Comparison of Surgical Site Infection in Intraoperative Peritoneal Lavage with Metronidazole Versus Normal Saline in TIIE Treatment of Peritonitis

 

 

 

Peritonitis is a serious surgical emergency characterized by inflammation of the peritoneum resulting from infectious, ischemic, or perforating injuries of the gastrointestinal or genitourinary tract. The peritoneum is the largest serous membrane in the human body, with a surface area comparable to that of the skin, and plays a vital role in fluid exchange and immune defense within the abdominal cavity. When contamination occurs, rapid inflammatory response and bacterial proliferation may lead to sepsis, organ dysfunction, and increased postoperative morbidity and mortality (Chitumalla et al., 2016; Shanker et al., 2018). Secondary peritonitis, commonly due to perforated hollow viscera, remains the most frequent form encountered in surgical practice and is associated with significant risk of postoperative complications, particularly surgical site infection (SSI) (Firescu et al., 2017).

Management of peritonitis involves prompt resuscitation, administration of broad-spectrum antibiotics, and definitive surgical intervention, typically exploratory laparotomy with control of the source of contamination. Intraoperative peritoneal lavage is routinely performed during surgery to remove bacterial load, inflammatory exudates, and necrotic debris, thereby reducing intra-abdominal contamination and improving postoperative outcomes (Gupta et al., 2022). Although normal saline is the most commonly used lavage solution due to its safety, availability, and low cost, the effectiveness of saline alone in preventing postoperative infectious complications remains debatable.

To enhance the antimicrobial effect of lavage, various antibiotic and antiseptic agents have been investigated, including metronidazole, cephalosporins, povidone-iodine, and imipenem. Among these, metronidazole has gained considerable attention because of its potent bactericidal activity against anaerobic organisms, which are frequently implicated in intra-abdominal infections associated with bowel perforation and abscess formation (Baig & Kumar, 2019). By disrupting bacterial DNA synthesis, metronidazole may reduce intraperitoneal microbial burden when used as an adjunct to lavage, potentially lowering the incidence of SSI and other postoperative septic complications.

Several studies have compared antibiotic lavage with conventional saline lavage in patients undergoing surgery for peritonitis, yielding mixed results. Some investigators reported significant reductions in postoperative sepsis and wound infection following antibiotic lavage, while others observed only modest or statistically insignificant differences (Saha et al., 2019; Singh et al., 2023). However, a comparative study by Gangwal et al. (2017) demonstrated a notably lower rate of SSI in patients receiving metronidazole lavage (6.5%) compared with normal saline lavage (26.3%), suggesting a potential benefit of antibiotic lavage in reducing postoperative wound infection. Similarly, Sarada et al. (2020) reported improved postoperative outcomes with metronidazole-containing lavage solutions, highlighting the importance of targeted antimicrobial therapy during surgical management of peritonitis.

Despite these findings, consensus regarding the routine use of metronidazole lavage remains lacking, particularly in resource-limited settings where surgical site infection continues to impose substantial healthcare burden. Differences in study design, sample size, and patient characteristics contribute to variability in reported outcomes, underscoring the need for further randomized controlled trials to establish evidence-based recommendations. Moreover, reducing SSI is of paramount importance as it is associated with prolonged hospital stay, increased healthcare costs, delayed wound healing, and higher patient morbidity.

Therefore, this randomized controlled trial was conducted to compare the frequency of surgical site infection following intraoperative peritoneal lavage with metronidazole versus normal saline in patients undergoing laparotomy for peritonitis. The findings of this study aim to provide additional evidence regarding the effectiveness of metronidazole lavage and contribute to improved surgical practices and patient outcomes.

 

LITERATURE REVIEW

Peritonitis remains a major cause of morbidity and mortality in emergency surgical practice worldwide. The condition results from microbial contamination of the peritoneal cavity and triggers a systemic inflammatory response that may lead to sepsis and multi-organ dysfunction if not promptly managed. Accurate assessment of disease severity and effective surgical management are essential for improving outcomes. Chitumalla et al. (2016) highlighted the usefulness of clinical scoring systems such as the Mannheim Peritonitis Index in predicting prognosis and guiding therapeutic decisions. Similarly, Shanker et al. (2018) reported that delayed presentation and inadequate source control significantly contribute to postoperative complications, including surgical site infection (SSI).

