Significant parental psychological or socioeconomic problems

Parent/carer unequipped to manage asthma emergency

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How this recommendation was developed

Consensus

Based on clinical experience and expert opinion (informed by evidence, where available)

Last reviewed version 2.0

More information

Theophyllines in acute asthma

Few studies have compared IV aminophylline with IV short-acting beta2 agonist in the management of acute asthma in adults and children.

Compared with salbutamol IV aminophylline is associated with a higher rate of adverse effects including giddiness, nausea and vomiting.14

It is used mainly as an add-on therapy when there is inadequate response to initial bronchodilator.

Aminophylline plus salbutamol in adults

Overall, evidence from randomised clinical trials in adults with acute asthma treated in emergency departments suggests that intravenous aminophylline given in addition to inhaled beta2 agonists does not achieve greater bronchodilation or reduce hospital admissions, compared with inhaled beta2 agonists alone.15 No sub-groups that benefit from intravenous aminophylline have been clearly identified.15

Aminophylline is associated with vomiting and cardiac arrhythmias.15

Theophylline is metabolised mainly by the liver and commonly interacts with other medicines. Its concentration in plasma should be monitored closely in older people or those with comorbid conditions.27

Aminophylline plus salbutamol in children

In children with acute asthma requiring hospital admission, the addition of intravenous aminophylline to beta2-agonists and corticosteroids (with or without ipratropium) may improve lung function within 6 hours of treatment, but does not appear to improve symptoms or shorten hospital stay.28

The optimal aminophylline dose in children has not been clearly identified. Evidence from clinical trials does not show a clear association between dose and clinical outcomes.12

Aminophylline is associated with a significant increased risk of vomiting in children.28 The rate of adverse effects appears to be higher among children receiving higher loading doses of IV aminophylline (7–10 mg/kg), compared with 5–6 mg/kg.12

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Oral montelukast in acute asthma

Evidence from randomised controlled clinical trials does not support routine use of oral leukotriene receptor agonists in acute asthma in adults or children.29

In children with acute asthma, the addition of oral montelukast to usual care does not reduce hospital admission rates, based on the findings of a systematic review and meta-analysis.29

One small study in adults with acute asthma reported that the addition of oral montelukast to usual care resulted in a slight reduction beta2 agonist requirement,29 but this difference was clinically nonsignificant.

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Role of ketamine in acute asthma

Ketamine has been proposed by some researchers as a suitable option for pre-intubation sedation in patients with respiratory failure caused by acute asthma (where not contraindicated) because it stimulates the release of catecholamines and may contribute to bronchodilation through direct relaxation effect on bronchial smooth muscle.30

Evidence does not strongly support the use of ketamine in non-intubated children with acute asthma.31 The results of small studies suggest that ketamine at a dose of approximately 1 mg/kg may have some benefit in bronchodilation and clinical symptoms in children.32 However, benefits compared with other add-on treatments for acute asthma and long-term effects have not been established.32 In children with acute asthma who have an inadequate response to initial bronchodilator therapy, the effect of IV ketamine on respiratory status may be equivalent to that to that of IV aminophylline.33

Adverse effects associated with ketamine include hypersecretion, hypotension and hypertension, arrhythmias, and hallucinations.30

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Antibiotics in acute asthma

Antibiotics are not used routinely in the management of acute asthma but should be used if they would otherwise be indicated.

The role of atypical bacterial infections (e.g. Chlamydophyla pneumonia, Mycoplasma pneumonae) in asthma is under investigation. Atypical bacterial infections may make acute asthma more severe, especially in patients with poorly controlled asthma. Macrolide antibiotics are active against atypical bacteria and have anti-inflammatory activity. However, their potential anti-inflammatory effects in the treatment of acute asthma have not been well studied.

