Respiratory
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A 6 year old boy is brought to the Emergency Department with an exacerbation of his asthma. His mother tells you his symptoms have been increasing over the last 2 days but today they were much worse. The triage nurse is concerned that the child looks unwell. You note the child is unable to talk due to his shortness of breath. Despite escalating therapy, including intravenous salbutamol and magnesium, the child does not improve. On reassessment you note a silent chest and the child appears exhausted. You call the paediatric intensive care team who plan to intubate the child. What is the most suitable induction agent in this situation?
Answer:
Of the sedative agents that are available to facilitate intubation, ketamine is most commonly used. Ketamine is often recommended as the induction agent of choice for the asthma patient requiring intubation because it has bronchodilatory as well as sedative effects.Paediatric Acute Asthma
Respiratory
Last Updated: 21st March 2023
The assessment of acute asthma in children under five can be difficult. Intermittent wheezing attacks are usually triggered by viral infection and the response to asthma medication may be inconsistent. Prematurity and low birth weight are risk factors for recurrent wheezing.
The differential diagnosis of symptoms includes:
- Aspiration pneumonia
- Pneumonia
- Bronchiolitis
- Viral-induced wheeze
- Tracheomalacia
- Congenital anomalies
- Cystic fibrosis
Viral-induced wheeze
Viral-induced wheeze is a condition which largely affects children between the ages of 6 months and 5 years. Wheeze is associated with respiratory tract infection and in the majority of children the tendency to wheeze remits by 6 years of age. The mechanism by which infection causes wheeze is complex and not fully understood, but it is known that these children have abnormally small airways.
Infective exacerbations of asthma and viral-induced wheeze are often indistinguishable in children under 5 years of age who present with wheeze and a respiratory tract infection, unless there is a history of wheeze in the absence of infection. Viral respiratory tract infections are self-limiting conditions. On average, fever settles after 3–7 days, and cough resolves within 3 weeks in most children.
The following guidelines are intended for children who are thought to have acute wheeze related to underlying asthma and should be used in caution in younger children who do not yet have a considered diagnosis of asthma, particularly those under two years of age. The guidelines are not intended for children under one year of age unless directed by a respiratory paediatrician.
Initial assessment
- Clinical features
- Heart rate
- Respiratory rate and degree of breathlessness
- Use of accessory muscles of respiration
- Amount of wheezing
- Degree of agitation or confusion
- Pulse oximetry
- Consider intensive inpatient treatment of children with SpO2 < 92% in air after initial bronchodilator treatment
- Peak expiratory flow
- A measurement of < 50% predicted PEF (best of three), with poor improvement after initial bronchodilator treatment is predictive of a more prolonged asthma attack
- Chest x-ray
- Chest x-rays rarely provide additional information and are not routinely indicated
- A chest x-ray should be performed if there is subcutaneous emphysema, persisting unilateral signs suggesting pneumothorax, lobar collapse or consolidation and/or life-threatening asthma not responding to treatment
- Blood gases
- Blood gas measurements should be considered if there are life-threatening features not responding to treatment
- Normal or raised PaCO2 levels are indicative of worsening asthma (a more easily obtained free flowing venous blood PaCO2 measurement of < 6 kPa excludes hypercapnia)
Classification
Levels of severity of acute asthma attacks in children:
| Severity | Criteria |
|---|---|
| Moderate |
|
| Severe |
|
| Life-threatening | Any one of the following in a child with severe asthma:
|
Management
- Oxygen therapy
- Children with life-threatening asthma or SpO2 < 94% should receive high-flow oxygen via a tight fitting face mask or nasal cannula at sufficient flow rates to achieve normal saturations of 94 – 98%.
- β2-agonist bronchodilators
- Inhaled β2-agonists are the first line treatment for acute asthma in children.
- A pressurised metered dose inhaler (pMDI) with spacer device is the preferred option in children with mild to moderate asthma. Children under three years of age are likely to require a face mask connected to the mouthpiece of the spacer for successful drug delivery. Increase β2-agonist dose by giving one puff every 30 - 60 seconds, according to response, up to a maximum of ten puffs.
