Asthma Management Handbook

Completing a rapid primary assessment and starting initial treatment

Recommendations

Assess severity of the acute asthma episode (moderate, severe or life-threatening) and administer a bronchodilator immediately:

  • Make a rapid clinical assessment with the person in a sitting position.
  • Measure pulse oximetry while the person is breathing air (unless life threatening).
  • Start bronchodilator according to severity and age.

Table. Rapid primary assessment of acute asthma in adults and children

Mild/Moderate

Severe

Life-threatening

Can walk, speak whole sentences in one breath

(For young children: can move around, speak in phrases)

Oxygen saturation >94%

Any of these findings:

  • Use of accessory muscles of neck or intercostal muscles or 'tracheal tug' during inspiration or subcostal recession ('abdominal breathing')
  • Unable to complete sentences in one breath due to dyspnoea
  • Obvious respiratory distress
  • Oxygen saturation 90–94%

Any of these findings:

  • Reduced consciousness or collapse
  • Exhaustion
  • Cyanosis
  • Oxygen saturation <90%
  • Poor respiratory effort, soft/absent breath sounds

Notes

If features of more than one severity category are present, record the higher (worse) category as overall severity level

The severity category may change when more information is available (e.g. pulse oximetry, spirometry) or over time.

The presence of pulsus paradoxus (systolic paradox) is not a reliable indicator of the severity of acute asthma.

Oxygen saturation measured by pulse oximetry. If oxygen therapy has already been started, it is not necessary to cease oxygen to do pulse oximetry.

Oxygen saturation levels are a guide only and are not definitive; clinical judgment should be applied.

Definitions of severity classes for acute asthma used in this handbook may differ from those used in published clinical trials and other guidelines that focus on, are or restricted to, the management of acute asthma within emergency departments or acute care facilities.

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Table. Initial bronchodilator treatment in acute asthma (adults and children 6 years and over)

  • Do not use IV short-acting beta2 agonists routinely for initial bronchodilator treatment.

  • Do not give oral salbutamol.

  • Monitor for salbutamol toxicity (e.g. tachycardia, tachypnoea, metabolic acidosis, hypokalaemia) – may occur with inhaled or IV salbutamol.

Mild/Moderate

Severe

Life-threatening

Give salbutamol 4-12 puffs (100 microg/actuation) via pMDI and spacer

Give one puff at a time followed by 4 breaths

Repeat every 20-30 minutes for the first hour if required (sooner, if needed to relieve breathlessness)

Give salbutamol plus ipratropium

Salbutamol†: 12 puffs (100 microg/actuation) via pMDI and spacer

If patient unable to breathe through a spacer, give 5 mg nebule via nebuliser

Ipratropium: 8 puffs (21 microg/actuation) via pressurised metered-dose inhaler and spacer every 20 minutes for first hour. Repeat 4–6 hourly for 24 hours.

If salbutamol delivered via nebuliser add 500 micrg ipratropium to nebulised solution every 20 minutes for first hour. Repeat 4–6 hourly.

Start oxygen therapy if oxygen saturation <92% in adults or <95% in children and titrate to target:

Adults: 93–95%
Children: 95% or higher

Repeat salbutamol as needed. Give at least every 20 minutes for first hour (3 doses)

Give salbutamol plus ipratropium

Salbutamol: 2 x 5 mg nebules via continuous nebulisation driven by oxygen

Ipratropium: 500 microg ipratropium added to nebulised solution every 20 minutes for first hour. Repeat 4–6 hourly.

Maintain oxygen saturations:

Adults: 93–95%
Children: 95% or higher

Arrange immediate transfer to higher-level care

When dyspnoea improves, consider changing to salbutamol via pMDI plus spacer or intermittent nebuliser (doses as for severe acute asthma)

* Give adrenaline if anaphylaxis suspected. Consider adrenaline if the patient is unresponsive, cannot inhale bronchodilators, or is considered to be peri-arrest. 

† See Table. Using pressurised metered-dose inhalers in acute asthma

‡ See Table. Using nebulisers in acute asthma

Note: To deliver nebulised bronchodilators in a patient receiving oxygen therapy, use an air-driven compressor nebuliser and administer oxygen by nasal cannulae.

