Comprehensive Strategies for Preoperative Pulmonary Risk Evaluation and Management

1. Age

Age is a significant independent predictor of surgical complications. Individuals aged ≥50 years have a greater risk of experiencing PPCs, and this risk increases 5-fold upon reaching ≥80 years [16,18].

2. Smoking

Smoking significantly enhances PPC risk. Current smokers have a higher incidence of PPCs compared to ex-smokers and non-smokers, with the risk increasing in correlation with pack-years smoked: adjusted odds ratios (ORs) are 1.20 for <20 pack-years, 1.57 for 41–60 pack-years, and 1.82 for >60 pack-years [19]. Smoking cessation significantly lowers the risk of PPCs; cessation for over 4 weeks reduces PPCs by 23% and over 8 weeks by 47% [19]. The 30-day post-surgery mortality rate is increased among current smokers (OR, 1.17), but not among ex-smokers or non-smokers [20].

3. Functional status

Functional or overall health status is another crucial predictor of PPCs. The ASA classification, which assesses chronic illnesses, comorbid conditions, and clinical acuity, correlates with enhanced PPCs risk; an ASA class ≥2 is associated with a substantial OR of 4.87 [16,21]. Patients with neuromuscular weakness also face an increased PPC risk due to increased propensity for hypoventilation and impaired cough [22]. Pooled analyses indicate that individuals with partial or total physical dependence are more likely to suffer from postoperative respiratory failure and pneumonia [23].

4. Obesity

Obesity can induce restrictive physiology and is known to reduce lung volumes in the perioperative setting. A retrospective cohort study demonstrated that in obese individuals (body mass index ≥25 kg/m²), a restrictive spirometry pattern was linked to a 4.3-fold increased risk of PPCs, in contrast to the non-obese group where there was no increased risk [24]. While retrospective studies and pooled analyses of small cohorts showed no significant association between obesity and an increased risk of postsurgical complications [25], larger cohort studies reported a higher incidence of PPCs among obese patients [26].

5. Cardiac comorbidity

Specific comorbidities significantly contribute to the risk of PPCs. Congestive heart failure, for example, has been consistently identified as a strong predictor of postoperative respiratory failure in multiple studies [23]. Other cardiac risk factors linked to PPCs include right atrial enlargement, pericardial effusion, the degree of leftward septal shift observed on a transthoracic echocardiogram, and right axis deviation on echocardiogram [5].

6. Pulmonary comorbidity

COPD is widely recognized as an independent risk factor for PPCs, irrespective of whether the surgery is thoracic or non-thoracic [27]. Comprehensive multivariate analyses have shown that COPD is associated with an increased risk of various postoperative complications, including pneumonia, respiratory failure, myocardial infarction, cardiac arrest, sepsis, the necessity for a return to the operating room, renal insufficiency or failure, and wound dehiscence [28].

Although interstitial lung diseases (ILDs) are associated with adverse respiratory events, the literature still presents controversial results. General anesthesia and mechanical ventilation may increase the risk of exacerbating the inflammatory process in fibrotic parenchymal diseases and promote adult respiratory distress syndrome [29]. However, performing an elective surgical lung biopsy for ILD is considered relatively safe and manageable, given the benefits and risks of the surgery [30].

1. Non-thoracic surgery

Being closer to the diaphragm serves as a predisposing factor, increasing the incidence of PPCs [31]. It is essential to consider the surgical site, as its proximity to the respiratory system significantly influences the likelihood of respiratory failure [32]. Aortic and thoracic surgeries carry the highest risk, followed by upper abdominal and neurosurgical procedures when assessing postoperative pneumonia and respiratory failure [33]. Additionally, the urgency level of non-thoracic surgery is crucial, as urgent or emergent procedures are associated with roughly a 2-fold increased risk of PPCs [34].

