Proactive Risk Assessment of Surgical Site Infection in Ambulatory Surgery Centers

Ebru Bish, Arturo Buzzalino, Michael Patti, Xin Zeng
Virginia Tech, Department of Industrial and Systems Engineering
Revised: April 2012

Abbreviations Used:
ASC: Ambulatory Surgical Center
HAI: Healthcare Associated Infections
SSI: Surgical Site Infection
SWI: Surgical Wound Infection
ASA: American Society of Anesthesiologists

Background: Definition, Consequences, General Risk Factors

Definition of a SSI

The most widely used definition for SSI was provided by the Centers for Disease Control in 1992 and updated in 2003. It broadly categorizes SSIs into incisional and organ/space infections. Incisional SSIs are further split into 2 categories: superficial (involving the skin and subcutaneous tissue) and deep (involving fascia and muscle layers). This categorization is important because “the etiology, risk factors, and clinical consequences vary depending on the location” [Blumetti et al. (2007)].

However, some articles argue that this definition leads to subjectivity about the classification of an infection as an SSI [e.g., Ashby et al. (2010)].

Consequences of a SSI

SSI is the most common healthcare-associated infection in surgical patients [Hedrick et al. (2006)]. Up to 355,500 surgical patients develop SSIs after orthopaedic surgery each year [Whitehouse et al. (2002)], as high as 1,000 SSIs per day. Orthopedic SSIs cause substantial morbidity, prolonging hospital stay by a median of 2 weeks, doubling rehospitalization rates, and more than tripling overall healthcare costs [Eiselt (2009) and the references therein].

On Staphylococcus aureus:

“Staphylococcus aureus is the most important pathogen after surgical procedures, and its nasal carriage is the main risk factor for SSI caused by S. aureus, since carriers are two to nine times more likely to acquire S. aureus SSIs than noncarriers. The mean carriage rate in the general population is 37.2%. Several studies have been conducted on nasal decolonization in patients undergoing orthopedic surgery by using perioperative intranasal mupirocin, an attractive prevention strategy, being a safe and simple method to eradicate nasal colonization. Preoperative patient decolonization significantly decreases incidence of S. aureus SSIs.” [Barbos et al. (2009)]

“SSI is a devastating complication of total joint surgery, and treatment is complicated by the frequent presence of multiresistant organisms. Methicillin-resistant Staphylococcus aureus (MRSA) is of particular concern, because a recent study and review suggest that the rates of periprosthetic joint infection with MRSA are increasing. Approximately 50% of SSIs in hip replacement are caused by S. aureus and up to 59% of the isolates are methicillin-resistant. In a recent review of periprosthetic joint infections in a community hospital for a period in 2005, 92% of the infections were caused by gram-positive organisms and 30% of the infections were caused by MRSA, a rate that is notably higher than the 13% rate of MRSA infection in periprosthetic joints observed in 1999.” [Eiselt (2009)]

It has been reported that nasal colonization with MRSA increases the risk of SSI with MRSA for patients treated in surgical intensive care units (Mest et al. 1994), patients admitted to hospital (Davis et al. 2004), and patients who have undergone continuous ambulatory peritoneal dialysis (CAPD) (Lye et al. 1993).

One study identified nasal carriage of Staphylococcus aureus as the only independent risk factor for the development of SSI following orthopaedic implant surgery [Kalmeijer et al. (2000)]

Risk Factors of a SSI

General risk factors for development of SSI include [Barie, 2005]:

• Patient factors (e.g., comorbidities, malnutrition, obesity, tobacco use, age, ASA score¹, positive nasal culture of Methicillin-resistant Staphylococcus aureus (MRSA)).
• Surgery related factors:
  • Type of surgery (surgical procedure)
  • Surgical factors (e.g., antibiotic prophylaxis, surgical duration, hypothermia, blood loss requiring transfusion, spillage of luminal contents)
  • Surgeon related factors (e.g., S. aureus carriers among orthopedic team members, wristwatch users versus nonwristwatch users)
• Operating Room (OR) environment (e.g., number of people in the OR, frequent opening of the OR door and movement of people in the OR — these disrupt the positive–pressure OR environment, thus limiting the effectiveness of OR ventilation).

Notes: “Although most SSIs originate from the patient's own flora, airborne contaminants can cause or aggravate SSI. These contaminants and microbial level in the OR are directly proportional to the number of people in the OR” [Barie, 2005].

