A Prospective, Randomized, Controlled Clinical Trial to Assess Use of 2% Lidocaine Irrigation to Prevent Abdominal Surgical Site Infection

Surgical site infections (SSI) are the third most common nosocomial infection, increasing morbidity and mortality rates of patients as well as their costs of care, but longer-term follow up studies and data are limited. Lidocaine, in addition to being a readily available and accessible local anesthetic, is known to have bacteriostatic properties. A prospective, descriptive, controlled, randomized clinical trial was conducted among patients scheduled to undergo abdominal surgery in the general surgical unit of a Mexican hospital. The purpose of the study was to assess the incidence of SSIs in general and to compare the 30-day postoperative infection outcomes of saline irrigation to saline irrigation followed by 2% lidocaine application before skin closure in wounds grade II to IV per the Centers for Disease Control and Prevention surgical wound classification.All patients received systemic antibiotics before surgery. Eighty-four (84) patients (40 men and 44 women; mean age 49.02 ± 19.9 years, range 18–92 years), 39 in the control and 45 in the experimental group, completed the 30-day follow-up without experiencing nonsurgery-related complications. The overall incidence of SSIs (specifically, seromas and abscesses) was 17.86%; the incidence of abscess formation was 7.14%. The overall incidence of SSIs in the lidocaine group was 8.89% compared to 28.2% in the saline only group (P = .02); the relative risk was 1.8 (P = .02; 95% CI 1.19-2.74) and 0.45 (P = .02; 95% CI 0.19-1.06) in the saline and lidocaine groups, respectively. Hemoglobin and albumin levels were significantly lower in patients who did compared to those who did not develop an SSI (P = .02 and .04, respectively). No significant SSI rate differences were seen between patients who did and did not have a drain placed. In patients who developed an abscess, Escherichia coli was the most prevalent bacteria and present in 40% of collected fluid. While carefully controlled clinical studies are needed, lidocaine appears to be a viable option to decrease the incidence of SSI if applied as irrigation before wound closure in patients undergoing abdominal surgery.

Surgical site infection (SSI) is the third most common nosocomial infection; it occurs in 5% to 16% of hospitalized patients^1,2 and is more common when patients undergo colon/rectal surgery.³ This is a major problem due to associated higher morbidity and mortality rates (2- to 11-fold risk of death)⁴ as well as increased cost and prolonged hospital stay for patients.^2,5-7

Prospective, randomized, double-blinded studies have found that in most SSI, the source of pathogens is endogenous, originating from the natural flora of the skin, mucous membranes, or hollow viscera of the patient; epidemiologic studies^8-12 report the pathogen most frequently isolated is Staphylococcus aureus, followed by coagulase-negative staphylococci, Enterococcus spp, Escherichia coli, and Pseudomonas aeruginosa. However, the National Healthcare Safety Network⁹ epidemiologic review, stratified by type of surgery, reported abdominal surgery-related SSIs have a more frequent incidence of E coli (18.6%), followed by S aureus (12.7%), E faecalis (7.8%), coagulase-negative staphylococci (6.4%), and P aeruginosa (6.1%).

Several reviews^13,14 on SSI based on randomized trials and epidemiologic studies have described the influence of different patient, surgical, and environmental variables such as patient age, nutritional status, laboratory values, comorbidities, antiseptic techniques and solutions used, type of surgery performed, region and system of the body involved, duration of surgery, operating room ventilation, and adequate sterilization of instruments; these factors may increase the risk for SSI.^2,3,15-20 Due to changes and developments in medicine aimed at performing more outpatient surgeries and enabling shorter hospital stays, SSI surveillance and monitoring has become more complex. In reviews and forums,^21,22 experts agree that because most hospitals do not have the resources to monitor the evolution of all surgical patients, and the level of surveillance is different depending on the risk of procedures, SSI rates may be underreported. 

