Incidence and Risk Factors of Postoperative Complications in General Surgery Patients

Background Postoperative complications, which are undesirable consequences of surgery, need to be minimized to ensure the quality of surgical care. In this study, we aimed to estimate the incidence and identify the risk factors for postoperative complications which may help in planning appropriate preventive measures. Methodology A prospective observational study was conducted in the general surgery department of a tertiary care hospital in a metropolitan city in India. Patients undergoing elective or emergency surgery were included. Patients transferred postoperatively from other hospitals and those undergoing day-care operations or endoscopic procedures were excluded. Age, gender, body mass index (BMI), comorbidities, surgical risk as per American Society of Anesthesiologists (ASA) grading, scheduling of surgery (emergency, semi-emergency, or elective), approach (open or laparoscopic), intraoperative complications, operative blood loss, the extent of surgery (superficial or deep cavity), indication (diagnostic, therapeutic, or palliative), duration of surgery, wound class (clean, clean-contaminated, contaminated, or dirty), and duration of hospital stay in days were recorded. Patients were followed up for 30 days postoperatively for complications (defined as any undesirable, unintended event as a direct result of an operation). Clavien-Dindo classification was used to grade the severity of complications. The chi-square test was used for categorical data, and the t-test was used for numerical data. P-values <0.05 were considered significant. Results Postoperative complications were observed in 31.50%; minor complications (Grade I and II) in 19.75% and major complications (Grade III and IV) in 8.0% of patients. Postoperative mortality (Grade V) was 3.75%. Significant risk factors were the presence of comorbidities, higher ASA grade, higher BMI, emergency surgery, open surgery, palliative surgery, deeper cavity surgery, higher intraoperative blood loss, prolonged surgical duration, intraoperative complications, and contaminated surgical wounds. Postoperative complications significantly prolonged the hospital stay. Conclusions Understanding risk factors can guide surgeons to adopt appropriate strategic measures to reduce postoperative complications and improve the quality of surgical care. Three key measures emerging from this study are (1) preoperative patient optimization; (2) diligence during surgery to reduce operative time, blood loss, and intraoperative complications; and (3) implementation of infection control practices.


Introduction
Postoperative complications are undesirable consequences of surgery and are a major area of concern adversely affecting the quality of surgical care and patient safety. These range from seemingly minor incidents which resolve without any harm to more serious incidents which may pose threat to life, need multiple interventions, prolong hospital stay and costs, and may at times cause disability or death [1]. In addition to the physical harm caused to patients, surgical complications can lead to psychological stress and worsen the quality of life [2].
To improve the quality of surgical care, complications need to be minimized. Hence, the incidence and risk factors of postoperative complications need to be understood. However, complications are varied and difficult to capture uniformly. Complications can be specific to the surgical disease, comorbidities, anesthesia, surgical procedure, intensive care interventions, prolonged recumbency, etc. They may affect different body systems such as respiratory, cardiovascular, renal, hepatobiliary, gastrointestinal, neurological, hemopoietic, coagulation, or skin and soft tissues. Complications have been subjectively graded as mild/moderate/severe, minor/major, non-life-threatening/life-threatening, etc. Various scoring systems are used for each complication. Therefore, there is a need to develop a uniform system to capture complications and grade their severity [3].
In 1992, Clavien et al. [3] defined and classified negative outcomes of surgical procedures by differentiating complications, sequelae, and failures: complications as unexpected events not intrinsic to the procedure, sequelae as events intrinsic to the procedure, and failures as events in which the purpose of the procedure is not fulfilled. They proposed a new system of classification that revolutionized the postoperative system of assessment. It graded complications into four grades (grade 4 being death) based on the treatment and interventions needed for the treatment of complications. This grading system was intended to achieve uniformity in reporting complications, compare results in a single center over time, compare results from different centers at the given time, complications of different treatment options, and provide a measuring scale for research [3].
In 2004, the modified version of the above system (the Clavien-Dindo classification) was published [4]. The grading of complications was proposed based on the therapy needed for treating complications. It has seven grades (grades 1 to 5) with two subgroups for grades 3 and 4. Grade 5 denotes death [4]. They reported a fiveyear experience of using the system which by then had found applications in many fields and had been validated using complex clinical situations from the University of Zurich's morbidity mortality conferences [5]. Surveys also showed that 90% of surgeons rated the Clavien-Dindo classification to be simple, reproducible, logical, useful, and comprehensive [4]. Hence, the Clavien-Dindo classification system was used in this study.
The objectives of this study were to determine the incidence of postsurgical complications and to study the risk factors associated with postoperative complications using the Clavien-Dindo classification to obtain some clues to plan preventive strategies.