ASCs: Numbers, Characteristics, and Infection Control Practices

In 2008, ASCs numbered 5174 [Barie (2010)], and 61% of ASCs are exclusively physician-owned, and 96% operate on a for-profit basis. Today, outpatient procedures represent more than three-quarters of all operations performed in the US [Ambulatory Surgery Center Association (2010)]. Some evidence suggests that cases of higher complexity are being performed in ASC's, and involving patients with greater co-morbidities [Barie (2010)].

The literature is mixed as to whether infection rates are lower for ASCs compared to hospital settings [Mlangeni et al. (2005); Rey et al. (2005)]. However, recent years have seen a significant increase in identification of outbreaks of HAIs originating in ASCs and other outpatient settings [Schaefer et al. (2010) and the references therein]. For example, in 2008, the largest outbreak of HAIs caused by the Hepatitis C virus was reported, and was traced to 2 Nevada ASCs (due to unsafe injection practices). This represents the largest Hepatitis C virus outbreak in the US history, with an estimated number of potential infectious contacts exceeding 63,000, and with 115 infections possibly related to the outbreak. Several such outbreaks, originating from US ASCs, are reported in the literature.

Infection Control in ASCs

Schaffer et al. (2010) present a recent study by the Centers for Medicare and Medicaid Services (CMS) on infection control assessment of ASCs. The study was conducted in randomly selected ASCs in three states (Maryland, North Carolina, and Oklahoma). Specifically, 68ASCs participating in the Medicare Program were assessed (32 in MD; 16 in NC; and 20 in OK). 31 of these ASCs performed procedures on both adults and children; and 37 performed only one type of procedure (21 of these single-procedure ASCs performed only endoscopic procedures, and 6 only ophthalmologic procedures). The most common medical procedures performed by these 68 ASCs include endoscopy (performed in 35 ASCs), orthopedics (26 ASCs), pain-related procedures (26 ASCs), ophthalmology (25 ASCs), plastic surgery (21 ASCs), podiatry (21 ASCs), and gynecology (20 ASCs). However, this ranking is based on the number of ASCs performing each of these procedures, and not on the volume of these procedures performed.

The surveyors used the CMS's infection control audit tool (available on-line) to assess, through unannounced on-site assessments, compliance with all Medicare ASC health and safety standards. Five infection control categories were evaluated by surveyors, including (i) hand hygiene and use of personal protective equipment; (ii) injection safety and medication handling; (iii) equipment reprocessing; (iv) environmental cleaning; and (v) handling of blood glucose monitoring equipment.

Conclusions

46 out of the 68 ASCs had lapses in infection control, with 12 having lapses in 3 or more of the 5 infection control categories evaluated by the surveyors. In particular, 12 had a lapse in adherence to hand hygiene or appropriate use of personal protective equipment (i.e., gloves); 19 had deficiencies related to injection practices or medication handling (primarily through the use of single-dose vials for more than one patient); 19 failed to adhere to recommended practices regarding reprocessing surgical equipment; 12 did not appropriately clean high-touch surfaces in patient care areas; and 25 had lapses in appropriate handling of equipment used for blood glucose monitoring.

Role of the Environment of the Operating Suite in Surgical Wound Infection Ayliffe. Reviews of Infectious Diseases 13.10 (1991):S800-804.

• Most healthy nasal carriers of S. aureus disperse few organisms into the environment. Air sampling in 10 operating rooms during surgical procedures showed a mean count of only 0.03 cfu of S. aureus/ft³. Most outbreaks are caused by heavy dispersers, who often have a skin condition such as eczema.
• Fifty percent off wounds contained strains from the patients themselves, and 20% contained strains acquired from the surgical team.
• Surfaces not in close contact with the surgical wound are unlikely to pose a major infection risk. Organisms shed from the staff and transferred directly to the wound before reaching the floor are a greater risk.
• Items coming into close contact with the wound are sterilized and are not an infection hazard as long as the sterilization process is monitored.
• The value of a ventilation system providing 20 air changes each hour remains uncertain, and many surgeons continued to operate in non-ventilated rooms without evidence of higher infection rates.
• The infection rate for clean, nondrained wounds was lower in ultraviolet irradiated rooms (2.8 % vs. 3.8% ), but there was no difference in overall infection rates.
• The mean bacterial counts in air, the mean counts of organisms in wound washings, and the rates of major wound infection and deep sepsis were all significantly lower with the ultraclean air systems.
• Infection rates were lowest with a combination of ultraclean air, an exhaust ventilated suite, and antibiotic prophylaxis.
• Organism dispersal is not influenced by cotton clothing but is considerably reduced by bacterium-impermeable clothing that fits tightly at the neck, wrists, and ankles.

