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Asthma

Table of contents

  1. Initial Assessment
  2. Assessment of Sevrity
  3. Inpatient Management of Asthma
    1. Mild
    2. Moderate
    3. Severe
    4. In Extremis
  4. Indications for ICU Admissions
  5. Assessment of Interval Asthma Symptoms
  6. Management of Interval Symptoms
  7. Inhalation Devices and Assessment of Technique
  8. Asthma Management Plan

Initial Assessment

These notes emphasise the inpatient management of acute asthma. The first thing to do when a child is admitted with acute asthma is to assess the severity of the attack. It is useful to classify children with acute asthma into 4 groups (mild, moderate, severe or in-extremis) by taking a careful history and performing a careful clinical examination.

The dose and type of maintenance asthma medications required to control symptoms between acute exacerbations, is useful information about the frequency and severity of the patient's interval symptoms. Knowledge of the frequency of ß2 agonist administration prior to presentation to the emergency department allows the clinical signs on presentation to be interpreted correctly.

During the examination look for the following :

  • tachypnoea
  • audible wheeze
  • chest hyperinflation
  • use of accessory muscles
  • cyanosis in air
  • chest auscultation
  • pulsus paradoxus
  • conscious state

NOTES:

  1. a patient with severe asthma may have a small tidal volume and therefore a wheeze may not be audible.
  2. the oxygen saturation of arterial blood (SaO2) and peak expiratory flow (PEF) may not be reliable indicators of the severity of airway obstruction, and must be interpreted in conjunction with the patient's clinical condition.
  3. a CXR is indicated in patients with severe respiratory distress or subcutaneous emphysema as they may have a pneumothorax. Patients with mild-moderate asthma do not usually require a chest X-ray. The crepitations heard in asthma are usually due to mucus plugging and not a bacterial infection.

Assessment of Severity

  1. Mild - a child with mild asthma will have an audible wheeze but little respiratory distress. There will be no palpable paradox and breath sounds over the two hemithoraces will be normal. PEFR > 50% predicted. (See predicted values of PEFR).
  2. Moderate - some respiratory distress with wheezing but no cyanosis in air, pulsus paradoxus probably not palpable, but may be up to 15 mmHg by auscultation. Normal breath sounds bilaterally. PEF 30-50% predicted.
  3. Severe - respiratory distress with the use of accessory muscles. Wheeze may be minimal because of a small tidal volume, cyanosis in air and palpable pulsus paradoxus (not always present). PEF < 30% predicted.

Inpatient Management of Asthma

Mild Asthma

  1. Inhaled salbutamol by puffer and spacer or nebuliser (1ml of 0.5% Ventolin solution + 3 ml saline) as required to control symptoms. The nebuliser should be driven with O2 at 8 l/min for 10 minutes.

    Dose for the puffer and spacer:

    Weight < 25 kg: 2 puffs of salbutamol at 1 min intervals for 3 minutes (6 puffs in total), every 20 minutes if required.

    Weight > 25 kg: 2 puffs of salbutamol at 1 minute intervals for 6 minutes (12 puffs in total), every 20 minutes if required.

  2. Oral prednisolone (1 mg/kg/day) for 3 days. The dose should be given once daily and should not exceed 50 mg/day. In some mild cases, only one dose of oral steroids is necessary whilst in others a 3-5 day course may be required. This duration of treatment with steroids will be guided by the expected response to treatment. If oral steroids are given for more than 3 days, the dose should not be stopped abruptly but tapered by approximately 5 mg/day.

    For patients receiving maintenance oral or inhaled corticosteroids the dose of steroids must be tapered to the maintenance dose once the acute exacerbation has resolved.

  3. Theophylline is not commonly prescribed as a maintenance asthma medication. Only continue oral theophylline if the patient is already in receipt of this drug.


Moderately Severe Asthma

  1. Oxygen: Assess the need for oxygen by performing oximetry. Oximetry is not a routine observation but should be considered in patients with moderate or severe exacerbations especially if deteriorating. Pulse oximetry needs to be interpreted with care and in association with the clinical state of the patient. Oxygen therapy can be given by face mask (maximum of 8 l/min) or nasal prongs (maximum of 2 l/min).
  2. Inhaled salbutamol by puffer and spacer or by nebuliser (1ml of 0.5% ventolin solution + 3 ml saline) x 3 in the first hour and then as often as necessary to control symptoms. The nebuliser should be driven with O2 at 8 l/min for 10 minutes. Children not responding to the initial 3 doses of salbutamol following presentation should be managed as severe.

