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A study of incidence and factors determining the occurrence of surgical site infection in abdominal surgeries

Skin is natural barrier against infection. Even with many precautions and protocols to prevent infection, any surgery causing break in skin can lead to infection. Most surgical site infections are caused by contamination of an incision with microorganisms from the patient’s own body during surgery. A surgical site infection may range from a spontaneously limited wound discharge within 710 days of an operation to a life-threatening postoperative complication, such as a sternal infection after open heart surgery.


INTRODUCTION
Surgical site infection (SSI) can be defined as infections which develops within 30 days after surgery involving the skin and subcutaneous tissue of the incision and/or the deep soft tissue and/or any part other than the incision handled during surgery. 1 Skin is natural barrier against infection. Even with many precautions and protocols to prevent infection, any surgery causing break in skin can lead to infection. Most surgical site infections are caused by contamination of an incision with microorganisms from the patient's own body during surgery. A surgical site infection may range from a spontaneously limited wound discharge within 7-10 days of an operation to a life-threatening postoperative complication, such as a sternal infection after open heart surgery. 2 preoperative preparation, antibiotic coverage, operation theatre environment and postoperative care.
This study has been taken up to determine the incidence of SSI in abdominal surgery and to determine factors responsible for its occurrence.

METHODS
It is a longitudinal descriptive study. The study was conducted in Dr. D.Y. Patil Medical College, Hospital and Research Centre located in Pimpri, Pune between July 2017 to September 2019.

Inclusion criteria
The patients having emergency and elective abdominal operations in age group 18 to 80 were included in the study.
All cases admitted to the hospital and underwent abdominal surgeries were considered for inclusion. All necessary baseline pre-operative information regarding case was taken. All details regarding preoperative preparation were noted in the cases sheet. Information collected from the patients included patient's age, gender, diabetes mellitus status, smoking status and haemoglobin and albumin levels. Intra operatively information like duration of surgery, antibiotics use during surgery, type of wound, emergency / elective surgery was documented. Following the surgical procedure, surgical sites were examined on postoperative day 3 and every 3 days thereafter. SSI was diagnosed as per CDC criteria.

Statistical analysis
Data from each patient will be collected and tabulated using Microsoft Excel. Qualitative variables were presented by frequency and percentage. Quantitative variables were presented by mean and standard deviation. Later on, cases were grouped in to those who developed SSI and those who did not develop SSI. Both groups were compared to assess associated factors using tests of significance like Chi square and t test using Epi Info version.

RESULTS
Total 150 cases were included in the study considering inclusion and exclusion criteria. Among them 29 patients developed SSI. Incidence of SSI among them was 19.3 %.
SSI was found in 3 (10.3%) cases of below 30 years age group, 16 (55.2%) cases of 30-50 years age group and 10 (34.5%) cases of above 50 years age group of patients. There was no significant age difference between both the groups (p=0.830) ( Table 1).
Among 29 SSI cases 18 (62.1%) were males while 11 (37.9%) were females. In non-SSI group, among 121 participants 58 (47.9%) were males while 63 (52.1%) were females. There was no significant difference among gender between both the groups (p=0.172) ( Table 2).       Table 5 shows comparison of pre-operative haemoglobin among SSI and non SSI cases. Median of pre-operative hemoglobin among SSI case was 11.9 g/dl while it was 12.2 g/dl among non SSI cases. There was no significant difference in pre-operative hemoglobin among both the groups.
Median of pre-operative albumin among SSI case was 30 g/l while it was 37 g/l among non SSI cases. Non SSI patients had higher level of pre-operative albumin in comparison to SSI patients. The difference in preoperative albumin between both group was found statistically significant (p=0.003) (  Median of duration of operation among SSI case was 178 minutes while it was 93 minutes among non SSI cases. SSI patients had higher duration of operation in comparison to non SSI patients. The median difference in duration of operation between both groups was found statistically significant (p<0.001) ( Table 8). Median of post-operative stay among SSI case was 17 days while it was 5 days among non SSI cases. SSI patients had higher post-operative stay in comparison to non SSI patients. The median difference in post-operative stay between both groups was found statistically significant (p<0.001) ( Table 9).  There exists a number of risk factors which predisposes to the development of SSI which can be divided into bacterial, patient and local factors. A combination of these factors predisposes to occurrence of SSI and thus it is not easy to establish association of specific factors as culprit for SSI. So, there is difference in rates of SSI in different studies. 10 Median of pre-operative hemoglobin among SSI case was 11.9 g/dl while it was 12.2 g/dl among non SSI cases. There was no significant difference in pre-operative hemoglobin among both the groups.
Median of pre-operative albumin among SSI case was 30 g/l while it was 37 g/l among non SSI cases. Non SSI patients had higher level of pre-operative albumin in comparison to SSI patients. The difference in preoperative albumin between both groups was found statistically significant (p 0.003). The overall infection in this study is 19.3% which equals the rate of SSI in developing countries and is higher than the SSI rate of developed countries. One of the reason behind this is the presence of systematic feedback system related to SSI which exists in developed countries, Secondly considering financial difficulties in developing countries and other factors like poorly trained staff responsible for infection control, disparency between size of ward and number of staff and inadequate participation from patients and relatives. 11 Duration of the surgery was also found to affect the incidence of SSI with maximum occurrence in operations requiring more than 2 hours and least in operations requiring less than one and a half hour. 12 Doherty et al, had similar results with duration of surgery and SSI rate. 13 Longer operative time reflects the complexity of the surgery. It would also increase the wound susceptibility to infection by increasing the exposure to potential contamination and decreasing the tissue concentration of antibiotic. 14 To overcome the decreased concentration of antibiotic that occurs with prolonged operations, readministration of the antibiotics is recommended. 15 Median of post-operative stay among SSI case was 17 days while it was 5 days among non SSI cases. SSI patients had higher post-operative stay in comparison to non SSI patients. This may be due to slow recovery due to SSI, may be due to emergency surgery or antibiotic resistance. The median difference in post-operative stay between both groups was found statistically significant. (p <0.001). These findings were similar to the data obtained from a Peruvian hospital where SSI increased the duration of hospital stay (14.0 Vs 6.1 days; p <0.001). 16

CONCLUSION
The incidence of Surgical Site Infection (SSI) among cases underwent abdominal surgery was 19.3 %. In our institute where most patients come from low economic state, poor hygiene and nutrition status, with current preoperative protocol for SSI prevention SSI rate is comparable to that of most developing countries. The SSI rate in Emergency surgery was 34.9%, significantly higher than elective operation (13.1%).
Incidence of SSI was not associated with age and sex of the patients. It was also not associated with smoking status of the case. However, development of SSI was significantly higher in cases having diabetes mellitus, lower serum albumin and incidence of SSI not associated with lower hemoglobin levels. Pre-operative bathing was important protective factor. SSI rate was also higher in case of longer duration of surgery.