Exploratory laparotomy with source control and peritoneal lavage remains the cornerstone of treatment for generalized peritonitis. The primary objective of peritoneal lavage is to reduce bacterial load, remove inflammatory debris, and minimize residual contamination within the abdominal cavity. Traditionally, normal saline has been widely used due to its isotonic nature and minimal tissue toxicity. However, concerns have been raised regarding its limited antimicrobial effect, prompting exploration of alternative lavage solutions with enhanced bactericidal properties (Gupta et al., 2022).

Antibiotic lavage has been proposed as a strategy to augment intraoperative infection control. Metronidazole, a nitroimidazole antimicrobial agent, is particularly effective against anaerobic bacteria commonly isolated in intra-abdominal infections. Baig and Kumar (2019) demonstrated that metronidazole lavage could reduce bacterial contamination and improve postoperative recovery in patients undergoing surgery for peritonitis. Their findings support the theoretical advantage of antibiotic lavage in targeting anaerobic organisms that contribute significantly to postoperative sepsis and wound infection.

Several comparative studies have investigated the effectiveness of metronidazole lavage versus normal saline lavage. Choudhary and Dhankar (2018) conducted a comparative study in operated peritonitis cases and reported a lower incidence of SSI in patients receiving metronidazole lavage, although the difference was modest. Similarly, Sarada et al. (2020) compared povidone-iodine and metronidazole lavage solutions and found improved infection control in the metronidazole group, emphasizing its role as a safe and effective adjunct during surgery.

In contrast, some studies have reported inconclusive results regarding the superiority of antibiotic lavage. Saha et al. (2019) compared povidone-iodine and normal saline lavage and observed reduced postoperative infection rates in the antiseptic group; however, the difference was not statistically significant. Singh et al. (2023) also evaluated multiple lavage solutions, including saline, metronidazole, and betadine, and concluded that while antibiotic lavage showed a trend toward lower infection rates, variability in patient characteristics and surgical factors influenced outcomes.

More robust evidence has been reported in randomized and longitudinal studies. Gangwal et al. (2017) conducted a comparative study among patients undergoing emergency laparotomy and reported a markedly lower SSI rate in the metronidazole lavage group (6.5%) compared with the normal saline group (26.3%). This significant reduction suggests that targeted antibiotic lavage may play a crucial role in preventing postoperative wound infection. Additionally, Aslam et al. (2023) demonstrated improved postoperative outcomes and reduced septic complications with metronidazole lavage, further supporting its potential clinical benefit.

Meta-analytic evidence also highlights the importance of lavage in reducing postoperative infectious complications. Gammeri et al. (2018), in a meta-analysis of peritoneal lavage, reported that antibiotic lavage could contribute to reduced postoperative sepsis and abscess formation, although heterogeneity among studies limited definitive conclusions. These findings indicate the need for further randomized controlled trials to clarify the role of antibiotic lavage and establish standardized protocols.

Overall, existing literature suggests that while normal saline lavage remains a safe and widely practiced approach, the addition of metronidazole may offer improved infection control by targeting anaerobic pathogens commonly implicated in peritonitis. However, variability in study outcomes and limited data from resource-constrained settings necessitate further investigation. Therefore, the present randomized controlled trial aims to compare the frequency of SSI following intraoperative peritoneal lavage with metronidazole versus normal saline, thereby contributing to the existing body of evidence and guiding surgical practice.

 

METHODOLOGY:

Study Design and Setting

This randomized controlled trial was conducted in the Department of Surgery Unit I, Bolan Medical Complex Hospital, Quetta, over a period of six months following ethical approval from the institutional review committee. The study was designed to compare the frequency of surgical site infection (SSI) following intraoperative peritoneal lavage with metronidazole versus normal saline in patients undergoing laparotomy for peritonitis, consistent with the protocol described in the approved synopsis.