A systematic review34 of antibiotic treatment in asthma flare-ups found that the few available randomised controlled trials were heterogeneous and that their findings were inconsistent. It  concluded that there was limited evidence that antibiotics given at the time of an asthma flare-up may improve symptoms and lung function at follow‐up, compared with standard care or placebo.34

The systematic review identified four studies that assessed the use of macrolide antibiotics in the management of asthma flare-ups. Combined results for two of these (416 participants) showed that macrolide treatment was associated with improvement in symptoms.34 One included study reported an increase in symptoms-free days at 10 days in adults treated with a macrolide, compared with placebo, which was independent of serological evidence for infection with chlamydia pneumonia or mycoplasma pneumoniae. However, the study drug (telithromycin) is no longer in use due to its association with severe liver toxicity.

In a study of adults attending emergency care for acute asthma, treatment with azithromycin 500 mg per day for 3 days was not associated with an improvement in symptoms or lung function, compared with placebo.35 However, 1 in 10 participants assessed for this trial were excluded as they had already commenced an antibiotic at the time of screening.

In a study of children aged 1–5 years presenting to the emergency department with acute wheezing illness,36 children were randomised to either azithromycin for 5 days or placebo. Azithromycin treatment did not reduce the duration of respiratory symptoms or the time to a respiratory flare-up in the following 6 months after treatment.36

A small (n=40) study assessing clarithromycin treatment in children aged 1–3 years with acute wheezing illness reported an increase in symptoms-free days at 3, 6 and 12 weeks, compared with usual care.37

The systematic review of antibiotic treatment in asthma flare-ups34 included two studies investigating penicillin treatment in patients admitted to hospital with asthma. Neither observed a significant difference in duration of admission, and one reported no difference in asthma symptoms at discharge.34

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Spirometry in acute asthma

Spirometry is used alongside clinical assessment and oximetry to assess severity of acute asthma and response to treatment. Clinical assessment alone may underestimate the severity of airflow limitation.25

However, no recent clinical trials have compared outcomes of spirometry-guided treatment of acute asthma with non-spirometry-guided treatment.

A study in adults with acute asthma found that, on its own, FEV1 (measured by spirometry) at 1 hour after admission to the emergency department did not closely correlate with clinicians’ decision for or against hospital admission, as assessed clinically.25 However, the combination at 1 hour of FEV1 and the patient’s ability to lie flat was significantly predictive of the decision for hospital admission.25

In adults with poor response to initial bronchodilator treatment, dyspnoea scores at 3 hours from presentation may predict relapse or clinicians’ assessment of the need for hospitalisation better than FEV1, but neither is a strong predictor.38

In children with acute asthma, clinical severity scores may be more sensitive than spirometry to detect change clinical status beyond the first 2 hours of treatment.39 The value of performing spirometry in children before hospital discharge is unclear.40

Feasibility and technique

Although some clinical guidelines recommend spirometry before treatment to assess baseline lung function, most children with severe acute asthma and many with mild-to-moderate acute asthma cannot perform spirometry at this time.41 Younger children (most children under 6 years) are unlikely to be able to perform spirometry, even when they do not have a flare-up.

Most adults with acute asthma can perform spirometry within the first hour of admission to the emergency department.42 (Hospital staff and primary care health professionals may need specific training in spirometry technique to be able to obtain acceptable spirometry in patients with acute asthma.42)

It may not be feasible to apply standard spirometry technique and manoeuvre acceptability criteria in patients with acute asthma:41, 42

  • 80% of patients older than 12 years with acute asthma can perform an FEV1 manoeuvre. A forced exhalation from total lung capacity for 2 seconds is sufficient and provides useful information about the severity of airflow obstruction
  • two attempts may suffice if patients are unable to make three attempts
  • variability between manoeuvres of < 10% should be considered acceptable
  • patients may not be able to tolerate nose clips
  • patients are unlikely to be able to exhale for long enough to demonstrate the time-volume plateau. Although patients should aim for forced exhalation of at least 6 seconds, 2 seconds is acceptable for measuring FEV1 in clinical assessment during acute asthma. A spirometry manoeuvre might be considered acceptable if back-extrapolated volume is either < 5% of FVC or 0.15 L (whichever is greater), or a time to peak flow < 120 ms.

