Chronic Obstructive Pulmonary Disease (COPD)

Anesthesia Implications

Anesthesia Implications

Airway Complications – Risk of airway complications in these patients is much higher. This is because the pathophysiology of the condition predisposes the patient to airway collapse, increased secretions, reactive airway, and bronchospasm.

Ventilation – To reduce the harmful effects of airtrapping, consider these interventions: Reduce the respiratory rate or the I:E ratio (typically to 1:3–1:5). This will allow more time for exhalation. However, this inevitably results in reduced minute volume, leading to hypercapnia, hypoxia, or acidosis, which may elevate pulmonary vascular resistance and worsen hemodynamic instability. If this is a concern, it may be preferable to increase the inspiratory flow rate and tolerate higher peak pressures. The risk of higher peak pressures is barotrauma. Theoretically, adding PEEP has the benefit of keeping the small airways open during late exhalation. However, studies on the effects of adding PEEP are inconclusive and unpredictable (in terms of gas exchange) on COPD patients.

Volatile Anesthetics – if volatile anesthetics are to be used, sevoflurane and isoflurane are favored for their bronchodilating affects. Desflurane, however, is discouraged due to the irritating affects it has on the bronchi and increases in airway resistance.

Nitrous oxide – should be used with caution or avoided altogether as it may cause expansion of coexisting bullae, which can result in a pneumothorax. Additionally, diffusion hypoxia may contribute to pulmonary hypertension.

Blocks – Interscalene blocks almost always cause an ipsilateral hemidiaphragmatic paralysis due to blockage of the phrenic nerve. This may be problematic, making it difficult for the patient to spontaneously breathe. For this reason, an interscalene block is generally avoided in patients with severe COPD. Any regional anesthetic technique above T6 is not recommended because it impairs ventilatory function.

Respiratory depressants – be especially cautious with sedatives and drugs that reduce respiratory drive (ie opioids). These patients are especially sensitive

Preoperative Drugs – Anticholinergics, inhaled corticosteroids, and long-acting bronchodilators should be continued until the morning of surgery. Check if the patient is taking systemic steroids and supplement if necessary.

Bullae – A common coexisting condition in COPD patients. Bullae are additional air-filled sacs in the lungs that can rupture, resulting in a pneumothorax. Rupture can occur with high PIPs and/or nitrous oxide administration. For this reason, nitrous is generally avoided and PIPs are kept under tight control. If the patient becomes hemodynamically unstable during the procedure, a pneumothorax must be ruled out.

High Risk Surgeries – Be aware of any abdominal or thoracic surgery which results in additional work or pain with respiration. Where these patients are already compromised, additional work or pain on respiration may predispose the patient to respiratory failure postoperatively.

Additional risks – COPD increases the risk of perioperative stroke, reduced cognitive function, and postoperative need for mechanical ventilation

ABGs – If an ABG is necessary, keep in mind that COPD patients typically have normal values until the COPD is considered severe.

Smoking Hx – If the patient is smoking, anticipate a reactive airway. Cessation of smoking 8 weeks prior to surgery is one of the most effective methods to optimize the patient and prevent postoperative respiratory complications. Short term abstinence, however, has NOT been shown to be effective at reducing postoperative risk.

Pathophysiology

This disease is characterized by the gradual loss of alveolar tissue and obstruction of airflow. COPD is irreversible. Bronchiolar and alveolar tissue destruction results in reduced elastic recoil and bronchiolar collapse during exhalation. Additionally, increases are seen in secretions and airway sensitivity.

COPD is a condition that results primarily from inhaled toxins. The most significant is cigarette smoke. Others include occupational exposure to chemicals and airborne pollution. Other risk factors include recurrent childhood respiratory infections, alpha 1 antitrypsin deficiency, and low birth weight.

Diagnosis is made with spirometry. Pulmonary function tests will show a decreased FEV1:FVC ratio, FEF25%-FEF75%, and expiratory flow rate. Increases are seen in FRC, TLC, and residual volume. If the patient is given bronchodilators and the FEV:FVC ratio remains less than 70% of predicted, the diagnosis is confirmed.

Symptoms of this condition include expiratory wheezes, reduced breath sounds, dyspnea (esp. with exertion), chronic cough, tachypnea, and an extended expiratory time.

Expiratory flow rate is limited because of airway narrowing. This results in the next inhalation occurring before expiration of the previous breath is complete, and leads to ‘breath stacking’ or ‘air trapping’ and the development of intrinsic positive end-expiratory pressure (PEEP). This PEEP reduces venous return to the heart and potentially the pulmonary artery, which will raise pulmonary vascular resistance and right heart strain. Other potential harmful effects of air trapping include pulmonary barotrauma or volutrauma, hypercapnia, and acidosis. Air trapping will make for potentially longer wakeups.

This disease is considered an obstructive respiratory disease.

Incidence of COPD increases significantly with age.

References

Hines. Stoelting’s anesthesia and co-existing disease. 7th edition. 2018.
Lumb. Chronic obstructive pulmonary disease and anaesthesia. 2014. p. 1-5 link
Khetarpal. Anesthetic considerations in the patients of chronic obstructive pulmonary disease undergoing laparoscopic surgeries. 2016. link
Duggappa. Anaesthesia for patient with chronic obstructive pulmonary disease. 2015. link