Effects of Preoperative Skin Preparation on Postoperative Wound Infection Rates: A Prospective Study of 3 Skin Preparation Protocols – Swenson et al.

Purpose

• To compare the effects of different skin preparation solutions on surgical-site infection rates.
• ChloraPrep (Cardinal Health) is a commercially available combination of 2% chlorhexidine and 70% isopropyl alcohol. The combination of chlorhexidine and isopropyl alcohol (or 70% isopropyl alcohol alone) has significantly better immediate antimicrobial activity than does 4% chlorhexidine. Also, the combination of chlorhexidine and isopropyl alcohol has demonstrated better residual antimicrobial activity than either 70% isopropyl alcohol alone or 4% chlorhexidine alone.

Methods

• The study focused on patients over 18 years of age undergoing general surgical procedures.
• The following measures were implemented before the study was conducted in line with the Surgical Infection Prevention and Surgical Care Improvement Project initiatives:
• Identification and treatment of infections remote to the surgical site before elective surgery.
• Clipping of hair (if necessary) immediately before the operation, rather than shaving.
• Use of established preoperative hand and/or forearm antisepsis by the surgical team with either iodophor- or chlorhexidine-based products.
• Appropriate surgical attire and drapes.
• Appropriate surgical antimicrobial prophylaxis. Specifically, 1 dose was given within 1 hour before incision, except for vancomycin, which was given 2 hours before incision; patients who were undergoing endocrine, breast, small bowel, or stomach procedures received cefazolin or, if allergic, clindamycin or vancomycin; patients who were undergoing colorectal surgery received cefoxitin or ertapenem or, if allergic, metronidazole and ciprofloxacin; antibiotics were re-dosed intraoperatively as needed; antimicrobial prophylaxis was not continued beyond 24 hours.
• Preoperative mechanical bowel preparation with Phosphosoda (Fleet) and enemas for colorectal surgery patients.
• Maintenance of normothermia (temperature more than 36.0 °C) during the perioperative period.
• Meticulous aseptic technique and appropriate tissue handling and surgical technique.
• Adequate intraoperative and postoperative serum glucose control in diabetic patients (target, less than 150 mg/dL).
• Maintenance of the postoperative dressing for 24–48 hours.
• Standardization of these measures resulted in a 3.6% absolute risk reduction in SSI incidence for all general surgery patients.
• Three skin preparation solutions were compared. Each skin preparation solution was adopted as the preferred modality for a 6-month period for all included patients.
• Period 1: the umbilicus was prepared using 2 cotton swabs soaked in povidone-iodine soap (povidoneiodine 7.5%). Foam sponges or sterile gauze was then used to apply 3 consecutive applications of povidone-iodine soap in concentric circles, starting at the incision and moving outward. The surgical site was washed with a single application of 70% isopropyl alcohol in the same manner, and a sterile towel was placed over the surgical site and patted dry. The process was then completed with 3 consecutive applications of a 10% povidone-iodine paint that was allowed to dry before the application of sterile drapes.
• Period 2: 2% Chlorhexidine and 70% Isopropyl Alcohol - the umbilicus was prepared using 2 cotton swabs soaked in solution from the applicator. The applicator was then used to scrub the incision site in a back-and-forth manner for 30 seconds. Staff were instructed to continue the scrub for 2 minutes in moist areas. The solution was given adequate time to dry completely before the application of surgical drapes. Postoperatively, the dried solution was left in place for at least 24 hours before active removal.
• Period 3: Iodine Povacrylex in Isopropyl Alcohol - the umbilicus was prepared using 2 cotton swabs soaked in solution from the applicator. The applicator was then used to paint the abdomen, starting at the incision site, in a single uniform application. The solution was given adequate time to dry completely before the application of surgical drapes. Postoperatively, the dried solution was left in place indefinitely without active removal.