2. Lung surgery

The European Thoracic Surgery Database project, analyzing 3,426 patients, identified dyspnea severity, ASA score, procedural class, and age as independent contributors to in-hospital mortality after lung resection, despite a low overall rate of 2% [35]. Laboratory test results indicated that preoperative fibrinogen and lactate dehydrogenase levels were linked to increased perioperative morbidity [11]. Further investigations revealed correlations between the extent of the tumor or surgical lung resection and higher morbidity risks [35].

3. Cardiac surgery

Underlying lung disease is associated with increased PPCs, arrhythmias, and higher mortality following cardiac surgery [36]. This association can be attributed to altered lung and chest wall mechanics following sternotomy [37], effects of cardiopulmonary bypass, and potential phrenic nerve thermal injury [38]. However, severe airflow limitation or functional impairment should not be considered an absolute contraindication for cardiac surgery, given the long-term benefits observed in these patients [39].

4. Esophagectomy

Esophagectomy is associated with a high risk of PPCs. A multicenter study involving 1,777 patients who underwent esophageal resection reported a pneumonia incidence of 21% and a respiratory failure incidence of 16% [40]. Additionally, a randomized trial involving 220 patients with adenocarcinoma found that the trans-hiatal approach significantly reduced the incidence of PPCs compared to the transthoracic approach (27% vs. 57%, p<0.001) [41].

5. Duration of surgery

Surgery lasting 2 hours or more has been shown to double the risk of PPCs [3,42]. Several prospective studies have also indicated that the duration of general anesthesia, especially in surgeries exceeding 2 hours, is linked to an approximately 3-fold increase in the risk of PPCs [43].

6. Type of anesthesia

Strategic planning in anesthesia management during surgical procedures is critical, due to the well-established correlation between the type of anesthesia used and the incidence of PPCs [23,33,43]. General anesthesia is associated with higher rates of respiratory failure and postoperative pneumonia compared to neuraxial anesthesia [44]. In patients with COPD, the use of general anesthesia significantly increases the risk of PPCs, ventilator dependence, and unplanned postoperative intubations compared to regional anesthesia [45]. Therefore, whenever possible, neuraxial or regional anesthesia should be preferred over general anesthesia [46].

During general anesthesia, to prevent barotrauma from volume-control ventilation, pressure-control ventilation is preferred. Excessive ventilation may lead to alkalosis [47], exacerbate bronchoconstriction, or provoke cardiovascular complications [48]. Moreover, a decrease rather than an increase in tidal volume [49], reduced compliance [50], increased mechanical power [51], and reduced end-tidal carbon dioxide have been independently linked to PPCs [51]. Mechanical hypoventilation may be beneficial, yet hypoxemia should be avoided [52].

During general anesthesia, inhaled anesthetics can impair surfactant function and alter the oxygen-to-nitric oxide ratio. This alteration potentially increases gas reabsorption and contributes to the development of atelectasis [53]. Additionally, the use of neuromuscular blockers reduces respiratory muscle strength for several days [54]. Intermediate and long-acting neuromuscular blockers are linked to postoperative complications including atelectasis, re-intubation, pneumonia, and pulmonary edema [55]. A prospective study showed a dose-dependent increase in the incidence of postoperative pneumonia and respiratory failure associated with these neuromuscular blockers [55]. Unfortunately, neither continuous intraoperative neuromuscular monitoring nor the use of reversal agents effectively reduce the risk of PPCs [56].

1. Pulmonary function test

Pulmonary function tests (PFTs) are essential for preoperative assessment in lung surgery, as predicted postoperative (ppo) lung function correlates strongly with PPCs. Particularly, low forced expiratory volume in 1 second (FEV₁) or diffusing capacity of the lungs for carbon monoxide (DL_CO) is significantly associated with complicated postoperative courses and poor surgical outcomes in patients undergoing lung resections [57]. Notably, the percentage of predicted values for FEV₁ and DL_CO is more indicative of PPCs than their absolute values [58].

