Strategies to reduce postoperative pulmonary complications in adults

INTRODUCTION — Postoperative pulmonary complications are common and a major cause of perioperative morbidity and mortality [1,2]. The major categories of clinically significant complications include [3,4]:

●Atelectasis detected on chest radiograph or computed tomography

●Pneumonia

●Acute respiratory distress syndrome

●Pulmonary aspiration (clinical history and imaging evidence)

●Unplanned need for supplemental oxygen or noninvasive or invasive mechanical ventilation

●Exacerbation of underlying chronic lung disease

●Bronchoconstriction

Strategies to reduce the risk of postoperative pulmonary complications in high risk patients will be reviewed here. The preoperative evaluation of pulmonary risk, the management of patients undergoing lung resection, and prevention of venous thromboembolism are discussed separately. (See "Evaluation of perioperative pulmonary risk" and "Perioperative medication management" and "Preoperative physiologic pulmonary evaluation for lung resection" and "Prevention of venous thromboembolic disease in adult nonorthopedic surgical patients" and "Prevention of venous thromboembolism in adults undergoing hip fracture repair or hip or knee replacement".)

RISK FACTORS — Strategies to reduce postoperative pulmonary complications should generally be reserved for those at higher than average risk, such as those undergoing upper abdominal or open thoracic surgery with at least one other risk factor. Patients undergoing other types of surgical procedures are at lower risk; these individuals are candidates for risk reduction strategies if multiple other risk factors are present.

A number of factors increase the risk of developing postoperative pulmonary complications (table 1) [3,5,6]. (See "Evaluation of perioperative pulmonary risk".)

Definite risk factors include [1,3,7]:

●Upper abdominal, thoracic (open), aortic, head and neck, neurosurgical, and abdominal aortic aneurysm surgery

●Emergency surgery

●Age >65 years

●Surgery lasting greater than three hours

●Poor general health status as defined by ASA class >2

●Heart failure

●Serum albumin <3 g/dL

●Chronic obstructive lung disease

●Cigarette use within the previous eight weeks

●Intraoperative long acting neuromuscular blockade

●Functional dependence

Probable risk factors include:

●General anesthesia (compared with spinal, epidural anesthesia, or other regional anesthetic techniques)

●Arterial tension of carbon dioxide (PaCO₂) >45 mmHg (5.99 kPa)

●Abnormal chest radiograph

●Current upper respiratory tract infection

●Postoperative nasogastric tube placement

PREOPERATIVE STRATEGIES — Treatment to reduce the risk of postoperative pulmonary complications begins prior to surgery. Potential preoperative strategies include cigarette cessation, optimization of underlying chronic lung disease, good oral care, and patient education (table 2). Antibiotics may be indicated for patients with lower respiratory tract infection as evidenced by purulent sputum or a change in the character of the sputum, but surgical delay should be considered for such patients given the substantially increased risk for postoperative pulmonary complications [8,9].

Smoking cessation — The preoperative evaluation provides an opportunity to discuss the benefits of smoking cessation [10]. Current cigarette smokers have an increased risk for postoperative pulmonary complications [11,12], although the incremental risk is small in the absence of chronic lung disease [1]. (See "Evaluation of perioperative pulmonary risk".)

Smoking cessation prior to elective surgery appears to improve a number of outcomes such as wound healing and postoperative pulmonary recovery [13-17]. The duration of abstinence from smoking necessary for a reduction in pulmonary complications is not well established although more than four to eight weeks may be preferable [13,14,16-22].

An important clinical question is whether quitting smoking less than eight weeks prior to surgery could actually increase postoperative pulmonary complications. This concern was first raised by a prospective study of 200 patients undergoing coronary artery bypass surgery in which patients who had stopped smoking for two months or less had a pulmonary complication rate almost four times that of patients who had stopped for more than two months (57.1 versus 14.5 percent) [23]. Subsequent systematic reviews and meta-analyses have not supported the concern about short-term smoking cessation being associated with a worse outcome.

Three meta-analyses addressed the question of the optimal duration of smoking cessation prior to surgery [15,16,24]. In one systematic review, there was no difference in total postoperative or pulmonary complications between current smokers and recent quitters (less than eight weeks) [15]. While they identified no increase in risk for recent quitters, they also found no benefit of a brief duration of cessation. In a separate analysis of a larger number of eligible trials (six randomized trials and 15 observational studies), the data supported different conclusions [16]. They found a reduction in both total (relative risk [RR] 0.76, CI 0.69-0.84) and pulmonary (RR 0.81, 95% CI 0.70-0.93) complications for past smokers as compared with current smokers. There was no difference between early and late quitters. Each week of cessation increased the beneficial effects of cessation.

