Acute Severe Asthma and Status Asthmaticus

Status asthmaticus is severe asthma that does not respond well to immediate care. It is a potentially life-threatening situation.

Much of this article is based on the SIGN guidelines and where appropriate the levels of evidence are given.¹

Related articles on asthma include:

• Asthma action plans
• Occupational asthma
• Peak flow recording
• Wheezing in children
• Which device in asthma

According to Asthma-UK:

• There were 69,000 hospital admissions for asthma in 2002.
• On average, 1,400 people die from asthma each year in the UK. About a third of deaths (34%) are in people under 65.
• An estimated 75% of admissions for asthma are avoidable and as many as 90% of the deaths from asthma are preventable.
• Most deaths occurred before admission to hospital.

Risk Factors

• Most deaths are in patients with chronic severe asthma and few in people with better controlled disease²
• Personal or passive smoking
• Frequent attenders with problems of asthma are at great risk
• Those who take long acting beta agonists such as salmeterol may be at increased risk, especially if not using a steroid inhaler too.³

Symptoms

• Shortness of breath may have developed over hours or days but is usually progressive rather than sudden
• A history of poor control is common
• Often they have been using their inhalers excessively with decreasing response
• Possible URTI or exposure to an irritant atmosphere

Signs

• The patient will usually appear pink but if cyanosed this is serious
• Respiratory rate is raised
• Tachycardia is usual and may be increased by excessive intake of beta agonists
• Accessory muscles of respiration are employed and the chest appears hyper-inflated
• In normal breathing the ratio of the duration of inspiration to expiration is about 1:2 but as asthma becomes more severe the expiratory phase becomes relatively more prolonged
• There are usually expiratory ronchi but they may be inspiratory too. A very tight chest may not wheeze at all. Beware the silent chest
• SIGN no longer recommend pulsus paradoxus as a useful guide for practical reasons¹
• Make an objective assessment of severity using a peak flow meter or spirometer

• Wheezing in children can be caused by a variety of conditions including RSV causing bronchiolitis, epiglottis and croup
• Inhalation of foreign body and other causes of stridor
• Pneumothorax with or without asthma
• Cardiac failure (cardiac asthma)

Take a very quick history and brief examination (conscious level (Glasgow Coma scale or AVPU), colour, pulse, BP, respiratory rate, listen to chest - Airway, Breathing, Circulation, etc.).
Supplement with bedside investigations if available:

• Peak Expiratory Flow Rate - This can be useful as an objective measurement but in distress, cooperation may be poor. PF can be unreliable below the age of 12 and may be impossible to measure in the very young.
• Pulse Oximetry - a good quick measure of oxygenation.

Use this to assess severity:

Assess Severity

• Consider need for 999 ambulance if in community.
• Give high flow oxygen (>60%) if available.
• Give nebulised salbutamol via oxygen driven nebuliser in adults or older children. In children under 2 initially give up to 10 puffs of salbutamol inhaler via spacer and face mask. Outside hospital, if no nebuliser is available, give beta agonist inhaler via a large spacer device until oxygen and nebuliser available.
• ALL patients - If severe or poor response give nebulised ipratropium¹ (Evidence level A). This can be mixed with nebulised salbutamol (i.e. combined with step above) in adults and children > 2 years. This is useful at the extremes of age as adrenergic receptors are poorly developed until about 12 to 18 months old and tend to wane after 40 years.
• Corticosteroids - give oral steroids (10mg if <2, 20 mg if aged 2-5, 30-40mg in older children and 40-50 mg in adults). If severe or oral route not available give hydrocortisone 100mg iv.

Further Assessment and Monitoring

• Reassess with further exam every 10-15 minutes.
• Arrange admission in moderate and severe cases
• Arterial blood gases should be checked (if available)
  The 4 stages of blood gas progression in status asthmaticus are as follows:
  • The 1st stage is characterised by hyperventilation with a normal pO₂ and low pCO₂
  • The 2nd stage has hyperventilation but hypoxemia so that both pO₂ and pCO₂ are low
  • The 3rd stage gives a "false-normal" pCO₂ as ventilation has decreased. This is extremely serious and indicates respiratory muscle fatigue with the need for admission to the ICU and, probably, intubation with mechanical ventilation
  • The 4th stage has a low pO₂ and a high pCO₂ as respiratory muscles fail. This is even more serious and requires intubation and ventilatory support
  Those in the first 2 stages do not necessarily require hospital admission if 1 hour after initial therapy the PF is at least 75% of predicted or best¹ (Evidence level C). Poorer response or any risk factors should require admission¹ (Evidence level B).
  
  The 3rd and 4th stages require admission to ICU.
• Consider the need for CXR. In asthma it may show some hyper-inflation but is rather unimpressive. It may still be required to exclude inhalation, pneumothorax, pulmonary oedema or COPD. Routine CXR is not recommended.¹
• Send sputum for culture.

• If acute asthma presents in the late afternoon or evening consider hospital admission as they are likely to have problems overnight
• Acute asthma in pregnancy requires hospital admission¹ (Evidence level D)
• Young children can be very difficult to assess the severity of asthma and they change rapidly
• Patients may be anxious or have had poor sleep for many nights but any sedative, especially benzodiazepines should be avoided as they reduce respiratory drive

IV rehydration and correction of hypokalaemia may be required but in primary care the first priority must be the reversal of airways obstruction. If the patient is a frightened and desperate child, it can be very difficult to get compliance with a nebuliser and to accept a face mask. Achieving IV access under such conditions may not be feasible.

Even the noise of a nebuliser scares small children and a spacer device may be as effective.⁵ It is certainly worth using if no nebuliser is to hand.

Some Further Notes

• Acute asthma is an inflammatory process and steroids are life-saving.¹ (Evidence level A)
• A typical initial dose for an adult is 40mg prednisolone, continued for at least 5 days or possibly longer.
  • There is no advantage to IV rather than oral administration under normal circumstances.^6,7
  • Give the patient 8 tablets of 5mg prednisolone and a large glass of water to help swallow them.
  • Soluble prednisolone is normally used for children.
• In severe or refractory cases IV magnesium sulphate may be considered¹ (Evidence level A). It is used more often in pregnancy.
• IV aminophylline has been abandoned as it is potentially dangerous and adds no benefit to modern treatment.⁸
• There is no evidence of benefit from leukotrine antagonists in the acute situation.⁹
• Antibiotics are not recommended unless there is evidence of infection¹ (Evidence level B).

Ventilation

• If the respiratory muscles are not coping, help will be required with ventilation
• Often the 3rd and always the 4th stages require ICU and ventilation
• If airways obstruction is marked, a higher pressure is required and this carries a poorer prognosis

The risk of death is increased where there is delay in starting steroids, other disease such as congestive heart failure or COPD and in smokers. Mortality is highest in the very young and very old.

• All patients with asthma, but especially those with poorly controlled disease should have regular review.
• In addition to an asthma register, an "at risk" asthma register may help.² If "at-risk" patients fail to attend for appointments this should be followed up.¹⁰
• Those who are difficult to control need referral to specialist services.
• Be especially vigilant about those with psycho-social adverse factors too.
• Only those with the mildest asthma should be permitted beta agonist therapy only.
• Receptionists, ambulance control and those who are first point of contact by patients must appreciate that an asthmatic having difficulty breathing needs to be seen as an emergency.
• Hospital admission should be an opportunity to review the patient's care plan¹ (Evidence level A).
• Anyone who has required admission should be followed up by a respiratory physician after.
• Education is essential so that the patient does not let a severe condition develop before seeking help.¹¹ Self managed action plans are valuable.¹²