Strategies To Reduce Postoperative Pulmonary Complications after Noncardiothoracic Surgery: Systematic Review for the American College of Physicians

Postoperative pulmonary complications are as common as cardiac complications for patients undergoing noncardiothoracic surgery (1-6). Further, these complications have similar mortality rates and length of stay after elective abdominal surgery or hip fracture repair (1, 2). In an accompanying systematic review (7), we identify patient, procedure, and laboratory risk factors for postoperative pulmonary complications. Our current systematic review synthesizes the evidence on preventive strategies and focuses on atelectasis, pneumonia, and respiratory failure. While we have written the review primarily for internists, this field crosses specialty disciplines. Methods Literature Search and Selection Criteria We performed a systematic MEDLINE English-language literature search from 1 January 1980 to 30 June 2005. The search strategy and inclusion and exclusion criteria are described in the accompanying review of risk factors and in further detail in its Appendix (7). The search strategy used 1) the Medical Subject Heading (MeSH) terms preoperative care, intraoperative care, postoperative care, intraoperative complications, and postoperative complications as a focus of the article; 2) the MeSH text term perioperative complications as a text term in the title or abstract; and 3) additional MeSH and text terms for pulmonary, respiratory, or cardiopulmonary conditions, complications, or care. In addition, we performed additional focused searches for preoperative chest radiography and spirometry, laparoscopic versus open major abdominal operations, general versus spinal or epidural anesthesia, intraoperative neuromuscular blockade, postoperative pain management, and postoperative lung expansion techniques. Eligible studies were randomized, controlled trials; systematic reviews; or meta-analyses. We excluded studies with less than 25 participants per group; studies from developing countries (because of potential differences in respiratory and intensive care technology); studies that used physiologic (for example, lung volumes and flow, oximetry) rather than clinical outcome measures; studies of gastric pH manipulation; studies of complications that are unique to the surgery (for example, upper airway obstruction after uvulectomy); studies of cardiopulmonary, pediatric, or organ transplantation surgery (because of profoundly immunosuppressive drugs); and studies that used only administrative data to identify postoperative complications (for example, International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM], codes) because of recent evidence that administrative data have poor validity for postoperative complications (8, 9). Assessment of Study Quality We used the Quality of Reporting of Meta-analyses (QUOROM) statement for reporting meta-analyses and the U.S. Preventive Services Task Force criteria for hierarchy of research design to assess internal validity and study quality (good, fair, or poor) and to make conclusions about strength of the evidence (10, 11). Statistical Analysis We used simple means and chi-square tests to calculate CIs and P values when they were not provided in publications. We did not perform quantitative pooling because multiple meta-analyses were beyond the scope of a broad review of multiple potential interventions. We report pooled results from previous meta-analyses when applicable. Role of the Funding Source The Veterans Evidence-based Research, Dissemination, and Implementation Center (VERDICT) (Veterans Affairs Health Services Research and Development, HFP 98-002) provided the research librarian and administrative support for the study. The funding source had no role in the design, conduct, or reporting of the study or in the decision to submit the manuscript for publication. Results The search and inclusion criteria identified 20 randomized clinical trials and 11 systematic reviews or meta-analyses (12-42). Figure 1 in the accompanying review (7) of risk factors for postoperative pulmonary complications details the search results. Appendix Tables 1, 2, 3, 4, 5, 6, and 7 provide detailed characteristics of the eligible randomized trials and systematic reviews. Appendix Table 1. Abstracted Data for Eligible Randomized Trials Appendix Table 2. Abstracted Data for Eligible Randomized Trials, Continued Appendix Table 3. Abstracted Data for Eligible Randomized Trials, Continued Appendix Table 4. Abstracted Data for Eligible Randomized Trials, Continued Appendix Table 5. Abstracted Data for Eligible Randomized Trials, Continued Appendix Table 6. Abstracted Data for Eligible Systematic Reviews and Meta-Analyses Appendix Table 7. Abstracted Data for Eligible Systematic Reviews and Meta-Analyses, Continued Preoperative Smoking Cessation In the only trial of preoperative smoking cessation (12), 108 older, relatively healthy men undergoing hip or knee replacement were randomly assigned to usual care or