Patients' perceptions of the post-pancreatectomy discharge process.

BACKGROUND: Complications after pancreatectomies contribute to poor outcomes. Patients are expected to identify signs/symptoms leading to these complications but may be poorly educated on how to identify them. We assessed the impact of an educational tool on patient perceptions of, and satisfaction with the discharge process, and its effect on readmission rates. METHODS: A prospective cohort study with retrospective chart review including patients who underwent pancreatic resection was undertaken. An interactive educational module (iBook) that provided information about the procedure, possible complications, and peri-discharge information was implemented. English-speaking patients were equally divided into the pre- and post-iBook cohorts. Primary outcome was patients' satisfaction with discharge; Secondary outcomes were 30- and 90-day readmission rates. RESULTS: 100 patients were included. Mean age was 65.5 ± 12.6, 46% were female, and 92.3% were white. Most patients underwent Whipple procedures (72%), and distal pancreatectomies (26%). In the post-implementation group, 92% were satisfied with the discharge process, and 89% reported it was a good tool. There were no statistical differences in 30- and 90-day readmission rates between cohorts. CONCLUSION: The iBook positively impacted patients' satisfaction and preparedness for discharge. Readmission rates were not statistically significantly impacted but could be investigated with further studies of greater sample sizes.

COVID-19 and cardiothoracic surgery: Effects on training and workforce utilization in a global pandemic.

BACKGROUND: The COVID-19 pandemic has disrupted all aspects of healthcare, including cardiothoracic surgery (CTS). We sought to determine the pandemic's impact on CTS trainees' educational experiences. METHODS: A survey was developed and distributed to members of the Thoracic Surgery Residents Association and other international CTS trainees. Trainees were asked to evaluate their cumulative experiences and share their overall perceptions of how CTS training had been impacted during the earliest months of the COVID-19 pandemic (i.e., since March 01, 2020). Surveys were distributed and responses were recorded June 25-August 05, 2020. In total, 748 surveys were distributed and 166 responses were received (overall response rate 22.2%). Of these, 126 of 166 responses (75.9%) met inclusion criteria for final analysis. RESULTS: Final responses analyzed included 45 of 126 (35.7%) United States (US) and 81 of 126 (64.3%) international trainees, including 101 of 126 (80.2%) senior and 25 of 126 (19.8%) junior trainees. Most respondents (76/126, 43.2%) lost over 1 week in the hospital due to the pandemic. Juniors (12/25, 48.0%) were more likely than seniors (20/101, 19.8%) to be reassigned to COVID-19-specific units (p < .01). Half of trainees (63/126) reported their case volumes were reduced by over 50%. US trainees (42/45, 93.3%) were more likely than international trainees (58/81, 71.6%) to report reduced operative case volumes (p < .01). Most trainees (104/126, 83%) believed their overall clinical acumen was not adversely impacted by the pandemic. CONCLUSIONS: CTS trainees in the United States and abroad have been significantly impacted by the COVID-19 pandemic, with time lost in the hospital, decreased operative experiences, less time on CTS services, and frequent reassignment to COVID-19-specific care settings.

Biliary palliation for unresectable pancreatic adenocarcinoma: surgical bypass or self-expanding metal stent?

BACKGROUND: Standard of care guidelines endorse self-expanding metal stents (SEMS) rather than open surgical biliary bypass (OSBB) for biliary palliation in the setting of unresectable pancreatic ductal adenocarcinoma (PDAC). This study used competing risk analysis to compare short- and long-term morbidity and overall survival among patients undergoing SEMS or OSBB after unresectable or metastatic disease is identified at the time of exploration. METHODS: Single institution retrospective cohort study (n = 127) evaluating outcomes after OSBB and SEMS for biliary palliation in patients found to have unresectable PDAC at exploration. Short-term, long-term, and lifetime risk of biliary occlusion and survival were compared after adjustment for stage and comprehensive complication index (CCI). RESULTS: Baseline demographics and tumor characteristics were equivalent between cohorts. Short-term complications were more frequent after OSBB, whereas late complications were greater after SEMS. The cumulative incidence of recurrent biliary obstruction was greater after SEMS, but lifetime complication burden and median survival were equivalent. CONCLUSION: OSBB was associated with longer hospital stays and more short-term complications, and SEMS was associated with a higher risk of recurrent biliary obstruction among surgical patients with unresectable PDAC. Patient preference should be defined pre-operatively in the case the unresectable disease is encountered during attempted resection.

