Asthma

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

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

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

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
(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 BPM and Systolic BP >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

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

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 mmHg, age >60 yrs, AF, confused, comorbidities; cannot talk, silent chest
• (Laboratory) urea > 7mmol/L, albumin <35 mmol/L, PO2 < 8 kPa (10%), WC <4.0 or >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