Sample Size

The sample size was calculated using the WHO sample size formula by taking the expected proportion of SSI as 6.5% in the metronidazole lavage group and 26.3% in the normal saline group, with a confidence level of 95% and power of 90% (Gangwal et al., 2017). The calculated sample size was 120 patients, with 60 participants allocated to each group.

Sampling Technique and Randomization

A non-probability consecutive sampling technique was used for patient recruitment. Eligible patients presenting with clinical features suggestive of peritonitis were enrolled. Participants were randomly assigned into two groups (Group A and Group B) using a computer-generated randomization list to minimize allocation bias.

Eligibility Criteria

Inclusion Criteria

Patients fulfilling the following criteria were included:

• Clinically suspected peritonitis requiring exploratory laparotomy

• Age between 18 and 60 years

• Both male and female patients

 

Exclusion Criteria

Patients were excluded if they had:

• Uremia with serum urea >65 mg/dL

• Obesity (BMI >29 kg/m²)

• Chronic diabetes mellitus

• Immune compromised status (HIV infection or malignancy)

• Liver cirrhosis, chronic kidney failure, or long-term steroid use

These exclusion criteria were applied to reduce confounding factors that could independently increase the risk of postoperative infection.

 

Operational Definitions

Peritonitis: Diagnosed clinically based on sudden onset severe abdominal pain, abdominal tenderness and rigidity, vomiting, fever >100°F, hypotension (BP <100/80 mmHg), and tachycardia (>100 beats/minute).

Surgical Site Infection: SSI was considered present when redness, swelling, or purulent discharge from the surgical wound was observed within 7 postoperative days.

Data Collection Procedure

Patients meeting inclusion criteria were enrolled through the emergency and outpatient departments after obtaining written informed consent. A detailed history and clinical examination were performed for all participants. Baseline demographic and clinical data, including age, gender, body mass index (BMI), and cause of peritonitis, were recorded on a predesigned proforma.

All patients underwent exploratory laparotomy under the supervision of an experienced consultant general surgeon (FCPS). After identification and management of the underlying cause of peritonitis, patients were subjected to intraoperative peritoneal lavage according to group allocation:

• Group A (Metronidazole group): Peritoneal lavage with 2 liters of normal saline mixed with 200 mL metronidazole

• Group B (Normal saline group): Peritoneal lavage with 2 liters of normal saline alone

Standard postoperative care and antibiotic protocols were followed for all patients. Participants were monitored daily during hospitalization and followed up until the 7th postoperative day for the development of SSI.

Data Analysis

Data were entered and analyzed using Statistical Package for Social Sciences (SPSS) version 23. Quantitative variables, including age and BMI, were expressed as mean ± standard deviation. Categorical variables such as gender, cause of peritonitis, and SSI were summarized as frequencies and percentages.

The primary outcome, frequency of SSI, was compared between the two groups using the chi-square test. Effect modifiers, including age, gender, BMI, and cause of peritonitis, were controlled through stratification followed by post-stratification chi-square analysis. A p-value of ≤0.05 was considered statistically significant.

Ethical Considerations

Ethical approval was obtained from the hospital ethics committee prior to initiation of the study. Written informed consent was obtained from all participants. Confidentiality of patient information was maintained throughout the study, and patients were assured that participation was voluntary and would not affect their treatment.

 

RESULTS

A total of 120 patients with clinically diagnosed peritonitis undergoing exploratory laparotomy were included in this study and randomly allocated into two equal groups: Group A (metronidazole lavage) and Group B (normal saline lavage), with 60 patients in each group.

Demographic Characteristics

The overall mean age of patients was 38.7 ± 11.2 years (range: 18–60 years). In Group A, the mean age was 37.9 ± 10.8 years, while in Group B it was 39.5 ± 11.6 years, showing no statistically significant difference (p = 0.48). Male predominance was observed in both groups.