In the largest single trial to address the benefits of preoperative smoking cessation, investigators studied 1335 subjects, including 522 smokers, undergoing gastric surgery for cancer [25]. Compared with nonsmokers, the odds ratio for postoperative pulmonary complications among those who continued smoking or stopped smoking less than two weeks was 2.92 (1.45-5.90), as compared with 0.98 (0.28-3.45) for those with four to eight weeks of cessation and 1.42 (0.66-3.05) for those with eight or more weeks of cessation.

As there is no evidence of harm related to a short duration of cigarette abstinence, we advise all patients anticipating elective surgery to quit smoking as soon as possible, regardless of the anticipated date of surgery. When time allows, a longer duration (at least eight weeks) of cessation is optimal.

Pharmacotherapy (eg, nicotine replacement and varenicline) and behavioral interventions for preoperative smoking cessation may be beneficial and are discussed separately [17,26]. (See "Behavioral approaches to smoking cessation" and "Overview of smoking cessation management in adults" and "Pharmacotherapy for smoking cessation in adults", section on 'Preoperative management'.)

Chronic obstructive lung disease — Known chronic obstructive lung disease is an important patient-related risk factor for postoperative pulmonary complications [1]. Patients with chronic obstructive pulmonary disease (COPD) should be aggressively treated in order to achieve their best possible baseline level of function. The indications for specific treatments (eg, inhaled bronchodilators and inhaled glucocorticoids) are the same as those for patients not preparing for surgery. The preoperative evaluation of patients with COPD is discussed separately. (See "Anesthesia for patients with chronic obstructive pulmonary disease", section on 'Preanesthesia consultation' and "Stable COPD: Initial pharmacologic management" and "Preoperative physiologic pulmonary evaluation for lung resection".)

For patients who present with symptoms or signs suggestive of an exacerbation of COPD, elective surgery should be delayed pending treatment and a return to baseline pulmonary function. (See "COPD exacerbations: Management" and "Management of infection in exacerbations of chronic obstructive pulmonary disease".)

Patients who currently or previously received exogenous glucocorticoids may be candidates for perioperative stress-dose glucocorticoids or testing of the hypothalamic pituitary adrenal axis depending on the current glucocorticoid dosing and the type and duration of surgery. This topic is discussed separately. (See "The management of the surgical patient taking glucocorticoids".)

Asthma — Poorly controlled asthma is a risk factor for the development of postoperative pulmonary complications [27,28], but well-controlled asthma appears to confer little additional risk [29]. Patients with asthma should undergo a preoperative evaluation to assess asthma control (table 3) [27]. Patients whose asthma is not well controlled should receive a step-up in asthma therapy; this may include a brief course of systemic glucocorticoids in patients whose forced expiratory volume in one second (FEV₁) or peak expiratory flow (PEF) are substantially below their predicted values or personal best. (See "An overview of asthma management in children and adults".)

For elective surgery, patients should be free of wheezing and have a peak expiratory flow rate greater than 80 percent of predicted or of their personal best prior to surgery. For patients who require endotracheal intubation, we suggest administering an inhaled rapid-acting beta agonist two to four puffs or a nebulizer treatment within 30 minutes before intubation. Inhaled beta agonists may be continued as needed in the perioperative period; they also can be used in the circuit of anesthesia tubing for prolonged procedures, and for patients still intubated immediately after surgery. (See "Anesthesia for adult patients with asthma", section on 'Preoperative medication management' and "Beta agonists in asthma: Acute administration and prophylactic use".)

One to two days of systemic glucocorticoid therapy has sometimes been advised as a method to prevent acute bronchoconstriction at the time of intubation. However, acute bronchoconstriction is uncommon among patients with well-controlled asthma. Thus, in the absence of clinical trial data, we suggest that preoperative systemic glucocorticoids be reserved for patients with poorly-controlled asthma. The safety of perioperative systemic glucocorticoid use in asthmatic patients has been demonstrated in numerous studies [29,30]. The use of systemic glucocorticoid therapy for preoperative management of asthma is discussed separately. (See "Anesthesia for adult patients with asthma", section on 'Treatment of poorly controlled asthma'.)

Patients with aspirin exacerbated respiratory disease (AERD) characterized by asthma, chronic rhinosinusitis with nasal polyposis, and aspirin sensitivity should not receive nonsteroidal anti-inflammatory agents (NSAIDs) for pain control (eg, ibuprofen, ketorolac), unless they have undergone desensitization. (See "Aspirin-exacerbated respiratory disease".)