Degree of surgical site (SS) contamination classifications were initially developed by the American College of Surgeons and then adapted by the Centers for Disease Control and Prevention (CDC) in 1985; currently, a globally accepted consensus classifies SS as Grade I (clean), Grade II (clean-contaminated), Grade III (contaminated), and Grade IV (dirty/infected). Guidelines and evidence-based recommendations have directly correlated the grade of contamination or wound classification with the subsequent probability of infection.^15-18 [Editor’s note: As of January 2017, the CDC is using “classes” in lieu of “groups.” This article was researched and written before the change.]

Various techniques and solutions have been implemented for irrigation purposes to prevent and avoid the formation of abscesses and infection of tissues and cavities in contaminated SSs (eg, grades II to IV).²³ A nosocomial infection rate of 9.0% among almost 8000 patients was reported in a 1-year prospective surveillance study conducted in a general hospital (Durango, Mexico) by Tinoco et al.²⁴ Vilar-Compte et al²⁵ performed an 18-month prospective study involving 3372 surgeries performed in their hospital (Mexico City, Mexico) and reported a general SSI incidence of up to 9.28% for grades I through IV (7.35%, 10.5%, 17.3%, and 21.5%, respectively). Of these, 27.16% were diagnosed during the hospital stay and 72.84% after hospital discharge, underscoring the need for extended monitoring of patients.^19,24,25

Although experimental studies^26,27  have demonstrated the antimicrobial and fungicidal activity of local anesthetics and the molecular and cellular mechanisms involved, the effectiveness of products in preventing SSI is not without controversy. Animal models²⁷ have shown an excessive inflammatory response and a decrease in the incidence of SSI when antimicrobials are provided. In their randomized clinical trial in 2011 comparing wound irrigation with 2% lidocaine versus saline solution among 22 patients from a rural clinic, Noriega-Salas et al²³ noted a decrease in the frequency of SSI in grade II and grade III wounds. The authors reported a SSI incidence of 27% (3 patients) in the saline group versus none in the lidocaine group. Although a statistical difference was observed, the sample size was limited.

Currently, Mexico does not have a national data repository. Some institutions report their prevalence independently through research. The General Hospital of Durango reported a SSI incidence rate of 4.9% in the surgery department; E coli (36%) and P aeruginosa (18%) were the most common pathogens.²⁴ The Instituto Nacional de Cancerología²⁵ reported E coli as the most common pathogen, followed by coagulase-negative staphylococci. This study characterized SSI incidence according to the procedure performed and the most frequently isolated pathogens and emphasized the need for surveillance up to postoperative (postop) day 30. Internationally, S aureus seems to be the most common microorganism isolated.² A general hospital in Mexico City recently reported a SSI incidence of 67.8%, with S aureus (70%), coagulase-negative staphylococci (15.3%), and E coli (9.4%) the most common strains.¹⁹ This along with other epidemiologic studies^19,25,28 noted the importance of establishing monitoring programs after patient discharge. 

Hospitals and institutions in Mexico need to improve SSI surveillance and data reports. The General Hospital of Ciudad Victoria, “Dr. Norberto Treviño Zapata,” does not have a well-established SSI surveillance or statistical data system. The objectives of this study were to: 1) assess the incidence of SSI in the general surgery department, and 2) compare the 30-day postoperative infection outcomes of saline irrigation to saline irrigation followed by 2% lidocaine application. 

A prospective, descriptive, randomized, controlled clinical trial was conducted from July 1 to October 31, 2014. The study was approved by the Ethics and Research Committee and the Department of Education of General Hospital “Dr. Norberto Treviño Zapata” Ciudad Victoria and performed following the guidelines of Good Clinical Practice and Research. 

Patients. All surgical patients 18 years or older who provided written consent to participate were eligible. Exceptions included patients who underwent grade I SS surgery, laparoscopic surgery, minor outpatient surgery, or recent surgery performed at another hospital; had a previously established SSI; or received prophylactic antibiotics. Patients requiring a re-intervention due to complications of their pathology or who experienced contamination from external factors, death in the first 30 postop days, or data lost in the follow-up period also were eliminated from the study and excluded from the analysis. 