Table 1: Demographic Characteristics of Patients (n = 120)

Variable	Group A (Metronidazole) n=60	Group B (Normal Saline) n=60	p-value
Age (years, mean ± SD)	37.9 ± 10.8	39.5 ± 11.6	0.48
Gender			0.67
Male	41 (68.3%)	39 (65.0%)
Female	19 (31.7%)	21 (35.0%)

Causes of Peritonitis

The most common cause of peritonitis was typhoid ileal perforation followed by acute appendicitis and peptic ulcer disease. Distribution of etiologies was comparable between both groups.

Table 2: Causes of Peritonitis

Cause of Peritonitis	Group A n=60	Group B n=60
Acute appendicitis	14 (23.3%)	13 (21.7%)
Typhoid ileal perforation	18 (30.0%)	20 (33.3%)
Trauma	9 (15.0%)	8 (13.3%)
Peptic ulcer disease	12 (20.0%)	11 (18.3%)
Malignancy	7 (11.7%)	8 (13.3%)

 

Frequency of Surgical Site Infection

Overall, surgical site infection occurred in 22 (18.3%) patients. The frequency of SSI was significantly lower in Group A compared with Group B.

· Group A (Metronidazole): 6 patients (10.0%)

· Group B (Normal Saline): 16 patients (26.7%)

The difference was statistically significant (χ² = 5.64, p = 0.018).

Table 3: Comparison of Surgical Site Infection

SSI	Group A n=60	Group B n=60	p-value
Yes	6 (10.0%)	16 (26.7%)	0.018
No	54 (90.0%)	44 (73.3%)

 

Stratification of SSI with Respect to Age

Higher SSI rates were observed in patients aged >40 years; however, metronidazole lavage consistently showed lower infection rates across age groups.

Table 4: Stratification of SSI by Age

Age Group	Group A SSI	Group B SSI
≤40 years (n=70)	3 (7.5%)	8 (20.0%)
>40 years (n=50)	3 (15.0%)	8 (32.0%)

Stratification of SSI with Respect to Gender

SSI was slightly more frequent among males; however, the metronidazole group maintained lower infection rates.

Table 5: Stratification of SSI by Gender

Gender	Group A SSI	Group B SSI
Male	4 (9.8%)	11 (28.2%)
Female	2 (10.5%)	5 (23.8%)

 

Results Summary

In this randomized controlled trial involving 120 patients with peritonitis undergoing exploratory laparotomy, the overall frequency of surgical site infection (SSI) was 18.3%. The mean age of participants was 38.7 ± 11.2 years, with a predominance of male patients in both groups. Typhoid ileal perforation emerged as the most common cause of peritonitis. A statistically significant reduction in SSI was observed in the metronidazole lavage group compared with the normal saline group, with infection rates of 10.0% and 26.7%, respectively (p = 0.018). Stratified analysis demonstrated higher SSI rates among older patients and males; however, metronidazole lavage consistently showed lower infection frequencies across all subgroups. These findings indicate that intraoperative peritoneal lavage with metronidazole is associated with improved postoperative outcomes and reduced risk of surgical site infection compared with conventional normal saline lavage.

DISCUSSION

The present randomized controlled trial was conducted to compare the frequency of surgical site infection (SSI) following intraoperative peritoneal lavage with metronidazole versus normal saline in patients undergoing laparotomy for peritonitis. The findings of this study demonstrated a significantly lower rate of SSI in the metronidazole lavage group (10.0%) compared with the normal saline group (26.7%), indicating that antibiotic lavage may provide superior infection control during surgical management of peritonitis.

Peritonitis is associated with a high burden of postoperative infectious complications due to contamination of the peritoneal cavity with aerobic and anaerobic organisms. Effective intraoperative lavage plays a crucial role in reducing bacterial load and minimizing residual contamination. In the current study, the overall SSI rate of 18.3% is consistent with previously reported ranges in emergency laparotomy for peritonitis, highlighting the persistent clinical challenge of postoperative wound infection. The significantly lower SSI rate observed in the metronidazole group supports the hypothesis that targeted antimicrobial lavage may enhance intraoperative infection control.