Results

• The study included 3,209 cases of which 182 developed SSI.
• The lowest SSI incidence 3.9% was observed in period 3, compared with 6.4% in period 1 and 7.1% in period 2.
• Most of this difference was observed in the superficial SSI category. No differences were observed in the incidence of deep or organ/space SSI.
• Factors associated with a higher incidence of SSI by univariate analysis included female sex, diabetes mellitus, cancer diagnosis, preoperative sepsis, and preoperative weight loss.
• Lower SSI rates overall were seen in the povidone-iodine preparation group (4.8%) and the iodine povacrylex in isopropyl alcohol group (4.8%), compared with the SSI rates in the 2% chlorhexidine and 70% isopropyl alcohol group (8.2%).

Conclusions

• Orthopedic surgery, for example, usually involves more soft-tissue destruction than does general surgery but rarely enters contaminated areas and might benefit from a different method of skin preparation.

Articles on General Surgery

The efficacy of infection surveillance and control programs in preventing nosocomial infections in U.S. hospitals, Haley RW, Culver DH, White JW, Morgan WM, Emori TG, Munn VP, Hooton TM., Am J Epidemiol, 121, pp 182-205, 1985.

Aims

• In January 1974, CDC initiated the SENIC Project (Study on the Efficacy of Nosocomial Infection Control). Three objectives: to estimate the magnitude of the nosocomial infection problem in US Hospitals; to describe the extent to which hospitals had adopted the new infection surveillance and control program approach; and to determine whether, and, if so, to what extent, this approach was effective in reducing nosocomial infection risks.

Methods

• Data collected in three phases: Phase I, Preliminary Screening Questionnaire Survey; Phase II, Hospital Interview Survey; and Phase III, the Medical Records Survey. Data used to calculate a surveillance index (measuring the extent to which each hospital conducted active surveillance over the occurrence of nosocomial infections) and a control index (measuring the intensity of efforts to intervene in the care of patients to reduce infection risks). Analyzed two hospital characteristics: dynamic (nurse to patient ratio) and structural (hospital size, medical school affiliation, region etc.).

Results

• Over 80 % of all nosocomial infections are urinary tract infection, surgical wound infection (SWI), pneumonia and bacteremia.
• With high-risk patients, the effective approach involved two components: (i) establishing a strong infection surveillance and control program with both surveillance and control activities (having a hospital epidemiologist); (ii) establishing a system for reporting SWI rates back to the hospital's practicing surgeon. Implementing one component led to a 20% reduction in SWI; using both resulted in a 35% reduction.
• With low-risk patients, the components were the same, but with a more stringent program. Having one component in place resulted in a 19% reduction in SWI; using both resulted in a 41% decrease.

Conclusions

• Nearly one third (32%) of all nosocomial infections can be prevented if all hospitals adopt the most effective program (Table 7). An infection control nurse working with a physician, who has a special interest in infection control and practicing epidemiologic surveillance and control techniques, can prevent up to 32% of nosocomial infections.

Surgical wound infection rates by wound class, operative procedure, and patient risk index. National Nosocomial Infections Surveillance System, Culver DH, Horan TC, Gaynes RP, Martone WJ, Jarvis WR, Emori TG, Banerjee SN, Edwards JR, Tolson JS, Henderson TS, Am J Med., 91, pp 152S-157S, 1991.

Aims

• SENIC has been reported to be a better predictor for SWIs than the traditional wound classification system (in use since 1964), which has four categories: clean, clean-contaminated, contaminated, and dirty-infected. This study reports on a modification to the SENIC risk index.

Methods

• The developed risk index score ranges from 0 to 3 and depends on the number of risk factors present among the following:
• A patient with an ASA preoperative score of 3, 4, or 5;
• An operation classified as contaminated or dirty-infected;
• An operation lasting over T hours, where T depends upon the operative procedure being performed (Table 1).

Results

• The four risk factors that are found to be associated with risk are:
  • An operation involving the abdomen;
  • An operation lasting longer than 2 hours;
  • An operation classified as either contaminated or dirty-infected;
  • A patient having three or more diagnoses at discharge.
    • SWI ranged from 1.5% with patients with none of the risk factors, to as high as 13% for those patients showing all three of the risk factors. Of the 49,333 patients with clean operative procedures, 44% had none of the risk factors, 46% had one risk factor, and the remaining 10% had both operations of long duration and an ASA score of 3, 4, or 5. SWI rates increased with the number of risk factors present (Table 3).
    • SWIs are shown to decline when surveillance programs have been implemented that include feedback of postoperative wound infection rates to practicing surgeons.
• In general, surveillance or screening have been shown to be effective preventative measures for reducing SSIs in hospital settings. The reduction in SSI rates (in hospital settings) as a result of each of these interventions is available from several studies in the literature (e.g., Geubels et al. (2006) and the references therein). Transmission of pathogens by the contaminated hands of healthcare workers is considered the major route of cross-infection [Solberg (2000)], and has received considerable attention.

