Asthma in Pregnancy Flashcards
Define
Chronic inflammatory airway disease characterized by variable reversible airway obstruction, a hyper-sensitive airway and bronchial inflammation (existing within pregnancy – i.e. there was a diagnosis of asthma before pregnancy)
- Most common chronic disease in pregnancy (3-12%)
- Most occur between 24-36 weeks
Aetiology – must exist before pregnancy (N.B. allergic predisposition)
Epidemiology
Worldwide prevalence of asthma is increasing with 2-4% of pregnant women affected
Exacerbations of asthma are more likely to occur in women with severe asthma than mild asthma
Aetiology
2 major elements: inflammation + airway hyper-responsiveness (AHR)
- The large airways and the small airways (with diameter < 2mm) are sites of inflammation and airway obstruction.
- Airway inflammation occurs secondary to a complex interaction of inflammatory cells, mediators and other cells and tissues in the airway. An initial trigger leads to the release of inflammatory mediators, consequently leading to the activation and migration of other inflammatory cells.
- It is a Th2 lymphocytic response.
- The products of the inflammatory response induce smooth muscle contraction and consequent AHR. The airway smooth muscle is also increased (possible as a result of hypertrophy and hyperplasia)
Symptoms and Signs
Wheeze, breathlessness, cough – worse in morning and at night
Precipitating factors – e.g. cold, drugs (beta blocker, NSAIDs), exercise
IMPORTANT: ask about previous hospitalisations- gives indication of severity
Signs O/E
- Tachypnoea
- Audible polyphonic wheeze
- Use of accessory muscles
- Prolonged expiratory phase
- Hyper-resonant percussion, reduced air entry
- Hyperinflated chest
Moderate Acute Asthma
- PEFR > 50-75%
- No features of acute severe asthma
Acute Severe Asthma
- PEFR 33-50% predicted
- HR > 110/min
- RR > 25/min
- Inability to complete sentences
Life-Threatening Asthma
- PEFR < 33% predicted
- Silent chest
- Cyanosis
- Bradycardia
- Hypotension
- Confusion
- Coma
Investigations
ACUTE
- Basic observations
- Peak flow
- Pulse oximetry
- ABG
- Bloods- FBC, U+E, CRP, sputum, cultures
CHRONIC
- Basic observations
- Peak flow monitoring (diary)
- Spirometry
- Bloods + cultures
Management
Acute attacks can be managed the same as in NON-pregnant individuals
Manage exacerbations aggressively and avoid delays in treatment
Optimal control and response to therapy throughout pregnancy
- Regular medications continued throughout labour bronchoconstrictors should be avoided
Re-educate on inhaler technique and smoking cessation
FLU VACCINE!!
Acute Asthma
Emergency:
ABCDE
Resuscitation
Monitor O2 saturation, ABG, and PEFR-PEF per 15-30 mins
- When interpreting ABGs, important to remember that progesterone drives increased minute ventilation which may lead to hypocapnia, respiratory alkalosis, and a higher PaO2 BUT O2 saturations are UNALTERED.
- Foetal poorly tolerates acidosis
High flow oxygen (maintain saturations ~ 94-98%) - prevent maternal and foetal hypoxia
Salbutamol nebuliser (5mg initially continuously then 2-4 hourly)
Steroid therapyj
- 100mg IV hydrocortisone
- Followed by 40-50mg PO prednisolone (continue 5-7 days after acute attack)
Ipratropium bromide (0.5mg every 6 hours- add to nebuliser)- added for patients with acute severe or life-threatening asthma or poor response to β2 agonist therapy
CONTINUOUS FOETAL MONITORING when asthma severe or uncontrolled
REASSESS EVERY 15 MINS
If NO improvement, consider:
- IV b2 agonists (salbutamol)
- IV aminophylline
- IV bolus magnesium sulphate (1.2-2g) for over 20 mins
During labour
- Acute attacks during labour are rare, possibly due to endogenous steroid production
- Regional anaesthesia is better than GA- avoids risk of bronchospasm
- Prostaglandin E2 is SAFE to use for labour inductions
- Prostaglandin F2a (carboprost + hemobate) should be used with EXTREME CAUTION due to risk of inducing BRONCHOCONSTRICTION. It is used to treat postpartum haemorrhage due to uterine atony but may cause bronchospasm.
- Ergometrine may cause BRONCHOSPASM, particularly when using it with GA.
- EXCEPTION- Syntometrin (syntocinon + ergometrine) is used for PPH prophylaxis, this is not an issue.
Chronic management
Complications
Uncontrolled asthma is associated with adverse maternal and foetal outcomes:
- Hyperemesis
- Gestational hypertension
- Pre-eclampsia
- Vaginal haemorrhage
- Complicated labour
- FGR
- Preterm birth
- Increased perinatal mortality
- Neonatal hypoxia
PO corticosteroid use in 1st trimester associated with increased risk of cleft lip/ palate
Women have acute attacks post-partum more if having Caesarean sections
Prognosis
- Proactive management of asthma-related symptoms and attacks during pregnancy decreases maternal and foetal morbidity
- Asthma severity and suboptimal control associated with adverse pregnancy outcomes
- FGR- more common with symptomatic asthma
- Foetal brain injury