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Table. Initial bronchodilator treatment in acute asthma (children 1–5 years)

  • Do not use IV short-acting beta2 agonists routinely for initial bronchodilator treatment.

  • Do not give oral salbutamol.

  • Monitor for salbutamol toxicity (e.g. tachycardia, tachypnoea, metabolic acidosis, hypokalaemia) – may occur with inhaled or IV salbutamol.

  • Closely monitor level of consciousness, fatigue, oxygen saturation, respiratory rate and heart rate. If symptoms do not respond, contact a paediatrician or senior clinician and reconsider the diagnosis. 

  • Wheezing infants younger than 12 months old should not be treated for acute asthma. Acute wheezing in this age group is most commonly due to acute viral bronchiolitis. Advice should be obtained from a paediatric respiratory physician or paediatrician before administering short-acting beta2 agonists, systemic corticosteroids or inhaled corticosteroids to an infant.

Mild/Moderate

Severe

Life-threatening*

Give salbutamol 2-6 puffs (100 microg/actuation) via pMDI and spacer plus mask

Give one puff at a time followed by 4 breaths

Repeat every 20-30 minutes for the first hour if needed (sooner, if needed to relieve breathlessness)

Give salbutamolplus ipratropium

Salbutamol: 6 puffs (100 microg/actuation) via pMDI and spacer plus mask

Give one puff at a time followed by 4 breaths

If patient unable to breathe through a spacer, give 2.5 mg nebule via nebuliser

Ipratropium: 4 puffs (21 microg/actuation) via pressurised metered-dose inhaler and spacer (+ mask if needed) every 20 minutes for first hour. Repeat 4–6 hourly for 24 hours.

If salbutamol delivered via nebuliser, add 250 microg ipratropium to nebulised solution every 20 minutes for first hour. Repeat 4–6 hourly.

Start supplementary oxygen if oxygen saturation <95%

Titrate to 95% or higher

Repeat salbutamol as needed. Give at least every 20 minutes for first hour (3 doses)

Give salbutamol plus ipratropium

Salbutamol: 2 x 2.5 mg nebules via continuous nebulisation driven by oxygen

Ipratropium: 250 microg ipratropium added to nebulised solution every 20 minutes for first hour. Repeat 4–6 hourly.

Maintain  oxygen saturation at 95% or higher

Arrange immediate transfer to higher-level care

When dyspnoea improves, consider changing to salbutamol via pMDI plus spacer or intermittent nebuliser (doses as for severe acute asthma)

*Give adrenaline if anaphylaxis suspected. Consider adrenaline if the patient is unresponsive, cannot inhale bronchodilators, or is considered to be peri-arrest.

† See Table. Using pressurised metered-dose inhalers in acute asthma

‡ See Table. Using nebulisers in acute asthma

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Table. Using pressurised metered-dose inhalers in acute asthma

Administration of salbutamol by health professionals for a patient with acute asthma

  1. Use a salbutamol pressurised metered-dose inhaler (100 microg/actuation) with a spacer that has already been prepared (see note).
  2. Shake inhaler and insert upright into spacer.
  3. Place mouthpiece between the person’s teeth and ask them to seal lips firmly around mouthpiece.
  4. Fire one puff into the spacer.
  5. Tell person to take 4 breaths in and out of the spacer.
  6. Remove the spacer from mouth. Shake the inhaler after each puff before actuating again. (This can be done without detaching the pressurised metered-dose inhaler from the spacer.)

Notes

The process is repeated until the total dose is given. Different doses are recommended for patients and carers giving asthma first aid in the community.

New plastic spacers should be washed with detergent to remove electrostatic charge (and labelled), so they are ready for use when needed. In an emergency situation, if a pre-treated spacer is not available, prime the spacer before use by firing at least 10 puffs of salbutamol into the spacer. (This is an arbitrary number of actuations in the absence of evidence that would enable a precise guideline.)

Priming or washing spacers to reduce electrostatic charge before using for the first time is only necessary for standard plastic spacers. Treatment to reduce electrostatic charge is not necessary for polyurethane/antistatic polymer spacers (e.g. Able A2A, AeroChamber Plus, La Petite E-Chamber, La Grande E-Chamber) or disposable cardboard spacers (e.g. DispozABLE, LiteAire).

For small children who cannot form a tight seal with their lips around the spacer mouthpiece, attach a well-fitted mask to the spacer.