Risk Factors for Postoperative Infection, Garibaldi, RA, Cushing, D, Lerer, T, The American Journal of Medicine, 91, 3B, pp 158S-163S, 1991.

Aims

• To identify the critical risk factors for postoperative wound infections.

Methods

• Data was collected on 1,852 patients over a 4-year period [January 1982 to January 1986]. During operative process, culture collected. Culture considered positive if > 30cfu of bacteria identified. Patient demographics are as follows:
  • 60% female and 40% male
  • 69% between the age of 31 and 70; 18% greater than 70.
  • 79% general surgery; 19% gynecology; 2% other.
  • 42% clean surgeries; 54% clean-contaminated; 3% contaminated; and 1% dirty.
  • Two most common procedures: cholecystectomies (31%) and hernia repairs (26%).
  • ASA physical status classes: class I (34%); class II (33%); class III (31%); class IV or V (2%) [The ASA physical status classification is a relatively standardized, numerical determination that is used routinely to stratify severity of illness for all patients undergoing general anesthesia].

Results

• 120 postoperative wound infections identified (6.5% rate).
  Most significant procedure-associated risk factors were the surgical wound class, identification of positive intraoperative wound cultures, duration of surgery, occurrence of glove punctures.
• Relationship Between Risk Factors and Postoperative Wound Infection:
  • Unadjusted predicted probability of infection for clean operations (2.2%);
  • Clean surgeries with long durations with patients in high ASA classes (8.3);
  • Clean-contaminated (8.5%) and [20% when two other variables were considered];
  • Contaminated operations (28%);
  • Dirty operations (41%);
    • Addition of positive wound culture increased to 17% in high-risk clean operations; 37% in high-risk clean-contaminated operations; 61% in high risk contaminated and dirty operations.
    • 38 of 276 (13.8%) patients with positive cultures during surgery developed wound infections vs 82 of 1,576 (5.2%) patients with negative cultures during surgery developed wound infections.
• Most frequently isolated bacteria in the intraoperative cultures: Coagulase-negative staphylococci (73%), Escherichia coli (11%), and Staphylococcus aureus (5%).
• Factors associated with the occurrence of positive intraoperative cultures: surgical wound class (35% of contaminated and dirty surgeries had positive cultures vs 14% of clean and clean-contaminated); emergency procedures (33% vs 15% for elective procedures); operations involving lower abdominal sites (22% vs 7% for upper abdominal sites).
• Of the 52 infected patients with positive postoperative wound cultures who received antibiotics perioperatively, 38(73%) developed infections with organisms that were resistant to the perioperative drug regimen.
• This assessment takes into account a variety of host factors that are directly related to the patient's risk for infection: including age, nutritional status, the presence of systemic disease and projected mortality.
• Confirmed an association between the duration of the surgical procedure and the occurrence of infection that was independent of both host-related and other surgery-related risk factors.
• It is possible that surgery duration served as a marker for additional risk factors that were not otherwise included in the model such as: skill of surgeon, complexity of surgery or extensiveness of tissue trauma in the wound.
• The importance of positive wound cultures at the time of surgery has long been acknowledged as a risk factor for subsequent infection. A variety of studies using different patient populations, study protocols, collection techniques and culture methodologies have reached conclusions similar to that found in the present study.

Surgical site infections in HIV-infected patients: Results from an Italian prospective multicenter observational study – Drapeau et al. Infection 37 (2009): 455-460.

Purpose

• The quality of life and survival expectancy of HIV-infected patients have substantially improved [1, 2], and the clinical barriers towards surgical treatment of HIV-infected patients, which were once associated with poor surgical outcomes and to the surgeon's concern about accidental exposure with the HIV, are gradually disappearing [3].