In the context of non-thoracic surgery, routine preoperative pulmonary function testing does not significantly reduce the incidence of PPCs [59]. The association between impaired lung function and increased risk of PPCs in non-thoracic surgery remains contentious. Although several cohort studies have indicated that lower FEV₁ or forced vital capacity (FVC) correlates with an increased risk of PPCs in patients undergoing non-thoracic surgery [59], comparisons of lung function between patients with and without PPCs reveal no substantial differences among those with obstructive lung patterns [60]. These results imply that underlying pulmonary conditions, rather than lung function per se, are main determinants of PPC risk. Hence, preoperative PFTs should be reserved for cases with a strong suspicion of underlying pulmonary conditions. The previous guidelines on preoperative PFTs are outlined in Table 2.

Table 2.

Guidelines on preoperative pulmonary function tests and chest X-rays

2. Chest radiographs

Routine preoperative chest X-rays do not reduce the incidence of PPCs. A systematic review found that the occurrence of PPCs was unaffected by whether a preoperative chest X-ray had been performed [61]. Even when abnormalities were detected, they had no significant effect on the frequency of PPCs [61]. Indeed, the influence of chest X-ray findings on preoperative management is negligible. One systematic review revealed that although 10% of preoperative chest X-rays demonstrated abnormalities, only 1.3% uncovered unexpected results, and a mere 0.1% affected management decisions [62]. In a large prospective study, 23% of chest X-rays exhibited abnormalities, yet only 1.1% led to modifications in management [63]. Consequently, preoperative chest X-rays should be reserved for cases with a strong suspicion of underlying pulmonary conditions that might influence the management plan. Summaries of previous guidelines on preoperative chest X-rays can be found in Table 2 [64-67].

3. Blood tests

Anemia is a significant risk factor for PPCs. The underlying pathophysiological mechanisms involve impaired oxygen delivery to tissues and diminished immune function, contributing to postoperative hypoxemia, respiratory infections, and other pulmonary issues. Untreated preoperative anemia, with a prevalence exceeding 30% in non-cardiac surgeries and higher in elderly patients, is associated with an increased risk of adverse surgical outcomes [68]. Additionally, the presence of anemia and the use of allogeneic blood transfusions individually correlate with a higher risk of PPCs and surgical site infections [69]. Even mild anemia, characterized by hemoglobin levels below 13 g/dL in males and below 12 g/dL in females, is associated with increased risks of adverse perioperative outcomes [70]. Although thorough evaluation and management of anemia are advocated, there is no evidence suggesting that preoperative red blood cell (RBC) transfusions reduce PPCs. Thus, preoperative RBC transfusions should be reserved for situations such as emergent surgery or life-threatening anemia.

Hypoalbuminemia is acknowledged as a significant predictor of increased PPC risk [16]. In cases of hypoalbuminemia, patients display poor nutritional status, which impairs immune function and reduces tissue repair capabilities. Although definitions of hypoalbuminemia vary, it is typically characterized by serum albumin levels below 20–40 g/L. OR for hypoalbuminemia range from 1.5 to 2.5 for PPCs, with lower serum levels corresponding to higher risks [71]. Despite the association, there is no present evidence supporting the effectiveness of albumin replacement or nutritional interventions in elevating serum albumin levels to reduce PPC risk.

1. ASA classification

The ASA classification, a commonly employed system, subjectively assesses and categorizes patients’ preoperative physical status. While it initially aimed to predict perioperative mortality, it has also been validated as a predictor of PPCs. A significant association has been reported between higher ASA classifications and an increased risk of PPCs; specifically, an ASA class of II or higher is associated with a substantially elevated risk (OR, 4.87; 95% confidence interval [CI], 3.34 to 7.10) compared to ASA class I. Furthermore, the risk increases when comparing ASA class III or higher to classes below III (OR, 2.25; 95% CI, 1.73 to 3.76) [74].

2. Arozullah respiratory failure index

The Arozullah respiratory failure index identified seven independent factors—type of surgery, emergency surgery, albumin, blood urea nitrogen, functional status, COPD, and age—that are associated with postoperative respiratory failure. Point scores based on their association strength in multivariate analysis are assigned, stratifying patients into five classes with respiratory failure rates ranging from 0.5% to 26.6% [75]. The predictive performance was assessed with a c-statistic of 0.828 in a validated cohort [23].