As with COPD, patients who are currently taking exogenous glucocorticoids may be candidates for perioperative stress-dose glucocorticoids or testing of the hypothalamic pituitary adrenal axis depending on the current glucocorticoid dosing and the type and duration of surgery. This topic is discussed separately. (See "The management of the surgical patient taking glucocorticoids".)

Occasionally, patients using high-dose inhaled glucocorticoids have developed hypothalamic-pituitary-adrenal suppression [31]. However, routine use of stress-dose glucocorticoids in these patients is not recommended. (See "The management of the surgical patient taking glucocorticoids".)

Antibiotics — Preoperative antibiotics are not useful for prevention of pneumonia in patients with stable COPD or asthma, unless other disorders, such as acute bronchitis or a flare of COPD or bronchiectasis, are present. Thus, preoperative antibiotics are only indicated in patients with a clinically apparent lower respiratory tract infection, manifest by purulent sputum or a change in the character of sputum [32]. Elective surgery should be cancelled until such treatment is completed and patient’s sputum production has returned to baseline. The use of perioperative antibiotics to prevent surgical site infection is discussed separately. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults".)

Upper respiratory infection — The risk of anesthesia and surgery in the setting of a viral upper respiratory tract infection (URI) is unknown; the sparse literature has focused upon the pediatric population. One study of 489 children undergoing myringotomy showed no difference in the incidence of pulmonary complications between those with URIs at the time of surgery and those free of upper respiratory symptoms [33]. However, myringotomy is a very low risk procedure not commonly associated with postoperative pulmonary complications. No studies have addressed the issue of risk in adults undergoing high-risk upper abdominal or thoracic surgery [34]. Nevertheless, pending pertinent data, it is reasonable to delay elective surgery in the presence of a viral URI particularly surgery requiring airway manipulation (ie, intubation).

COVID-19 — Available evidence suggests a drastically increased risk of pulmonary complications and mortality in surgical patients with concomitant SARS-CoV-2 infection [35,36]. The risk is particularly severe for patients who require hospitalization and intensive care unit (ICU) care for COVID-19. Risk of complications remains elevated for at least seven weeks after infection and even longer in patients with persistent symptoms [37]. (See "COVID-19: Perioperative risk assessment, preoperative screening and testing, and timing of surgery after infection", section on 'Risk of surgery in patients with COVID-19'.)

The American Society of Anesthesiologists and the Anesthesia Patient Safety Foundation have issued guidelines regarding the timing of elective surgery after COVID-19 infection. Decisions should include consideration of the severity of symptoms at the time of infection, ongoing symptoms, comorbidities, and complexity of surgery. These guidelines are discussed separately. (See "COVID-19: Perioperative risk assessment, preoperative screening and testing, and timing of surgery after infection", section on 'Timing of surgery after COVID-19 infection'.)

Preoperative oral care — Good preoperative oral care reduces the burden of oral bacteria and reduces rates of postoperative pulmonary complications in certain settings [38-42]. In a systematic review of five studies (2284 participants) of preoperative chlorhexidine mouthwash before cardiac surgery, rates of postoperative pneumonia were lower among those receiving this treatment (RR 0.52, CI 0.39-0.70) [39].

Other efforts to improve oral hygiene may be helpful in noncardiac surgery as well. In a retrospective study of patients undergoing lung resection that used propensity score matching, enhanced perioperative oral care was associated with a reduced rate of pneumonia from 9.3 percent to 4.6 percent [38]. Oral care included a preoperative dental consult, a dental hygiene visit, and removal of tongue coating with a toothbrush. A multicenter, case-control study of esophageal cancer surgery found that a lack of such oral care was significantly associated with postoperative pneumonia [42]. Perioperative pulmonary care bundles incorporating oral hygiene interventions have also reported decreased postoperative respiratory complications [43,44].

For patients undergoing cardiac surgery, we suggest preoperative chlorhexidine oral rinses (eg, 0.12 to 0.2 percent, 15 mL swished in mouth for 30 seconds twice daily for the two to three days before surgery) to reduce postoperative pneumonia [39,45-49]. Given the lack of any likely risk, we also recommend counseling all surgical patients to use best oral hygiene practices recommended by the American Dental Association for the general population: twice daily tooth brushing, daily flossing, and regular dental health visits.

Pulmonary prehabilitation — Pulmonary prehabilitation includes activities such as aerobic exercises, breathing exercises, and inspiratory muscle training [50]. A preoperative exercise program may reduce postoperative pulmonary complications among patients undergoing elective lung [51-54], cardiac, or abdominal surgery [55-59]. For patients who are at moderate to high risk of postoperative pulmonary complications and are preparing for thoracic or abdominal surgery, we suggest participation in a preoperative exercise and/or respiratory training program. (See "Pulmonary rehabilitation".)

