Key facts:
Authors: Ruth de Souza and Ricky Jones
Top Tip: Reassess patients with asthma regularly
Key Differential Diagnoses
- Exacerbation COPD
- Pulmonary oedema ('cardiac asthma')
- Upper airway obstruction
Key Investigations
- ABG, ECG, CXR
- FBC, CRP, U+E, LFT, Bone, Glucose
- Sputum culture
- Peak flow
Key Treatment
- NEB SALBUTAMOL 5.0 mg qds (or continuously until improvement noted)
- NEB IPATROPIUM BROMIDE 500 mcg qds
- IV HYDROCORTISONE 100 mg qds (severe) or PO PREDNISOLONE 30 mg od (less)
- OXYGEN, if hypoxic, to achieve saturation of 95-97%
- ± IV MAGNESIUM SULPHATE 2 g, over 20 minutes; can be repeated
- ± PO AMOXYCILLIN 500 mg tds
Key Management
Decision
- IV magnesium
- Ventilation
Background
Asthma is very common; and is characterised by attacks of SOB, cough and wheese, due to reversible bronchospasm
Introduction
- 'Asthma' comes from a Greek word meaning 'panting'. Asthma is a disease of diffuse airway inflammation caused by a variety of triggering stimuli resulting in partially or completely reversible bronchoconstriction
- Symptoms and signs include SOB, chest tightness, cough, and wheezing. The diagnosis is based on history, physical examination, and pulmonary function tests. Attacks can start over minutes, hours or days
- Wheeze is not an essential feature. Indeed, a silent chest can occur in a severe attack
- In older patients, distinguishing severe chronic asthma from COPD can be difficult and the two disorders sometimes merge in those who have smoked cigarettes
- 50% of those who die in an acute attack do so in the first 24 hrs. If they make it to ITU, they usually survive (ie problems occur before ITU). Death is associated with medical and psychosocial factors
Definition
- Reversible lower airway obstruction
Epidemiology
- The prevalence of asthma has increased continuously since the 1970s, and it now affects an estimated 4 to 7% of people worldwide, ie it is very common
Types
- Normal
- Brittle
Precipitants
- URTI/LRTI
- Known triggers (eg specific allergens, cold air, exercise)
- Psychosocial
- Betablockers
Symptoms
- SOB
- Wheeze
- Cough
Key questions
- "How many times have you used inhalers today? What's your normal usage?"
- "When did the attack start?"
- "Have you had any previous ITU admissions?"
Signs
- Distressed, tachypnoeic
- Expiratory wheeze, prolonged expiratory phase
- Use of accessory muscles
Note: a silent chest is very worrying (cannot get air in or out); if rapid reduction in breath sounds, think about pneumothorax
Investigation
Blood
- ABG
- Less severe attacks have low CO2
- A normal or raised CO2 in a distressed patient identifies a severe attack
- Notify ITU and repeat gas in 1 hour after maximal therapy
- FBC, CRP
- U+E, LFT, Bone, Glucose
Other
- Sputum culture
- Peak flow
- ECG
- CXR (a CXR is done in asthma to exclude other diagnoses, eg pneumothorax and pneumonia; 85% normal, 15% not: [Ref]
)
Note: you can die of asthma with a normal CXR
CXR (note pneumomediastinum)
Key investigation
- ABG
Differential diagnoses
- COPD
- Pulmonary oedema ('cardiac asthma')
- Upper airway obstruction (foreign body, neoplasm)
Note: Churg Strauss vasculitis may present as asthma
Treatment
Treatment
(first line)
Drugs
- NEB SALBUMATOL 2.5-5.0 mg qds (or continuously until improvement noted)
- NEB IPATROPIUM BROMIDE 500 mcg qds
Note: if patient very unwell, can have O2 via nasal cannulae, whilst having nebulisers - IV HYDROCORTISONE 100 mg qds (severe) or PO PREDNISOLONE 30 mg od (less); 7-14d then stop; early steroids can reduce admission rate, IF GIVEN WITHIN ONE HOUR OF ADMISSION: [Ref]
- ± IV MAGNESIUM SULPHATE 2 g infused over 20 minutes; can be repeated; the use of IV Magnesium is controversial, with little controlled data. It may improve PEFR, and readmission rate, in severe asthma but has not been shown to affect mortality: [Ref] and [Ref] and [Ref]
- ± PO AMOXYCILLIN 500 mg tds (Penicillin Allergy: PO DOXYCYCLINE 200 mg od)
- ± BECLOMETASONE 2 puffs bd; it is unlikely that inhaled steroids have any extra benefit to oral (eg prednisolone) if they are prescribed on discharge: [Ref]
Procedures
- IV line (for access, and to correct fluid and electrolyte imbalance; usually dry; give crystalloid until HR 100 mmHg))
- OXYGEN, according to needs (40-60%, via Venturi Mask, or 100% via rebreathe bag);
- MAINTAIN SATURATION 95-97%
[Ref] - Sit up
- Peak flow baseline to monitor progress
Key management decision
- Ventilate/not
Stop
- Betablockers, if thought to be cause
Treatment
(second line)
Drugs
- IV AMINOPHYLLINE BOLUS (NOT IF ON ORAL MAINTENANCE THEOPHYLLINE: GIVE INFUSION ONLY) 5 mg/kg over 20 to 30 mins (not > 25 mg/min) and then maintenance infusion of 0.5 mg/kg/hr (0.3 mg/kg/hr in elderly, or those with cardiac failure). Levels should be performed at 12 to 24 hrs and infusion rate adjusted
- The evidence that aminophylline is effective in asthma, is not good. If you are thinking of it, they probably need to be on ITU - so involve a senior; [Ref]
- If critically ill and benefit outweighs risk, use IM ADRENALINE (1/1000) 1 ML (1mg/ml)
Procedures
- Ventilation
Prescribing issues
- Check inhaler technique
Admit?
- Usually
Bed plan
- Observation ward, if predicted LoS <24h
- Medical admission ward, if 24-48h
- Respiratory, if >48h
- ± ITU
Referrals
Medical
- Respiratory
- ± ITU
Other
- Asthma nurse
The Rest
Death is associated with psychosocial factors
Maxim
- "A clear CXR in asthma means nothing"
Complications
- Pneumothorax or atelectasis due to mucus plugging
- Hypoxia, progressing from hypocapnoea to hypercapnoea with worsening severity
Follow-up
- Asthma clinic, if attacks recurrent, or severe
Prognosis
Poor, if
- (History) Death associated with poor compliance, multiple medications started in last year, 1+ psychosocial problems and >1 life-threatening attack in last year
- (Examination) respiratory rate > 30 bpm, diastolic BP 60 yrs, AF, confused, comorbidities; cannot talk, silent chest
- (Laboratory) urea > 7mmol/L, albumin 20, bacteraemia
Note: death is rare, if patient makes it to ITU; the main problem is before ITU ie slow response to deteriorating patient
2° Prevention + Health promotion
- Attend asthma clinics
- Psychosocial problems
- Smoking cessation
Don't forget
- Reassess patients regularly
- Consider ITU early
Red flags
- Type 1 respiratory failure (especially if oxygen < 8 kPa); 10% patients have this level O2 or less
- A normal or raised CO2 is very serious
- Reduced conscious level
- Unable to speak
- Severe asthma and ≥1 psychosocial factor(s) significantly worsens prognosis
