Pharmacology
Respiratory
Question 93 of 180
A 19 year old student presents to ED with severe acute asthma. You prescribe a salbutamol and ipratropium bromide nebuliser. What is the most appropriate dose of ipratropium bromide to prescribe initially for this patient:
Answer:
The BTS/SIGN guidelines state: Add nebulised ipratropium bromide (0.5 mg 4 – 6 hourly) to nebulised beta2-agonist treatment for patients with acute severe or life threatening asthma or those with a poor initial response to beta2-agonist therapy to provide greater bronchodilation.Management of Acute Asthma
Pharmacology / Respiratory
Last Updated: 3rd April 2019
Asthma is a common chronic inflammatory condition of the airways characterised by bronchoconstriction. The most frequent symptoms are cough, wheezing, chest tightness, and shortness of breath. The bronchoconstriction is usually reversible (either spontaneously or with the aid of medication) leading to intermittent symptoms, but in some patients with chronic asthma the inflammation may result in irreversible airway obstruction. Occasionally, asthma symptoms can get gradually or suddenly worse provoking an acute asthma attack that, if severe, may require hospitalisation.
Classification of Acute Asthma in Adults
The nature of treatment required for the management of acute asthma depends on the level of severity, described as follows:
| Severity | Criteria |
|---|---|
| Moderate |
|
| Severe | Any one of:
|
| Life-threatening | Any one of the following in someone with severe asthma:
|
| Near-fatal | Respiratory acidosis (increased arterial PaCO2) and/or requiring mechanical ventilation with increased inflation pressures |
BTS/SIGN Management of Acute Asthma in Adults
Patients with moderate asthma should be treated at home or in primary care according to response to treatment, while patients with severe or life-threatening acute asthma should start treatment as soon as possible and be admitted to hospital immediately following initial assessment.
Management of acute asthma:
- Oxygen therapy:
- Give controlled supplementary oxygen therapy for all hypoxaemic patients with severe acute asthma to maintain saturations of 94 – 98% (unless patient at risk of hypercapnic respiratory failure)
- High-dose inhaled short-acting beta2-agonists are the first line treatment (salbutamol or terbutaline):
- A pressurised metered dose inhaler with spacer device is preferred in patients with moderate to severe asthma (4 puffs initially, followed by 2 puffs every 2 minutes according to response, up to 10 puffs, whole process repeated every 10 – 20 minutes if necessary)
- The oxygen-driven nebulised route is recommended for patients with life-threatening features or poorly responsive severe asthma (salbutamol 5 mg at 15 - 30 minute intervals)
- Consider continuous nebulisation in patients with severe acute asthma that is poorly responsive to initial bolus dose (salbutamol at 5 - 10 mg/hour)
- Reserve intravenous route for those in whom inhaled therapy cannot be used reliably
- Ipratropium bromide (muscarinic antagonist):
- Add nebulised ipratropium bromide (0.5 mg 4 – 6 hourly) to nebulised beta2-agonist treatment for patients with acute severe or life threatening asthma or those with a poor initial response to beta2-agonist therapy to provide greater bronchodilation
- Steroid therapy:
- Steroids reduce mortality, relapses, subsequent hospital admission and requirement for β2 agonist therapy. The earlier they are given in the acute attack the better the outcome.
- Give steroids in adequate doses (prednisolone 40 - 50 mg) to all patients with an acute asthma attack; steroid tablets are as effective as injected steroids, provided they can be swallowed and retained
- Continue oral prednisolone (40 – 50 mg) daily for at least five days or until recovery (steroids can usually be stopped abruptly, dose does not need tapering)
- Parenteral hydrocortisone (100 mg every 6 h, 400 mg daily) or intramuscular methylprednisolone (160 mg) are alternatives in patients who are unable to take oral prednisolone
- Magnesium sulphate:
- Nebulised magnesium is not recommended for treatment in adults with acute asthma
- Consider giving a single dose of IV magnesium sulphate (1.2 - 2 g IV infusion over 20 minutes) to patients with acute severe asthma who have not had a good initial response to inhaled bronchodilator therapy
- Aminophylline:
- Intravenous aminophylline is not likely to result in any additional bronchodilation compared to standard care with inhaled bronchodilators and steroids and may cause side effects such as arrhythmias and vomiting.
- However, some patients with near-fatal asthma or life-threatening asthma with a poor response to initial therapy may gain additional benefit from IV aminophylline (5 mg/kg loading dose over 20 minutes unless on maintenance oral therapy, then continuous infusion of 0.5 – 0.7 mg/kg/hr)
- Intravenous magnesium sulphate or aminophylline should only be used following consultation with senior medical staff
- Routine prescription of antibiotics is not indicated for patients with acute asthma
| Drug | Dose |
|---|---|
| Oxygen | Give controlled supplementary oxygen therapy for all hypoxaemic patients with acute severe asthma to maintain saturations of 94 - 98% |
| Salbutamol |
|
| Ipratropium bromide | Add nebulised ipratropium bromide 0.5 mg 4 - 6 hourly to nebulised beta2-agonist treatment for patients with acute severe or life threatening asthma or those with a poor initial response to beta2-agonist therapy |
| Steroid |
|
| Magnesium sulphate |
|
| Aminophylline | Some patients with near-fatal asthma or life-threatening asthma with a poor response to initial therapy may gain additional benefit from IV aminophylline 5 mg/kg loading dose over 20 minutes unless on maintenance oral therapy, then continuous infusion of 0.5 - 0.7 mg/kg/hr |
| Antibiotics | Not routinely prescribed in acute asthma |
Patient Disposal
Patients whose PEFR is > 75% of predicted or best one hour after initial treatment may be discharged from ED (unless there are other reasons why admission is appropriate). It is essential that the patient’s primary care practice is informed within 24 hours of discharge from the emergency department or hospital following an asthma attack.
Admit all patients:
- with any features of life-threatening or near-fatal asthma attack
- with any feature of severe asthma attack persisting after initial treatment
Refer to ITU any patient:
- requiring ventilatory support
- with acute severe or life-threatening asthma, who is failing to respond to therapy, as evidenced by:
- deteriorating PEF
- persisting or worsening hypoxia
- hypercapnia
- ABG analysis showing decreased pH or increased H+
- exhaustion, feeble respiration
- drowsiness, confusion, altered conscious state
- respiratory arrest
https://www.brit-thoracic.org.uk/quality-improvement/guidelines/asthma/
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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 |