●In a meta-analysis, preoperative physical therapy (mixed interventions such as aerobic exercises, breathing exercises, inspiratory muscle training) compared with no therapy or sham therapy reduced postoperative atelectasis after elective cardiac surgery in four trials (RR 0.52, 95% CI 0.32-0.87) and pneumonia in five trials (RR 0.45, 95% CI 0.24-0.83), but not the need for mechanical ventilation longer than 48 hours or mortality [55]. The duration of postoperative hospital stay was significantly shorter for those in the physical therapy groups (mean difference in three studies -3.21 days, 95% CI -5.73 to -0.69).

●A systematic review (11 studies; 916 participants) examined the effect of preoperative exercise therapy for patients undergoing lung surgery [53]. Meta-analysis was not possible due to study heterogeneity, but the review found that a moderate to intense exercise program before lung surgery improved aerobic capacity, physical fitness, and quality of life, with a possibility that it might reduce postoperative complications and length of hospital stay.

●A systematic review for the Cochrane database that included 12 eligible trials (695 participants) of preoperative inspiratory muscle training prior to cardiac or abdominal surgery, inspiratory muscle training was associated with reductions in atelectasis and pneumonia (risk ratios 0.53, 95% CI 0.34-0.82 and 0.45, 95% CI 0.26-0.77, respectively) [58]. The length of hospital stay was also reduced in a meta-analysis of eight trials (MD -1.33, 95% CI -2.53 to -0.13). Lack of adequate blinding, small-study effects, and publication bias reduced the overall quality of the evidence.

●A subsequent independent meta-analysis in 2016 found that before abdominal surgeries, preoperative inspiratory muscle training, aerobic exercise, and/or resistance training decreased postoperative complications (odds ratio [OR] 0.59, 95% CI 0.38-0.91) [60].

●A randomized trial from 2018 found that a 30-minute physiotherapy and breathing exercise training intervention reduced postoperative pulmonary complications within two weeks after abdominal surgery (absolute risk reduction 15 percent and number needed to treat of seven) [61].

Patient education about lung expansion maneuvers — Lung expansion maneuvers such as coughing, incentive spirometry, and voluntary deep breaths are best taught prior to surgery [43,44]. It is more difficult to emphasize the importance of these strategies to a postoperative patient who may be in pain and sedated from analgesic medication. (See 'Lung expansion' below.)

INTRAOPERATIVE STRATEGIES — The selection of the type of anesthesia and neuromuscular blockade both affect the incidence of postoperative pulmonary complications (table 2). Briefer, lower-risk procedures should be used whenever possible in high-risk patients.

Anesthetic technique — Studies evaluating the incremental risk of pulmonary complications due to general anesthesia when compared with spinal or epidural (neuraxial) anesthesia have reported differing results [62-64]. However, the weight of the evidence suggests that when both general and spinal or epidural anesthesia are safe and appropriate for a particular procedure, spinal or epidural anesthesia should be favored over general for patients who are at high risk for postoperative pulmonary complications [63,65]. Furthermore, the majority of related literature suggests benefit from addition of neuraxial anesthesia to general anesthesia [66-69]. (See "Evaluation of perioperative pulmonary risk", section on 'General anesthesia versus neuraxial or regional anesthesia' and "Overview of anesthesia", section on 'Types of anesthesia' and "Anesthesia for patients with chronic obstructive pulmonary disease", section on 'Neuraxial anesthesia'.)

Similarly, regional anesthesia (nerve block), when this is an option, may reduce risk in orthopedic surgery and high-risk patients [70-72].

Reversal of neuromuscular blockade — During general anesthesia, neuromuscular blocking agents (NMBA) are usually administered to facilitate laryngoscopy for endotracheal intubation and as needed during the procedure to facilitate surgical exposure and/or guarantee absence of patient movement. Short or intermediate acting nondepolarizing NMBAs (eg, cisatracurium, mivacurium, rocuronium, vecuronium) are preferred over longer acting agents, as they are less likely to be associated with postoperative pulmonary complications. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Avoidance of residual neuromuscular blockade'.)

Best practices for monitoring and pharmacologic reversal of neuromuscular blockade (NMB) remain controversial. Complete reversal of NMB at the conclusion of the surgical procedure is essential, particularly in patients with underlying lung disease. Residual postoperative NMB is associated with hypoventilation, which may increase the risk of postoperative pulmonary complications [73-75]. Many experts recommend quantitative NMB monitoring over qualitative monitoring. (See "Clinical use of neuromuscular blocking agents in anesthesia".)