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Table. Using nebulisers in acute asthma

Driving nebuliser

Nebulisers can be driven by air, piped oxygen, or an oxygen cylinder fitted with a high-flow regulator capable of delivering >6 L/min.

Salbutamol

Intermittent nebulisation with salbutamol

Use one nebule:

Adults: 5 mg nebule

Children 6 years and over: 5 mg nebule

Children aged 1-5 years: 2.5 mg nebule

Continuous nebulisation with salbutamol using nebules

Put two nebules into nebuliser chamber at a time and repeat to refill when used up.

Adults: use two 5 mg nebules (10 mg) at a time

Children 6 years and over: use two 5 mg nebules (10 mg) at a time

Children aged 1-5 years: use two 2.5 mg nebules (5 mg) at a time

Ipratropium

Add one nebule to salbutamol nebuliser solution:

Adults and children 6 years and over: 500 microg nebule

Children aged 1-5 years: 250 microg nebule

  • If using oxygen to drive a nebuliser, do not exceed 8–10 L/minute and avoid over-oxygenation (increases risk of hypercapnoea).
  • The use of nebulisers increases the risk (to staff and patients) of nosocomial aerosol infection. If using a nebuliser, follow your organisation’s infection control protocols to minimise spread of respiratory tract infections.

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Notes

  • If oxygen therapy has already been started, it is not necessary to stop oxygen to measure pulse oximetry.

  • Pregnancy is not a contraindication for bronchodilators in acute asthma.

 

How this recommendation was developed

Consensus

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

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Start oxygen therapy for adults with SpO2 <92% or children with SpO2 <95%

  • In adults, avoid over-oxygenation (SpO2>95%), because this increases the risk of hypercapnoea.
How this recommendation was developed

Consensus

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

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For patients with life-threatening asthma, arrange immediate transfer to the resuscitation area (or arrange transfer to acute service).

Figure. Initial management of life-threatening acute asthma in adults and children Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/figure/show/94

How this recommendation was developed

Consensus

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

If the patient is unresponsive, cannot inhale bronchodilators, or is considered to be peri-arrest, consider adrenaline. Use any of the following according to the clinical situation:

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.

If cardiac or respiratory arrest has occurred, initiate resuscitation, start mechanical ventilation and support circulation.

  • 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.

Figure. Initial management of life-threatening acute asthma in adults and children Opens in a new window Please view and print this figure separately: http://www.asthmahandbook.org.au/figure/show/94

How this recommendation was developed

Consensus

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

  • Australian Medicines Handbook1
  • ASCIA 20172

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Identify anaphylaxis and manage it according to national guidelines or your organisation’s protocols.

Anaphylaxis should be suspected in a patient with sudden-onset asthma-like symptoms and either of the following:

  • features of anaphylaxis (e.g. urticaria or angioedema)
  • a history of allergy to food, insects or medicines.

If anaphylaxis is suspected or cannot be excluded, give adrenaline.

If adrenaline is indicated, administer before salbutamol.

Note: Anaphylaxis is defined as (either of):

  • Any acute onset illness with typical skin features (urticarial rash or erythema/flushing and/or angioedema) plus involvement of respiratory symptoms and/or cardiovascular symptoms and/or persistent severe gastrointestinal symptoms

  • Any acute onset of hypotension or bronchospasm or upper airway obstruction where anaphylaxis is considered possible (even if typical skin features not present).

How this recommendation was developed

Consensus

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

  • ASCIA 20172
  • ANZCOR3

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Ensure that pregnant women who present with acute asthma receive treatment immediately to minimise risk to the foetus and to the woman.

Note: Salbutamol and oral corticosteroids should be administered as indicated, just as for non-pregnant patients.

