What are the pulmonary function guidelines that indicate an increased risk for morbidity and mortality?
Answer:
The reported mortality from lung resection is between 2% and 4%, mainly as a result of pneumonia, respiratory failure, bronchopleural fistula, empyema, and pulmonary embolism. Respiratory insufficiency occurs in approximately 5% of patients following lung resection and is associated with a 50% mortality rate. Advanced age and the associated increased incidence of concomitant nonpulmonary disease seem to contribute to this outcome. An increased risk of postoperative complications can be predicted by the following:
Spirometry: Spirometric parameters, such as FEV1/FVC ratio and FEV1 (reflective of the degree of airway obstruction), as well as static volumes (such as inspiratory and TLC), are used to define the severity of COPD. Several studies have indicated a strong correlation between predicted postoperative FEV1 and DLCO and a respective increase in morbidity and mortality, especially for open procedures and extensive dissection. Concerning values are summarized in Table 2.1.
Arterial blood gases: Historically, hypercapnia (PaCO2 greater than 45 mmHg) was considered an exclusion criterion for lung resection. However, no independent correlation has been found with an increased mortality. Patients who are hypercapnic often have a low predicted postoperative FEV1 and an abnormal exercise capacity, which may preclude surgery. Preoperative hypoxemia (PaO2 less than 50 mmHg and percentage of available hemoglobin saturated with oxygen [SaO2] less than 90%) has been associated with an increased risk of postoperative complications. However, baseline hypoxemia can be the result of ventilatory mismatch caused by obstructive tumors that once resected may theoretically improve gas exchange.
Other factors influencing outcome include patient comorbidities and functional status, the extent and location of the proposed surgical resection, and whether the patient has undergone preoperative induction chemotherapy. Improvements in both surgical and anesthesia techniques have broadened the criteria for surgical respectability. As evident from lung volume reduction studies, patients with severely impaired pulmonary function (e.g., FEV1 less than 1 L) can still undergo surgical resection with general anesthesia without prohibitive risk for postoperative complications. Moreover, the development of minimally invasive surgical techniques has raised the question of whether standard selection criteria should always be adopted.
Although preoperative pulmonary function tests are valid indices of physiologic performance, the actual predictive utility of a range of values for a single parameter is poorly defined. Overall, emphasis has been directed toward integrating multiple aspects of the preoperative evaluation (e.g., spirometry, ventilation-perfusion scanning, extent of planned resection, patient functional status) into the estimate of postoperative function. 'Enhanced Recovery After Surgery' (ERAS) protocols have contributed to improve outcomes. Multimodal analgesia, early ambulation, and thromboprophylaxis are among the recommendation for the perioperative period that have affected outcome after major lung resection in patients at high risk.