Methods

• The study followed 305 HIV-infected patients undergoing the following surgical procedures: caesarean sections, gastrointestinal, biliary, and hepatosplenic interventions, cervico-facial district, plastic, and dermatological interventions, cardiovascular interventions, lymphoadenectomies, and orthopedic, genitourinary tract, and thoracic interventions.
• There was postdischarge surveillance for the first 30 days following the procedure in order to detect SSI.
• To assess potential risk factors for SSI, we first conducted a univariate analysis that included the following variables: gender, age, body mass index (BMI), diabetes, hepatitis C virus (HCV) infection, hepatitis B virus (HBV) infection, presence of lipodistrophy, HIV viral load, CD4 cell count and WBC at intervention time, preoperative hospital stay, which was stratified according to the median value for overall interventions, NNIS risk index score, and any preoperative antimicrobial prophylaxis.

Results

• SSI occurred in 29 of 305 (9.5%) of patients.
• Most of the SSI (72.4%) were superficial. Organ/space infection and sepsis accounted for 13.7% of all SSI.
• The SSI rate for orthopedic surgery was 18.2%.
• Age ≥ 45 years and HCV co-infection were significantly associated with SSI and the NNIS risk index score was closely significant.
• Total hospital stay was significantly associated to SSI (SSI rate = 15.1% among patients with total hospital stay > 5 days vs 4.8% for those with total hospital stay ≤ 5 days.

Conclusions

• The findings suggest that SSI occur more frequently and are more severe in the population of HIV-infected patients than in the general population.
• In the literature, the SSI rate in HIV patients undergoing orthopedic surgery ranges from 16.7% in orthopedic trauma patients [27], to 71.4% [18, 19] in patients with open reduction of fractures.
• In terms of risk factors for SSI in HIV-infected patients, we found that HCV infection was the only risk factor independently associated with SSI occurrence.
• Another interesting finding of our study was that the CD4+ cell count and the HIV viral load were not associated to SSI occurrence.

Risk Factors for Postoperative Infection – Garibaldi et al. The American Journal of Medicine 2nd ser. 91.3 (1991): S158-163.

Purpose

• The study collected prospective information on more than 1,800 operations at a university-affiliated community hospital in order to analyze the relative contributions of specific risk factors in predisposing to postoperative wound infections.

Methods

• The study population included 1,852 patients undergoing operations with skin incisions greater than 6 cm in length.
• During the operative procedure, a semiquantitative culture was collected from subcutaneous fat in the superficial wound margin just prior to closing. The culture technique utilized a 5 nanometer Millipore filter in a holder that was pressed on the wound surface for 5 seconds and subsequently placed directly on trypticase-soy agar with 5% sheep blood for culture [1]. Cultures were considered to be positive if greater than 30 cfu of bacteria were identified; most of the positive cultures had colony counts that were too numerous to count.
• Postoperatively each patient was followed-up three times weekly for the duration of their hospitalization to identify infections; information was collected on all patients for at least 2 weeks after surgery.
• The groupings of cases by surgical wound class included 42% clean surgeries, 54% clean-contaminated, 3% contaminated, and 1% dirty.
• 34% of patients were in the American Society of Anesthesiologists (ASA) physical status class I, 33% were in class II, 31% were in class III, and 2% were in classes IV or V.

Results

• Overall, 120 postoperative wound infections were identified, for a rate of 6.5%.
• There was a direct association between the occurrence of wound infections and high ASA classification, lengthier preoperative hospitalizations, and the presence of an infection at another site at the time of operation.
• The most significant procedure-associated risk factors were the surgical wound class, identification of positive intraoperative wound cultures, duration of surgery, and occurrence of glove punctures.
• Of 276 patients with positive cultures during surgery, 38 (13.8%) subsequently developed wound infections, compared with 82 of 1,576 patients (5.2%) with negative cultures.

Conclusion

• We identified four independent variables-the surgical wound classification, ASA physical status, duration of surgery, and results of intraoperative cultures-that are highly associated with the subsequent occurrence of infection.

Reduction of Nosocomial Infections in the Surgical Intensive-Care Unit by Strict Glycemic Control – Grey et al. Endocrine Practice 10.2 (2004): 46-52.

