Postoperative pulmonary complications constitute a significant cause of morbidity and mortality following surgery. Managing patients at risk for postoperative pulmonary problems requires an understanding of the predictable changes in pulmonary physiology that occur with surgery and anesthesia, as well as knowledge of factors associated with development of postsurgical respiratory compromise. Despite the availability of several screening tests, a careful history and physical examination continue to be the cornerstone of preoperative pulmonary evaluation. Although a number of measures can be employed before and after surgery to minimize the risk of respiratory complications, close patient monitoring and early detection are essential.
This chapter focuses initially on changes in pulmonary function with surgery. Pulmonary risk factors before, during, and after surgery are reviewed prior to discussion of preoperative evaluation of the patient for surgery, including lung resectional surgery. Finally, recommendations are made regarding preoperative preparation and postoperative prophylactic measures. A more detailed discussion of the perioperative care of the patient undergoing resectional lung surgery is provided in Chapter 105 and development of acute respiratory failure in the surgical patient is addressed in Chapter 104.
Changes in Pulmonary Function with Surgery
Many postoperative respiratory complications relate to exaggerations of the expected postoperative changes in pulmonary function that occur as a result of the surgery itself, anesthesia, or various pharmacologic interventions.1,2 Hence, an appreciation of normal postoperative pulmonary physiology is useful in understanding a number of pulmonary problems seen following surgery. Five principal categories of change in pulmonary function with surgery may be considered: (1) lung volumes, (2) diaphragm function, (3) gas exchange, (4) control of breathing, and (5) lung defense mechanisms (Table 103-1).
Table 103-1Changes in Pulmonary Function with Surgery ||Download (.pdf) Table 103-1Changes in Pulmonary Function with Surgery
|Reduction in lung volumes
|Impaired gas exchange
|Respiratory depression due to residual effects of anesthesia or postoperative narcotics
|Impaired cough and mucociliary clearance
The pattern of pulmonary function abnormalities following thoracic and abdominal surgery is restrictive, characterized by moderate-to-severe reductions in vital capacity (VC) and smaller, but more important, reductions in functional residual capacity (FRC). The degree of impairment is similar after upper abdominal and thoracic surgery3–5 and is less for laparoscopic procedures compared with open abdominal procedures.6 Smaller changes in VC and FRC are noted with lower abdominal surgery; superficial or extremity surgery is usually not associated with any significant or persistent changes in lung volumes.7,8 During the first 24 hours following upper abdominal surgery, VC and FRC may be reduced by more than 70% and 50%, respectively, and they may remain depressed for more than a week.7...