The Beneficial Effects of Minimizing Blood Loss in Pancreatoduodenectomy.

OBJECTIVE: The aim of this study was to elucidate the impact of intraoperative blood loss on outcomes following pancreatoduodenectomy (PD). BACKGROUND: The negative impact of intraoperative blood loss on outcomes in PD has long been suspected but not well characterized, particularly those factors that may be within surgeons' control. METHODS: From 2001 to 2015, 5323 PDs were performed by 62 surgeons from 17 institutions. Estimated blood loss (EBL) was discretized (0 to 300, 301 to 750, 751 to 1300, and >1300 mL) using optimal scaling methodology. Multivariable regression, adjusted for patient, surgeon, and institutional variables, was used to identify associations between EBL and perioperative outcomes. Factors associated with both increased and decreased EBL were elucidated. The relative impact of surgeon-modifiable contributors was estimated through beta coefficient standardization. RESULTS: The median EBL of the series was 400 mL [interquartile range (IQR) 250 to 600]. Intra-, post-, and perioperative transfusion rates were 15.8%, 24.8%, and 37.2%, respectively. Progressive EBL zones correlated with intra- but not postoperative transfusion in a dose-dependent fashion (P < 0.001), with a key threshold of 750 mL EBL (8.14% vs 40.9%; P < 0.001). Increasing blood loss significantly correlated with poor perioperative outcomes. Factors associated with increased EBL were trans-anastomotic stent placement, neoadjuvant chemotherapy, pancreaticogastrostomy reconstruction, multiorgan or vascular resection, and elevated operative time, of which 38.7% of the relative impact was "potentially modifiable" by the surgeon. Conversely, female sex, small duct, soft gland, minimally invasive approach, pylorus-preservation, biological sealant use, and institutional volume (≥67/year) were associated with decreased EBL, of which 13.6% was potentially under the surgeon's influence. CONCLUSION: Minimizing blood loss contributes to fewer intraoperative transfusions and better perioperative outcomes for PD. Improvements might be achieved by targeting modifiable factors that influence EBL.

Transversus abdominis plane block reduces pain and narcotic consumption after robot-assisted distal pancreatectomy.

BACKGROUND: Minimizing pain and disability are key postoperative objectives of robot-assisted distal pancreatectomy (RADP). This study tested effects of bupivacaine transversus abdominis plane (TAP) block on opioid consumption and pain after RADP. METHODS: Retrospective case-control study (June 2012 -Oct 2017) evaluating bilateral intraoperative bupivacaine TAP block as an interrupted time series. Linear regression evaluated opioid consumption in terms of intravenous (IV) morphine milligram equivalents (MME) and controlled for preoperative morbidity. Secondary outcomes included numerical rating scale (NRS) pain scores. RESULTS: 81 RADP patients met eligibility, 48 before and 33 after implementation of TAP. Baseline characteristics were equivalent with a trend toward higher age, Charlson comorbidity, and ASA score among the TAP cohort. TAP patients consumed on average 4.52 fewer IV MME than controls during the first six postoperative hours (p = 0.032) and reported lower mean NRS scores at six (p = 0.009) and 12 h (p = 0.006) but not at 24 h (p = 0.129). Postoperative morbidity and lengths of stay (LOS) were equivalent (5 vs. 6 days, p = 0.428). CONCLUSION: Bupivacaine TAP block was associated with significant reductions in opioid consumption and pain after RADP but did not shorten hospital LOS consistent with bupivacaine's limited half-life.

Braden scale for pressure ulcer risk predicts rehabilitation placement after pancreatic resection.