- Children with severe or life-threatening asthma should receive frequent doses of nebulised salbutamol (2.5 - 5 mg) using a nebuliser driven by oxygen and repeated every 20 - 30 minutes as necessary.
- Individualise drug dosing according to severity and adjust according to the patient's response.
- Ipratropium bromide
- If symptoms are refractory to initial β2-agonist treatment, add ipratropium bromide (250 micrograms/dose mixed with the nebulised β2-agonist solution given every 20 - 30 minutes)
- Steroid therapy
- Give oral steroids early in the treatment of acute asthma attacks in children.
- Treatment for up to three days is usually sufficient, but the length of course should be tailored to the number of days necessary to bring about recovery.
- Oral prednisolone is the steroid of choice for asthma attacks in children unless the patient is unable to tolerate the dose.
- Use a dose of 10 mg of prednisolone for children under 2 years of age, a dose of 20 mg for children aged 2 – 5 years and a dose of 30 – 40 mg for children older than 5 years.
- Repeat the dose of prednisolone in children who vomit and consider intravenous steroids in those who are unable to retain oral medication.
- Intravenous hydrocortisone (4 mg/kg repeated four hourly) should be reserved for severely affected children who are unable to retain oral medication.
- Do not use inhaled corticosteroids in place of oral steroids to treat children with an acute asthma attack.
- Nebulised magnesium sulphate
- Nebulised magnesium sulphate is not recommended for children with mild to moderate asthma attacks.
- Consider adding 150 mg magnesium sulphate to each nebulised salbutamol and ipratropium in the first hour in children with a short duration of acute severe asthma symptoms presenting with an SpO2 < 92%.
- Antibiotics
- Do not give antibiotics routinely in the management of children with acute asthma.
- Second line treatments:
- In children who respond poorly to first-line treatments, consider the addition of intravenous magnesium sulphate as first-line intravenous treatment (40 mg/kg/day).
- Consider early addition of a single bolus dose of intravenous salbutamol (15 micrograms/kg over 10 minutes) in a severe asthma attack where the child has not responded to initial inhaled therapy. A continuous intravenous infusion of salbutamol should be considered when there is uncertainty about reliable inhalation or for severe refractory asthma.
- Aminophylline is not recommended in children with mild to moderate acute asthma. Consider intravenous aminophylline (5 mg/kg loading dose over 20 minutes followed by continuous infusion at 1 mg/kg/hr) for children with severe or life-threatening asthma unresponsive to maximal doses of bronchodilators and steroids.
Discharge planning and follow up
Children can be discharged when stable on 3 - 4 hourly inhaled bronchodilators that can be continued at home. PEF and/or FEV1 should be > 75% of best or predicted and SpO2 >94%.
- Arrange follow up by primary care services within two working days.
- Arrange follow up in a paediatric asthma clinic at about one month after admission.
- Arrange referral to a paediatric respiratory specialist if there have been life-threatening features.
Drug Doses
| Drug | Dose |
|---|---|
| Oxygen | High-flow oxygen at sufficient rates to achieve SpO2 94 - 98% |
| Inhaled salbutamol |
|
| Ipratropium bromide | 250 micrograms/dose mixed with the nebulised β2 agonist solution, given every 20 - 30 minutes |
| Oral prednisolone |
|
| Intravenous hydrocortisone | 4 mg/kg repeated four hourly (reserved for severely affected children who are unable to retain oral medication) |
| Nebulised magnesium sulphate | Consider adding 150 mg to each nebulised salbutamol and ipratropium in the first hour in children with a short duration of acute severe asthma symptoms presenting with an SpO2 < 92% |
| Antibiotics | Not given routinely in acute asthma |
| Intravenous salbutamol |
|
| Intravenous aminophylline | Consider a 5 mg/kg loading dose over 20 minutes followed by continuous infusion at 1 mg/kg/hr for children with severe or life-threatening asthma unresponsive to maximal doses of bronchodilators and steroids |
| Intravenous magnesium sulphate | Consider the addition of 40 mg/kg/day as first-line intravenous treatment in children who respond poorly to first-line treatments |
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