SS were classified according to the surgical procedure and location in accordance with CDC guidelines. Using dice, patients were randomly assigned between the control (even numbers) and experimental (odd numbers) groups before the procedure. Variables, including age, brief medical history, type of surgery, wound classification, and laboratory parameters (hemoglobin, creatinine, and albumin), and the use of a drain, were obtained by direct interrogation of the patient and review of medical chart and entered manually on a spreadsheet for each patient. Surgeries were classified according to their degree of contamination.

Procedure. The control group was provided subcutaneous tissue irrigation with 100 mL of 0.9% saline solution after aponeurotic closure but before subcutaneous and skin closure using blunt forceps and sterile gauzes to clean the SS. The same procedure was performed for patients in the experimental group with the addition of 10 mL of norepinephrine 2% lidocaine irrigation following the saline solution irrigation. No gauze was used. All patients were given intravenous antibiotics before the surgical procedure relative to surgical pathology. A standardized dose of cephalosporin was indicated in all patients; if the colon was breached before or during the surgery, metronidazole was added and if intra-abdominal infection or abscess was evident, amikacin was added and cultures and antibiograms were taken from the site. 

Patients were observed during their hospital stay and followed through scheduled appointments in the general surgery outpatient clinic 7 to 10 days and 28 to 30 days after discharge. Patients also could schedule emergency appointments through the clinic or go to the emergency room at any time if they developed redness, swelling, heat, pain, loss of function, or suppuration at the SS. If an SSI was suspected, the suspicious area was either punctured or drained to obtain a sample for bacteriological cultivation. If the content drained from the SS was transparent, clear yellow, or red without any other signs of inflammation, it was considered a seroma. If the SS exhibited redness and/or the drainage was purulent, white, green, brown, or had a foul smell, the area was classified as an abscess. Patients were treated either as outpatients or hospitalized depending on the severity of the SSI. If needed, adjustments were made once antibiotic sensitivity results from antibiogram cultures were reported. 

Data and statistical analyses. All collected data were entered into an Excel database (Microsoft, Redmond, WA). Descriptive statistics were obtained using Pearson’s chi-squared and Fisher’s exact tests to compare nominal values in each grade classification. The Kolmogórov-Smirnov test was used to assess the distribution of the data; depending on the results, an unpaired Students t-test was used for normal distribution and Mann-Whitney U test applied for nonparametric distribution.  The confidence level was determined by 1 - α of <0.05. Statistical significance was calculated using SPSS Version 20 (IBM Corp, Armonk, NY) using Fisher’s exact formula.

The study included patients who experienced any type of abdominal surgery during the 4-month study and completed the 30-day follow-up. Surgeries included exploratory laparotomy, open biliary tract surgery, and conventional appendectomy as well as surgeries that included opening, repair, resection, and/or anastomosis of the stomach and small and large intestine either due to trauma or disease. A sample of 100 patients (51 male and 49 female) was obtained. Of those, 48 were in the control and 52 were in the experimental group. Data from 16 patients (9 control and 7 experimental group, 11 male and 5 female) were not eligible for data analysis for reasons of re-intervention (7), death (8), or loss to follow-up (1). This left a total of 84 patients, 39 in the control and 45 in the experimental group (see Table 1). Overall, no statistical difference in the mean age between the control and the experimental groups was noted (51.4 ± 21.5 versus 46.9 ± 18.6 years, respectively; P = .30). 