BACKGROUND: Patients undergoing pancreatic resection frequently require rehabilitation facilities after hospital discharge. We evaluated the predictive role of validated markers of frailty on rehabilitation facility placement to identify patients who may require this service. METHODS: Single-center retrospective cohort study of patients who underwent pancreatic resection from 2010 to 2015. 90-day morbidity and mortality were calculated. Postoperative validated markers of frailty (Activities of Daily Living scale, Braden scale [assesses pressure ulcer risk, lower scores = higher risk] and Morse fall scale) were evaluated via multivariate regression to identify predictors of discharge to rehabilitation facility. RESULTS: 470 patients with complete data were included. Mean age was 62 and 49.2% were male. Postoperative median length of stay (LOS) was 8 (IQR 7-10). 92 (19.66%) patients were discharged to rehabilitation facilities and 138 (29.49%) patients were readmitted within 90 days. On multivariate analysis, age, sex, LOS > 8 days, inpatient Comprehensive Complication Index (CCI) and initial Braden scale were predictive of rehabilitation placement. CONCLUSION: A marker of frailty routinely collected daily by nursing staff, the Braden scale, is available to help surgeons predict the need for postoperative rehabilitation placement after pancreatic resection. Engaging discharge planning services for at-risk patients may help prevent delayed hospital discharge and should be further evaluated.

What Patients Look for When Browsing Online for Pancreatic Cancer: The Bait Behind the Byte.

BACKGROUND: Suitability is a patient-centered metric defined as how appropriately health information is targeted to specific populations to increase knowledge. However, suitability is most commonly evaluated exclusively by healthcare professionals without collaboration from intended audiences. Suitability (as rated by intended audiences), accuracy and readability have not been evaluated on websites discussing pancreatic cancer. METHODS: Ten healthy volunteers evaluated fifty pancreatic cancer websites using the suitability assessment of materials (SAM instrument) for the materials' overall suitability. Readability and accuracy were correlated. RESULTS: Ten recruited volunteers (ages 23-63, 50% female) found websites to be on average "adequate" or "superior" in suitability. Surgery, radiotherapy and nonprofit websites had higher suitability scores as compared to counterparts (p ≤ 0.03). There was no correlation between readability and accuracy levels and suitability scores (p ≥ 0.3). Presence of visual aids was associated with better suitability scores after controlling for website quality (p ≤ 0.01). CONCLUSION: Suitability of websites discussing pancreatic cancer treatments as rated by lay audiences differed based on therapy type and website affiliation, and was independent of readability level and accuracy of information. Nonprofit affiliation websites focusing on surgery or radiotherapy were most suitable. Online information should be assessed for suitability by target populations, in addition to readability level and accuracy, to ensure information reaches the intended audience.

Multicenter outcomes of robotic reconstruction during the early learning curve for minimally-invasive pancreaticoduodenectomy.

BACKGROUND: Perceived excess morbidity during the early learning curve of minimally-invasive pancreaticoduodenectomy (MIPD) has limited widespread adoption. It was hypothesized that robot-assisted reconstruction (RA) after MIPD allows anastomotic outcomes equivalent to open pancreaticoduodenectomy (PD). METHODS: Intent to treat analysis of centrally audited data accrued during early adoption of RA-MIPD at five centers. RESULTS: CUSUM analysis of operating times at each center identified 92 RA-MIPD during the early learning curve. Mean age was 65 ± 12 years with body mass index 25.8 ± 5.0. Surgical indications included malignant (60%) and premalignant (38%) lesions. Median operating time was 504 min (interquartile range 133) with 242 ml median estimated blood loss (IQR 398) and twelve (13%) conversions to open PD. Major complication rate (Clavien-Dindo III/IV) was 24% with 2 (2.2%) deaths and ten (10.9%) reoperations. Nine (9.9%) clinically significant pancreatic fistulae were observed (4 grade B; 5 grade C). Margin negative resection rate for malignancy was 90% (75% for PDA) with mean harvest of 16 ± 8 lymph nodes. CONCLUSIONS: These multicenter data during the early learning curve for RA-MIPD do not demonstrate excess anastomotic morbidity compared to open. Further studies are required to determine whether surgeon proficiency and evolving technique improve anastomotic outcomes compared to open.

Nationwide Evaluation of Patient Selection for Minimally Invasive Distal Pancreatectomy Using American College of Surgeons' National Quality Improvement Program.