weekly meetings with a nurse for advice about smoking cessation and nicotine withdrawal plus individualized nicotine replacement for 6 to 8 weeks before surgery until 10 days after surgery. The mean age of the men was 65 years, and 95% were American Society of Anesthesiologists (ASA) physical status class I or II. Of 56 patients in the intervention group, 36 stopped smoking and 14 reduced smoking before surgery. Overall complications rates were lower in the intervention group (18% vs. 52%; P< 0.001), primarily due to fewer wound complications and urinary tract infections. The only pulmonary outcome, postoperative ventilator support, occurred in 1 patient in each group. Nonstatistically significant trends favored shorter mean hospital stay (11 days vs. 13 days; P= 0.41) and fewer cardiac complications (0% vs. 10%; P= 0.08) in the intervention group. Although the trial was of good quality, several factors limit its ability to demonstrate decreased risk for postoperative pulmonary complications. Pulmonary risk is inherently low with hip and knee replacement. Furthermore, the timing of smoking cessation seems important. A previous cohort study showed paradoxically higher postoperative pulmonary complication rates for smokers who stopped or reduced smoking within 2 months before noncardiothoracic surgery (43). Smoking cessation may increase short-term risk because of transiently increased mucus production due to improved mucociliary activity and reduced coughing due to less bronchial irritation. Anesthetic and Analgesic Techniques Anesthetics disrupt central regulation of breathing and result in uncoordinated neural messaging. Due to resulting hypoventilation plus positional dependence, regional atelectasis occurs shortly after induction. It persists postoperatively and is compounded by ongoing disruption of respiratory muscles, limited respiratory excursion due to pain, and disruption of neurally mediated diaphragmatic functions after manipulation of abdominal viscera (43). Neuromuscular Blockade One good-quality trial found no difference in rates of postoperative pulmonary complications between intermediate-acting (atracurium, vecuronium) and long-acting (pancuronium) neuromuscular blocking agents among 691 patients undergoing elective abdominal, gynecologic, or orthopedic surgery (13). However, the incidence of residual neuromuscular block was higher among patients receiving pancuronium (26% vs. 5%; P< 0.001). Patients with residual blockade after pancuronium were 3 times more likely to develop postoperative pulmonary complications than those without residual block (17% vs. 5%; P< 0.02). In contrast, among patients receiving intermediate-acting agents, postoperative pulmonary complication rates did not differ between those with (4%) and without (5%) prolonged blockade. Therefore, pancuronium may directly lead to higher rates of prolonged neuromuscular blockade and indirectly to increased pulmonary risk compared with shorter-acting agents. Anesthesia and Analgesia Neuraxial blockade (either spinal or epidural anesthesia) blocks a constellation of stress responses to surgery (neuroendocrine, cytokine, and pain threshold) and may improve recovery and prevent complications (44). Postoperative epidural analgesia may reduce respiratory muscle dysfunction and pain-related hypoventilation. The epidural approach involves either a single injection or an infusion and can be used for both intraoperative anesthesia and postoperative analgesia. Spinal anesthesia has a faster onset (5 to 10 minutes vs. 15 to 20 minutes), produces denser sensory and motor block, and is technically easier than epidural anesthesia. However, spinal anesthesia is administered only as a single injection because of practical constraints of indwelling intrathecal catheters. The possible benefit of neuraxial blockade has generated studies of general versus neuraxial blockade anesthesia, followed by trials comparing epidural analgesia to other modes of analgesic delivery (for example, oral, intramuscular, intravenous, patient-controlled analgesia) and, more recently, trials of combined epidural intraoperative anesthesia and epidural postoperative analgesia. Intraoperative General Anesthesia versus Neuraxial Blockade A recent good-quality meta-analysis combined 141 trials (n= 9559) comparing general anesthesia and neuraxial blockade in patients undergoing a variety of operations (32). The authors compared patients receiving neuraxial blockade (with or without concomitant general anesthesia) with those receiving only general anesthesia. Neuraxial blockade reduced overall mortality (2% vs. 3%; odds ratio, 0.70 [95% CI, 0.54 to 0.90]), pneumonia (3% vs. 5%; odds ratio, 0.61 [CI, 0.48 to 0.76]), and respiratory failure (0.5% vs. 0.8%; odds ratio, 0.41 [CI, 0.23 to 0.73]). In a subgroup analysis of trials of neuraxial blockade alone versus general anesthesia alone, results were similar (odds ratio, 0.63 [CI, 0.46 to 0.87] for pneumonia; odds ratio, 0.37 [CI, 0.11 to 1.21] for respiratory failure). Potential sources of bi