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  • Nathan Riley, MD

Obgyno Wino Podcast Episode 60 - Asthma in Pregnancy

Updated: Mar 9

“The majority believes that everything hard to comprehend must be very profound. This is incorrect. What is hard to understand is what is immature, unclear and often false. The highest wisdom is simple and passes through the brain directly into the heart."

- Viktor Schauberger



2019 Chardonnay from Sean Minor


PB#86 - Published October 2009 (Reaffirmed 2016)


Five Pearls

1. Poorly controlled asthma is associated with prematurity, preeclampsia, growth restriction, and maternal morbidity and mortality.

2. Nonselective β-blockers, carboprost, ergonovine, indomethacin, misoprostol, and dinoprostone can trigger bronchospasm, and they are all commonly used agents in pregnancy/postpartum.

3. Short-acting β2-agonists (e.g. albuterol) are the mainstay for acute asthma exacerbations

4. Long-acting inhaled corticosteroids and inhaled long-acting β2-agonists are the mainstays of maintenance asthma therapy. Oral corticosteroids may be required in the most severe cases.

5. For pregnant patients with poorly-controlled asthma or asthma classified as moderate or severe persistent, fetal growth should be monitored by serial ultrasound beginning around 32 wga.


Background

- asthma is a state of chronic airway inflammation

- the airways can become constricted in response to just the right stimuli making it hard to breathe

- this is so terrifying that treating asthma in pregnancy nearly always outweighs the risks of the medications

- poorly controlled asthma is associated with prematurity, preeclampsia, growth restriction, and maternal morbidity and mortality

- think about it: if mom is hypoxic, fetus (and other end organs) aren't properly oxygenated


Common pregnancy/postpartum meds that can trigger bronchospasm

- carboprost (15-methyl prostaglandin F2α, aka Hemabate), and ergonovine (yes...methergine)

- misoprostol (prostaglandin E1 analog, aka Cytotec) and dinoprostone (prostaglandin E2 analog, aka Cervidil) --> though the risk is very low; in fact, prostaglandins are produced by lung endothelium, so perhaps the risk has something to do with their synthetic nature?

- indomethacin (NSAID that works through inhibition of Cox 1 and Cox 2, both enzymes that participate in prostaglandin synthesis) especially in patients who are sensitive to aspirin (mag sulfate is actually a bronchodilator, though!)

- non-selective β-blockers


Recall: Non-selective β-blockers include propranolol (Inderal, InnoPran), nadolol (Corgard), timolol maleate (Blocadren), penbutolol sulfate (Levatol), sotalol hydrochloride (Betapace), and pindolol (Visken). This means that they block both β1 and β2 receptors. Blocking β1 causes decreased heart contractility, decreased heart rate, and decreased renin secretion from the kidneys. Blocking β2 increases airway resistance among other things.

Management

- two categories of meds: long-acting ("maintenance") and rescue

- maintenance meds include inhaled corticosteroids, cromlyn, long-acting β-agonists, and theophylline

- rescue meds include inhaled short-acting β-agonists

- oral corticosteroids can be used as maintenance or rescue


Classification of asthma

- based on symptoms and pulmonary function testing (PFTs; aka spirometry)

- the two commonly used PFTs are: peak expiratory flow rate (PEFR) and forced expiratory volume in the first second of expiration (FEV)

- it's reasonable to order PFTs even if asthma is well-controlled because women with asthma generally experience worse symptoms in pregnancy

- a decrease in FEV₁ during pregnancy is associated with low birth weight and prematurity

How is asthma diagnosed in pregnant women?

- same as outside of pregnancy

- there's a good chance you'll find some pertinent positives on review of symptoms including wheezing, shortness of breath, or chest tightness all of fluctuating intensity with likely identifiable triggers like allergens, exercise, or infections

- you may detect wheezing on chest auscultation but its absence does not exclude the diagnosis

- ideally, you would confirm airway obstruction that's at least partially reversible (>12% increase in FEV₁ after administration of a bronchodilator), but this isn't always practical

- if the clinical picture fits, a trial of asthma therapy is appropriate

- pregnant patients often become dyspneic due to the normal physiology of pregnancy

- GERD, postnasal drip, and bronchitis can also present with a nasty cough


How is asthma assessed in pregnant women?

- spirometry is preferable, but peak expiratory flow with a peak flow meter is also sufficient

- chest auscultation also important at outpatient visits

- repeat evaluations are indicated if symptoms worsen

- patients with history of hospitalization for severe symptoms or history of requiring oral corticosteroids to manage their disease should be watched extra closely


Are allergy shots safe in pregnancy?

