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INTRODUCTION

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 preexisting 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 pre-surgical 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.1,2 In addition to its adverse impact on survival, respiratory failure prolongs intensive care and hospital stay, delays convalescence, and increases health care 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.

ASSESSING THE RISK OF POSTOPERATIVE RESPIRATORY FAILURE

Several calculators have been developed to estimate the risk of postoperative respiratory failure. All were constructed based on data derived from large national databases, but, notably, none has been externally validated. Furthermore, these calculators share a common definition of postoperative respiratory failure as mechanical ventilation beyond the initial 48 h following surgery or need for reintubation. This definition fails to distinguish patients requiring what most physicians (and patients) would consider to be an acceptable period of limited postoperative ventilatory support from those who truly would require prolonged ventilatory support and its attendant risks and complications. Arozullah et al. developed the first major calculator to focus specifically on respiratory failure, utilizing a database of more than 81,000 cases from 44 Veterans Affairs (VA) hospitals in their derivation cohort.3 Respiratory failure developed in 3.4%. The type of surgical procedure was the strongest independent predictor of postoperative respiratory failure; those with the highest odds ratio for developing respiratory failure included abdominal aortic aneurysm repair, thoracic surgery, upper abdominal surgery, and neurosurgical procedures. Other independent variables included in the derived risk calculator were emergency surgery, albumin <3.0 mg/dL, blood urea nitrogen >30 mg/dL, partially or fully dependent functional status, history of chronic obstructive pulmonary disease (COPD), and age 60 or greater. Points assigned to each of these parameters are shown in Table 103-1, and the predicted risk of respiratory failure based on cumulative points ...

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