Acute Asthma in Adults

Question 1

What is acute asthma?

Answer 1

A rapid deterioration in asthma symptoms

Question 2

What can trigger acute asthma?

Answer 2

Any of the typical asthma triggers such as infection, exercise or cold weather.

Question 3

Presentation

Answer 3

Progressively worsening shortness of breath

Use of accessory muscles

Fast respiratory rate (tachypnoea)

Symmetrical expiratory wheeze on auscultation

The chest can sound “tight” on auscultation with reduced air entry

Question 4

How can acute asthma be graded?

Answer 4

Moderate
Severe
Life threatening

Question 5

What is moderate asthma?

Answer 5

PEFR 50 – 75% predicted

Resp rate < 25

Heart rate <110

SaO2 > 92%

PaO2 > 8kPa

Normal speech

Question 6

What is severe asthma?

Answer 6

PEFR 33-50% predicted

Resp rate >25

Heart rate >110

SaO2 > 92%

PaO2 > 8kPa

Unable to complete sentences

Question 7

What is life threatening asthma?

Answer 7

PEFR <33%

Sats <92%

Becoming tired

No wheeze. This occurs when the airways are so tight that there is no air entry at all. This is ominously described as a “silent chest”.

Haemodynamic instability (i.e. shock)

Brachycardia

Confusion

Exhaustion

Cyanosis

Poor respiratory effort

SaO2 < 92%

PaO2 <8kPa

PCO2 normal or decreased (hypoventilation) NORMAL: 38 to 42 mm Hg (5.1 to 5.6 kPa)

Question 8

What is near fatal asthma?

Answer 8

Increased PaCO2 NORMAL: 38 to 42 mm Hg (5.1 to 5.6 kPa)

Question 9

Investigations

Answer 9

ABG: type 2 respiratory failure (low PaO2 and high PaCO2) is a sign of a life-threatening attack.

Routine blood tests (including FBC, CRP): to look for precipitating causes of an asthma attack, such as an infection.

Chest x-ray: to exclude differentials and possibly identify a precipitating infection.

Question 10

Management of moderate acute asthma

Answer 10

Increased inhaler use (i.e. salbutamol 5mg repeated as often as required)

Steroids. Oral prednisolone or IV hydrocortisone. These are continued for 5 days

Nebulised ipratropium bromide in those who do not respond to the beta 2 agonist

Treat cause of exacerbation - antibiotics if there is convincing evidence of bacterial infection

Question 11

Management of severe acute asthma

Answer 11

Nebuliased SABA/SAMA

Oral/IV steroid - oral Prednisolone or IV Hydrocortisone

Oxygen if required to maintain sats 94-98%

Magnesium

Aminophylline infusion

Consider IV salbutamol

Admit to Level 2/3 care, HUD, ICU - if fail to respond to initial treatment

Question 12

Management of life threatening acute asthma

Answer 12

IV magnesium sulphate infusion

Nebulised SABA

Admission to HDU / ICU

Intubation in worst cases – should be early, very difficult to intubate with severe bronchoconstriction

Question 13

ABGs in asthma

Answer 13

Respiratory alkalosis as tachypnoea causes a drop in CO2.

A normal pCO2 or hypoxia is a concerning sign as it means they are tiring and indicates life threatening asthma.

A respiratory acidosis due to high CO2 is a very bad sign in asthma.

Question 14

How should you monitor response to treatment?

Answer 14

Respiratory rate
Respiratory effort
Peak flow
Oxygen saturations
Chest auscultation

Question 15

Why should serum potassium be monitored when on salbutamol?

Answer 15

As it causes potassium to be absorbed from the blood into the cells.

Salbutamol also causes tachycardia (fast heart rate).

Question 16

Hospital admission criteria

Answer 16

All patients with life-threatening should be admitted in hospital

Patients with features of severe acute asthma should also be admitted if they fail to respond to initial treatment

Other admission criteria include a previous near-fatal asthma attack, pregnancy, an attack occurring despite already using oral corticosteroid and presentation at night

Question 17

What should be given to ALL patients who have had an acute asthma attack?

Answer 17

40-50mg of prednisolone orally (PO) daily

Continued for at least five days or until the patient recovers from the attack

Question 18

Discharge criteria

Answer 18

Stable on their discharge medication (i.e. no nebulisers or oxygen) for 12–24 hours
Inhaler technique checked and recorded
PEF >75% of best or predicted

Question 19

When is ipratropium bromide used?

Answer 19

severe or life-threatening asthma, or in patients who have not responded to beta₂-agonist and corticosteroid treatment, nebulised ipratropium bromide, a short-acting muscarinic antagonist