OBJECTIVE: To assess current nationwide case selection factors for minimally invasive distal pancreatectomy (MIDP) and identify actual risk factors for adverse outcomes compared with open distal pancreatectomy (ODP). BACKGROUND: Patient selection criteria that predict outcomes after MIDP remain unknown. As a result, widespread adoption of this surgical technique may have been delayed and its potential benefits possibly under-exploited. METHODS: Retrospective cohort study of elective ODP and MIDP performed at 106 centers in 2014, using the pancreas-targeted American College of Surgeons' National Quality Improvement Program (ACS-NSQIP) database. Exclusion criteria were neoadjuvant treatment or pancreatitis as only diagnosis. Primary outcome includes a composite major morbidity metric, reflecting adverse events including mortality and reoperation. Multivariable modeling was used to detect current selection factors and to identify actual risk factors of composite major morbidity. RESULTS: A total of 928 patients underwent ODP (n = 472) or MIDP (n = 456) using a laparoscopic or robot-assisted approach, 24% for pancreatic ductal adenocarcinoma (PDAC). Current selection factors for MIDP were benign disease (odds ratio: OR: 1.56, CI: 1.10-2.21) and body mass index (BMI) 30-40 (OR: 1.41, CI: 1.04-1.91). Current selection factors for ODP were PDAC (OR: 0.45, CI: 0.31-0.64), benign tumor size >5 centimeters (OR: 0.40, CI: 0.23-0.67), and multivisceral procedures (OR: 0.39, CI: 0.26-0.59). Risk factors for composite major morbidity did not differ between ODP and MIDP. A trend was observed between MIDP and a lower risk of composite major morbidity compared with ODP (OR: 0.43, CI: 0.17-1.07). CONCLUSIONS: Current selection factors for ODP or MIDP (benign disease, tumor size, and BMI) do not mitigate the risk of major morbidity. We found no evidence that MIDP should be avoided based on tumor etiology or size, BMI, or patient physical status.

Incorporation of Procedure-specific Risk Into the ACS-NSQIP Surgical Risk Calculator Improves the Prediction of Morbidity and Mortality After Pancreatoduodenectomy.

OBJECTIVE: This multicenter study sought to evaluate the accuracy of the American College of Surgeons National Surgical Quality Improvement Program's (ACS-NSQIP) surgical risk calculator for predicting outcomes after pancreatoduodenectomy (PD) and to determine whether incorporating other factors improves its predictive capacity. BACKGROUND: The ACS-NSQIP surgical risk calculator has been proposed as a decision-support tool to predict complication risk after various operations. Although it considers 21 preoperative factors, it does not include procedure-specific variables, which have demonstrated a strong predictive capacity for the most common and morbid complication after PD - clinically relevant pancreatic fistula (CR-POPF). The validated Fistula Risk Score (FRS) intraoperatively predicts the occurrence of CR-POPF and serious complications after PD. METHODS: This study of 1480 PDs involved 47 surgeons at 17 high-volume institutions. Patient complication risk was calculated using both the universal calculator and a procedure-specific model that incorporated the FRS and surgeon/institutional factors. The performance of each model was compared using the c-statistic and Brier score. RESULTS: The FRS was significantly associated with 30-day mortality, 90-day mortality, serious complications, and reoperation (all P < 0.0001). The procedure-specific model outperformed the universal calculator for 30-day mortality (c-statistic: 0.79 vs 0.68; Brier score: 0.020 vs 0.021), 90-day mortality, serious complications, and reoperation. Neither surgeon experience nor institutional volume significantly predicted mortality; however, surgeons with a career PD volume >450 were less likely to have serious complications (P < 0.001) or perform reoperations (P < 0.001). CONCLUSIONS: Procedure-specific complication risk influences outcomes after pancreatoduodenectomy; therefore, risk adjustment for performance assessment and comparative research should consider these preoperative and intraoperative factors along with conventional ACS-NSQIP preoperative variables.

Early surgical bypass versus endoscopic stent placement in pancreatic cancer.

INTRODUCTION: The optimal treatment for biliary obstruction in pancreatic cancer remains controversial between surgical bypass and endoscopic stenting. METHODS: Retrospective analysis of unresected pancreatic cancer patients in the Healthcare Cost and Utilization Project Florida State Inpatient and Ambulatory Surgery databases (2007-2011). Propensity score matching by procedure. Primary outcome was reintervention, and secondary outcomes were readmission, overall length of stay (LOS), discharge home, death and cost. Multivariate analyses performed by logistic regression. RESULTS: In a matched cohort of 622, 20.3% (63) of endoscopic and 4.5% (14) of surgical patients underwent reintervention (p < 0.0001) and 56.0% (174) vs. 60.1% (187) were readmitted (p = 0.2909). Endoscopic patients had lower median LOS (10 vs. 19 days, p < 0.0001) and cost ($21,648 vs. $38,106, p < 0.0001) as well as increased discharge home (p = 0.0029). No difference in mortality on index admission. On multivariate analysis, initial procedure not predictive of readmission (p = 0.1406), but early surgical bypass associated with lower odds of reintervention (OR = 0.233, 95% CI 0.119, 0.434). DISCUSSION: Among propensity score-matched patients receiving bypass vs. stenting, readmission and mortality rates are similar. However, candidates for both techniques may experience fewer subsequent procedures if offered early biliary bypass with the caveats of decreased discharge home and increased cost/LOS.

