User Tools

Site Tools


asthma_adult

acute asthma in the adult patient

introduction

patients at risk of developing near-fatal or fatal attacks

  • 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
    • learning difficulties
    • employment or financial problems
    • social isolation
    • childhood abuse
    • severe marital, domestic or legal stress

Mx of acute asthma in the ED

Manage in resus area for severe presentations

  • 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:
  • arterial gases are unnecessary and only cause more distress to the patient
  • venous gases are suitable if hypercarbia is suspected

standard moderate-to-severe-asthma care

  • 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
    • 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)

could it be something else?

assess and recognise severity

near fatal asthma attack

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

life threatening asthma attack

  • 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)

severe asthma attack

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

moderate attack

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

brittle 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

further Mx according to response to initial Rx and severity

  • 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
    • 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

references

asthma_adult.txt · Last modified: 2020/01/07 14:00 (external edit)