Table. Tips for performing spirometry in patients with acute asthma

  • Ask the patient to sit straight upright, either in a chair or on a stretcher with their legs over the side.
  • Make sure the person forms a tight seal around the mouthpiece.
  • Tell the patient to take as deep a breath as possible, then blast out air as fast and hard as they can, then keep blowing until asked to stop. Aim for exhalation of maximal force for at least 2 seconds (6 seconds if FVC is measured).

You may need to give the patient lots of coaching, repeat instructions, and give immediate feedback on technique.

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Peak expiratory flow measurement in acute asthma

Peak expiratory flow rate obtained using a peak flow meter underestimates the severity of airflow limitation in patients with acute asthma, compared with FEV1 obtained by spirometry.43

Peak expiratory flow is not a sensitive measure of small clinical improvements as perceived by the patient.44

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Non-invasive positive pressure ventilation in acute asthma

Few large studies have evaluated non-invasive positive pressure ventilation in patients with acute asthma.

Adults

Few randomised clinical trials have evaluated non-invasive positive pressure ventilation (biphasic positive airway pressure or continuous positive airway pressure) for adults with severe acute asthma.45

This technique has not been shown to reduce risk of death or the need for intubation, but may reduce hospital admissions, length of hospital stay and length of ICU stay.45 It may also improve lung function, but evidence is inconsistent.45

Children

A Cochrane systematic review of non-invasive positive pressure ventilation in hospitalised children with acute asthma46 found insufficient evidence to ascertain whether or not it is beneficial.

A recent randomised clinical trial reported that non-invasive positive pressure ventilation had no advantage over standard care in children aged 2–18 years with acute asthma treated in a paediatric emergency department, with no significant difference between groups in lung function, need for additional treatment, length of stay in the emergency department.47

Delivering bronchodilators in patients undergoing noninvasive positive-pressure ventilation

When delivering nebulised salbutamol while using noninvasive positive-pressure ventilation set at pressures commonly used in clinical practice, the amount of salbutamol inhaled is likely to be significantly higher than with a nebuliser alone (based on a bench model of a spontaneously breathing adult). This increase may be because the ventilator tubing acts as a spacer.48

The position of the nebuliser in the ventilator circuit significantly affects the total dose of salbutamol inhaled. Salbutamol is delivered most effectively when the nebuliser is positioned immediately after the expiration port (i.e. starting from the facemask, the expiration port is positioned before the nebuliser).48

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Salbutamol in acute asthma

Route of administration

Inhaler plus spacer, or nebuliser

Among patients with acute asthma who do not require mechanical ventilation, salbutamol delivered via a pressurised metered-dose inhaler with spacer is at least as effective as salbutamol delivered via nebuliser in preschool children (with viral-induced wheezing or acute asthma)49 and adults,5051 and is equivalent or superior in school-aged children.3, 52, 2, [REFERENCE991]

The use of nebulisers increases the risk of transmitting respiratory infections to staff and other patients,53 and increases the risk of adverse effects.

Intravenous salbutamol

IV salbutamol is generally reserved for use in patients with severe acute asthma that does not respond to inhaled bronchodilators.

Efficacy

Overall, intravenous short-acting beta2 agonists do not appear to be superior to inhaled short-acting beta2 agonist.54

Adults

Benefits have not been demonstrated in adults.54 

Children

Very limited evidence from one study suggested that the addition of IV salbutamol to inhaled salbutamol reduced recovery time in children with severe acute asthma in the emergency department.54

However, there is a lack of consensus on the appropriate dose of IV salbutamol for children.10 Recommendations differ between guidelines in Australia55 and elsewhere.10 Doses have not been calculated based on age-specific pharmacokinetic and pharmacodynamic data. The doses recommended in guidelines are generally relatively higher than for adults on a micrograms per kilogram body weight basis.

Adverse effects

Compared with inhaled salbutamol, intravenous salbutamol is associated with increased risk of adverse effects including tremor and hypokalaemia.5410  Concomitant use of the inhalation and IV routes may increase the risk of salbutamol toxicity.56

Note: Salbutamol concentrate for infusion is available in 5 mL ampoules containing salbutamol sulfate equivalent to 5 mg (1 mg/mL) salbutamol in a sterile isotonic solution (Ventolin obstetric injection). Salbutamol for injection is also available in ampoules of salbutamol sulphate equivalent to 500 microg salbutamol in 1 mL sterile isotonic solution (Ventolin injection).

