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Acute Asthma
Last updated 14th September 2022
Risk of Dying From Asthma
- Most asthma deaths are preventable. Disease factors, poor medical management and patient’s behaviour/psychosocial status all predict a poor outcome
- Disease factors – most deaths occur in chronic severe asthma
- Poor medical management – inadequate assessment, treatment, follow up and referral. Beware inappropriate prescription of Beta blockers and NSAIDs
- Behavioural/psychosocial factors -see section below
SIGN/BTS Recognise 5 Categories of Acute Asthma As Follows
1 Near Fatal Asthma
- Raised PaCO2 and/or requiring mechanical ventilation with raised inflation pressures
2 Life Threatening Asthma
Any one of the following in a patient with severe asthma
- Altered conscious level
- Exhaustion
- Hypotension
- Cyanosis
- Silent chest
- Poor respiratory effort
- PEF <33% of best or predicted
- SpO2 <92%
- PaO2 <8kPa
- “normal” PaCO2 4.6-6.0kPa
3 Acute Severe Asthma
Any one of:
- inability to complete sentences in one breath
- PEF 33-50% best or predicted
- RR >25/min
- HR > 110/min
4 Moderate Asthma
Increasing symptoms but…
- No features of acute severe asthma and…
- PEF 50-75% best or predicted
5 Brittle Asthma
- Type 1 – wide PEF variabilty >40% diurnal variation for >50% of the time over a period of >150 days despite intensive therapy
- Type 2 – sudden severe attacks on a background of apparently well controlled asthma
Investigations
- PEFR or FEV1 – PEFR easier during acute attack
- SpO2 – noting whether on or off oxygen
- Gases if SpO2 <92% on or off oxygen
- CXR – to exclude pneumothorax and consolidation
- Routine bloods including WCC and CRP
Interpretation of Arterial Blood Gases
- Hydrogen ions >45 indicates acidosis
- Normal PaO2 >10.6 kPa – significantly hypoxic if < 8 kPa
- Normal PaCO2 4.7-6.0 kPa isn’t normal in the context of acute asthma – indicates potentially life threatening asthma
- CO2 retention if >6.0 kPa – indicates near fatal asthma
Immediate Management Acute Severe Asthma
- Oxygen – for all hypoxaemic patients with acute severe asthma using face mask, venturi mask or nasal cannulae to maintain SpO2 94-98%
- Salbutamol – 5mg 4-6 hourly by oxygen driven nebuliser.
- Ipratropium – 0.5mg 4-6 hourly by oxygen driven nebuliser
- Prednisolone – 40-50mg od unless tabs cannot be swallowed and retained in which case Hydrocortisone 100 mg qds IV. Continue Prednisolone at 40-50mg daily for at least 5 days or until recovery. Doses do not need tapering unless on maintenance steroid or steroid required for three or more weeks
- Do not give antibiotics routinely and avoid sedatives
If Life Threatening Features Present
- Discuss further options with senior clinician ± intensivists
- Consider single dose Magnesium 1.2-2.0g IV (which is 2.4 – 4.0ml of 50% magnesium sulfate injection) in 50ml or 100ml of 0.9% sodium chloride over 20 minutes.
- Consider nebulised Salbutamol more frequently eg 5mg up to every 15-30 minutes or continuously at 5-10mg/hr using an appropriate nebuliser.
Additional Measures if Not Settling
- Discuss with senior clinician, consider magnesium if not already given, more frequent nebulised salbutamol as above
- Senior clinician may recommend IV salbutamol, IV aminophylline or progression to NIV/full ventilation. If NIV should be on ICU because of risk of cardiovascular collapse.
- IV salbutamol – use infusion formulation 5mg/ml. Add 5ml solution to 500ml Dextrose 5% or Saline 0.9% to give concentration 10 micrograms/ml and infuse at 5 micrograms/min (30ml/hr) adjusting according to response and heart rate , in range 3-20 micrograms/min (18-120ml/hr)
- IV Aminophylline – 5mg/kg (usually 250mg) in 5% dextrose over 20 min unless already taking oral theophylline. Can be continued as infusion of 500 micrograms/kg/hr, adjusted to maintain plasma concentration 10-20mg/L, if necessary
When to Call The Anaesthetist
- If any features if life threatening asthma present.
- Or if PaO2 < 6kPa despite high flow O2, or if PaCO2 > 6 kPa or rising.
Referral to Respiratory Nurse Specialist
- All patients with asthma should be referred to a respiratory nurse specialist within 48 hours of admission.
- Those based at DGRI are Phyllis Murphie (33860) and Yvonne Scott (32007)
Asthma Discharge Bundle
- The Respiratory Team have prepared an asthma discharge bundle which can be accessed by clicking on the link below. If printing this for a patient, please ensure you send to the COLOUR print queue – “followyou_colour” as there is coloured text on the reverse.
- It has a tear-off slip at the bottom which is double sided. This provides the patient with a temporary asthma action plan, worsening advice, advice on when to see their GP and links to asthma education.
Behavioural/Psychosocial Factors Predicting Poor Outcome
These are one or more of:
- Poor compliance
- Failure to attend appoinments
- Fewer GP contacts
- Frequent home visits
- Self discharge from hospital
- Psychosis, depression, self harm
- Major tranquilliser use
- Denial
- Alcohol or drug abuse
- Learning difficulties
- Employment/income problems
- Social isolation
Aspirin, NSAIDs and Asthma
- A significant number of asthmatics are allergic to aspirin/NSAIDs
- Avoid in patients with previous asthmatic reaction to aspirin/NSAIDs and in those at high risk ie asthma with nasal polyps or chronic rhinitis.
- For all other asthmatics in whom aspirin or NSAID indicated, inform patient of risk and observe for 3 hours after first dose
Links
- SIGN Guideline 158 – British Guideline on the Management of Asthma
- Respiratory Care Bundle [pdf]
- Adult Acute Asthma Bundle [pdf]
Content updated by Yvonne Scott & Alison Moore