- why do you ask? well allergy shots are effective in improving asthma symptoms in patients with allergies

- no adverse effects of continuing allergy shots in pregnancy apart from the risk of anaphylaxis from these injections, however, and that could be catastrophic in pregnancy

- given risk of anaphylaxis is higher early in the titration of allergy shots, risk may outweigh benefit


Rescue therapy in pregnancy

- inhaled short-acting β2-agonists (e.g. albuterol) are the mainstay

- 1-2 treatments (two to six puffs per treatment) at 20-minute intervals should do the trick; higher doses may be required for more severe symptoms

- they can use PEFR on a peak flow meter to determine how well the medication is working, PEFR should reach 80% of personal best if bronchodilation has been sufficient

- if inadequate response or she notices a decrease in fetal activity, she should seek medical attention


Maintenance therapy

- summarized in the box to the right

- inhaled steroid regimens summarized in Table 2 below

- inhaled corticosteroids are safe in pregnancy

- if inhaled steroids are insufficient, a long-acting inhaled β2-agonist can be added, too (salmeterol and formoterol)

- inhaled long-acting β2-agonists are more effective than leukotriene receptor antagonists or theophylline and with fewer side effects

- theophylline also requires serum monitoring due to a narrow therapeutic index


Any non-pharmacologic options?

- well...first remove the eliciting factors (smoke, allergens, etc.)

- fix GERD if this might be responsible (e.g. decrease/neutralize stomach acid, smaller meals, less frequent meals, propping up the head while lying supine)

- other non-pharmacologic therapies include preparations of chickweed, nettle preparations, and pear tree mistletoe; however, there is insufficient data to support or negate their safety in pregnancy

- homeopathic treatments like nux vomicum and arsenicum album are also proposed therapies for asthma; however, like most homeopathic remedies, there is very little quality evidence to support or negate the claims or their safety in pregnancy (meanwhile, 2% of the American population uses homeopathic preparations)


Note: medications such as antacids, H2 antagonists, and proton pump inhibitors can help with symptoms by decreasing or neutralizing the acid (hydrogen chloride, HCl) made by the stomach, but the reflux of undigested food could also reflect poor digestion in the stomach due to a lack of sufficient HCl. You can try supplementing with HCl.


- a functional medicine approach through lifestyle modification (e.g. elimination diet) can cure the underlying inflammatory condition as opposed to merely mitigating it (asthma is likely an autoimmune condition), though this will likely be easier outside of pregnancy


Special considerations for a sever acute asthma attack in pregnancy

- may require hospitalization depending on severity

- continuous EFM or biophysical profile may be warranted depending on severity and viability status of the pregnancy

- treat with short-acting β2-agonist like albuterol, oral/IV steroids may also be warranted

- if patient's symptoms resolve, FEV₁ or PEFR 70% and sustained for at least 60 minutes, and fetal status is reassuring, discharge home w/ close follow-up is likely appropriate

- on the other hand, if response to albuterol is poor (e.g. FEV₁ or PEFR <70%), hospitalization may be warranted, particularly if <50%

- if response is poor and the patient's symptoms or disposition become worse (e.g. confused, drowsy), ICU-level care may be warranted, particularly if CO2 > 42 mmHg (don't be afraid to intubate if necessary)

- when finally discharged home, patient should continue using a short-acting β2-agonist every 3-4 hrs as needed (two to four puffs) + start an oral corticosteroid (like prednisone 40-60 mg daily or equivalent (see table below) for 3-10 days (taper is not required if course is <14 days)



Anything special I should know about fetal surveillance in pregnancies affected by asthma?

- in patients with either poorly controlled asthma or otherwise moderate to severe asthma, serial growth US should begin around 32 wga


How about when asthmatic patients are in labor?

- continue all meds

- avoid dehydration or poor anesthesia, as either can trigger bronchospasm (having said that, regional anesthesia has been reported to incur a 2% incidence of bronchospasm in and of itself)

- ACOG recommends starting anybody who was taking oral corticosteroids on IV steroids (e.g. hydrocortisone 100 mg q8hrs in labor until 24 hrs postpartum) to prevent adrenal crisis

- expediting birth may be appropriate, as the pregnancy state itself carries a propensity for asthma exacerbation


Any considerations in breastfeeding regarding medications used to managed asthma?

- Nopers

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