    Dose for the puffer and spacer:

    Weight < 25 kg - 2 puffs of salbutamol at 1 min intervals for 3 minutes (6 puffs in total), every 20 minutes if required.

    Weight > 25 kg - 2 puffs of salbutamol at 1 minute intervals for 6 minutes (12 puffs in total), every 20 minutes if required.

  3. Ipratropium bromide (Atrovent) by puffer and spacer (2 puffs) or add a 1ml Atrovent UDV to the salbutamol nebuliser solution 4-6 hourly.
  4. Oral prednisolone (1 mg/kg) stat. Consider 1 mg/kg/day for 3 days or a tapering dose over several days (reduce by approximately 5 mg/day). The duration of treatment with steroids will be guided by the expected response to treatment. The dose should be given once daily and should not exceed 50 mg/day.
  5. Continue oral theophylline if in receipt of this drug.


Severe Asthma

  1. Oxygen: Give oxygen continuously by face mask, nasal prongs or oxygen cot. A patient who is tiring with incipient respiratory failure may have normal oximetry as their PaCO2 rises.
  2. Inhaled salbutamol (1ml of 0.5% solution + 3 ml saline) by nebuliser x 3 in the first hour then 1-2 hourly as required. For each dose the nebuliser should be driven with O2 at 8 l/min for 10 minutes. Inhaled salbutamol may be given continuously if necessary.
  3. Ipratropium bromide (Atrovent) 1ml UDV to the salbutamol nebuliser solution 2-4 hourly.
  4. Methylprednisolone 1 mg/kg IV stat, and then 6 hourly for the first 24 hours, 12 hourly for the second 24 hours and then daily from day The dose is reduced to minimise unwanted acute steroid side-effects (eg GI ulceration).
  5. Aminophylline IV by slow infusion from a burette through an infusion pump (IVAC).

    Loading dose = 10 mg/kg (< 250 mg) over one hour. Give half this dose if the patient is on maintenance slow release theophylline and the serum theophylline is not known.

    Maintenance dose = 5 mg/kg, 6 hourly by slow infusion over 30 minutes.


In Extremis

  1. Oxygen: Give oxygen continuously by face mask, nasal prongs or oxygen cot. A patient who is tiring with incipient respiratory failure may have normal oximetry as their PaCO2 rises.
  2. Inhaled salbutamol (1ml of 0.5% solution in 3 ml saline) or undiluted (3 ml of 0.5% salbutamol solution) continuously by nebuliser driven with O2 at 8 l/min. A patient receiving continuous 'neat' salbutamol must be discussed with the Paediatric ICU Consultant on call

    If no response, give salbutamol 5 mcg/kg IV, after discussion with the Paediatric ICU consultant. A continuous infusion should be commenced in ICU. If there is any difficulty contacting the ICU Consultant, the Paediatric Respiratory Physician (Dr Freezer) should be contacted.

  3. Atrovent 1ml UDV to the salbutamol nebuliser solution, 2 hourly and monitor for anticholinergic side-effects (dilated pupils, blurred vision, urinary retention).
  4. Methylprednisolone 1 mg/kg IV stat, and then 6 hourly for the first 24 hours, 12 hourly for the second 24 hours and then daily from day The dose is reduced to minimise unwanted acute steroid side-effects (eg GI ulceration).
  5. Aminophylline IV by slow infusion from a burette through an infusion pump (IVAC).

    Loading dose = 10 mg/kg given over one hour. Give half this dose if the patient is on maintenance slow release theophylline and the serum theophylline is not known.

    Continuous Infusion - commence within 3 hours of the loading dose. The infusion should be given by IVAC with a burette and made to the following formula to ensure there is never more than 7 hours supply in the burette at any time.

    Infusion Formula: 5 mg/kg of aminophylline (0.2 ml/kg) made up to a total of 50 mls with 4% Dextrose and 0.18 % saline = 1 mg/kg/10 mls.

    Using this formula the infusion rates are:

    1-9 years: 1.1 mg/kg/hour = 11 ml/hour.

    10+ years: 0.7 mg/kg/hour = 7 ml/hour.

    NOTE: In children less than 2 years of age: Monitor the serum theophylline level closely to avoid theophylline toxicity.

    If the intravenous aminophylline is to be used in a patient on maintenance oral theophylline, take blood for a theophylline level before commencing the infusion. The loading dose needs to be varied according to the level using the formula:

    (85 - serum theophylline (umol/l))/ 8.5 = dose in mg/kg.