3. Gupta calculator for postoperative respiratory failure and pneumonia

The Gupta calculator for postoperative respiratory failure utilizes five preoperative factors (type of surgery, emergency surgery, functional status, preoperative sepsis, and ASA class) to predict the risk of postoperative respiratory failure [76]. It calculates a probability percentage of postoperative respiratory failure using the logistic regression equation e^x/(1+e^x)–1.7397, where x is the sum of the coefficients of the variables in the multivariable model. The predictive performance of this model was assessed, yielding a c-statistic of 0.897 in a validated cohort.

The Gupta calculator for postoperative pneumonia was constructed similarly to the respiratory failure calculator [77]. It incorporates seven preoperative factors (age, ASA class, COPD, functional status, preoperative sepsis, smoking status, and type of surgery) to formulate the likelihood of postoperative pneumonia. It generates a probability percentage of postoperative pneumonia using the equation e^x/(1+e^x)–2.8977, where x is derived from the sum of the variable coefficients in the multivariable model. The predictive performance of this model was validated with a c-statistic of 0.860 in a cohort.

4. ARISCAT

The ARISCAT model includes seven preoperative risk factors (age, oxygen saturation [SpO₂], recent history of respiratory infection, anemia, type of surgery, duration of surgery, and emergency surgery) for estimating the likelihood of PPCs [31,43]. It transforms beta-coefficients into a risk score, categorizing individuals as low risk if they score below 26 points, high risk if they score 45 points or above, and intermediate risk for scores in between. PPC probabilities were 1.6% in the low-risk group, 13.3% in the intermediate-risk group, and 42.1% in the high-risk group. The predictive accuracy of the ARISCAT model was assessed with a c-statistic of 0.88 in a validated cohort [43].

1. Non-thoracic surgery

In patients at risk of PPCs, an evaluation for respiratory symptoms, smoking history, occupational history, recent respiratory infections, or underlying chronic lung disease is recommended. Before undergoing non-thoracic surgery, chest X-rays and PFTs are necessary if there are respiratory symptoms indicative of respiratory disease (Figure 1) [78]. Even in individuals without a history of lung disease or respiratory symptoms, smokers should refrain from smoking for 2 to 4 weeks preoperatively. Additionally, the implementation of incentive spirometry and postoperative breathing exercises should be actively considered.

Fig. 1.

Algorithm for the preoperative evaluation of patients undergoing non-thoracic surgery. Adapted from Diaz-Fuentes et al. [78] PPC: postoperative pulmonary complication; ARISCAT: Assess Respiratory Risk in Surgical Patients in Catalonia.

2. Lung resection surgery

In patients undergoing lung resection surgery, calculating their ppo FEV₁ and DL_CO is essential. Various studies have evaluated postoperative pulmonary function at different time points following lobectomy or pneumonectomy [79]. Results showed that FEV₁ achieved 84% to 91% of preoperative values after lobectomy and 64% to 66% after pneumonectomy. DL_CO registered 89% to 96% of preoperative values post-lobectomy and 72% to 80% post-pneumonectomy. Maximal oxygen consumption (VO₂max) measurements indicated a recovery to 87% to 100% of preoperative levels post-lobectomy and 71% to 89% post-pneumonectomy.

Across studies involving more than 2,000 patients from three large datasets in the 1970s, a mortality rate under 5% was observed when the preoperative FEV₁ exceeded 2 L for pneumonectomy and 1.5 L for lobectomy [80]. According to standard guidelines, pneumonectomy is deemed suitable if the preoperative FEV₁ is over 2 L, and lobectomy if the FEV₁ exceeds 1.5 L [80]. Moreover, if the patient exhibits no dyspnea on exertion or ILD, an FEV₁ above 80% of the predicted value or more than 2 L is considered sufficient for pneumonectomy without further physiological evaluation, while an FEV₁ exceeding 1.5 L is suitable for lobectomy without additional assessments [80].

