Advances in surgical technique, anesthesia and analgesia, and postoperative supportive care have emboldened surgeons to consider an expanding spectrum of patients for surgical interventions. In most instances, the success or failure of the surgery is defined not in the operating room, but postoperatively, when the adverse effects of surgery may first become apparent and when intercurrent complications may jeopardize the patient's recovery. The respiratory system is particularly vulnerable to the effects of general anesthesia and surgery, and postoperative respiratory impairment is common. While generally mild and well tolerated in otherwise healthy, young patients, postoperative respiratory compromise may have serious consequences in the elderly and in patients with pre-existing lung disease. A number of postoperative complications, such as pneumonia, aspiration pneumonitis, and acute respiratory distress syndrome (ARDS) may lead to respiratory compromise independent of the patient's presurgical status.
This chapter focuses on the most serious consequence of perioperative respiratory compromise—acute respiratory failure. This complication is associated with a 30-day mortality rate in the range of 25% following major surgical procedures, compared to approximately 1% for unaffected patients.1 In addition to its adverse impact on survival, respiratory failure prolongs intensive care and hospital stay, delays convalescence, and increases healthcare costs among survivors. Clinicians who provide preoperative evaluation and postoperative care must be able to identify high-risk patients who require a greater degree of vigilance, and to rapidly recognize and appropriately treat the complications that result in postoperative respiratory failure.
Identification of the High-Risk Patient
There have been several published studies using large databases that have provided insight into the incidence of postoperative respiratory failure, its impact on survival, and factors associated with increased risk. In one of the earliest surveys involving over 7000 patients undergoing various gastrointestinal, urological, gynecological, and orthopedic procedures, respiratory failure requiring mechanical ventilation beyond 24 hours occurred in only 0.8%.2 More recently, analysis of a database of 180,359 patients undergoing major general or vascular surgical procedures at 128 Veterans Affairs hospitals and 14 private sector hospitals documented a 3% incidence of postoperative respiratory failure (defined as mechanical ventilation beyond 48 hours after surgery or need for reintubation).1 Thirty-day mortality was 27% for the group with respiratory failure compared to only 1.4% for those without. Twenty-eight variables were identified that were independently associated with increased risk. These included higher American Society of Anesthesiologists (ASA) class, preoperative sepsis, emergency as opposed to elective procedure, impaired preoperative renal function, history of smoking or COPD, and older age. The type of procedure also impacted risk (Table 104-1), with the greatest incidence of respiratory failure associated with upper aerodigestive tract surgery, thoracic or thoracoabdominal aneurysm repair, thoracic surgery, and gastrointestinal and hepatobiliary surgery. The investigators incorporated the 28 variables (Table 104-2) into a respiratory risk index (Table 104-3) to predict the likelihood that a patient will develop respiratory failure and validated it using a ...