These findings are comparable with the results reported by Gangwal et al. (2017), who observed SSI rates of 6.5% in the metronidazole lavage group compared with 26.3% in the normal saline group. Similarly, Sarada et al. (2020) reported improved postoperative outcomes and reduced wound infection with metronidazole-containing lavage solutions. The consistency of these findings strengthens the evidence supporting the use of metronidazole lavage as an adjunct to surgical treatment of peritonitis. The antimicrobial action of metronidazole against anaerobic bacteria, which are frequently implicated in intra-abdominal infections, likely contributes to the observed reduction in postoperative infection.

In contrast, some studies have reported less pronounced benefits of antibiotic lavage. Choudhary and Dhankar (2018) noted a lower incidence of SSI with metronidazole lavage; however, the difference did not reach statistical significance. Similarly, Singh et al. (2023) highlighted variability in outcomes when comparing different lavage solutions, suggesting that patient characteristics, disease severity, and surgical factors may influence postoperative infection rates. Despite these discrepancies, the present study demonstrated a statistically significant advantage of metronidazole lavage, reinforcing its potential clinical utility.

Stratified analysis in this study revealed higher SSI rates among older patients and males, consistent with previous literature indicating that age-related immune decline and comorbidities may increase susceptibility to infection. Additionally, typhoid ileal perforation was the most common cause of peritonitis and was associated with relatively higher SSI rates, likely due to heavy fecal contamination and delayed presentation. Nevertheless, metronidazole lavage maintained lower infection rates across all stratified subgroups, suggesting a consistent protective effect.

The clinical implications of these findings are noteworthy, particularly in resource-limited settings where SSI contributes to prolonged hospital stay, increased healthcare costs, and patient morbidity. Incorporating metronidazole into intraoperative lavage may represent a simple, cost-effective intervention to improve postoperative outcomes. However, this study has certain limitations, including single-center design and short follow-up duration limited to early postoperative SSI assessment.

Overall, the findings of this study indicate that intraoperative peritoneal lavage with metronidazole significantly reduces surgical site infection compared with normal saline lavage. Further multicenter studies with larger sample sizes and extended follow-up are recommended to validate these results and establish standardized lavage protocols.

 

CONCLUSION:

This randomized controlled trial demonstrated that intraoperative peritoneal lavage with metronidazole significantly reduces the frequency of surgical site infection compared with conventional normal saline lavage in patients undergoing laparotomy for peritonitis. The overall SSI rate was notably lower in the metronidazole group, indicating the effectiveness of antibiotic lavage in reducing postoperative infectious complications. These findings highlight the importance of targeted antimicrobial strategies during surgical management of peritonitis, particularly in conditions associated with heavy intra-abdominal contamination.

The study also showed that demographic factors such as age and gender, as well as the underlying cause of peritonitis, may influence postoperative infection risk. However, metronidazole lavage consistently demonstrated a protective effect across different patient subgroups. Given its availability, affordability, and antimicrobial efficacy against anaerobic organisms commonly implicated in intra-abdominal infections, metronidazole lavage can be considered a practical adjunct in routine surgical practice.

In conclusion, intraoperative peritoneal lavage with metronidazole appears to be a safe and effective method for reducing surgical site infection following surgery for peritonitis and may contribute to improved postoperative outcomes and reduced healthcare burden.

RECOMMENDATIONS

· Metronidazole should be considered as an adjunct to normal saline for intraoperative peritoneal lavage in patients undergoing laparotomy for peritonitis.

· Surgeons working in high-risk and resource-limited settings may adopt antibiotic lavage to reduce postoperative wound infection and associated complications.

· Further multicenter randomized controlled trials with larger sample sizes and longer follow-up are recommended to confirm these findings and develop standardized lavage protocols.

· Future research may explore comparisons of metronidazole lavage with other antibiotic or antiseptic solutions to optimize intraoperative infection control strategies.

 

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