Salbutamol dosing regimens

There is very little evidence from clinical trials to guide dosing intervals for salbutamol treatment in acute asthma.

One placebo-controlled study conducted in the emergency department among adults with acute asthma (FEV1 <60% predicted or normal) showed that, in those who did not show a clear response to the first salbutamol dose, repeating the dose at intervals of 30 minutes or less was more effective than every 60 minutes.57 However, for patients who showed clear improvement after the first dose of salbutamol via pressurised metered-dose inhaler and spacer, there was no advantage in repeating the dose more often than every 60 minutes until full recovery (extra doses can be given as needed).57

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Ipratropium in acute asthma

Adults

In adults and older adolescents with severe acute asthma treated in the emergency department, the combination of ipratropium and short-acting beta2 agonist reduces hospitalisation rate and improves lung function, compared with short-acting beta2 agonist alone.1 Hospitalisation rates are not reduced in patients with mild or moderate acute asthma.1

In adults, the combination of ipratropium and short-acting beta2 agonist is associated with a higher rate of adverse effects (e.g. tremor, agitation, and palpitations) than short-acting beta2 agonist alone.1

Children

Recent systematic reviews have reported that initial treatment with ipratropium in addition to salbutamol markedly reduces hospitalisation rate and improves clinical scores in children with moderate to severe acute asthma.3, 2, 5

However, in children hospitalised due to acute asthma, the combination of ipratropium and short-acting beta2 agonist was not more effective than short-acting beta2 agonist alone.4

The combination of ipratropium and short-acting beta2 agonist appears to be well tolerated in children.5

Ipratropium bromide alone is less effective than salbutamol alone in acute asthma.58

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Magnesium sulfate in acute asthma

Magnesium sulfate in acute asthma

Clinical trial evidence does not support the use of magnesium sulfate as a substitute for inhaled beta2 agonists.59

Its main use is in addition to salbutamol, either in combination with initial bronchodilator treatment, or as an add-on treatment in patients with inadequate response to initial bronchodilator treatment.

Intravenous magnesium sulfate

Adults

IV magnesium sulfate may have a small effect in reducing hospital admissions and may improve lung function in adults with acute asthma who have failed to respond to standard treatment.6, 7

In a large, well-conducted randomised controlled trial in adults with moderate-to-severe acute asthma treated in an emergency department (excluding those with life-threatening asthma), IV magnesium sulfate improved dyspnoea scores but did not reduce hospital admission rates.60

Current evidence does not indicated whether or not IV magnesium sulfate is more effective for patients with a more severe acute asthma.6

The optimal dose and infusion regimen has not been identified.6

IV magnesium sulfate IV appears to be well tolerated in adults.6 Minor flushing is the most common adverse event.6 Other adverse effects reported in clinical trials include fatigue, nausea, headache and hypotension.7

Children

IV magnesium sulfate may reduce hospitalisation rates and improve lung function among children with acute asthma in presenting to the emergency department,61, 8 but there is limited evidence.8

A small randomised controlled trial reported that IV magnesium sulfate was ineffective in reducing respiratory distress in very young children (6 months to 4 years) with acute virus-induced wheezing.62

IV magnesium sulfate is generally well tolerated.8, 9

Nebulised magnesium sulfate

Nebulised magnesium sulfate may achieve small additional improvement in lung function and reduction in hospital admission rates when added to salbutamol and ipratropium in adults and children with acute asthma, but these benefits have not been clearly demonstrated on current evidence.59

Randomised controlled trials have reported conflicting findings. The larger and more recent studies typically show a smaller effect than some of the older, smaller studies.59 Large, well-designed trials in adults60, 63 and children64, 65, 66 have generally not demonstrated clinically important benefits.59 A systematic review of randomised controlled trials found no overall improvement in lung function when magnesium sulfate was added to salbutamol and ipratropium.59

Nebulised magnesium sulfate is well tolerated and does not appear to be associated with an increase in serious adverse events.59

Adults

It is uncertain whether nebulised magnesium sulfate improves lung function or symptoms, or reduces hospital admissions, when added to standard treatment in adults.6

Some studies suggest that patients presenting with severe acute asthma may benefit, but the data are not conclusive.6

A large, well-designed RCT showed no reduction in hospitalisation or dyspnoea rates in adults with acute asthma given add-on nebulised magnesium, compared with standard therapy alone,60, 63 but this study excluded patients with life-threatening acute asthma.