A total of 15 SSIs (9 seromas, 6 abscesses) occurred for an overall rate of 17.86% (see Table 2). If a seroma was considered a minor complication and abscess a SSI, the overall rate would drop to 7.14% for the study population (grade II to IV abdominal SSs). For the purposes of this study, seroma and abscess were both considered a SSI. When only saline solution was used for wound irrigation, the relative risk for infection was 1.8 (P = .02; 95% CI 1.19-2.74); with the use of 10 mL of 2% lidocaine after irrigation, the relative risk for SSI was 0.45 (P = .02; 95% CI 0.19-1.06). Overall comparisons among SS classification grades demonstrated a statistically lower incidence of SSI in the lidocaine groups (P = .02) (see Table 3). The difference between the control (11, 28.2%) and experimental patients (4, 8.89%) who developed a SSI is notable but statistically requires a larger sample, stratified by type of SS, to establish significance in each grade (see Figure 1). 

Age and laboratory values were compared between patients who developed a SSI and uninfected patients (see Table 4). Age and creatinine were not statistically significantly different, but hemoglobin and albumin were significantly different between the study and control groups (P = .02 and P = .04, respectively). 

Of the 51 patients who did and 33 who did not have a drain placed, 10 patients (19.6%) and 5 (15.2%), respectively, had a SSI (see Table 5). The difference was not statistically significant (P = .77). Four (4) patients from the lidocaine group with a cavity drain had a SSI (2 seromas and 2 abscesses); none of the lidocaine group without drain developed a SSI. 

All 15 patients with a SSI had a sample taken for culture and antibiotic sensitivity analysis, regardless of the characteristics (seroma or abscess). The most frequently isolated strains for abdominal surgery were E coli (6, 40%), followed by S  aureus (3, 20%), and Klebsiella and P aeruginosa (1 each, 6.67%). It was noteworthy that 4 (26.6%) of the SSI cultures were negative for bacterial growth; however, all of these occurred in seromas in which microbial growth usually is absent.

Review studies^29,30 of clinical trials for diverse commercial antiseptic solutions for wound irrigation have proven they are effective in eradicating bacteria, fungi, and viruses, significantly decreasing the rate of SSIs. However, patients with limited finances cannot afford some of these products, and many of these products are not available in the operating room or for purchase for use in public institutions. The authors’ hospital is a public health reference center for the state of Tamaulipas, Mexico, and the majority of patients have few economic resources. Lidocaine is less expensive, easy to obtain, and readily available in public institutions, including rural health centers. Its proven effectiveness may impact SSI if used for SS irrigation before closure in addition to prophylactic and therapeutic antibiotic therapy. 

Variables analyzed in this study included age, creatinine, hemoglobin, and albumin. Results suggest hemoglobin and albumin levels below standardized normal values before surgery increased the incidence of SSI. In a prospective, descriptive, comparative study of patients undergoing surgery (N = 94 patients), Gunningberg et al³¹ confirmed an albumin level below 3.4 g/dL was a predictor for SSI. According to a cohort study by Michelson et al¹⁹ (N = 2400 surgeries), diabetes, alcohol consumption, creatinine level, American Society of Anesthesiologists (ASA) score, and surgery location were considered SSI risk factors. Per his review of the literature and relevant guidelines, Cheadle² included patient exposure to radiation, smoking, and obesity as risk factors for SSI. 

Similar to the prospective analysis of 54 patients with Jackson-Pratt drains by Reiffel et al,³² drain use did not affect the incidence of SSI. E coli was the most common strain isolated, equal to that described by Hidron et al⁹ in abdominal surgery. The current study also confirmed the findings of Noriega-Salas et al,²³ using a larger sample of patients and standardized protocols to demonstrate how 2% lidocaine for SS irrigation reduces SSI. 

