A comprehensive preoperative evaluation must include assessment of the risk of postoperative pulmonary complications. While few would argue this point, pulmonary risk is often underappreciated as clinicians typically focus the majority of their energy on the preoperative cardiac evaluation. Highlighting the risk of this approach, postoperative pulmonary complications occur with similar frequency and greater morbidity than cardiovascular complications.
Clinicians intuitively recognize several risk factors for pulmonary complications, but some predictors of postoperative respiratory problems are not obvious. Additionally, clinicians may struggle with the appropriate utilization of preoperative pulmonary diagnostic testing. Recently published risk indices and practice guidelines provide valuable assistance in the identification of risk factors and the performance of evidence-based preoperative evaluation.
Pulmonary complications following anesthesia and surgery result from central nervous system suppression and altered respiratory dynamics. Administration of sedating agents and neuromuscular blockade exposes the patient to the risk of aspiration. Furthermore, regardless of the type of anesthetic technique utilized, patients will experience a reduction in lung volumes perioperatively. Reduction in lung volumes is the primary mechanism that may lead to atelectasis and predispose a patient to the additional complications of pneumonia and respiratory failure. This reduction in lung volumes is greatest for patients undergoing thoracic and upper abdominal surgery. Table 55-1 lists specific postoperative pulmonary complications and diagnostic considerations for each.
Table 55-1 Postoperative Pulmonary Complications |Favorite Table|Download (.pdf)
Table 55-1 Postoperative Pulmonary Complications
- Potential cause of mild hypoxia.
- Generally not a cause of postoperative fever or moderate to severe hypoxia.
- Diagnostic criteria vary—utilize same as nosocomial pneumonia.
- Often polymicrobial—common pathogens include Pseudomonas, Staphylococcus aureus, Streptococcuspneumoniae, and enteric gram-negative bacilli.
- Though aspiration of secretions is a likely contributor to development, anaerobic bacteria rarely cause postoperative pneumonia.
- The inability to wean off ventilator support within 48 hours of surgery or unplanned reintubation.
- Typically a combination of hypoxic and hypercapnic respiratory failure.
|Chronic obstructive pulmonary disease (COPD) exacerbation|
- Diagnostic criteria and assessment are the same as in the nonoperative population.
Several different patient characteristics increase postoperative pulmonary risk (Table 55-2). While most of these patient-specific factors are nonmodifiable, their identification is important for providing patients, surgeons, and anesthesiologists with an accurate assessment of perioperative risk and to identify patients for whom one should employ risk reduction strategies.
Table 55-2 Patient-Specific Risk Factors for Postoperative Pulmonary Complications |Favorite Table|Download (.pdf)
Table 55-2 Patient-Specific Risk Factors for Postoperative Pulmonary Complications
- Chronic lung disease
- Advanced age (age > 50)
- Functional dependence
- Comorbid disease (ASA class ≥ 2)
- Congestive heart failure
- Pulmonary hypertension
|Minor or Indeterminate|
- Obstructive sleep apnea
- Acute alteration of mental status
- Abnormal chest examination
- Abnormal chest radiography
- Alcohol use > 2 drinks/day
- Weight loss > 10% of body weight
- Chronic corticosteroid use
- Stroke (past history)
- Preoperative blood transfusion