 

How this recommendation was developed

Consensus

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

  • Namazy et al. 20124

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More information

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)5 and adults,67 and is equivalent or superior in school-aged children.8, 9, 10, [REFERENCE991]

The use of nebulisers increases the risk of transmitting respiratory infections to staff and other patients,11 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.12

Adults

Benefits have not been demonstrated in adults.12 

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.12

However, there is a lack of consensus on the appropriate dose of IV salbutamol for children.13 Recommendations differ between guidelines in Australia14 and elsewhere.13 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.1213  Concomitant use of the inhalation and IV routes may increase the risk of salbutamol toxicity.15

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.16 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).16

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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.17 Hospitalisation rates are not reduced in patients with mild or moderate acute asthma.17

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.17

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.8, 10, 18

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.19

The combination of ipratropium and short-acting beta2 agonist appears to be well tolerated in children.18

Ipratropium bromide alone is less effective than salbutamol alone in acute asthma.20

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Assessment of oxygen status in acute asthma

Hypoxia is the main cause of deaths due to acute asthma.21

Routine objective assessment of oxygen saturation at initial assessment of acute asthma is needed because clinical signs may not correlate with hypoxaemia.

Pulse oximetry is the internationally accepted method for routine assessment of oxygen status in patients with acute asthma. It should be available in all situations in which oxygen is used.22

Pulse oximetry does not detect hypercapnoea, so blood gas analysis is necessary if hypercapnoea is suspected in patients with severe or life-threatening acute asthma. Thoracic Society of Australia and New Zealand clinical practice guidelines for acute oxygen use in adults22 recommend that arterial blood gas analysis should be considered if oxygen saturation falls below 92% and in those at risk of hypercapnoea. Venous blood gas analysis can be used to assess acid–base balance and lactate,22 but performs poorly in identifying hypercapnoea.23

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Oxygen therapy in acute asthma

Oxygen is a treatment for hypoxaemia, not breathlessness.22 Oxygen has not been shown to improve the sensation of breathlessness in non-hypoxaemic patients.22 When oxygen supplementation is used, pulse oximetry is necessary to monitor oxygen status and titrate to target.

The aim of titrated oxygen therapy in acute care is to achieve adequate oxygen saturation without causing hypercapnoea.22 Adults with acute asthma and those with overlapping asthma and COPD are at greater risk of hypercapnoeic respiratory failure.

Drying of the upper airway is a potential complication of oxygen therapy,24, 25 and might contribute to bronchoconstriction.25

Few studies have investigated optimal oxygen supplementation protocols for patients with asthma.

Adults

In adults with acute asthma, titrated oxygen therapy using pulse oximetry to maintain oxygen saturation at 93–95% while avoiding hyperoxaemia achieves better physiological outcomes than 100% oxygen at high flow rate (8 L/min).26 High-concentration and high-flow oxygen therapy cause a clinically significant increase in blood CO2 concentration in adults with acute asthma.26, 27

Thoracic Society of Australia and New Zealand (TSANZ) clinical practice guidelines for acute oxygen use in adults22 recommend that, in patients with COPD, oxygen should be administered if the SpO2 is less than 88%, and titrated to a target SpO2 range of 88–92%. For other acute medical conditions, the TSANZ guidelines recommend that oxygen should be administered if the SpO2 is less than 92%, and titrated to a target SpO2 range of 92–96%.

Humidification of oxygen via high flow nasal cannulae may improve comfort and tolerance.22

Children

There is very little evidence available to inform recommendations for oxygen saturation targets in children with asthma.28 Studies in infants with bronchiolitis suggest that targets as low as >90%29 or >92%30 may be achieve similar clinical outcomes as higher targets. Recommendations for oxygen saturation targets during supplemental oxygen vary between clinical guidelines and vary between protocols used in Australian hospitals.

Humidified oxygen can be considered if necessary. Humidification is usually not needed for low flow oxygen (<4 L/minute in children or 2 L/minute in infants) for short term. Humidification may be considered if the oxygen is required for longer than 48 hours or if the nasal passages are becoming uncomfortable or dry.24

Guidance on oxygen delivery techniques and practical issues is available from Sydney Children's Hospital Network and The Royal Children's Hospital Melbourne.

Humidified oxygen via high-flow nasal cannulae

Humidified high flow nasal oxygen is a system that has the ability to provide a humidified high-flow mix of air and oxygen via a specialised nasal cannula system. It is able to deliver positive end expiratory pressure of approximately 4–8 cm H20.

Delivery of high-flow oxygen via nasal cannulae is increasingly common practice in Australian emergency rooms. There is very little evidence to support its use in acute asthma treatment,22 but it does not appear to be associated with significant risks.

It has been reported to be feasible and safe in children with severe acute asthma in ICU,31 and at least as effective as conventional oxygen therapy in children with acute asthma with inadequate response to initial bronchodilator treatment.31 No published studies have evaluated its use in adults with acute asthma.