Trends and comparative outcomes between operative approaches for segmentectomy in lung cancer.

BACKGROUND: Segmentectomy is increasingly performed for non-small cell lung cancer. However, comparative outcomes data among open, robotic-assisted, and video-assisted thoracoscopic approaches are limited. METHODS: A retrospective cohort study of non-small cell lung cancer segmentectomy cases (2013-2021) from the Society of Thoracic Surgeons General Thoracic Surgery Database was performed. Baseline characteristics were balanced using inverse probability of treatment weighting and compared by operative approach. Volume trends, outcomes, and nodal upstaging were assessed. RESULTS: Of 9927 patients who underwent segmentectomy, 84.8% underwent minimally invasive surgery, with robotic-assisted thoracoscopic surgery becoming the most common approach in 2019. Open segmentectomy is more likely to be performed at low-volume centers (P < .0001), whereas robotic-assisted thoracoscopic surgery is more likely to be performed at high-volume centers (P < .0001). Video-assisted thoracoscopic surgery had a higher open conversion rate than robotic-assisted thoracoscopic surgery (odds ratio, 11.8; CI, 7.01-21.6; P < .001). Minimally invasive surgery had less 30-day morbidity compared with open segmentectomy (video-assisted thoracoscopic surgery odds ratio, 0.71; 95% CI, 0.55-0.94; P = .013; robotic-assisted thoracoscopic surgery odds ratio, 0.59; CI, 0.43-0.81; P = .001). The number of nodes and stations harvested were highest for robotic-assisted thoracoscopic surgery; however, N1 upstaging was more likely in open compared with robotic-assisted thoracoscopic surgery (odds ratio, 0.63; CI, 0.45-0.89; P < .007) and video-assisted thoracoscopic surgery (odds ratio, 0.61; CI, 0.46-0.83; P = .001). CONCLUSIONS: Segmentectomy volume has increased considerably, with robotic-assisted thoracoscopic surgery becoming the most common approach. Minimally invasive surgery has less major morbidity compared with open segmentectomy, with no difference between video-assisted thoracoscopic surgery and robotic-assisted thoracoscopic surgery. However, risk of open conversion is higher with video-assisted thoracoscopic surgery. Robotic-assisted thoracoscopic surgery had increased nodal harvest, whereas hilar nodal upstaging was highest with thoracotomy. This study reveals significant differences in outcomes exist between segmentectomy operative approach; the impact of approach on survival merits further investigation.

Robotic Mediastinal Surgery.

The robotic platform can be viewed as an advanced thoracoscopic instrument and can be utilized for any pathology amenable to thoracoscopic surgery. This ultimately comes down to surgeon comfort, but many have demonstrated the robotic approach to be useful in benign and malignant mediastinal disease in all compartments with at least equivalent-if not superior-outcomes compared to sternotomy for many metrics. There are various robotic approaches to the same compartments (such as with thymectomy), and no one robotic approach has proven superior to another. Here we describe our robotic approach to common mediastinal pathology.

Pembrolizumab Improves Survival After Resection of Intracardiac Metastatic Cervical Carcinoma.

Intracardiac metastasis of cervical squamous cell carcinoma (C-SCC) is rare, with historically poor long-term survival. We report the case of a 55-year-old woman with prior metastatic C-SCC who was found to have a right ventricular mass causing functional pulmonic stenosis and multiple pulmonary emboli 19 months after her initial diagnosis. She underwent surgical resection to prevent further embolization and heart failure. Pathology confirmed metastatic C-SCC and she was maintained on adjuvant pembrolizumab. She remained well 32 months later without further disease progression. Surgical resection of intracardiac metastasis of C-SCC combined with pembrolizumab therapy may result in improved postoperative life expectancy.