Children

A recent systematic review found that nebulised magnesium sulfate had no effect on hospitalisation rates or lung function in children with acute asthma.61

However, one large, well-designed randomised controlled trial in children reported that nebulised magnesium sulfate was associated with a small improvement in asthma symptom scores at 60 minutes. The effect was greatest in the subgroups of children with more severe acute asthma (SaO2<92%), and those with more sudden onset (symptoms less than 6 hours before acute attack).64, 65

Nebulised magnesium sulfate is well tolerated in children.64, 65

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The 1-hour assessment

Very little evidence is available to determine when it is safe to discharge a patient with severe acute asthma from the emergency department. Few studies have correlated features of clinical history, examination, response to medications  or objective measures of airflow obstruction with outcomes after discharge including relapse.

Timing of decision to admit or discharge

An Australian ‘real world’ prospective observational study,67 which included children and adults aged 1–55 years with acute asthma presenting to emergency departments, correlated severity class assessed at initial presentation and at the 1-hour assessment with clinicians’ assessment of need for hospital admission or intensive care unit admission. Compared with assessed severity class at initial presentation, severity class assessed at 1 hour better predicted:67

  • the decision for hospital admission among patients initially assessed as having ‘moderate’ acute asthma (e.g. able to speak in phrases, oxygen saturation 92–95%, FEV1 50–75% predicted, pulse rate 100–120/min)
  • the decision to admit to the intensive care unit among patients initially assessed as having ‘severe’ acute asthma (e.g. physical exhaustion, unable to speak more than a word at time, oxygen saturation < 92%, FEV1 < 50% or <1 L, pulse rate >120/min).

The ‘lie flat’ test (adults)

In adults, at 1 hour after initial treatment, the ability to lie flat without dyspnoea may be a useful indicator of adequate recovery without the need for hospital admission, particularly when combined with adequate improvement in FEV1 measured by spirometry.25

Spirometry

A study in adults with acute asthma found that, on its own, FEV1 (measured by spirometry) at 1 hour after admission to the emergency department did not closely correlate with clinicians’ decision for or against hospital admission, as assessed clinically.25 However, the combination at 1 hour of FEV1 and the ‘lie flat’ test was significantly predictive of the decision for hospital admission.25

Most adults with acute asthma can perform spirometry within the first hour of admission to the emergency department.42

Table. Tips for performing spirometry in patients with acute asthma

  • Ask the patient to sit straight upright, either in a chair or on a stretcher with their legs over the side.
  • Make sure the person forms a tight seal around the mouthpiece.
  • Tell the patient to take as deep a breath as possible, then blast out air as fast and hard as they can, then keep blowing until asked to stop. Aim for exhalation of maximal force for at least 2 seconds (6 seconds if FVC is measured).

You may need to give the patient lots of coaching, repeat instructions, and give immediate feedback on technique.

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References

  1. Kirkland SW, Vandenberghe C, Voaklander B et al. Combined inhaled beta-agonist and anticholinergic agents for emergency management in adults with asthma. Cochrane Database Syst Rev. 2017; Issue 1: CD001284. Available from: https://www.ncbi.nlm.nih.gov/pubmed/28076656
  2. Pollock M, Sinha IP, Hartling L et al. Inhaled short-acting bronchodilators for managing emergency childhood asthma: an overview of reviews. Allergy. 2017; 72: 183-200. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27588581
  3. Castro-Rodriguez, J. A., Rodrigo, G. J., Rodriguez-Martinez, C. E.. Principal findings of systematic reviews for chronic treatment in childhood asthma. J Asthma. 2015; 52: 1038-45. Available from: https://www.ncbi.nlm.nih.gov/pubmed/26303207
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