Pharmacologic reversal of NMB reduces the risk of residual NMB, but reversal using neostigmine or sugammadex may also be associated with risk and requires careful attention to the depth of NMB. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Reversal of neuromuscular block'.)

Duration of surgery — Surgical procedures performed using a general anesthetic technique lasting more than three to four hours are associated with a higher risk of pulmonary complications (table 1) [76,77]. As an example, a study of risk factors for postoperative pneumonia in 520 patients found an incidence of 8 percent for procedures lasting less than two hours versus 40 percent for those lasting more than four hours [77]. This observation suggests that, when available, a less ambitious, briefer procedure should be considered in a very high risk patient.

Type of surgery — Upper abdominal, open aortic aneurysm repair, open thoracotomy, and head and neck operations carry the greatest risk of postoperative pulmonary complications [77,78]. Thus, a different surgical procedure should be considered, if possible, for a very high-risk patient in whom there are few opportunities to significantly reduce operative risk. As an example, percutaneous cholecystostomy could be substituted for cholecystectomy in a critically ill, high-risk patient with acute cholecystitis.

Lung protective ventilation — Use of a lung protective ventilation strategy with low tidal volume (6 to 8 mL per kg of predicted body weight), higher levels of positive end-expiratory pressure (6 to 8 cm of water), and use of alveolar recruitment maneuvers have been inconsistently associated with a reduction in adverse pulmonary events. Lung protective ventilation is discussed in greater detail separately. (See "Overview of initiating invasive mechanical ventilation in adults in the intensive care unit", section on 'Tidal volume' and "Anesthesia for the patient with obesity", section on 'Ventilation management'.)

PA catheterization — In high-risk patients, providers frequently consider using a pulmonary artery catheter (PAC) to guide hemodynamic management in the perioperative period. However, the best performed study to date found no benefit with perioperative use of a PAC; we do not recommend PAC as a routine strategy to reduce perioperative mortality or postoperative pulmonary complications [79].

On the other hand, intensivists and anesthesiologists may value the information that can be obtained from PAC placement in select populations, such as patients with severe underlying cardiopulmonary disease (eg, congenital heart disease, left-to-right shunt, severe valvular disease, pulmonary hypertension) who are undergoing corrective or other surgery. (See "Pulmonary artery catheterization: Indications, contraindications, and complications in adults", section on 'Indications'.)

POSTOPERATIVE STRATEGIES — Risk reduction strategies continue into the postoperative period and include lung expansion maneuvers and adequate pain control (table 2). Routine use of nasogastric tube decompression after abdominal surgery increases the risk of postoperative pulmonary complications.

Noninvasive ventilatory support — High-flow nasal oxygen, continuous positive airway pressure (CPAP), and noninvasive ventilation may reduce the rate of reintubation among postoperative patients who develop respiratory insufficiency (eg, tachypnea, shallow respirations, labored breathing, hypoxemia) postoperatively. However, subsequent studies suggest that routine use in the postoperative setting does not reduce pulmonary complications [80,81]. These and other stabilizing interventions are discussed separately. (See "Extubation following anesthesia" and "Postoperative airway and pulmonary complications in adults: Etiologies and initial assessment and stabilization" and "Extubation management in the adult intensive care unit".)

Lung expansion — A variety of lung expansion maneuvers reduce postoperative pulmonary complications in selected patients, including chest physical therapy, deep breathing exercises, incentive spirometry, intermittent positive pressure breathing, and CPAP. These maneuvers increase lung volumes after surgery through inspiratory effort. All of these interventions are more effective if patient teaching begins before surgery.

Deep breathing exercises or incentive spirometry should be used in patients undergoing thoracic, aortic, and upper abdominal surgery who are at higher than average risk for pulmonary complications [77,78,82]. CPAP may be beneficial in selected patients.

Studies of these interventions have been confounded by a lack of standard definitions of complications and imprecise descriptions of the involved techniques [83,84]. Many trials have included primarily healthy patients; those with preexisting lung disease at the highest risk of postoperative complications have been underrepresented.

●Deep breathing and incentive spirometry – Deep breathing exercises and incentive spirometry appear to be equally effective [85] and capable of reducing the risk of postoperative pulmonary complications although studies are conflicting about the degree of benefit [78,83]. While the findings have been mixed, given the safety and low cost, we advise using incentive spirometry after upper abdominal and thoracic surgery.