Improving surveillance of SSI in patients with elevated morbidity and mortality in the authors’ country is important. A follow-up study of a cohort of 255 patients by Kirkland et al³³ reported a 2.2 times increased risk of death in patients with SSI. In the United States, SSIs comprise approximately 5% to 16% of nosocomial infections and up to 45% in coloproctology surgery, causing a financial strain on the health care system^1-3; the World Health Organization estimates range from 3% to 21%. Studies conducted in the United Kingdom^20,34 (1997–2001) reported SSI incidence of approximately 10%, resulting in an added cost of 1 billion pounds or $1.8 billion (US) annually on the health system. In Mexico, reports of SSI incidence vary between 4.9% and 9.28%^24,25; the reported SSI prevalence of 17.86% in general surgery in this study may be considered high. However, only 7.14% were abscesses — a wound dehiscence or seroma without evidence of infection should not be considered a SSI.¹⁹ 

It is also important to emphasize that all grade I SS, laparoscopic, and minor outpatient surgery wounds were excluded in the current study. These represent approximately 70% to 80% of the surgeries performed by the authors’ department, making the overall SSI incidence even lower (estimated <3%). The implementation of lidocaine effectively reduced the incidence of abscesses, with only 2.22% in the experimental group versus 12.82% in the control group, which was the traditional procedure (saline solution irrigation) for SS closure in all of the authors’ patients.

Limitations of this study include a small sample size and the absence of considering other variables that may affect SSI rates such as comorbidities, anthropometric measurements to assess nutritional status and body mass index, characteristics of the surgery such as emergency versus scheduled surgery, length of the procedure, ASA score, need for blood transfusion, and occurrence of shock.^2,3,15-20 The sample size was small and did not include all surgeries to correctly report the SSI incidence. Experimental and case studies^35,36 have shown comorbidities such as diabetes mellitus and obesity increase the risk of complications, but these were not considered in the current study. Future studies should take patient history and comorbidities into account and include a larger population in order to help determine how SSs could benefit from lidocaine irrigation. 

The present study demonstrated that the SSI incidence in a Mexican facility was similar to other national and international research. It also was shown that patients who received irrigation of subcutaneous tissue with 10 mL of 2% lidocaine, in addition to the standard intravenous antibiotics, had a lower SSI rate than those who did not. The impact of this approach was most evident in grade III SS with anticipated statistical significance in a larger population. The grade of SS was the most important factor in determining the likelihood of complications and infection, increasing from 9.8% in grade II wounds to 36.4% in grade IV (3.7 times higher); in addition, hemoglobin and serum albumin levels with below normal values were found to increase the likelihood of SSI. Adequate surveillance of complications and SSI does not exist in most institutions in Mexico but should be implemented and improved, along with techniques, such as lidocaine irrigation, to reduce SSI. 

The authors thank Dr. Jose Isabel Perales Lopez, Head of the Department of General Surgery at the General Hospital of Ciudad Victoria, for his support in the implementation of this project, as well as Dr. Neri Alejandro Alvarez-Villalobos for his help with the statistical analysis. 

Dr. Quiroga-Garza was a general surgeon, Department of General Surgery, General Hospital of Ciudad Victoria, “Dr. Norberto Treviño Zapata,” Ciudad Victoria, Tamaulipas, Mexico; he is currently a PhD student and professor, Universidad Autonoma de Nuevo Leon, Facultad de Medicina, Human Anatomy Department, Monterrey, Nuevo León, Mexico. Dr. Valdivia-Balderas and Dr. Trejo-Sánchez are general surgeons, Department of General Surgery, General Hospital of Ciudad Victoria, “Dr. Norberto Treviño Zapata.” Dr. Espinosa-Uribe is a physician completing social service in research; Dr. Reyes-Hernandez is a physician and PhD student; and Dr. Elizondo-Omana is Head of Research and General Coordinator, Universidad Autonoma de Nuevo Leon, Facultad de Medicina, Human Anatomy Department.

Please address correspondence to: Dr. Alejandro Quiroga-Garza, Departamento de Anatomía Humana, Facultad de Medicina, Universidad Autónoma de Nuevo León; Ave, Madero y Dr. Aguirre Pequeño s/n, Col. Mitras Centro, Monterrey, NL, CP 64460; email: Dr.AQuirogaG@gmail.com.