Asthma in pregnancy: Difference between revisions
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As with non-pregnant asthmatics, pregnant asthmatics have reduced [[FEV1]] and increased [[residual volume]], [[functional residual capacity]], and [[total lung capacity]] which can be reversed with [[bronchodilator]]s. | As with non-pregnant asthmatics, pregnant asthmatics have reduced [[FEV1]] and increased [[residual volume]], [[functional residual capacity]], and [[total lung capacity]] which can be reversed with [[bronchodilator]]s. | ||
===Methacholine Challenge Test=== | |||
Methacholine challenge test is usually not recommended in pregnancy as it can have teratogenic effects<ref>[http://www.fda.gov/ohrms/dockets/dailys/04/aug04/080904/04p-0359-cp00001-03-Attachment-02-vol1.pdf FDA]</ref> (Pregnancy Category C). | |||
==Treatment [http://www.nhlbi.nih.gov/guidelines/asthma/asthsumm.pdf]== | ==Treatment [http://www.nhlbi.nih.gov/guidelines/asthma/asthsumm.pdf]== | ||
Revision as of 16:09, 28 September 2011
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Varun Kumar, M.B.B.S. [2]; Lakshmi Gopalakrishnan, M.B.B.S. [3]
Overview
Asthma is one of the most common pulmonary conditions occurring during pregnancy[1] with a prevalence rate of 3.7% to 8.4% in United States during the period 1997-2001[2].
Pathophysiology
During pregnancy, due to high levels of progesterone, minute ventilatory rate is increased causing compensated respiratory alkalosis.[3] Hence the arterial blood gases may reveal a higher PO2 and lower PCO2 with mild alkalotic PH. Normal PCO2 during pregnancy is suggestive of impending respiratory failure.
Asthma is characterized by broncho-constriction or inflammation of airways with production of thick mucoid secretions. In a small prospective study involving 16 asthmatic pregnant women, hyper-reactivity was seen to be lower as evidenced by a reduction in minimum medication requirements.[4]
Natural History, Complications and Prognosis
Severe or poorly controlled asthma cause maternal hypoxia, hypercapnia and respiratory alkalosis which may impair fetal oxygenation and uteroplacental blood flow. Asthma during pregnancy may have negative impact on both mother and the child especially in severe or poorly controlled cases. Complications include:
- Complications during labor[5]
- Congenital anomalies
- Complications of corticosteroid use[6]
- Cesarean delivery[5]
- Hyperemesis
- Hypertensive conditions[7][5]
- Low birth weight infants[5][8]
- Neonatal hypoglycemia
- Neonatal mortality
- Neonatal seizures
- Preterm labor and premature delivery[5][8]
- Preeclampsia[9]
- Respiratory failure
- Uterine hemorrhage
Diagnosis
History and Symptoms
Majority of patients have personal or family history of other atopic diseases. The clinical presentation of asthma in pregnancy varies with individuals both spontaneously and with therapy. In some, asthma is characterized by chronic respiratory impairment and others experience episodic attacks secondary to a number of triggering events including upper respiratory tract infection, stress, cold air, exercise, exposure to allergen (such as pets, dust, mites, pollen) or air pollutants (such as smoke or traffic fumes). The cardinal symptoms of asthma include:
- Loud expiratory wheeze
- Nocturnal cough
- Dyspnea
- Chest tightness
- Stridor in the absence of a wheeze may be confused with a COPD-type of disease and hence it is difficult to diagnose asthma based upon the history alone.[10][11][12]
Physical Examination
General appearance
- Anxious and agitated
- Altered consciousness, fatigue and lethargy in patients with acidosis
Vitals
- Tachypnea
- Tachycardia
- Pulsus paradoxicus
- Fever in presence of respiratory infection
Respiratory Examination
Inspection
Retraction of accessory muscles of respiration such as sternocleidomastoid, abdominal and pectoralis muscles with each breath
Percussion
Hyper-resonant in all lung feilds.
Auscultation
- Long, high-pitched expiratory wheeze
- Ronchi
- Bronchovesicular breath sounds
- Silent chest among patients in distress is a sign of severe and complicated asthma
Cardiology Examination
- Jugular venous distension secondary to increased intrathoracic pressure in presence of pneumothorax
- Tachycardia
Extremities
Lab Tests
- Blood tests: Leukocytosis may be noted as a physiologic response to pregnancy or corticosteroid therapy
- Arterial blood gases: Low PCO2 and elevated PO2 may be noted initially secondary to hyperventilation resulting in respiratory alkalosis. Elevated PCO2 may be noted in patients with severe asthma with impending respiratory failure.
- Compensated respiratory alkalosis is the physiologic change noted in pregnancy secondary to hyperventilation due to high levels of progesterone. Asthma causes overlapping of respiratory acidosis over physiologic respiratory alkalosis and hence a modest elevation in PCO2 may be noted.