Deep breathing exercises are a component of chest physical therapy. Incentive spirometry involves deep breathing facilitated by a simple mechanical device. Deep breathing exercises entail a slow, deep inspiration (as close as possible to total lung capacity), followed by a breath-hold of two to five seconds, and finally a slow exhalation approximately to functional residual capacity (FRC). The optimal number of repetitions is not known; up to 30 deep breaths (with 30 to 60 second rests between sets of 10) may be done hourly during waking hours [86]. In theory, deep breathing exercises open collapsed alveoli, reduce atelectasis, promote secretion removal, and restore lung volume. Incentive spirometry involves deep breathing facilitated by a simple mechanical device to provide visual feedback. The efficacy of incentive spirometry in preventing postoperative pulmonary complications has been assessed by systematic reviews of patients undergoing coronary bypass grafting and upper abdominal surgery [84,87]. In both cases, the systematic reviews concluded incentive spirometry was not clearly beneficial, but the size and methodology of the studies were of low quality. In a small study, deep breathing exercises did not reduce postoperative pulmonary complications after high-risk upper abdominal surgery when added to early mobilization [88].

Rather than focusing on individual interventions, the ICOUGH multidisciplinary program incorporates incentive spirometry, coughing and deep breathing, oral care (brushing teeth and using mouthwash twice daily), understanding (patient and family/caregiver education), getting out of bed at least three times daily, and head-of-bed elevation. In before-and-after designed trials, the ICOUGH program reduced the incidence of postoperative pneumonia (2.6 to 1.6 percent) and unplanned reintubation (2 to 1.2 percent) [43,44]. A follow-up study found that adherence to the ICOUGH program waned over time, associated with an increase in adverse outcomes [89]. With coordinated rededication to the program, a favorable trend in outcomes ensued.

Other data also suggest less benefit of these interventions in low-risk individuals [84,90,91]. In a systematic review of the efficacy of incentive spirometry in reducing pulmonary complications after upper abdominal surgery, the quality of studies was felt to be only moderate and results were mixed [84]. In three eligible trials, incentive spirometry was no more effective than no respiratory treatment. On the other hand, complication rates among patients who received incentive spirometry did not differ from those who received deep breathing exercises (two trials) or chest physiotherapy (two trials).

●Intermittent positive pressure breathing – Intermittent positive pressure breathing (IPPB) was used commonly in the 1960s and 1970s, but was associated with more complications than other methods of lung expansion and is not part of routine management. In a prospective study, the rates of postoperative pulmonary complications in an IPPB-treated group were similar to those in patients receiving incentive spirometry or voluntary deep breathing exercises [92], but 18 percent of the IPPB-treated group required discontinuation of therapy due to abdominal distension. In addition, IPPB is more costly than other methods of lung expansion.

●Continuous positive airway pressure – Postoperative CPAP offers the potential advantage of being effort-independent and may be particularly beneficial in patients who are unable to cooperate with effort-dependent strategies to increase lung volumes such as deep breathing exercises or incentive spirometry. It appears to be as effective as other lung expansion maneuvers and can be used intermittently or continuously in patients who are unable to adequately perform effort-dependent measures to increase postoperative lung volumes.

In a trial that randomly chose 500 patients to receive prophylactic nasal CPAP (CPAP at 10 cm H₂O continuously for six hours) or the institution's usual care (CPAP at 10 cm H₂O for 10 minutes every four hours) after cardiac surgery, continuous (≥6 hours) CPAP improved oxygenation and reduced the incidence of pneumonia, reintubation, and admission to an ICU [93]. A systematic review and meta-analysis of postoperative CPAP following major abdominal surgery found low-quality evidence of a reduction in atelectasis, pneumonia, and reintubation, but uncertain benefits on mortality, hypoxia, and invasive ventilation [94]. A subsequent meta-regression analysis of high-risk abdominal surgery patients concluded that immediate postoperative institution of intermediate levels of CPAP for short duration (as little as one hour) was as effective at reducing pulmonary complications as higher levels of CPAP for extended duration [95].

Further research is needed to determine the role of CPAP in the primary prevention of pulmonary complications among postoperative patients in general and those with a high risk of complications (eg, obesity, sleep-disordered breathing). CPAP may be associated with complications, including patient discomfort, gastric distension, hypoventilation, difficulty clearing respiratory secretions, and barotrauma. Measures to improve tolerance of CPAP are described separately. (See "Assessing and managing nonadherence with continuous positive airway pressure (CPAP) for adults with obstructive sleep apnea", section on 'Side effect management'.)