Materials And Methods
The study was conducted in the department of general surgery in a tertiary care medical college hospital and was designed as a prospective observational study after obtaining approval from the institutional ethics committee (Ethics Committee for Academic Research Projects (ECARP); reference number: ECARP/2019/47). It was conducted over a one-year period from March 2020 to February 2021.
The sample size was calculated using the following formula: N = (z) 2 p (1-p)/e 2 Where N is the sample size, z at 1.96 (at 95% confidence level according to normal distribution), p at 0.5 (estimated proportion), and e (allowable error) of 0.05. This gave a sample size of 384. Considering the possibility of dropouts, it was increased by approximately 5% to 400.
After obtaining informed consent, patients were enrolled in the study. All patients admitted to the surgical ward for undergoing elective or emergency surgery were included. Patients who were operated on elsewhere and referred were excluded. Daycare and short-stay procedures and gastrointestinal endoscopies were also excluded. Patients' history, clinical examination, reports of investigations, diagnosis, and operative details were noted. Age, gender, body mass index (BMI, weight in kilograms/square of height in meters), presence of comorbidities, surgical risk as per American Society of Anesthesiologists (ASA) grading, scheduling of surgery (emergency (life-saving surgery), urgent or semi-emergency (early surgery after optimization), and elective (planned)), approach (open or laparoscopic), intraoperative complications if any as documented in surgical notes, operative blood loss in milliliters as estimated and recorded by anesthesiologists, the extent of surgery (superficial limited to the skin and soft tissues of the body wall or deep cavity, mostly abdominal cavity), purpose or indication of surgery (diagnostic, therapeutic, or palliative), duration of surgery and class of surgical wound (clean, clean-contaminated, contaminated, or dirty) were recorded. Patients were followed up for 30 days postoperatively and complications, if any, were noted. The duration of postoperative stay was noted in days.
A complication was defined as any undesirable, unintended event as a direct result of an operation affecting the patient that would not have occurred had the operation gone well as could reasonably be expected. The complication was graded as per the Clavien-Dindo classification ( Table 1) [4].  The data were tabulated and compiled in Microsoft Excel 2016. SPSS version 16 (IBM Corp., Armonk, NY, USA) was used for analysis. The chi-square test was applied for categorical data while the t-test was used for numerical data. The likelihood ratio test was used for estimating the association between risk factors and complications. A p-value of less than 0.05 was considered significant.

Results
A total of 400 patients undergoing operations in the department of general surgery were included. Surgeries included surgeries for inguinal hernia, ventral hernia, appendicectomy, colectomy, anterior and abdominoperineal resections, cholecystectomy, excision of lumps, mastectomy, thyroidectomy, splenectomy, distal pancreatectomy, Whipple's operation, reversal of stoma, feeding gastrostomy or jejunostomy, exploratory laparotomy for intestinal obstruction or peritonitis, and surgeries for skin and softtissue infections.
Age ranged from 13 to 85 years with the mean (±SD) of 42.4 (±15.8) years. The most common age group was less than 40 years (18- Complications were observed in 126 (31.5%) patients. Table 2 provides the distribution of patients with complications based on the Clavien-Dindo classification. Table 3 shows a bivariate analysis of the association of risk factors with complications. Table 4 depicts the likelihood ratio test.