Pulmonary Function Testing
In normal pregnancy, FEV1, vital capacity, total lung capacity, FEV1/FVC remains unchanged while functional residual capacity, residual volume decreases with increase in tidal volume. FEV1 may decrease when pregnant women lie in supine position. Hence pregnant women with acute asthma should rest in seated position rather than lying down[13].
As with non-pregnant asthmatics, pregnant asthmatics have reduced FEV1 and increased residual volume, functional residual capacity, and total lung capacity which can be reversed with bronchodilators.
Methacholine Challenge Test
Methacholine challenge test is usually not recommended in pregnancy as it can have teratogenic effects[14] (Pregnancy Category C).
Treatment [4]
- Monitor asthma control during all prenatal visits.
- Asthmatic symptoms worsen in about a third during pregnancy and improve in a third; hence, medications should be adjusted accordingly.
- Regular monitoring and maintenance of lung function to ensure adequate oxygen supply to the fetus.
- It is safer to treat asthma with medications than to have poorly-controlled asthma.
- Drug of choice in pregnancy:
- Albuterol is preferred to short-acting β2-agonist (SABA)
- Inhaled corticosteroid such as budesonide is preferred for long-term control of symptoms.
References
- ↑ Rey E, Boulet LP (2007). "Asthma in pregnancy". BMJ. 334 (7593): 582–5. doi:10.1136/bmj.39112.717674.BE. PMC 1828355. PMID 17363831.
- ↑ Kwon HL, Belanger K, Bracken MB (2003). "Asthma prevalence among pregnant and childbearing-aged women in the United States: estimates from national health surveys". Ann Epidemiol. 13 (5): 317–24. PMID 12821270.
- ↑ Wise RA, Polito AJ, Krishnan V (2006). "Respiratory physiologic changes in pregnancy". Immunol Allergy Clin North Am. 26 (1): 1–12. doi:10.1016/j.iac.2005.10.004. PMID 16443140.
- ↑ Juniper EF, Daniel EE, Roberts RS, Kline PA, Hargreave FE, Newhouse MT (1989). "Improvement in airway responsiveness and asthma severity during pregnancy. A prospective study". Am Rev Respir Dis. 140 (4): 924–31. PMID 2679270.
- ↑ 5.0 5.1 5.2 5.3 5.4 Liu S, Wen SW, Demissie K, Marcoux S, Kramer MS (2001). "Maternal asthma and pregnancy outcomes: a retrospective cohort study". Am J Obstet Gynecol. 184 (2): 90–6. doi:10.1067/mob.2001.108073. PMID 11174486.
- ↑ Perlow JH, Montgomery D, Morgan MA, Towers CV, Porto M (1992). "Severity of asthma and perinatal outcome". Am J Obstet Gynecol. 167 (4 Pt 1): 963–7. PMID 1415433.
- ↑ Lehrer S, Stone J, Lapinski R, Lockwood CJ, Schachter BS, Berkowitz R; et al. (1993). "Association between pregnancy-induced hypertension and asthma during pregnancy". Am J Obstet Gynecol. 168 (5): 1463–6. PMID 8498428.
- ↑ 8.0 8.1 Breton MC, Beauchesne MF, Lemière C, Rey E, Forget A, Blais L (2009). "Risk of perinatal mortality associated with asthma during pregnancy". Thorax. 64 (2): 101–6. doi:10.1136/thx.2008.102970. PMID 19008298.
- ↑ Triche EW, Saftlas AF, Belanger K, Leaderer BP, Bracken MB (2004). "Association of asthma diagnosis, severity, symptoms, and treatment with risk of preeclampsia". Obstet Gynecol. 104 (3): 585–93. doi:10.1097/01.AOG.0000136481.05983.91. PMID 15339773.
- ↑ Pratter MR, Hingston DM, Irwin RS (1983) Diagnosis of bronchial asthma by clinical evaluation. An unreliable method. Chest 84 (1):42-7. PMID: 6861547
- ↑ Irwin RS, Curley FJ, French CL (1990) Chronic cough. The spectrum and frequency of causes, key components of the diagnostic evaluation, and outcome of specific therapy. Am Rev Respir Dis 141 (3):640-7. PMID: 2178528
- ↑ Pratter MR, Curley FJ, Dubois J, Irwin RS (1989) Cause and evaluation of chronic dyspnea in a pulmonary disease clinic. Arch Intern Med 149 (10):2277-82. PMID: 2802893
- ↑ Nørregaard O, Schultz P, Ostergaard A, Dahl R (1989). "Lung function and postural changes during pregnancy". Respir Med. 83 (6): 467–70. PMID 2623214.
- ↑ FDA