    Serum theophylline therapeutic range = 55-100 umol/l.


Indications for ICU Admissions

  1. Intravenous Salbutamol.
  2. No response to Salbutamol nebs given at least every hour for 3-4 hours.
  3. PaCO2 > 50 mmHg.
  4. Inability to maintain SaO2 > 92% while receiving supplemental oxygen at 8 l/min via a face mask.
Blood gases are only performed on severely ill children who do not respond to initial therapy.

Periodic Assessment Once Treatment Has Commenced

A child with acute asthma needs frequent reassessment. This will be mainly clinical but measurement of the PEF may be a useful objective method for assessing improvement. When the intravenous line is removed the child should go onto oral corticosteroids (1 mg/kg/day; max. 50 mg) and the dose tapered by approximately 5 mg/day. If the child is on maintenance slow release theophylline, this should be recommenced. If the child has not been on maintenance theophylline, it should be not be commenced.


Assessment of Interval Asthma Symptoms

Any child admitted with an acute exacerbation of asthma should have his therapy reviewed prior to discharge. In particular, a serum theophylline should be checked if the child is receiving oral theophylline.

The following questions are helpful in determining the severity of a patient's asthma between acute exacerbations:

  1. How often do you wake at night with wheeze or cough and need to use medication?
  2. How often do you wheeze or cough and have to use your medication when you wake in the morning?
  3. How often does wheeze, chest tightness or cough interfere with your sport or normal physical activity?
  4. How often do you have to use additional doses of bronchodilator because of wheezing or chest tightness? How long does a puffer last you? (A Ventolin puffer has 200 puffs therefore, if it lasts only 1 week, 28 puffs a day are being used).
  5. How much school do you miss because of asthma?

Management of Interval Symptoms

Infrequent Episodic Asthma

Exacerbations of asthma less frequently than every 3-4 weeks and usually in association with a viral upper respiratory tract infection. These patients are completely asymptomatic between exacerbations. They not usually require daily asthma medications and are usually managed by inhalation of a ß2 agonist as required.

Frequent Episodic Asthma

Frequent asthma symptoms occurring at least every 2-3 weeks but with symptom-free intervals. These patients usually require inhaled cromoglycate or corticosteroids to control their symptoms. As it has no known side-effects, cromoglycate is the drug of first choice in patients with mild-moderate asthma symptoms.

Persistent asthma

Asthma symptoms on most days. These patients are managed with regular inhaled corticosteroids to control their asthma symptoms. They may also require a long acting bronchodilator (Serevent ). These patients do not usually require daily oral corticosteroids and/or oral theophylline.

Inhalation Devices and Assessment of Technique

Children less than 3 years of age require a nebuliser or puffer via a small volume spacer with a face mask, such as an Aerochamber or a Breath-a-Tech. The child should breathe normally from the spacer for 20-30 seconds. No more than 2 puffer doses should be used in the spacer at any one time.

Children who are 3 years or older should be able to use a large volume (750 ml) spacer without a face mask (e.g. Volumatic, Nebuhaler) and take 4 or 5 slow deep breaths on command. The child does not need to hold his/her breath and must not pant from the spacer.

Children over the age of 7 years may use a Turbuhaler, Rotahaler or other dry powder device, or a puffer with a spacer device.

When using turbuhalers to give inhaled corticosteroids, the patient must be instructed to mouth rinse and spit out after the dose. If using a puffer, it should always be used with a spacer device for the delivery of inhaled corticosteroids. The use of a spacer and mouth rinsing will significantly increase the pulmonary deposition of the drug and also reduce the oropharyngeal and total body drug deposition, and reduce the risk of unwanted local and systemic side-effects.

Asthma Management Plan

All children should have an individually devised asthma management plan outlining the continuing management of their acute exacerbation and the recommencement of their regular maintenance therapy (if necessary). A written crisis plan for the management of future acute exacerbations should also be provided.

In general, a patient with an acute exacerbation of asthma requiring inhaled bronchodilators more often than every 2-3 hours should seek medical advice and treatment.

For frequent severe acute exacerbations of asthma, consider:

  • placing the patient's name on the MICA priority list.
  • giving home oxygen to drive the home nebuliser.

These services may be arranged after consultation with the Paediatric Respiratory Physician (Dr. Freezer).

Follow Up

It is essential that follow-up is arranged for every child admitted with asthma by either the local GP (in which case he/she should be phoned), or a Paediatrician.