Discussion
Postoperative complications, although undesirable, are a reality. The incidence of such complications and the risk factors need to be determined for planning preventive strategies. The incidence of postoperative complications after general surgical operations was observed to be 31.50%. As per the Clavien-Dindo classification, the incidence of minor complications (grades I and II) was 19.75% and the incidence of major complications (grades III and IV) was 8.0%. Overall postoperative mortality was 3.75% (grade V). Risk factors associated with postoperative complications were the presence of comorbidities, higher ASA grade, higher BMI, emergency surgery, open surgery, palliative surgery, deeper cavity surgery, higher intraoperative blood loss, prolonged duration of surgery, the occurrence of intraoperative complications, and contaminated and dirty class of surgical wound. In patients with postoperative complications, hospital stay was significantly prolonged.
Contemporary published literature supports our observations. Tevis and Kennedy in a review of literature on postoperative complications in general surgery patients reported an incidence of complications of 5.8-43.5%, with mortality ranging from 0.79% to 5.7%. They reported an overall complication rate of 37%, with 25.7% of complications classified as grade I, 48.6% as grade II, 17.1% as grade III, 5.7% as grade IV, and 2.9% as grade V [1]. A European study in general surgery patients published in 2018 reported an overall complication rate of 12.5%, of which 19% were rated as grade I, 20.7% as grade II, 13.8% as grade IIIA, 27.6% as grade IIIB, 8.6% as grade IVA, and 10.3% as grade V. No grade IVB complications occurred in their investigation [6]. In this study, the overall complication rate was 31.5%, of which grade-wise occurrences were 20.6%, 42%, 15.1%, 7.1%, 3.2%, 0%, and 11.9%, respectively. Both studies did not report grade IVB complications which indicate the death of patients with multiorgan failure (grade V).
A higher incidence of postoperative complications has been reported with advancing age [7]. Unlike the present study, a lower incidence has been observed in women [8]. Women have been observed to report postoperative minor complications such as nausea, vomiting, and headache more often compared to men [9]. The risk of postoperative complications has been reported to be higher in obese individuals [10]. The presence of comorbidities such as cardiac, pulmonary, renal, hepatic, or neurological disease is associated with a significant increase in postoperative complications after major abdominal surgery [11]. In addition, higher postoperative complications have been noted in patients with anemia and perioperative hypoalbuminemia, particularly in low-resource settings [12,13]. A meta-analysis revealed an association between diabetes mellitus with postoperative complications and mortality after non-cardiac surgery [14]. Perioperative hyperglycemia is associated with increased rates of surgical-site infection (SSI), myocardial infarction, stroke, and death [15]. Since 1996, the ASA perioperative risk grading has been a predictor of postoperative complications and outcomes [16]. This study also found higher complications among patients with comorbidities and higher ASA grades.
The study results noted a higher incidence of complications after emergency surgery. Emergency surgery has been observed to have a higher incidence of SSI, pneumonia, myocardial infarction, major bleeding, and stroke with higher subsequent mortality [17]. Focused attention to preoperative optimization may be needed for quality improvement [17]. In this study, the minimal access or laparoscopic approach had fewer complications in comparison to open surgery. This could be because of selection bias as laparoscopic surgeries are usually performed in patients who have good cardiorespiratory reserves and with localized and early disease. However, several papers on different surgeries have also stated that minimal access surgery has fewer postoperative complications [1]. Abdominal surgeries involving the peritoneal cavity (deep cavity surgeries) had a significantly higher incidence of postoperative complications. Gastrointestinal surgeries have been reported to have a significantly higher incidence of SSI, particularly deep or organ space infection [18]. Surgeries in infected or dirty sites or cavities have been observed to have the highest incidence of complications (48%) compared to contaminated wounds (29%) or clean wounds (17%) [18]. Palliative surgeries, done usually for advanced disease (cancer) or in patients unfit due to comorbidities, were associated with significantly higher postoperative complications. This has been reported by other studies as well [19,20].
Longer duration of surgery and increased blood loss during surgery enhance the negative impact on postoperative complications. While studying adverse events in hospitalized patients, it has been observed that postoperative complications in longer surgeries were due to increased blood loss, longer anesthesia requirements, and the indication of the surgery itself [21]. Although the Clavien-Dindo classification does not capture intraoperative complications, in this prospective study, the occurrence of any complication during surgery was specifically noted. Duration of surgery, amount of blood loss, intraoperative hypotension, and transfusion requirement can serve as surrogate markers for the complexity of the surgery and intraoperative complications. In a systematic review and meta-analysis published in 2018, prolonged operative duration was found to be associated with complications [22]. Intraoperative hypotension and blood transfusions have also been observed to be associated with morbidity and mortality [23,24]. Therefore, all efforts must be made to control bleeding during surgery. A multimodal and multidisciplinary approach has been recommended. Correction of anemia and optimization of erythropoiesis, management of antiplatelet and anticoagulant therapy, and risk stratification should be done in the preoperative phase. Use of antifibrinolytics (tranexamic acid), use of a tourniquet and meticulous surgical technique, use of electrosurgery and topical agents for hemostasis, use of cell savers, and autologous blood transfusion can be practiced by surgeons. Anesthesiologists can help in controlling blood loss by implementing permissive hypotension and hemostatic resuscitation, appropriate patient positioning, preventing hypothermia, and maintaining ventilation. The availability of viscoelastic assays in patients undergoing complex surgeries is also a useful strategy [25]. A significant increase in hospital stay has been reported in patients undergoing more complex surgeries and with higher Clavien-Dindo grades similar to the observations of this study [6].
The Clavien-Dindo classification was initially reported for general surgical patients. It has been used in many other surgical settings and is useful. In one paper, while applying it to emergency surgical patients, complications were reported in nearly 26% of patients, however, the authors recommended that preoperative organ dysfunction should be taken into account when defining postoperative grade IV complications [26].
The study has some limitations. The patient population was rather heterogenous and included all patients operated in a general surgical department including operations for different diseases, on different organs, and performed by different surgeons with different levels of experience. Such a design was necessary to identify different risk factors. The incidence will be different if a population is more homogeneous. The follow-up period was limited to 30 days postoperatively. Delayed complications and long-term effects of complications on quality of life have not been studied. Complications such as recurrence of hernia, chronic pain, development of incisional hernia, recurrence, and survival in malignant cases take much longer to develop and need long-term follow-up. However, most serious complications do occur in the early phase within 30 days [27]. Complications can also result from medical errors, which have not been separately recorded and studied in this study [28,29]. Although the Clavien-Dindo classification is simple, reproducible, logical, useful, and comprehensive and has been validated and found applicable worldwide in many fields of surgery, the incidence of a specific complication cannot be estimated using the classification, for example,