Asthma for USMLE Step 2

• published: 15 Jun 2015
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Asthma will be discussed, in particular its pathophysiology, causes, sign and symptoms chronic management and management of acute exacerbation. This handwritten asthma lecture is for medical students planning on taking the USMLE. Asthma is defined based on it pathophysiology, airway inflammation and intermitten obstruction due to bronchial hyperresonsive. This is typically mediated by mast cells, eosinophils and other markers which leads to airway edema and mucus plug. This obstruction increases restriction and decreased expiratory flow rate. Therefore asthma is considered an obstructive disease. CAUSES Environmental allergen Viral infection such as rhinovirus and RSV Sinusitis Exercise induced GERD - acid in esophagus trigger vagus response and bronchoconstriction Aspirin induced increase leukotrienes leading to bronchoconstriction Obesity Occupational Exposure Emotional CLINICAL SIGN AND SYMPTOMS OF ASTHMA Begins at any age, but generally diagnosed before 7 years old and remit at adolescents. Cough - nonproductive, paroxysmal in night and early morning Chest Tightness and Chest Pain Wheeze which is initially end expiratory then present in entire expiration and then present on expiration and inspiration. Finally silent chest which is an emergency. Tachypnea initially and when severe hypoventilation with use of accessory muscles (Sternucleiodomastoid). Pulsus parodoxus where on inspiration there is a drop in blood pressure. Asthma patients also become breathless and can only speak in phrases and words. EVALUATION Astham can be diagnosed by clinical findings. Also use spirometry and rule out other alternatives. Bronchoprovocation test is the gold standard by giving asthma patient methacholine and mannitol or exercise and wait for symptoms to occur. If positive need to rule our COPD, rhinitis and other causes. However, negative rules out asthma. In spirometry the asthma patient pushes out air in one second (FEV1) and the ratio of FEV1/FVC is less than 80%. And asthma will be reversed with bronchodilator and the COPD, Emphysema and Bronchiectasis is not reversible. The peak expiratory flow monitor will be low in asthma patients. Patient should be greater than 80% of peak value depending on values in chart. Blood and sputum eosinophils tend to be greater than 4% in asthma and if greater than 8% there are more differentials. Also helps guide therapy. Chest X-ray in asthma patients is normal, but it helps rule out other causes. STAGING Intermittent asthma, the patient is asymptomatic between exacerbations. Will have less than 2 episodes per week and 2 night episodes per month. Normal Activity Level. Severe exacerbation defined as requirement of oral glucocorticoid less than once a year. FEV1 is greater than 80% Mild Persistent asthma the patient has 2-6 episodes per week, 3-4 nights out of the month. Moderate persistent asthma the patient has daily episodes and more than 1 night symptom a week. Some acitivity limitation. FEV1 is between 60-80% and the FEV1/FVC ratio is decreased by 5% Severe persistent asthma the patient has symptoms throughout the day and night symptoms every night. Severe Activity limitation. Acute exacerbation of asthma more than 2 times a year. FEV1 is less than 60% and FEV1/FVC is decreased by more than 5%. MANAGEMENT of ASTHMA Education has decreased mortality the most with discussion of asthma action plan and avoiding triggers. Step system for asthma management a step up is required with 2 days a week requirement of SABA and step down with well controlled for 3 months. Step 1 - Short Acting Beta Agonist (SABA) as needed Step 2 - Low dose Inhaled Corticosteroids (ICS) Daily Step 3 - Low dose ICS and LABA Step 4 - LABA and Medium dose ICS Step 5 - LABA and High Dose ICS and omalizumab Step 6 - LABA and High Dose ICS and Oral Glucocorticoid and Omalizumab due to allergies Alternative to LABA is LTRA, Zileuton, and Theophylline. MANAGEMENT OF ACUTE EXACERBATION OF ASTHMA If Peak Expiratory Flow is 50-79% then take 2-6 puffs of SABA 3 times ever 20 minutes and repeat PEF. If better continue SABA and change medication. If doesn't improve, take Oral glucocorticoids continue SABA and change medications. If Less than 50% then go to emergency Department. Managing asthmatic patient in emergency department is first by doing physical examination to confirm asthma. Start management with oxygen. If cannot reach greater than 90% then intubate and admit to ICU. Otherwise start SABA and if PEF is less than 40% start with SABA, Ipratropium and oral Glucocorticoid. Reassess with PEF and if improving (70%) then observe and discharge. If not improving then admit into wards monitor vitals. If worsening admit to ICU and give IV glucocorticoids and mechanical ventilation.