Pulmonary Disease and Preoperative Pulmonary Evaluation

Pulmonary Disease and Preoperative Pulmonary Evaluation is a topic covered in the Washington Manual of Medical Therapeutics.

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General Principles

Postoperative pulmonary complications are the second most common postoperative complication; their incidence ranges from 2% to 5.6% in the general surgical population.1 Clinically significant pulmonary complications include atelectasis, pneumonia, bronchospasm, exacerbation of preexisting chronic lung disease, and respiratory failure.2 Postoperative respiratory failure, defined as ventilator dependency for more than 48 hours or unplanned reintubation, carries a 30-day mortality rate as high as 26.5%.3

Risk Factors

Both patient-dependent and surgery-specific risk factors determine overall risk.4

  • Surgical site is generally considered the greatest determinant of risk of pulmonary complications, with proximity to the diaphragm correlating with increasing risk.5 Neurosurgery and surgeries involving the mouth and palate also impart increased risk.3,6
  • Duration of surgery also correlates strongly with risk.7,8,9
  • Regional anesthesia may reduce risk of pneumonia and respiratory failure as compared with general anesthesia, though it is difficult to draw firm conclusions.10,11,12,13 Prolonged neuromuscular blockade is also strongly associated with postoperative pulmonary complications.14
  • COPD is a well-known risk factor, with disease severity associated with risk of serious complications.15 However, even patients with advanced lung disease can safely undergo surgery if deemed medically necessary; in contradistinction to hepatic disease (see “Liver Disease”), there is no identified threshold that precludes surgery.16,17
  • Interstitial lung disease places patients at elevated risk for surgical lung biopsy and resection of malignancy but is not as well studied in patients undergoing general surgery.18,19,20
  • Pulmonary hypertension is associated with significant morbidity in patients undergoing surgery.21,22
  • Conversely, treated asthma and restrictive physiology associated with obesity do not appear to be significant risk factors.4,23
  • Congestive heart failure may increase the risk of pulmonary complications to an even greater degree than that seen with COPD.24
  • Multiple indices of general health status including degree of functional dependence and American Society of Anesthesiologists class have been linked to poor pulmonary outcomes.24,25 Odds ratios for postoperative respiratory failure of 2.53 and 2.29 were observed for hypoalbuminemia (<3 g/dL) and azotemia (BUN > 30 mg/dL), respectively, in a large cohort.6
  • Age > 50 years has been identified as an independent predictor of postoperative pulmonary complications. Risk increases linearly with age, in contrast to postsurgical cardiac risk (see “Preoperative Cardiac Evaluation”). Large observational studies informing currently used risk prediction models (see “Risk Stratification” below) have further validated these observations.
  • Smoking is a well-established risk factor for both postoperative pulmonary and nonpulmonary complications.26 As with malignancy, risk appears to be dose-dependent and associated with active use.9,27
  • Obstructive sleep apnea (OSA) is increasingly being recognized as a risk factor for both cardiac and pulmonary complications.28,29 OSA increases the odds of postoperative complications two- to fourfold.30 Unrecognized OSA may pose an even greater risk; it is estimated that over 50% of patients with OSA presenting for surgery are undiagnosed.31,32,33

Risk Stratification

  • Several validated risk indices have been developed for quantitating risk of postoperative pulmonary complications. Of these, the Arozullah respiratory failure index offers both practicality (in terms of a clearly defined outcome) and ease of use. It consists of six factors for which point scores are assigned based on multivariate analysis to stratify patients into five classes of postoperative respiratory failure risk (ranging from 0.5% to 26.6%).6,34,35,36

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General Principles

Postoperative pulmonary complications are the second most common postoperative complication; their incidence ranges from 2% to 5.6% in the general surgical population.1 Clinically significant pulmonary complications include atelectasis, pneumonia, bronchospasm, exacerbation of preexisting chronic lung disease, and respiratory failure.2 Postoperative respiratory failure, defined as ventilator dependency for more than 48 hours or unplanned reintubation, carries a 30-day mortality rate as high as 26.5%.3

Risk Factors

Both patient-dependent and surgery-specific risk factors determine overall risk.4

  • Surgical site is generally considered the greatest determinant of risk of pulmonary complications, with proximity to the diaphragm correlating with increasing risk.5 Neurosurgery and surgeries involving the mouth and palate also impart increased risk.3,6
  • Duration of surgery also correlates strongly with risk.7,8,9
  • Regional anesthesia may reduce risk of pneumonia and respiratory failure as compared with general anesthesia, though it is difficult to draw firm conclusions.10,11,12,13 Prolonged neuromuscular blockade is also strongly associated with postoperative pulmonary complications.14
  • COPD is a well-known risk factor, with disease severity associated with risk of serious complications.15 However, even patients with advanced lung disease can safely undergo surgery if deemed medically necessary; in contradistinction to hepatic disease (see “Liver Disease”), there is no identified threshold that precludes surgery.16,17
  • Interstitial lung disease places patients at elevated risk for surgical lung biopsy and resection of malignancy but is not as well studied in patients undergoing general surgery.18,19,20
  • Pulmonary hypertension is associated with significant morbidity in patients undergoing surgery.21,22
  • Conversely, treated asthma and restrictive physiology associated with obesity do not appear to be significant risk factors.4,23
  • Congestive heart failure may increase the risk of pulmonary complications to an even greater degree than that seen with COPD.24
  • Multiple indices of general health status including degree of functional dependence and American Society of Anesthesiologists class have been linked to poor pulmonary outcomes.24,25 Odds ratios for postoperative respiratory failure of 2.53 and 2.29 were observed for hypoalbuminemia (<3 g/dL) and azotemia (BUN > 30 mg/dL), respectively, in a large cohort.6
  • Age > 50 years has been identified as an independent predictor of postoperative pulmonary complications. Risk increases linearly with age, in contrast to postsurgical cardiac risk (see “Preoperative Cardiac Evaluation”). Large observational studies informing currently used risk prediction models (see “Risk Stratification” below) have further validated these observations.
  • Smoking is a well-established risk factor for both postoperative pulmonary and nonpulmonary complications.26 As with malignancy, risk appears to be dose-dependent and associated with active use.9,27
  • Obstructive sleep apnea (OSA) is increasingly being recognized as a risk factor for both cardiac and pulmonary complications.28,29 OSA increases the odds of postoperative complications two- to fourfold.30 Unrecognized OSA may pose an even greater risk; it is estimated that over 50% of patients with OSA presenting for surgery are undiagnosed.31,32,33

Risk Stratification

  • Several validated risk indices have been developed for quantitating risk of postoperative pulmonary complications. Of these, the Arozullah respiratory failure index offers both practicality (in terms of a clearly defined outcome) and ease of use. It consists of six factors for which point scores are assigned based on multivariate analysis to stratify patients into five classes of postoperative respiratory failure risk (ranging from 0.5% to 26.6%).6,34,35,36

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