Early mobilization — Early mobilization after surgery facilitates deep breathing. A plausible mechanism by which it may work relates to increased lung volumes shortly after surgery with a decrease in the potential for postoperative pulmonary complications. In a small trial (n = 116) of patients undergoing surgery for gastrointestinal cancer, outcomes were evaluated before and after a protocol that included structured mobilization by nursing staff and walking supervised by a physical therapist beginning on the first postoperative day [96]. Using a broad definition, postoperative pulmonary complications were fewer among patients who received early mobilization (OR 0.38, 95% CI 0.12-1.20).

In a second trial of patients undergoing high risk abdominal surgery, postoperative pulmonary complications increased with each additional day of delay before beginning mobilization (OR 3.0, 95% CI 1.2-8.0 per day) [97].

Intravenous mucolytics — Several small studies of the intravenous mucolytic ambroxol have provided conflicting evidence for benefit in reducing postoperative pulmonary complications. A meta-analysis concluded that evidence was low quality but that intravenous mucolytics probably reduce the risk of pulmonary complications [98]. In light of the variable evidence and lack of data on side effects in these studies, we do not recommend routine use of intravenous mucolytics for prevention of postoperative pulmonary complications.

Goal-directed hemodynamic therapy — Multiple studies have investigated standardized perioperative hemodynamic targets and protocols to achieve these targets. Results from these studies have been mixed for the variety of outcomes that have been evaluated, but two meta-analyses found that postoperative pneumonia and acute respiratory distress syndrome were significantly reduced with the utilization of goal-directed hemodynamic therapy (GDHT) [98,99]. For institutions with available resources for implementation of GDHT protocols, we suggest use of GDHT for reduction of postoperative pulmonary complications in patients at high risk for these, as described separately. (See "Intraoperative fluid management", section on 'Major invasive surgery'.)

Pain control — Adequate postoperative pain control may help to minimize postoperative pulmonary complications by enabling earlier ambulation and improving the patient's ability to take deep breaths. This is particularly important after thoracic and upper abdominal surgery. Studies of the effect of postoperative pain management on pulmonary complications have focused on the use of epidural analgesia and intercostal nerve blocks as alternatives to more traditional parenteral opioids.

Postoperative pain control has been consistently improved with epidural analgesia compared with parenteral opioids, although results have been mixed with regard to reduction in postoperative pulmonary complications [100-104]. A systematic review and meta-analysis (15 trials, 1498 participants) found better pain management and reduced pulmonary complications with postoperative epidural analgesia compared with systemic opioid analgesia after abdominal aortic aneurysm surgery [104]. Epidural analgesia decreased postoperative respiratory failure (RR 0.69 [95% CI 0.56 to 0.85]) and time to tracheal extubation (by approximately 36 hours).

In a subsequent observational study, investigators restricted their analysis to patients with COPD undergoing major abdominal surgery [100]. In this report, epidural analgesia was associated with a reduction in postoperative pulmonary complications (OR 0.5, 95% CI 0.3-0.9) that persisted after propensity score matching to adjust for potential confounders.

The choice of nonopioid analgesic medication may influence development of postoperative pulmonary complications. As an example, perioperative gabapentinoids administered on the day of hip or knee arthroplasty are associated with an increased risk of pulmonary complications [105,106].

Intercostal nerve blocks have been investigated in patients undergoing upper abdominal surgery. In a study of 417 patients, for example, intercostal blocks reduced the incidence of postoperative pulmonary complications in those who had subcostal but not midline abdominal incisions [107]. This benefit was seen only in patients under the age of 50 years. A second uncontrolled study of 76 unselected patients undergoing cholecystectomy who received a continuous postoperative intercostal nerve block reported no postoperative pulmonary complications [108]. In the above meta-analysis, intercostal nerve blocks reduced pulmonary complication rates, but the differences were not statistically significant and risk ratios overlapped one [109].

Avoid routine use of nasogastric tube — A meta-analysis of studies comparing routine use of a nasogastric tube (NGT) to decompress the stomach after abdominal surgery with performing NGT placement only in patients who develop a need for decompression postoperatively concluded that the routine use of an NGT significantly increased postoperative pulmonary complications including pneumonia (RR 1.7) and atelectasis (RR 1.9) [110]. A subsequent systematic review similarly found a trend toward increased pulmonary complications (combined endpoint of pneumonia and atelectasis) with routine postoperative use of an NGT (OR 1.35, 95% CI 0.98-1.86) [111]. We recommend avoiding routine use of NGT decompression after abdominal surgery to decrease the risk of pulmonary complications. Instead, clinicians should use NGT only when indicated due to abdominal distension or nausea.