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Anaphylaxis guidelines and resources

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Roles of adrenaline in the management of acute asthma

Adrenaline is not used routinely in the management of severe acute asthma.

Its use should be reserved for situations where inhaled salbutamol cannot be given in a patient with respiratory arrest or pre-arrest status, or when anaphylaxis is suspected.

Anaphylaxis

Anaphylaxis is rare among people with acute asthma. An estimated 3.4% of adults admitted to the intensive care unit for acute severe asthma also meet criteria for anaphylaxis, according to one retrospective study32

Intramuscular adrenaline (or intravenous adrenaline in clinical settings with appropriately trained staff) is indicated for patients with anaphylaxis and angioedema, and patients with known allergies to food or other relevant allergens (other than aeroallergens) who have sudden-onset breathing problems, even if they have no other signs of anaphylaxis.2

Australasian Society of Clinical Immunology and Allergy recommends that adrenaline should be given before bronchodilators for a patient with sudden-onset breathing problems and known allergy to foods, insects or medicines.2

Asthma

Few studies have compared adrenaline in addition to, or in comparison with, currently recommended bronchodilator treatment in patients with acute asthma, either in hospital emergency departments or pre-hospital acute services.

Hospital or emergency department setting

Nebulised adrenaline

Nebulised adrenaline does not have a significant benefit over salbutamol or terbutaline in the management of moderate-to-severe acute asthma in adults and children.33

Intramuscular, intravenous or subcutaneous adrenaline

Adrenaline given IV, subcutaneously or intramuscularly has no benefit over inhaled short-acting beta2 agonists in the management of acute asthma.34, 35, 36, 37

Three small clinical trials comparing subcutaneous adrenaline with nebulised salbutamol in children with acute asthma reported equivalent respiratory outcomes including peak expiratory flow rate.34, 35, 36 Adrenaline was associated with higher rates of adverse effects, including a short-term increase in systolic blood pressure and heart rate.34, 35

Another trial in children with acute asthma reported that subcutaneous adrenaline was more effective than nebulised terbutaline in increasing oxygen saturation and FEV1, but was associated with a higher rate of adverse events including pallor, tremor, dizziness, headache, palpitation, soreness of legs, numbness of extremities, cold sweating, general weakness and nausea.38

A clinical trial comparing subcutaneous adrenaline with nebulised terbutaline in adults with acute asthma reported equivalent efficacy.37 The adrenaline group, but not the terbutaline group, showed an increase in pulse rate.37 A non-comparative retrospective study of 220 adults who had received IV adrenaline for acute asthma reported that adverse events were common but mostly minor and self-limiting.39 Major adverse events occurred in approximately 4% of patients and included 2 cases of supraventricular tachycardia, 1 case of chest pain with ECG changes, 1 case of incidental elevated troponin, and 4 cases of hypotension requiring intervention.39

Prehospital setting

There is limited evidence to guide the use of adrenaline in patients with acute asthma in the prehospital setting. However, it has no benefit over inhaled salbutamol in patients with acute asthma and is associated with a worse adverse effect profile.

Subcutaneous adrenaline was associated with increased heart rate and increased blood pressure, compared with a nebulised bronchodilator (metaproterenol), in a randomised controlled trial in adults presenting to ambulance services with acute asthma.40

In some states, ambulance services give adrenaline to patients with severe, life-threatening acute asthma. In this circumstance inhaled/nebulised salbutamol is preferable initially. When there is an inadequate response with acute and rapid deterioration or when the inhaled route is impractical because the person is not breathing, some ambulance protocols recommend administration of either IM Adrenaline (500 mg, 1:1000), if needed at intervals of 5–10 minutes or IV adrenaline 50–100 mg at intervals of 2–5 minutes.41

Ventilation must be adequately supported. If cardiac or respiratory arrest occurs, appropriate resuscitation procedures should be followed.3

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Technical notes: pressurised metered-dose inhalers with spacers

Manufacturers of most pressurised metered-dose delivery devices recommend shaking the device before actuating. The physical characteristics of each formulation, including the effects of shaking, differ widely,42 but for simplicity it is best always to recommend shaking of pressurised metered-dose inhalers.

