Detailed Patient History
The foundation of effective anesthetic management begins with an exhaustive preoperative history. In patients with obstructive lung disease, anesthesia providers should assess the severity of the disease, understand the patient's baseline lung function, and identify potential triggers for exacerbation. Key elements of the history include:
Frequency and severity of exacerbations: frequent exacerbations, defined by GOLD as two or more moderate exacerbations, or one requiring hospitalization, in the past year, are an indicator of poorly controlled disease and correlate with a higher risk of postoperative pulmonary complications. In asthma, control is judged over the past four weeks with the GINA symptom-control questions: daytime symptoms more than twice a week, any night waking from asthma, reliever use more than twice a week, and any activity limitation. None of these means well-controlled asthma, which adds little perioperative risk; three or four means uncontrolled asthma, which should be treated before elective surgery.
Use of maintenance medications: The patient’s current medication regimen should be reviewed, including bronchodilators, inhaled corticosteroids, and long-acting muscarinic antagonists (LAMAs). It's also important to note the use of systemic corticosteroids, which can suggest more severe disease and pose additional risks such as adrenal suppression.
Home oxygen therapy: Long-term oxygen therapy is often used in patients with advanced COPD. A review of patients' home oxygen needs, flow rates, and whether they require oxygen at rest or during exertion provides valuable insight into their disease severity.
Recent respiratory infections: respiratory infections are a common exacerbation trigger in patients with obstructive lung disease. A history of recent upper respiratory infections or pneumonia should prompt a delay in elective surgery, as active infection significantly increases perioperative risk.
Assessing comorbid conditions is equally important. Cardiovascular diseases such as ischemic heart disease, arrhythmias, or pulmonary hypertension frequently coexist with obstructive lung disease, which necessitates adjustments in anesthetic plans and hemodynamic management. Cardioselective beta-blockers such as metoprolol or bisoprolol do not worsen FEV1 or symptoms in COPD and should be continued when indicated for cardiac disease; stopping them perioperatively carries its own risk.
Physical Examination
A focused physical examination should evaluate the patient’s respiratory and cardiovascular status. Key findings include:
Wheezing or decreased breath sounds: wheezing indicates airway narrowing, while decreased breath sounds can suggest hyperinflation or poor air entry due to severe obstruction.
Use of accessory muscles: accessory muscles during breathing, such as the intercostals or sternocleidomastoids, suggest increased respiratory effort and potentially poor pulmonary reserve.
Cyanosis and digital clubbing: these signs can indicate chronic hypoxia, commonly seen in advanced COPD.
Signs of right heart failure: Right ventricular failure, or cor pulmonale, occurs in advanced COPD because of chronic pulmonary hypertension. Jugular venous distension, peripheral edema, and hepatomegaly are signs that may be present in these patients.
Risk Stratification
Patients with obstructive lung disease undergoing surgery have a higher risk of perioperative pulmonary complications. Risk factors that increase perioperative morbidity include:
- Poorly controlled or unstable lung disease.
- Need for supplemental oxygen.
- Recent exacerbations or respiratory infections.
- Advanced age and significant comorbidities such as heart failure or pulmonary hypertension.
The ARISCAT score puts numbers on this risk from seven predictors available at the bedside: age over 50, preoperative oxygen saturation below 96% on room air, a respiratory infection in the past month, preoperative anemia (hemoglobin 10 g/dL or less), an upper abdominal or intrathoracic incision, surgery expected to last more than 2 hours, and emergency surgery. Low (under 26), intermediate (26-44), and high (45 or more) scores predicted postoperative pulmonary complication rates of about 1.6%, 13%, and 42% in the derivation cohort.
Pulmonary Function Tests (PFT)
Pulmonary function tests can assess the severity of airflow obstruction and predict perioperative risk. The most relevant measurements are:
Forced Expiratory Volume in One Second (FEV1): FEV1 measures the amount of air a person can forcefully exhale in one second. A value less than 50% of the predicted value is a marker of severe obstruction and increased perioperative risk. GOLD grades the severity of airflow limitation by the post-bronchodilator FEV1 as a percentage of predicted: grade 1 (mild) 80% or more, grade 2 (moderate) 50-79%, grade 3 (severe) 30-49%, and grade 4 (very severe) below 30%.
FEV1/FVC Ratio: This ratio compares the amount of air exhaled in the first second (FEV1) to the total amount of air exhaled (forced vital capacity, FVC). A post-bronchodilator value less than 0.70 confirms persistent airflow obstruction, the spirometric hallmark of COPD; in asthma the ratio may be normal between attacks.
Bronchodilator Response: A reversible component of obstruction (an increase in FEV1 of at least 12% and 200 mL by the long-standing ATS/ERS criteria; the 2022 ERS/ATS standard defines a response as a change greater than 10% of the predicted value) suggests an asthmatic component, which may guide preoperative optimization.
DLCO (Diffusing Capacity for Carbon Monoxide): This measurement reflects the integrity of the alveolar-capillary interface. Reduced DLCO values indicate emphysema, while preserved DLCO suggests chronic bronchitis or asthma without significant parenchymal involvement.
In patients with more severe disease, an arterial blood gas (ABG) analysis may be warranted to assess for hypoxemia, hypercapnia, or chronic respiratory acidosis. Chest X-rays or computed tomography (CT) scans can also help identify structural abnormalities, such as bullae or areas of consolidation, that may impact perioperative management.
Pulmonary Function Optimization
Strategies to optimize the patient’s pulmonary function before surgery include:
Bronchodilator therapy: Long-acting beta agonists (LABAs) and long-acting muscarinic antagonists (LAMAs) should be continued throughout the perioperative period to ensure maximum bronchodilation. Short-acting bronchodilators like albuterol may be administered preoperatively to reduce airway resistance further.
Inhaled corticosteroids: These should be continued to control underlying airway inflammation, especially in patients with asthma.
Systemic corticosteroids: For patients with poorly controlled asthma or a recent exacerbation, a short course of systemic steroids (for example prednisone 40-60 mg daily, or the equivalent, for 5 days before surgery) reduces airway inflammation and hyperreactivity; a course this short does not increase wound infection or impair healing. However, patients on chronic steroid therapy may require perioperative stress-dose steroids to prevent adrenal insufficiency.
Smoking cessation: Every smoker should be advised to stop before surgery, and the earlier the better. Carboxyhemoglobin and the cardiovascular effects of nicotine clear within 12-48 hours, ciliary function and sputum volume improve over 4-6 weeks, and the reduction in pulmonary complications, pneumonia, and wound infection grows with each week of abstinence, becoming clear after about 8 weeks. The older concern that quitting within a few weeks of surgery increases complications has not held up: a meta-analysis found no increase in risk from stopping shortly before surgery, so cessation should be encouraged whatever the interval.
Pulmonary rehabilitation: In patients with severe COPD, pulmonary rehabilitation programs that include breathing exercises, physical conditioning, and nutrition counseling can improve lung function and reduce the risk of postoperative respiratory complications.