Prevention of venous thromboembolism — Pulmonary embolism is the most common preventable cause of hospital death, accounting for approximately 150,000 to 200,000 deaths per year in the United States. Strategies to prevent venous thromboembolism in surgical patients are discussed separately. (See "Prevention of venous thromboembolic disease in adult nonorthopedic surgical patients".)

Enhanced recovery pathways — Enhanced recovery pathways are increasingly utilized for a wide range of surgical procedures, and many of these incorporate strategies, including early mobilization, opioid minimization, and avoidance of routine NGT use, to reduce pulmonary complications [98]. Although studies of such pathways suffer from a high risk of bias and overall quality of evidence is low, enhanced recovery protocols show promise for reducing postoperative pulmonary complications.

SUMMARY AND RECOMMENDATIONS

●Patients undergoing upper abdominal, thoracic, or aortic aneurysm surgery with additional risk factors for postoperative pulmonary complications (table 1) are candidates for risk reduction strategies. Interventions should begin in the preoperative period and continue through the postsurgical period. Clinicians should employ multiple strategies to reduce the risk of postoperative pulmonary complications to the fullest possible extent (table 2). Patient education regarding lung expansion maneuvers should begin prior to surgery. (See 'Risk factors' above.)

●Smoking cessation prior to elective surgery appears to improve a number of outcomes such as wound healing and postoperative pulmonary recovery. The optimal duration of abstinence from smoking necessary for a reduction in pulmonary complications is not well established, although more than eight weeks may be preferable to shorter durations. (See 'Smoking cessation' above.)

●For patients with symptoms or signs suggestive of an exacerbation of COPD or poorly controlled asthma, elective surgery should be delayed pending treatment (eg, oral glucocorticoids, possibly antibiotics) and a return to baseline pulmonary function. (See 'Chronic obstructive lung disease' above and 'Asthma' above.)

●For patients with asthma who will require endotracheal intubation, we suggest administering an inhaled rapid-acting beta agonist (two to four puffs) or a nebulizer treatment within 30 minutes before intubation. (See 'Asthma' above.)

●COVID-19 significantly increases the risk of postoperative pulmonary complications and mortality for at least seven weeks and even longer in patients with persistent symptoms. Nonurgent surgery should be delayed depending on the severity and duration of COVID-19, associated comorbidities, and complexity of surgery, as described separately. (See 'COVID-19' above and "COVID-19: Perioperative risk assessment, preoperative screening and testing, and timing of surgery after infection".)

●For patients who are at moderate to high risk of postoperative pulmonary complications and are preparing for thoracic or abdominal surgery, we suggest participation in a preoperative exercise program (Grade 2B). Preoperative exercise programs typically include activities such as aerobic exercises, breathing exercises, and inspiratory muscle training. Lung expansion maneuvers (eg, voluntary deep breaths, coughing, incentive spirometry) are best taught prior to surgery. (See 'Pulmonary prehabilitation' above and 'Patient education about lung expansion maneuvers' above.)

●For patients undergoing cardiac surgery, we suggest preoperative use of chlorhexidine mouthwash (Grade 2B). A sample regimen is chlorhexidine oral wash 0.12 percent, 15 mL swished in mouth for 30 seconds twice daily for two days prior to surgery. Preoperative chlorhexidine mouthwash may also be of benefit in patients at increased risk of postoperative pulmonary complications prior to major thoracic or abdominal surgery (eg, open thoracotomy, esophagectomy), although data are mixed. Other efforts to improve oral hygiene, such as preoperative dental consultation and dental hygienist care, may be prudent depending on the needs of the patient. (See 'Preoperative oral care' above.)

●While data are conflicting, neuraxial (spinal or epidural) anesthesia appears preferable to general anesthesia for patients who are at high risk for postoperative pulmonary complications, when both general and neuraxial anesthesia are appropriate options for the particular procedure. Procedures that are less invasive and of shorter duration generally carry less risk for postoperative pulmonary complications. Similarly, regional anesthesia (nerve block), when this is an option, may reduce risk in very high-risk patients. (See 'Intraoperative strategies' above.)

●Short- or intermediate-acting neuromuscular blocking agents (eg, cisatracurium, mivacurium, rocuronium, vecuronium) are less likely to result in hypoventilation and postoperative respiratory failure than longer-acting agents. (See 'Reversal of neuromuscular blockade' above.)

●Postoperative interventions that are beneficial for high risk patients include deep breathing exercises or incentive spirometry and use of epidural analgesia, where appropriate, in place of parenteral opioids. Continuous positive airway pressure (CPAP), intercostal nerve blocks, and limiting use of nasogastric tubes (for symptoms only) after abdominal surgery, and early mobilization are probably beneficial postoperative interventions. (See 'Postoperative strategies' above.)