However, studies have indicated that the percentage of the normal predicted value, rather than absolute values, is more predictive of patient risk and outcomes following surgery [58]. The 2009 European Respiratory Society guidelines suggest that if the percent ppo FEV₁ and ppo FVC exceed 80%, the patient is considered at low risk for complications following lung resection [81]. According to the 2013 American College of Chest Physicians guidelines, patients with ppo FEV₁ and ppo FVC greater than 60% are considered at low risk for postoperative complications (Figure 2) [82]. Patients not categorized as low risk, but with ppo FEV₁ above 30%, should have their exercise capacity assessed through validated tests such as stair climbing or shuttle walk tests. For those with a ppo FEV₁ less than 30% or poor exercise capacity, a cardiopulmonary exercise test should be conducted. If the VO₂max is below 10 mL/kg/min or less than 35% of the predicted value, surgery should be avoided due to the high risk of complications.

Fig. 2.

Evaluation for patients undergoing pulmonary resection. Adapted from Brunelli et al. [82], with permission from Elsevier. *High cardiac risk: (1) Newly diagnosed heart disease; (2) Heart disease requiring medication; (3) ThRCI (thoracic revised cardiac risk index) ≥2 points (where: pneumonectomy: 1.5 points; previous ischemic heart disease: 1.5 points; previous stroke or transient ischemic attack: 1.5 points; serum creatinine >2 mg/dL: 1 point); (4) Serum creatinine >2 mg/dL: 1 point; (5) Other factors such as comorbidities, age, surgical approach (thoracotomy vs. minimally invasive) and center experience. ppo: predicted postoperative; FEV₁ : forced expiratory volume in 1 second; DL_CO : diffusing capacity of the lungs for carbon monoxide; VO₂ max: maximal oxygen consumption; SCT: stair climb test; SWT: shuttle walk test.

1. Smoking cessation

Preoperative smoking cessation is highly encouraged for current smokers, as it significantly reduces the risk of PPCs, especially if cessation occurs more than 8 weeks prior to surgery [19]. Although previously uncertain, recent studies indicate that cessation periods shorter than 8 weeks can also be beneficial. A systematic review of 25 studies found that abstaining from smoking for at least 3 to 4 weeks before surgery can decrease the incidence of respiratory and wound-healing complications [83]. Therefore, it is crucial for current smokers to receive clear counseling on the risks associated with smoking and the advantages of cessation before undergoing surgery.

2. Respiratory tract infections

Given that airway inflammation may persist after the resolution of an infectious pathogen, it is advisable to postpone elective surgery for approximately 6 weeks in patients who have recently experienced a respiratory tract infection. While most studies on preoperative respiratory infections focus on the upper respiratory tract, fewer studies have examined the consequences of lower respiratory tract infections. However, existing evidence suggests that preoperative pneumonia is linked to increased postsurgical mortality [84], and heightened postoperative morbidity [84].

3. Respiratory rehabilitation

Postoperative changes in lung volumes, respiratory muscle function, mucociliary clearance, and inadequate pain management in respiratory muscles are primary factors causing PPCs, including pneumonia and severe atelectasis [6]. Current studies are focusing on interventions designed to improve respiratory function, such as incentive spirometry, deep breathing exercises, physiotherapy, and inspiratory muscle training [85]. All lung expansion techniques appear effective in reducing the incidence of PPCs, although the specific effectiveness of incentive spirometry remains uncertain. A single 30-minute preoperative physiotherapy session has been demonstrated to significantly reduce the occurrence of PPCs, including atelectasis observed on chest radiographs, in patients undergoing upper abdominal surgery [86]. Inspiratory muscle training usually involves five to seven supervised sessions per week, each lasting 15 to 30 minutes, for 2 weeks before surgery. This regimen may be halted if postoperative pain or other symptoms hinder participation. A Cochrane review, involving 695 patients across 12 studies, indicated that preoperative inspiratory muscle training significantly reduced rates of postoperative atelectasis and pneumonia, and also shortened the duration of hospital stays following cardiac and major abdominal surgeries [87].