Pressurised metered-dose inhalers (except for those that are breath-actuated) can be used with a spacer. When a spacer is used with a pressurised metered-dose inhaler, delivery of the medicine to the patient’s airways is maximised when the patient takes a slow, deep breath from the spacer after each actuation.4327 Multiple actuations of a pressurised metered-dose inhaler into a spacer can reduce the amount of respirable medicine available because aerosol particles can agglomerate into larger particles or become attached to the spacer walls.43

Therefore, the ideal way to deliver inhaled medicines via pressurised metered-dose inhaler and spacer is to shake the device, ask the person to breathe out all the way into the spacer, actuate a single puff into the spacer, and have the person immediately take a slow deep breath from the spacer, then hold their breath for 5 seconds. This process should be repeated until the total intended number of actuations is taken. Patients should be trained to follow these instructions when using their inhalers. Inhaling slowly with a single breath maximises delivery of the medicine to the lungs and minimises deposition in the upper airways when using a manually actuated pressurised metered-dose inhaler with or without a spacer, or when using a breath-actuated pressurised metered-dose inhaler.44 However, slow breathing may not be possible for patients with acute asthma. Tidal breathing through the spacer (e.g. four breaths in and out without removing the spacer) is used in acute asthma and for very young children. First aid instructions should include how to use inhaler and spacer.

In practice, optimal delivery of inhaled medicines involves a balance between maximising the proportion of respirable medicine and maximising efficiency of inhalation by the patient within real-world constraints. The optimal delivery of salbutamol in real-world circumstances is not well defined. For day-to-day use of salbutamol, most adults gain sufficient relief from symptoms when using a pressurised metered-dose inhaler on its own. A spacer may only be needed during a flare-up. By contrast, the use of a spacer is always recommended for inhaled corticosteroids delivered by manually actuated pressurised metered-dose inhalers, to reduce the risk of local adverse effects and increase delivery to the airways.

Many available in vitro studies of aerosol particle deposition in the airways were performed using older CFC-propelled formulations, which are now obsolete. Similar studies have not been performed for current non-CFC pressurised metered-dose inhalers.

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Instruments for assessing acute asthma

Validated scoring systems for assessing the severity of acute asthma, response to treatment, and predicting the need for hospital admission are used in research studies and by some clinicians. These include:

  • Pediatric Respiratory Assessment Measure (PRAM)45 for assessing acute asthma severity and response to treatment in children and adolescents, based on oxygen saturation, effort of breathing (suprasternal retraction and scalene muscle contraction), air entry (assessed by auscultation of the chest) and wheezing
  • the CHOP classification tree for predicting need for hospitalisation in adults,46 based on change in peak expiratory flow severity category, history of acute admission for asthma (‘ever hospitalisation’), oxygen saturation while breathing room air, and initial peak expiratory flow.

These instruments are not routinely used in Australian emergency departments.

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References

  1. Australian Medicines Handbook. Last modified July 2018: Australian Medicines Handbook Pty Ltd. 2018
  2. Australasian Society of Clinical Immunology and Allergy. Guidelines. Acute management of anaphylaxis: ASCIA. 2017. Available from: https://www.allergy.org.au/images/stories/pospapers/ASCIA_Guidelines_Acute_Management_Anaphylaxis_2017_Updated.pdf/.
  3. Australian and New Zealand Committee on Resuscitation. ANZCOR Guideline 9.2.7 – First aid management of anaphylaxis. Australian Resuscitation Council; 2016 [September 2018]; Available from: https://resus.org.au/guidelines/
  4. Namazy, J A, Murphy, V E, Powell, H, et al. Effects of asthma severity, exacerbations and oral corticosteroids on perinatal outcomes. Eur Respir J. 2012; 41: 1082-1090. Available from: http://erj.ersjournals.com/content/41/5/1082.long
  5. Mitselou N, Hedlin G, Hederos CA. Spacers versus nebulizers in treatment of acute asthma - a prospective randomized study in preschool children. J Asthma. 2016; 53: 1059-62. Available from: https://www.ncbi.nlm.nih.gov/pubmed/27186989
  6. Cates CJ, Crilly JA, Rowe BH. Holding chambers (spacers) versus nebulisers for beta-agonist treatment of acute asthma. Cochrane Database Syst Rev. 2006; Issue 2: CD000052. Available from: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000052.pub2/full
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