Acute Severe Asthma (Status asthmaticus)

Introduction

Acute severe asthma or status asthmaticus is a severe asthma that is unresponsive to repeated courses of standard medication. It is a medical emergency that requires immediate recognition and treatment.

Clinical Features

Patients with acute severe asthma typically have:

  • The inability to complete a sentence in one breath
  • A respiratory rate of 225 breaths per minute.
  • Tachycardia ≥ 110 beats per minute (pulsus paradoxus not particularly useful as it is only present in 45% of cases)
  • Peak expiratory flow rate (PEFR) of less than 50% of predicted normal or best

Features of life-threatening attack are:

  • A silent chest cyanosis or feeble respiratory effort
  • Exhaustion, confusion or coma
  • Bradycardia or hypotension
  • PEFR < 30% of predicted normal or best (approximately 150L/min in adults)
  • Arterial blood gases: -Normal or high PaCO2 > 6kPa (45mmHg)
    • Severe hypoxaemia PaO₂ < 8 kPa (60mmHg) despite oxygen therapy
  • A low and falling arterial PH
    • e.g. <7.35
  • SPO₂ <92%

Differential Diagnosis

  • Acute infective exacerbation of COPD
  • Acute pulmonary oedema
  • Tension pneumothorax
  • Pulmonary embolism
  • Anaphylaxis

Complications

  • Respiratory failure (type 1)
  • Pneumothorax or pneumomediastinum
  • Cardiac arrest
  • Hypoxaemia with hypoxic ischaemic CNS injury
  • Toxicity from medications

Investigations

  • Pulmonary function tests
  • Arterial blood gases
  • CXR
  • Sputum culture if yellowish, offensive or copious.
  • Blood culture if pyrexial
  • FBC and ESR
  • EUCr

Management

A medical emergency thus intervention is started immediately along with history taking and physical examination.

  • Quickly assess severity of attack.
  • Alert ICU if life-threatening
  • Sit patient up and give high dose Oxygen 40-60% via a non rebreathing bag
  • Nebulised salbutamol 5mg is given.
    • This can be repeated 4 hourly for 4 doses
  • IV Hydrocortisone sodium succinate 200mg 4 hourly for 24 hours.
  • Prednisolone is continued at 40-60mg orally daily for 2 weeks.
  • Nebulised ipratropium bromide 0.5mg may be added.

If life-threatening features are present:

  • Inform ICU and senior colleagues.
  • Add MgSO, 1.2-2g IV over 20mins
  • Give salbutamol nebulizer every 15mins or 10mg continuously per hour.
  • Monitor ECG; watch for arrhythmias.

Further management

  • If patient is improving: 40-60% oxygen
  • Tab Prednisolone 40-50mg per day for at least 5days.
  • Nebulised salbutamol 4 hourly
  • Monitor peak flow and oxygen saturations

If patient is not improving after 15-30mins:

  • Continue 100% oxygen and steroids
  • IV Hydrocortisone 100mg or Tab prednisolone 30mg if not already given..
  • Give salbutamol nebulizer every 15mins or 10mg continuously per hour.
  • Continue ipratropium 0.5mg every 4 – 6hrs

If patient still not improving:

  • Discuss with ICU and seniors
  • Continue 100% oxygen
  • Repeat nebulised salbutamol every 15mins or give IV infusion 3-20ug/min –
  • consider Aminophylline: load with 5mg/kg IVI over 20mins, then 500ug/kg/hr.

If still no improvement or life-threatening features are present;

  • consider transfer to ICU.
  • Do arterial blood gases and if PaCO, >7kPa, ventilation may be required.

Monitoring Treatment

  • Repeat peak expiratory flow (PEF) 15-30mins after initiating treatment
  • Pulse oximeter monitoring: maintain SAPO,>92%
  • Check Arterial blood gas (ABG) within 2hrs if: initial PaCO, was normal or raised or initial PaO, <8kPa (60mmHg) or patient is deteriorating.
  • Record PEF pre- and post-ß-agonist in hospital at least 4 times.

Once patient is improving,

  • Wean down and stop Aminophylline over 12-24hours.
  • Reduce nebulised salbutamol and switch to inhaled ß-agonist
  • Initiate inhaled steroids and stop oral steroids if possible.
  • Continue to monitor PEF.
  • Look for deterioration on reduced treatment and beware of early morning dips in PEF
  • Look for the cause of the acute
    exacerbation and admission and take care of it.

Discharge

Patients before discharge, must have:

  • Been stable on discharge medications
  • Had inhaler technique checked
  • PEF >75% Predicted or best with diurnal variability <25%
  • Steroids (inhaled and oral) and
    bronchodilator therapy
  • Own a PEF meter and have management plan
  • Respiratory clinic appointment within 4 weeks and GP appointment within a week.

Common Adverse Drug Effects

  • Oxygen: seizure, retinal detachment, Acute respiratory distress syndrome (ARD) etc
  • Steroids: diabetes mellitus, osteoporosis, proximal myopathy, PUD, Cushing’s syndrome, growth retardation.
  • Beta-agonists: fine tremors, nervous tremors, palpitation, headache ,muscle cramps, tachycardia, arrhythmias,
    peripheral vasodilatation, insomnia, hypokalemia
  • Ipratropium: taste disorders, GERD, Pharyngitis, dysuria, insomnia
  • Aminophylline: palpitations,
    tachycardia, arrhythmia, nausea,
    vomiting, gastric irritation, headache, convulsion, hypertension (better avoided in the elderly, patients with arrhythmias, high BP)
  • MgSO: nausea, vomiting, flushing of
    skin, hypotension, arrhythmias,
    respiratory depression and muscle
    weakness.