A scoping review of artificial intelligence applications in thoracic surgery.

OBJECTIVES: Machine learning (ML) has great potential, but there are few examples of its implementation improving outcomes. The thoracic surgeon must be aware of pertinent ML literature and how to evaluate this field for the safe translation to patient care. This scoping review provides an introduction to ML applications specific to the thoracic surgeon. We review current applications, limitations and future directions. METHODS: A search of the PubMed database was conducted with inclusion requirements being the use of an ML algorithm to analyse patient information relevant to a thoracic surgeon and contain sufficient details on the data used, ML methods and results. Twenty-two papers met the criteria and were reviewed using a methodological quality rubric. RESULTS: ML demonstrated enhanced preoperative test accuracy, earlier pathological diagnosis, therapies to maximize survival and predictions of adverse events and survival after surgery. However, only 4 performed external validation. One demonstrated improved patient outcomes, nearly all failed to perform model calibration and one addressed fairness and bias with most not generalizable to different populations. There was a considerable variation to allow for reproducibility. CONCLUSIONS: There is promise but also challenges for ML in thoracic surgery. The transparency of data and algorithm design and the systemic bias on which models are dependent remain issues to be addressed. Although there has yet to be widespread use in thoracic surgery, it is essential thoracic surgeons be at the forefront of the eventual safe introduction of ML to the clinic and operating room.

Trimodality Approach for Esophageal Malignancies.

Trimodality therapy, or the use of concurrent chemoradiation followed by surgery, is the cornerstone of contemporary management of esophageal cancer. This article discusses the landmark trials and most current data to understand the concepts, applications, and outcomes from trimodality therapy in locally advanced esophageal cancer.

Robotic-Assisted Complex Pulmonary Resection: Sleeve Lobectomy for Cancer.

The use of robotic assistance for complex pulmonary resections such as segmentectomy and sleeve lobectomy has steadily increased in recent years. These operations are technically challenging as they require fine dissection and suturing, which is often difficult to perform using traditional minimally invasive techniques. Robotic surgery is well-suited for complex pulmonary surgery given its specific advantages related to superior optics and precise tissue manipulation and dissection. Herein we describe our technique for robotic-assisted complex pulmonary surgery with a specific focus on right upper sleeve lobectomy for cancer, including associated video case demonstration. The principles discussed are generalizable to other complex lung and tracheobronchial operations and highlight the benefits of the robotic platform.

National Survey of Burnout and Distress Among Cardiothoracic Surgery Trainees.

BACKGROUND: Burnout has been linked to poor job satisfaction and increased medical errors, and is prevalent among health care professionals. We sought to characterize burnout and distress among US cardiothoracic surgery (CTS) trainees. METHODS: A 19-question survey was sent to CTS trainees in collaboration with the Thoracic Surgery Residents Association. We queried sociodemographic variables, balance/quality of life, and indicators of depression and regret. We included questions along the emotional exhaustion, depersonalization, and personal accomplishment subscales of the Maslach Burnout Inventory. RESULTS: The survey was sent to 531 CTS trainees across 76 institutions and there were 108 responses (20.3%). More than 50% of respondents expressed dissatisfaction with balance in their professional life and more than 40% screened positively for signs of depression. More than 25% of respondents (n = 28) would not complete CTS training again, given a choice. More than half met criteria for burnout on emotional exhaustion and depersonalization subscales. The CTS residents with children were more likely to express regret toward pursuing CTS training. A greater proportion of women than men reported poor levels of balance/quality of life during training as measured by missed health appointments, negative impact on relationships, and self-perception. Similarly, those in the final 3 years of training were more likely to report poor levels of balance/quality of life. CONCLUSIONS: High rates of burnout, regret, and depression are present among US CTS trainees. Efforts to promote trainee well-being and implement interventions that support those at high risk for burnout are warranted, to benefit trainees as well as the patients they serve.

Surgical Adjuncts During Esophagectomy.

Esophagectomy is a major operation whereby intraoperative technique and postoperative care must be optimal. Even in expert hands, the complication rate is as high as 59%. Here the authors discuss the role of surgical adjuncts, including enteral access, nasogastric decompression, pyloric drainage procedures, and anastomotic buttressing as adjuncts to esophagectomy and whether they reduce perioperative complications.