Sun21November0437PM 11

A 22-year-old male is admitted wheezing with a respiratory rate of 35/min, a pulse of 120 beats per min, blood pressure 110/70 mmHg, peak expiratory flow rate <50% predicted.

He has been given back-to-back nebulisers of salbutamol 5 mg and ipratroprium 0.5 mg for the last 45minutes and is on face mask oxygen. He has been given hydrocortisone 100 mg IV. The intensive care team are aware of the patient.

His arterial blood gas (done on high-flow oxygen) reveals:

pH 7.42 (7.36-7.44)

PaCO2 5.0 kPa (4.7-6.0)

PaO2 22 kPa (11.3-12.6)

Base excess -2 mmol/L (+/-2)

SpO2 98

Which therapy should be implemented next?

(Please select 1 option)

Magnesium 1-2 g IV Correct

Intubation and ventilation

Oral aminophylline

Oral prednisolone

Non-invasive ventilation

Explanation

This patient fits the criteria for life threatening asthma.

A normal PaCO2 in an asthmatic is a warning of impending respiratory failure as the patient becomes too tired to ventilate adequately.

Initial treatment has been given: ß2-agonists should be administered as soon as possible, preferably nebulised driven by oxygen. Repeat doses should be given at 15-30 minute intervals, or continuous nebulisation can be used where there is inadequate response to bolus therapy.

Nebulised ipratropium bromide should be added for patients with acute severe or life threatening asthma, or those with a poor initial response. Its addition produces significantly greater bronchodilation than a ß2-agonist alone.

Oxygen should be given to maintain saturations at 94-98%. Patients with saturations less than 92% on air should have an ABG to exclude hypercapnia. However, starting treatment should not be delayed to do the ABG. Initially high-flow oxygen is used, and then weaned to maintain adequate saturations. Unless you suspect COPD there is no need to be cautious with oxygen therapy.

This gentleman is receiving adequate ipratropium and oxygen, and repeating/increasing these are unlikely to help the situation markedly.

Failure to respond to the above treatment steps warrants the use of intravenous magnesium sulphate (or aminophylline, but this is not an option here). Magnesium has been shown to result in bronchial smooth muscle relaxation. Before intubation and ventilation it is appropriate to trial magnesium sulphate first.

Intensive care is indicated for patients with severe acute or life threatening asthma who are failing to respond to therapy. Consider it in patients with:

Deteriorating peak flow

Persisting or worsening hypoxia

Hypercapnia

Acidosis

Exhaustion, or

Altered conscious state.

All patients who are transferred to an intensive care unit should be accompanied by a doctor who can intubate if necessary. This would be considered if this gentleman fails to respond to magnesium, and in a clinical setting you would want to discuss him with your ITU colleagues whilst the magnesium was being given.

Chest radiographs are not indicated unless you suspect pneumothorax or consolidation, or there is life threatening asthma, a failure to respond to treatment or a need for ventilation.

As an additional point, steroids reduce mortality, relapses, subsequent hospital admission and requirement for ß2-agonists1. The earlier they are given in the attack, the better the outcome.

A dose of 40-50 mg prednisolone (or IV equivalent) should therefore be given once oxygen and nebuliser therapy has been established. This should be continued for five days, or until recovery, and can then be stopped abruptly unless the patient has taken long term oral corticosteroids.

Reference:

British Thoracic Society. Asthma Guideline.

Answer Statistics

1

52%

2

8%

3

1%

4

10%

5

31%

Times answered: 294