1. COPD

2) Management

The algorithm for perioperative management of patients with COPD is outlined in Figure 4. Stable individuals should continue their medication regimen uninterrupted, even on the day of surgery. For symptomatic individuals undergoing major elective surgery, hospitalization three to 5 days prior to the procedure is advantageous. This period allows for the administration of intravenous corticosteroids and rapidly acting inhaled bronchodilators on a prescribed schedule [5].

Fig. 4.

Algorithm for the perioperative management of patients with chronic obstructive pulmonary disease (COPD). Adapted from Diaz-Fuentes et al. [78] ICU: intensive care unit; NIPPV: non-invasive positive pressure ventilation.

Exacerbations may necessitate the use of corticosteroids, either alone or combined with antibiotics, which can lead to a recommended postponement of surgery. The duration of this postponement is tailored to the patient, extending until symptoms return to baseline levels. During this period, primary interventions typically involve the use of inhaled bronchodilators, muscarinic antagonists, short-term systemic steroids, and antibiotics [91].

Individuals prescribed prednisone for over 30 days or at a dose exceeding 20 mg for more than 2 weeks within the past year are at risk for postoperative adrenal insufficiency. In high-risk patients, diagnostic assessment prior to surgery is recommended; if time constrains, empirical administration of corticosteroids, such as 100 mg of hydrocortisone every 8 hours intravenously, is justified [92]. However, routine administration of stress-dose glucocorticoids is not recommended for patients using high doses of inhaled glucocorticoids [93].

2. Asthma

1) Evaluation

The preoperative evaluation for asthma entails assessing current control under existing treatment, performing laboratory tests, and identifying comorbidities [94]. Table 4 outlines the criteria for assessing asthma control. The evaluation should consider the patient’s daily activities and physical condition. It is crucial to assess for infectious symptoms, sputum characteristics and quantity, allergic status, triggers of exacerbation, and the current medication plan [52]. Additionally, documenting any history of emergency visits, hospitalizations, ICU admissions, and use of systemic corticosteroids before surgery is important [95].

Table 4.

Assessment of asthma control status

The preoperative physical examination should include an assessment of respiratory rate and auscultation of both lung fields to identify signs of acute exacerbation, acute respiratory infection, chronic lung disease, and right heart failure. PFTs are essential for identifying patients with uncontrolled asthma. While abnormal radiological findings are common among asthma patients, they typically do not significantly impact management strategies. However, a chest X-ray is indispensable for excluding conditions such as pneumonia, pulmonary edema, and hyperinflation, which may necessitate a delay in surgery [96].

2) Management

Implementing a structured approach is advisable to ensure adequate disease management in asthma patients scheduled for surgery under general anesthesia (Table 5) [97,98]. It is crucial to optimize asthma control preoperatively to minimize the risk of PPCs. For patients with well-controlled asthma, continuing their inhaled controller therapy, including inhaled corticosteroid (ICS), is recommended.

Table 5.

Stepwise approach to the preoperative treatment of asthmatic patients based on their asthma control level

In patients with uncontrolled asthma, it is advisable to defer surgery and focus on optimizing asthma management. If surgery cannot be postponed, initiating ICS and long-acting beta-agonists in previously untreated patients, increasing the ICS dose in those already receiving therapy, and using short-term oral corticosteroids to reduce airway inflammation can be effective in reducing PPCs. Several studies have supported the safety of perioperative short-term systemic glucocorticoid therapy in asthmatic patients [99].

In patients experiencing an acute exacerbation of symptoms, preoperative administration of 40 mg of oral methylprednisolone for 5 days has proven effective in reducing post-intubation wheezing. This is especially pertinent for newly diagnosed individuals or those exhibiting poor compliance with reversible airway obstruction [99]. For asthma patients previously prescribed systemic glucocorticoids within the last 6 months, maintaining adequate systemic levels throughout the perioperative period is recommended to decrease the risk of adrenal insufficiency. This may include intravenous administration of 100 mg of hydrocortisone every 8 hours or an equivalent dose.