Asthma Flashcards
Define Asthma
Chronic respiratory disease characterised by periods of variable and recurring symptoms, airflow obstruction and bronchial hyperresponsiveness that manifest clinically as attacks of impaired breathing
Discuss risk factors for death from Asthma
History (8)
- Previous sever exacerbations (intubation or ICU admission)
- Two or more hospitalizations for asthma in the past year
- Three or more ED visits for asthma in the past year
- Hospitalization or an ED visit for asthma in the past month
- Use of more than two MDI short acting beta 2 agonist canisters per month
- Requiring three or more calsses of asthamticf medications
- current use of or recent withdrawal from systemic corticosteroids
- difficulty perceiving ashtam symtpoms or severity of exacerbations
Socail
- low socioeconomic status or innercity residence
- serious psychosocial problems
- ETOH or illicit drug use especially inhaled cocaine and heroin
Co-morbidities
- CVS disease
- other chronic lung conditions
- chronic psychiatric disorders
Discuss diagnostic studies in asthma patients
PFT-
VBG -
- Usual to see hypercapnia due to hyperventilation – if t2 failure severe
- can be a transient fall in pao2 despite improved PFTs secondary to pulmonary vasodilation and initial worsening of VQ mismatch
- Hyperlactaemia often due to b2 agonists and icnrease WOB
CXR
- Little value aside from excluding other conditions such as pneumonia, CCF, pneumothorax, pneumomediastinum, subcutaneous emphysema
Discuss objective finding in severe asthma
HR >120 RR >40 Pulsus parodoxus >10mmhg but if not present can be equally as severe Use of acessory muscles ABG - pao2 <60, pco2 >45
Discuss management of asthma exacebration
-O2 to maintain spo2 >92% (95% in pregnancy or with co-existant heart failure)
Adrenergic medications - salbutamol,
MDI plus a valved holding chamber provides similar bronchodilation and side effects even, in severe asthma when compared to nebulization.
- Long acting b2 agonist such as salmeterol is an effective addition to management of poorly controled asthma
Anticholinergics
Ipratropium -0.5mg or 8puffs MDI 20 minutely three times
Corticosteroids
IV - indicated for all moderate to severe asthma, should also be considered in those who are taking oral corticosteorids, or ICS, have relapsed or have prolonged symptoms
-Use of systemic steroids speeds the resoution of airflow obsturction, reduces the rate of relapse and may decrease admissions
Magnesium
Relaxes bronchial smooth muscle and dilates asthmatic airways in vitro - mechanisms include CA channel blockign properties, inhibition of cholinergic neuromuscular transmission, stabilization of mast cells and t lymphocytes
-There is evidence that IV MG2 for severe attacks can obviate the need for intubation- reasonable to admisinster 2-3 grams of IV MG2 over 20 minutes
01-0.2mmol/kg for children with a max of 10mmol
Leukotriene modifiers
- The cysteinyl leukotriens are highly potent mediators of inflammation that play a large role in the pathogensis of asthma
- Asthmatic generally have eleavted levels of leukotriens and in acute attacks the amount in the urine can be markedly increased
- Montelujast
MABS
Discuss management of asthma in pregnancy
Complicates 4-8% of pregnancies
Acute exacerbations should be treated as if not pregnant
Oral and IV steroids are safe during pregnancy and should be administered in a similar fashion to the non pregnant patient
HELIOX and NIV have both been used in pregnant asthmatics without detrimental effect
Pregnancy hyperventilation means that a normal C02 is hypercapnic
Perimenstrual asthma affects up to 40% of asthmatic women
Define CAS
Critical asthma syndrome refers to acute episodes of bronchospasm requriing immediate multimodal therapies to prevent progression to irreversible hypoxia and cardiopulmonary arrest
Status asthmaticus and near fatal asthma are on this sprectrum
- status is defined as bronchospasm that does not respond to aggressive therapies within 30-60 minutes
- near fatal: asthma that is refractory to treatment and progresses to acute repiratory failure requiring ventilatory support
Two forms of CAS are recognised
1) slow CAS - slow onset mechani
2) rapid CAS– progression to life threatening asthma in 3 hours or less
Discuss clinical picture of CAS
The CAS patient appears agitated assumes an upright position and appears to be in severe respiratory distress
Tachypnoea, diaphoresis and accessory muscle use are evident – speech is fragmented into single or short bursts of syllables or words - abscence of wheeze indicates severe exipiratory obstruction and minimal air movement
Discuss management approach to CAS
A: sitting up
o2 titrated to above 92%
Continous beta 2 agnoist inhaled + anticholinergics inhaled
Steroids IV hydrocort
IV Magnesium – up to 80mmol have been given
IV B agonist - bolus 250mc infuse 1-20 mcg/min
Aminophylline 5mg/kg lod –> 0.3-0.6mg/kg/hr
non-established treatments
- Adrenaline nebulised +IV load with 1mg –> 1-20mcg/min
- Heliox – reduces turbulent air flow, 70:30 (He:O2)
- Ketamine infusion 0.5-2mg/kg/hr
- inhalational agents
Discuss NIV in severe asthma
May benefit carefully slected patints
Continuous positive airway pressure improves oxygenation and reduces respiratory muscle fatigue by increasing functional residual capacity and lung compliance
Advantages
- helps overcoome intrinsic PEEP from gas trapping
- augmentation of insipriation, decrease WOB
- Can decrease expiratory work by opposing dynamic airway compression
- reduce V/Q mismatch
- Decrease hospitalisation rate
- significant increase in EV1
- Signficant decrease in hospital admission rates
Disadvantages
- Claustrophobia
- agitation
- gastric distension
- dyssynchrony
- increased expiratory work and hyperinflation
Discuss indication for intubation and RSI technique `
Indications
- Coma,
- Altered GCS
- Cardiac or respiratory arrest
- Paradoxical breathing pattent
- Refractory hypoxemia
- Failure of NPPV
RSI H-fluid resus 40ml/kg with inotropes running -- adrenaline infusion H- -- NIV - delayed sequence A- maintain hyperventilation R:bronchodilator max as above M: M S:
