European Journal of Cardiovascular Medicine

The incidence of postoperative wound infections, commonly referred to as surgical site infections (SSIs), can vary significantly depending on the surgical procedure, hospital environment, patient characteristics, and surgical methods employed. For example, clean surgical procedures typically exhibit an infection rate ranging between 2% and 5%, while clean-contaminated procedures have higher infection rates, approximately 5% to 15%. In more complicated or emergency procedures classified as contaminated, these rates can escalate substantially, often reaching 30% or higher.

Several factors contribute to the variability of SSI rates. Patient-specific factors, including advanced age, obesity, diabetes mellitus, compromised immunity, smoking habits, and malnutrition, significantly elevate infection risks [1]. Similarly, surgical factors such as prolonged operative duration, emergency nature of the procedure, and the use of surgical drains or implants also increase susceptibility to infection. Hospital-related factors like infection control protocols, sterilization practices, and appropriate antibiotic prophylaxis further impact infection rates.

In India specifically, studies indicate a wide variation in SSI incidence, often reflecting the variability in healthcare infrastructure, patient population characteristics, and adherence to surgical protocols. Reports from various hospital settings across India suggest that SSI rates commonly range between 4% and 30%. For instance, research conducted in rural and semi-urban healthcare facilities reported an average SSI incidence of about 7%, with notably higher rates seen in procedures involving contaminated or dirty wounds. In contrast, a study carried out in a tertiary care hospital in Mumbai documented an SSI incidence rate of approximately 11%, particularly heightened in elderly patients, those with diabetes, and individuals undergoing emergency procedures or extended hospital stays. Obstetric surgical procedures, especially cesarean sections, have been specifically studied, revealing an SSI rate of around 5.63%, which significantly impacts hospital length-of-stay and healthcare expenditures, these varied findings, it becomes evident that there is a critical need to strengthen infection control practices, particularly in resource-limited regions, to effectively lower the incidence and overall burden of postoperative wound infections in India [2].

Hence, this study was undertaken to study the risk factors for surgical site infections in patients admitted under general surgery in a tertiary hospital in Central India.

This study was conducted as a prospective, randomized, single-blind observational study done at our hospital from January 1, 2023, to December 31, 2024. The study adhered to the tenets of the Declaration of Helsinki, and approval from the institutional research ethics board was obtained for the study.

A total of 180 post-operative patients who developed wound infections during the course of their post-surgical care were enrolled in the study. The sampling technique adopted was convenience sampling, allowing the inclusion of patients who met the inclusion criteria and were available during the study period. Although not random in nature, this technique ensured a diverse patient population reflective of the hospital’s caseload.

Inclusion Criteria

Patients were included in the study if they met the following criteria:

1. Patients of any age and either gender who underwent surgical intervention and developed wound infections post-operatively.
2. Patients who provided informed consent for participation in the study.
3. Patients who developed infection either within 30 days of surgery (without implant) or within 90 days (with prosthetic implant), in accordance with CDC-NHSN (Centers for Disease Control and Prevention – National Healthcare Safety Network) definitions.

Exclusion Criteria

Patients were excluded from the study based on the following criteria:

1. Patients with a previously infected wound site at the time of surgery.
2. Patients unwilling to provide informed consent or unable to comply with the follow-up protocol.
3. Patients whose wound infections were not related to surgical intervention or could not be reliably classified under SSI categories.

Operational Definition of Surgical Site Infection

Surgical Site Infections (SSI) were defined based on CDC-NHSN guidelines:

• Superficial Incisional SSI: Infection involving only the skin and subcutaneous tissue of the incision, exhibiting signs such as purulent drainage, positive microbial culture, localized swelling, redness, heat, or pain.
• Deep Incisional SSI: Infection involving deeper soft tissues (e.g., fascia and muscle layers) that may manifest with dehiscence, abscess formation, or purulent drainage from a deep incision.
• Organ/Space SSI: Infection involving any anatomical structure that was manipulated during the operative procedure (e.g., peritoneum, joint, pleural space), not limited to the incision site, and associated with clinical or radiological evidence of infection.

Data Collection Procedure

Each participant was monitored from the time of hospital admission through the surgical intervention and into the postoperative period until discharge. Clinical data were recorded using a structured proforma, and postoperative follow-up was conducted through the Outpatient Department (OPD) to detect delayed onset of infection.

Statistical Analysis

All data collected were coded and entered into a secure database. Analysis was performed using SPSS (Statistical Package for Social Sciences) software. Descriptive statistics were applied to calculate mean, median, standard deviation, and frequency distribution. Inferential analysis included:

• Chi-square test: For categorical variables.
• One-way ANOVA: To compare means across different types of SSIs (superficial, deep, organ-space).
• P-values < 0.05 were considered statistically significant.
• Variables like age, hemoglobin (HB), total leukocyte count (TLC), random blood sugar (RBS), total protein, and length of hospital stay were analyzed against SSI severity and type.

A total of 180 patients were studied of which 122 were males and 58 were females. The largest age group undergoing surgery was 51-60 years (31.11%), followed by 41-50 years (22.22%). The youngest group (0-10 years) comprised 6.11%, while the 11-20 age group was 5.56%.

The majority of surgeries were contaminated (56.11%), followed by clean-contaminated (23.89%) and clean surgeries (18.89%). Dirty surgeries accounted for only 1.11%.

The most common duration was 2 hours (37.22%), followed by 3 hours (23.89%) and 4 hours (18.33%). A small percentage of surgeries lasted 5 hours (7.22%), while 13.33% were completed in 1 hour.

Table 1 showing socio-clinical profile of the patients undergoing surgery.

Table 2 showing types of surgical site infections and based on if drain/ mesh used

Table 3: ANOVA Analysis of Various factors Based on Type of SSI

A majority of patients (63.33%) had drains, while 34.44% did not. Mesh usage was minimal (2.22%).

The mean age for superficial SSI was 36.96 ± 18.80 years, while deep SSI had a significantly higher mean age of 53.29 ± 10.54 years. The organ-spaced infections had a fixed age of 32 years. The ANOVA P-value (0.0001) indicates a highly significant difference in age distribution among SSI types, suggesting that older individuals are more prone to deep SSIs.

The mean hemoglobin levels were highest in superficial SSI (11.27 ± 1.10 g/dL), while deep SSIs showed a slightly lower mean of 10.56 ± 1.08 g/dL. The organ-spaced infections had a constant HB level of 10.70 g/dL. The ANOVA P-value (0.0001) indicates a statistically significant difference, suggesting that lower hemoglobin levels may be associated with deeper infections.

Patients with deep SSI had the highest mean TLC (10820.78 ± 3914.32), followed by superficial SSIs (9530.93 ± 3354.28). The lowest TLC was found in organ-spaced infections (7400.00). The ANOVA P-value (0.0132) suggests a moderate statistical significance, indicating that higher leukocyte counts may correlate with deeper infections.

The mean RBS values were similar across all SSI types:

• Superficial SSI: 132.07 ± 50.34 mg/dL
• Deep SSI: 133.44 ± 34.42 mg/dL
• Organ-spaced SSI: 145.00 mg/dL

The ANOVA P-value (0.7773) indicates no statistically significant difference, suggesting that blood sugar levels do not play a major role in the severity of SSIs.

The mean total protein levels were almost identical across all SSI types:

• Superficial SSI: 5.05 ± 0.43 g/dL
• Deep SSI: 5.08 ± 0.37 g/dL
• Organ-spaced SSI: 5.10 g/dL

The ANOVA P-value (0.8500) indicates no significant difference, suggesting that total protein levels do not influence the severity of SSIs.

Patients with organ-spaced SSIs had the longest hospital stays (25.50 ± 10.32 days), followed by deep SSIs (16.53 ± 5.72 days) and superficial SSIs (12.93 ± 3.99 days). The ANOVA P-value (0.0001) indicates a highly significant difference, highlighting that deeper infections lead to prolonged hospitalization.

Postoperative wound infections (POWIs), a subset of surgical site infections (SSIs), are infections that develop at or near the surgical incision site, typically within 30 days post-surgery. In cases involving implanted devices, infections may manifest up to a year later. These infections can affect superficial tissues, deeper layers such as fascia and muscle, or even internal organs and spaces manipulated during surgery. POWIs represent a significant category of healthcare-associated infections (HAIs), posing substantial clinical and economic challenges. The objectives of this study were to determine the incidence of postoperative wound infections, identify the risk factors contributing to surgical site infections, analyze the most frequently encountered bacterial organisms along with their antibiotic sensitivity and resistance patterns, evaluate the efficacy of different preoperative preparation methods in preventing wound infections, and examine the distribution of postoperative wound infections across various surgical categories, including clean, clean-contaminated, contaminated, and dirty surgeries.

Our findings reveal a male predominance (64.44%) in the sex distribution of surgical site infections (SSIs), suggesting potential sex-based vulnerability or differential exposure. Female representation was significantly lower (31.67%), and pediatric and non-binary cases were minimal. The small proportion of children (3.34%) may reflect fewer surgical interventions or reduced complication rates. These results align with Langelotz C et al. (2014) [3], who found women had significantly lower SSI rates than men, potentially due to hormonal influences—specifically, the immunosuppressive effects of testosterone and the anti-inflammatory properties of estrogens. Similarly, Aghdassi SJ et al. (2019) [4] further supported these findings, reporting significantly higher SSI rates in male patients undergoing orthopedic, trauma, and abdominal surgeries, while female patients had higher rates in cardiac and vascular procedures. The consistency of our findings with these studies underscores the importance of considering sex-specific physiological and anatomical factors in surgical outcomes. Together, these correlations suggest a multifactorial interplay of biological, hormonal, and procedural factors influencing the observed male predominance in SSIs [87,88].

Our findings indicate the highest incidence of infections in patients aged 51–60 years (31.11%), followed by those aged 41–50 years (22.22%), suggesting a clear trend of increased SSI risk with advancing age. The lowest incidence was noted in the 0–20 age group (≤6.11%), likely reflecting fewer surgical interventions or more robust wound healing capacities in younger individuals. This age-related vulnerability aligns with Bischoff P et al. (2023) [5], who demonstrated a strong correlation between increasing age and SSI occurrence, with patients aged 76–80 years facing significantly higher risk compared to the 61–65 age group, while those ≤50 years had markedly lower risk. Similarly, Meena R et al. (2023) [6] found that older age, alongside factors such as higher BMI, elevated glycemic index, and prolonged preoperative hospitalization, significantly increased SSI risk. Cheng K et al. (2015) [7] also reported a higher SSI incidence in patients over 75 years (5.6%) compared to those under 75 years (3.0%). Although their findings lacked statistical significance, they emphasized the need for vigilant monitoring of elderly patients due to declining immune and physiological defenses. Collectively, these studies corroborate our findings, highlighting age as a critical determinant in SSI susceptibility, especially among middle-aged and older populations [89,90,91].

Our findings demonstrate that contaminated surgeries accounted for the majority of postoperative wound infections (56.11%), indicating a high infection risk associated with increased microbial exposure. Clean-contaminated and clean surgeries showed progressively lower infection rates (23.89% and 18.89%, respectively), consistent with the expected sterility gradient. Dirty surgeries, though inherently high-risk, were underrepresented (1.11%), possibly due to fewer such procedures being performed. These results are supported by Mioton LM et al. (2013) [8], who reported SSI rates of 2.1% in clean, 3.3% in clean-contaminated, 6.4% in contaminated, and 7.1% in dirty cases, clearly demonstrating a stepwise increase in infection rates with wound contamination levels. Onyekwelu I et al. (2017) [9] similarly emphasized that accurate surgical wound classification is critical for SSI prediction and prevention, noting that higher contamination levels strongly correlate with increased infection incidence. Wang-Chan A et al. (2017) [10] further reinforced this by showing that contaminated and dirty-infected wounds had higher SSI rates (3.3% and 2.9%, respectively), while clean and clean-contaminated wounds had a 0% infection rate. Together, these studies validate our observations and highlight the importance of surgical wound classification as a predictive factor for postoperative infections, reinforcing the infection risk gradient from clean to dirty procedures [92,93,94].

Our findings indicate that the majority of postoperative wound infections occurred following emergency surgeries (65%), emphasizing the higher infection risk associated with urgent, less-controlled operative environments. Elective surgeries accounted for only 35% of infections, likely benefiting from comprehensive preoperative preparation, optimized patient conditions, and stringent adherence to aseptic protocols. These observations are consistent with the study by Jadoon SK et al. (2023) [11], which reported a wound infection rate of 18.6%, with emergency surgeries contributing 13.6% compared to only 5% from elective procedures. The authors attributed the elevated infection rates in emergency settings to inadequate preoperative preparation and suboptimal sterile conditions. Similarly, Reji RG et al. (2024) [12] found an overall surgical site infection (SSI) rate of 11%, with emergency surgeries showing a higher incidence (13%) versus 9% in elective cases. They highlighted that advanced patient age, underlying comorbidities, and higher wound contamination levels significantly increased the risk of SSIs in emergency surgeries. These studies collectively support our findings, reinforcing that emergency procedures inherently carry a greater risk of infection due to time constraints, uncontrolled surgical environments, and patient-related factors. This correlation underscores the need for enhanced infection control strategies, especially in emergency surgical settings, to mitigate postoperative complications.

Our findings reveal that surgeries lasting approximately 2 hours were most frequently associated with postoperative wound infections (37.22%), suggesting a potential link between moderate procedural complexity and infection risk. Interestingly, infection rates decreased with procedures lasting 3 hours or more, despite the generally accepted notion that prolonged surgeries elevate infection risk due to extended tissue exposure and increased operative field contamination. In contrast, shorter surgeries, averaging around 1 hour, were associated with fewer infections (13.33%), likely attributable to limited tissue manipulation and reduced contamination risk. These patterns are consistent with prior research. Marzoug OA et al. (2023) [13] identified prolonged operative time as a significant risk factor for surgical site infections (SSIs), reporting that procedures exceeding 2 hours demonstrated markedly higher infection rates. The study emphasized that extended durations contribute to increased tissue trauma, thermal injury, and opportunities for microbial contamination, all of which facilitate SSI development. Similarly, Papadopoulos A et al. (2021) [14] found a strong association between operative durations greater than 90 minutes and heightened SSI incidence. Their multivariate analysis confirmed that longer surgeries independently increase infection risk, underscoring the clinical relevance of surgical efficiency and timely procedural execution. Collectively, these findings stress the importance of optimizing operative time to mitigate postoperative infection risk [97,98].

Our findings demonstrate that the majority of surgical site infections (SSIs) emerged between postoperative days 3 to 7, peaking on day 5 (28.33%), followed by day 7 (27.22%) and day 3 (24.44%), indicating a critical window for the clinical manifestation of SSIs. This pattern aligns with the inflammatory response and microbial incubation period typical in postoperative wound healing. Early detection (days 1–2) and late detection (day 10) were infrequent, suggesting that most SSIs become apparent within the first postoperative week. Conversely, Alemayehu MA et al. (2023) [15] observed that many SSIs were detected after discharge, especially between days 9 and 16, highlighting the need for extended surveillance beyond hospitalization. Although our findings emphasize earlier infection detection, they collectively reinforce the importance of both early in-hospital monitoring and continued post-discharge follow-up to effectively capture the full spectrum of SSI onset [76,99].

Our findings indicate that the majority of postoperative wound infections occurred in patients with surgical drains (63.33%), likely due to their role as foreign bodies and potential pathways for bacterial entry. In contrast, patients without drains had a significantly lower infection rate (34.44%), suggesting that avoiding drain use when possible may reduce the risk of surgical site infections (SSIs). Mesh use was minimal (2.22%), limiting definitive conclusions but possibly reflecting either heightened surgical caution or a lower frequency of mesh-requiring procedures such as hernia repairs. These observations align closely with previous research. Mujagic E et al. (2019) [16] found a significant association between the use of surgical drains and an increased risk of SSIs in general surgical procedures, attributing this to the potential for drains to disrupt wound healing and serve as a nidus for infection. Similarly, Lee HM et al. (2023) [17] emphasized that prolonged drain placement significantly increases the risk of SSIs. Their study highlights the importance of minimizing the duration of drain use and ensuring timely removal to reduce infection risk. Together, these studies support our findings and underscore the need for careful consideration of both the necessity and duration of drain use in surgical practice [100,101].

Our findings show significant associations between the type of surgical site infection (SSI) and factors such as age, hemoglobin (HB), total leukocyte count (TLC), and hospitalization duration (p < 0.05). Deep SSIs were more common in older patients (mean age 53.29 years) than in those with superficial infections (mean age 36.96 years), indicating increased vulnerability with age. Lower HB and elevated TLC were linked to more severe infections, suggesting a strong systemic inflammatory response. Longer hospital stays were also associated with deeper infections. These findings align with Zhang J et al. (2023) [18], who identified older age, elevated preoperative WBC, and prolonged hospitalization as risk factors for SSIs. Similarly, Zhao H et al. (2022) reported that older age, lower hematocrit (a proxy for HB), and extended hospital stays were strongly associated with deep SSIs. Together, these studies support our results and emphasize the importance of early identification of high-risk patients through individualized risk assessment for effective SSI prevention and management [19].

This study provides critical insight into the magnitude, profile, and patterns of SSIs in a high-burden tertiary care setting. The high prevalence of superficial infections is reassuring but still underscores the need for better preventive practices. The significant incidence of deep and organ-space infections in certain surgical types, especially contaminated and emergency surgeries, shows that SSI remains a real threat to surgical outcomes.

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