14. Respiratory Disease Flashcards
FEV1/FVC
Represents the proportion of vital capacity that is expired in the first second of forced expiration (normal value 80%)
Define Asthma
Asthma is a chronic obstructive disease with bronchiolar inflammation and hyperresponsiveness that displays reversible, variable, and recurrent airway obstruction
Obstructive lung diseases
Asthma, COPD, cystic fibrosis
Restrictive parenchymal lung diseases
Pulmonary fibrosis, sarcoidosis, radiation-induced interstitial lung disease
Restrictive extraparenchymal lung diseases
Myasthenia gravis, diaphragm paralysis, muscular dystrophy, obesity, kyphoscoliosis
What is status asthmaticus
Bronchospasmic episode that does not respond to treatment and is considered life threatening
Treatment of status asthmaticus
- Supplemental O2 to maintain SaO2 of >90%
- B2-agonists by metered dose inhaler every 15-20 mins
- IV corticosteroids
- IV magnesium sulfate
- Epinephrine 0.3mg 1:1000 administered subcutaneously
- Tracheal intubation for PaCO2 >50 mm Hg
Classification of asthma
Mild intermittent (<2 symptoms per week, FEV >80%)
Mild persistent (>2 symptoms per week, FEV >80%)
Moderate persistent (Daily symptoms, FEV 60-80%)
Severe persistent (Continuous symptoms, FEV <60%)
What is cystic fibrosis?
Cystic fibrosis is an autosomal recessive disease resulting in altered chloride and water transport (CFTR gene) across epithelial cells; this prevents sodium reabsorption by epithelial sodium channels. Can impact respiratory, gastrointestinal, and reproductive systems.
How is cystic fibrosis diagnosed?
Sweat chloride concentration exceeding 60 mEq/L in addition to one or more of the following:
- Chronic airway disease
- Exocrine pancreatic insufficiency
- Cystic fibrosis in first-degree relative
- Failure to pass meconium at birth is highly suggestive
Treatment of cystic fibrosis
No cure
Proactive treatment of airway infection (prophylactic antibiotics, often azithromycin)
Chest therapy
Involvement of pancreas leading to diabetes is common
Lack of digestive enzymes may lead to malabsorption and difficulty absorbing Vit A, D, E, K. Treated with pancreatic enzyme replacement.
Anesthetic considerations for cystic fibrosis
Optimize pulmonary status, r/o active infection
Chest physiotherapy prior to surgery
Electrolytes, LFTs, chest XR
Risk of pneumothorax is high (avoid nitrous oxide)
Procedure later in the day (allow clearance of night-time secretions)
Ketamine relatively contraindicated (secretions)
Prophylactic beta agonist
What is COPD?
COPD is an irreversible disease that causes airway obstruction by either chronic bronchitis and/or emphysema
How is COPD classified?
I (mild), II (moderate), III (severe), IV (very severe)
Based on FEV1/FVC
Treatment starts with short acting bronchodilator (albuterol) and transitions to long acting bronchodilator (salmeterol, formoterol, bambuterol), anticholinergics (atrovent, spiriva, combivent), then to inhaled steroid and oxygen/pulmonary rehabilitation
Chronic bronchitis
“Blue bloaters” - results in chronic hypersecretion of mucus in the bronchi resulting in increased resistance to airflow and irreversible airway obstruction
Emphysema
“Pink puffers” is enlargement of the airway due to destruction of the airway walls distal to bronchioles. This leads to loss of elasticity/recoil. Symptoms include dyspnea, cough, sputum production, and decreased exercise tolerance. “Barrel Chest” due to hypertrophy of the accessory muscles used during respiration.
Diagnosis of COPD (tests, labs, imaging, etc)
PFTs including spirometry
Bronchitis = productive cough at least 2 consecutive years
Blood labs = hypercarbia, polycythemia, decreased serum alpha 1 antitrypsin levels, and leukopenia.
Chest radiographs may demonstrate lung nodules, bullae, hyperinflated lungs, masses, or fibrotic changes.
Pulse oximetry at rest, during exertion, and during sleep is useful to examine for hypoxemia and need for supplemental oxygen
Anesthesia considerations for COPD patients
Smoking cessation for 6 weeks
EKG to r/o right-sided heart disease and ischemic heart disease
CXR (extensive bullae = higher risk of pneumothorax)
Chest physiotherapy to loosen secretions and dislodge mucus plugs.
Avoid nitrous oxide
Consider B2 agonist and antimuscarinic (robinul) to increase airway patency
Avoid over oxygenation (ventilation-perfusion mismatch) Maintain O2 sats 88-92%
Watch out for breath-trapping (intrinsic positive PEEP) if intubated
Diminished response to hypercarbia
Local anesthesia preferred.
Sources of pulmonary emboli
Thrombus from vein in lower extremity
Mural thrombus from atrial fibrillation
Fat embolism from long bones
Virchow’s Triad
Stasis, damage to endothelium, and hypercoagulable state
These are risk factors for pulmonary embolus
- Immobility, malignancy, disability, obesity, oral contraceptives, pregnancy, factor V leiden, antiphospholipid syndrome, and protein C and S deficiency, DVT, recent long bone fracture, hormone replacement therapy)
Diagnosis of PE
Signs/symptoms: pleuritic chest pain, dyspnea, tachypnea, hemoptysis, coughing, JVD, cyanosis, rales and rhonchi, diminished breath sounds.
D-dimer assay: highly sensitive, if negative PE unlikely
CXR may show cardiomegaly, atelectasis, pulmonary effusions, raised diaphragm
CT angiography
Venous ultrasonography to rule out DVT
Arterial blood gas: hypoxemia, respiratory alkalosis, and hypocapnia
Wells criteria >4 = probable PE (clinical signs/symptoms, high suspicion of PE as diagnosis, HR >100, surgery within 1 month or immobility >3 days, history of PE or DVT, malignancy, hemoptysis)
Treatment for PE
Anticoagulation to prevent progression of thrombus and decrease additional thrombotic episodes. Consideration given for fibrinolytics and embolectomy for massive PE.
- Initial treatment with unfractionated heparin (goal PTT 60-85), low molecular weight heparin with bridging to warfarin for goal INR 2-3.
- If anticoagulation is contraindicated, inferior vena cava filter is indicated
- 3 months anticoagulation is recommended for most patients.
- Lifelong anticoagulation for patients with unprovoked PE, recurrent DVTs, massive PEs, and malignancies associated with thrombosis.
What is montelukast?
leukotriene receptor antagonist
What is ipratropium?
anticholinergic bronchodilator
What is albuterol?
B2 agonist
The most objective and relevant tests for measuring the degree of airway obstruction in asthmatic patients
FEV1
Peak expiratory flow (PEF)
Well controlled asthma: FEV1 should be 80% of FVC
Preferred general anesthetic for asthmatic patient
Propofol
