acute asthma in the adult patient

see also:

• paediatric asthma
• asthma
• beta 2 adrenergic agonists
• Mx of the wheezy elderly patient - acute pulmonary oedema versus asthma
• AFTB's lecture notes - Mx of acute asthma

• most patients who die from asthma have chronic severe asthma
• a minority who die from asthma have mild-mod chronic symptoms and develop a sudden severe attack
• some die following inappropriate prescribing of sedatives, hypnotics and anxiolytics, beta adrenergic blockers, aspirin (acetylsalicylic acid) or non-steroidal anti-inflammatory drugs (NSAIDs)

• severe asthma:
  • PH near-fatal attack resulting in respiratory acidosis or requiring intubation, or,
  • PH admission for asthma in previous year, or,
  • requiring 3 or more classes of asthma therapy medications, or,
  • heavy use of beta 2 adrenergic agonists, or,
  • repeated attendances to ED for asthma care in past year, or,
  • “brittle” asthma
• AND adverse behavioural patterns such as:
  • non-compliance
  • failure to attend appointments
  • few contacts with GP
  • frequent home visits by GP
  • self-discharge from hospital
  • mental health illness
  • major tranquilliser use
  • denial
  • alcohol or substance abuse
  • obesity
  • learning difficulties
  • employment or financial problems
  • social isolation
  • childhood abuse
  • severe marital, domestic or legal stress

• prioritise therapy in an achievable sequence
• continuous nebulised salbutamol (in oxygen)
• use high flow intranasal oxygen if needed to maintain sats above 92%
• IV hydrocortisone 250mg bolus
• MgSO4 infusion IV (20mmol in 100ml saline over 30-60 minutes)
• nebulised ipratropium bromide (0.5 mg 4-6 hourly) if inadequate response to beta 2 agonists
• consider sub-dissociative bronchodilator doses of IV ketamine at 0.1mg/kg/hr.
• in the agitated patient use IV ketamine 20 to 40mg (0.5mg/kg) to achieve mild dissociation
• if using ketamine, co-administer antiemetic (Ondansetron 8mg)
• prepare for modified rapid sequence induction (RSI) for emergency intubation but temporize with maximal medical therapy in conjunction with trial of bilevel non-invasive ventilation (initial settings iPAP 12, ePAP 5, 80% FiO2)
• the aim is to avoid intubation if at all possible
• if intubation can't be avoided, ketamine is the induction agent of choice
  • pre-oxygenate with high flow intranasal cannula at 60Lm/min
  • give 25% of the total dose over 1 minute, wait a minute for it to circulate
  • give 50% of the total dose, wait a minute for it to circulate
  • then give the remainder of the ketamine dose along with Rocuronium at 1.2mg/kg lean weight
  • after 15 secs, lay patient down and proceed to intubation
  • aim for RR 6, tidal volume 6ml/kg ideal body weight, prolonged exp. time to decrease autoPEEP, and aim for a plateau pressure of < 30mmHg
• be prepared for post-intubation hypotension and look out for hyperinflation of the chest
• titrated crystalloid boluses to offset hypovolaemia
• bedside CXR to exclude other diagnoses or complications if:
  • suspected pneumomediastinum or pneumothorax
  • suspected consolidation
  • failure to respond to treatment satisfactorily
• arterial gases are unnecessary and only cause more distress to the patient
• venous gases are suitable if hypercarbia is suspected

• oxygen to maintain SaO2 94-98%
• nebulised beta 2 adrenergic agonists (or metered-dose-inhaler via spacer device)
  • repeat bolus doses every 15-30 minutes initially if still SOB but not needing continuous nebs
• oral corticosteroids
  • steroid tablets are as effective as injected steroids, provided they can be swallowed and retained
  • use oral prednisolone 50mg once daily (equivalent to IV hydrocortisone 100mg qid)

• diagnosis is based on recognition of characteristic pattern of symptoms and signs and the absence of
• inhaled foreign body / aspiration
• acute pulmonary oedema (APO)
• chronic obstructive pulmonary disease (COPD)
• Acute Respiratory Distress Syndrome (ARDS)
• pneumothorax
• pneumonia
• pulmonary embolism (PE)
• pulmonary fibrosis
• bronchiectasis
• sarcoidosis
• strongyloidiasis - in those who have lived in the tropics - Loffler's syndrome (acute onset eosinophilic pneumonitis) can also be caused by Ascaris lumbricoides, and the hookworms Ancylostoma duodenale and Necator americanus.
• large airway stenosis
• hyperventilation

• raised PaCO2 and/or requiring mechanical ventilation with raised inflation pressures

• severe asthma signs plus any one of:
  • altered conscious level
  • exhaustion
  • arrhythmia
  • hypotension
  • cyanosis
  • silent chest
  • poor respiratory effort
  • PEF <33% best or predicted
  • SpO2 <92%
  • PaO2 <8 kPa
  • “normal” PaCO2 (4.6–6.0 kPa)

• any one of:
  • unable to complete a sentence in one breath
  • respiratory rate >= 25
  • heart rate >= 110/min
  • PEF 33-50% best or predicted

• increasing symptoms
• PEF >50-75% best or predicted
• no features of acute severe asthma

• Type 1:
  • wide PEF variability (>40% diurnal variation for >50% of the time over a period >150 days) despite intense therapy
• Type 2:
  • sudden severe attacks on a background of apparently well controlled asthma

• closely monitor for hypoxia, hypercapnoea, exhaustion, drowsiness, confusion, hypokalaemia or complications
• if near-fatal or life threatening attack with inadequate response, consider:
  • *use high flow intranasal oxygen
  • single dose of iv magnesium sulphate (1.2-2 g IV infusion over 20 minutes) should only be used following consultation with senior medical staff, although it does appear to be safe as a single dose and may offer benefit
  • iv aminophylline (5 mg/kg loading dose over 20 minutes unless on maintenance oral therapy, then infusion of 0.5-0.7 mg/kg/hr).
    • measure the serum theophylline concentration if aminophylline is continued for more than 24 hours (aim at a concentration of 10-20mg/l or 55-110 mol/l)
  • trial of BiPAP if underlying chronic obstructive pulmonary disease (COPD) and patient in resus area or ICU
  • rapid sequence induction (RSI) for emergency intubation using iv ketamine
  • transfer to ICU with experienced medical escort capable of intubation
• assess need for antibiotic Rx, although most cases are NOT bacterial and thus do NOT need antibiotics
  • there may be a role for procalcitonin levels to assist in this decision¹⁾
• admit if either:
  • life threatening or near fatal attack
  • any feature of severe attack persisting despite initial Rx
  • PEFR < 75% of expected 1 hour after initial Rx
  • high risk patients such as poor compliance, lives alone, PH brittle asthma, night-time, pregnant, exacerbation despite oral steroids
• discharge:
  • patient should have clinical signs compatible with home management, be on reducing amounts of β2 agonist (preferably no more than four hourly) and be on medical therapy they can continue safely at home
    • NB. patients discharged with PEF <75% best or predicted and with diurnal variability >25% are at greater risk of early relapse and readmission
  • patient should be given a written asthma management plan
  • patient should have 5 days of oral prednisolone 50mg per day

• British Thoracic Society. Scottish Intercollegiate Guidelines Network (SIGN). British guideline on the management of asthma. A national clinical guideline. Published May 2008, revised June 2009. (pdf)