Purpose

• To investigate whether hyperglycemia in glucose-intolerant patients without diabetes could lead to increased nosocomial infections in the surgical intensive care unit (ICU).
• Humoral immunity depends on antibody function. Antibodies neutralize the effect of bacteria by attaching directly to the microbes and preventing attachment to host cells. In addition, antibody attachment induces complement activation and aids in the eventual phagocytosis of bacteria by host leukocytes. After ingestion, phagocytes become stimulated and create an oxidative burst that is lethal to microbes.
• Pomposelli et al (12) found that hyperglycemia on postoperative day 1 was associated with a threefold increase of all nosocomial infections in patients with diabetes undergoing an elective operation. Furnary et al (13) demonstrated reduction in the rate of deep sternal wound infection after cardiac surgical procedures in patients with better glycemic control.
• Hyperglycemia, defined as a fasting blood glucose level of more than 126 mg/dL or a random blood glucose value in excess of 140 mg/dL, is extremely common among hospitalized patients.

Methods

• Randomization to receive standard glucose control or strict glucose control was determined by coin toss.
• Intravenous insulin infusions were administered to maintain serum glucose values in the range of 180 to 220 mg/dL in the standard control group and from 80 to 120 mg/dL in the strict control group.
• Outcome measures included serum glucose values and incidence of nosocomial infection.

Results

• The study was completed by 61 critically ill patients, including 27 in the standard glucose control group and 34 in the strict glucose control group.
• Episodes of hypoglycemia (glucose values <60 mg/dL) occurred in 32% of the patients (0.8% of the total serum glucose values) in the strict glucose control group in comparison with 7.4% of the patients (0.1% of serum glucose values) in the standard glucose control group (P<0.001).
• Bloodstream infections, IVDI (intravascular device infection) or IVDI-related bloodstream infections, and surgical site infections developed in a significantly higher percentage of patients in the standard glucose control group than in the strict glucose control group (Fig. 4).
• A 4-fold increase in IVDI and bloodstream infections was noted in the standard glucose control group; also observed was a 3.5-fold increase in IVDI-related bloodstream infections and surgical site infections.

Conclusions

• These results show that hyperglycemia (that is, serum glucose levels of >180 mg/dL) can predispose critically ill surgical patients to the development of nosocomial infections.
• Intravenous treatment with insulin to reduce the serum glucose concentration can lead to a significant reduction in the rates of nosocomial infections in patients in the surgical ICU, even patients without diabetes.

The Effect of Increasing Age on the Risk of Surgical Site Infection – Kaye et al. The Journal of Infectious Diseases 191.7 (2005): 1056-062.

Purpose

• An increasing number of older persons undergo surgery, but the relationship between increasing age and risk of surgical site infection (SSI) has not been established. The objective of the present study was to determine the relationship between increasing age and risk of SSI.
• In a recent study by
• McGarry et. al., older patients with Staphylococcus aureus SSIs had a 3-fold increase in mortality, longer post- operative hospital stays, and higher hospital charges than did younger patients with S. aureus SSIs [8].

Methods

• During the study period, a total of 144,485 patients underwent surgical procedures at the 11 hospitals. Orthopedic surgical procedures accounted for 41.8% of surgeries.
• 1684 patients developed an SSI (1.2%).

Results

• The mean age of patients with an SSI (57.1 years) was significantly greater than the mean age of patients without an SSI (52.3 years).
• Between the ages of 17 and 65 years, the rate of SSI increased for each decade of increasing age and peaked at age 65–74 years. Age ≥ 65 years was a significant predictor of SSI.

Conclusion

• The risk of SSI increased with age until age 75 years [13]. Potential explanations for this finding include increasing immune dysfunction and accumulation of comorbid conditions with increasing age.

Risk Index for Prediction of Surgical Site Infection after Oncology Operations – Velasco et al. American Journal of Infection Control 26.3 (1998): 217-23.

Purpose

• In general, surgical cancer patients are no more susceptible to nosocomial infections than the rest of the hospital population, but those with altered immunologic and neutrophilic functions undergoing complex surgical procedures have a higher degree of morbidity and mortality, mainly because of postoperative infectious complications.

Methods

• All consecutive patients with a diagnosis of malignancy who underwent a surgical procedure were prospectively followed up by well-trained infection control nurses. Patients were visited three to four times per week.

Results

• The study enrolled 1205 consecutive patients undergoing operations for malignant disease.
• Overall, 317 patients (26.3%) had 413 nosocomial infections (34.3%). The crude rate of SSI was 17.3% (209 of 1205).
• Among all postoperative infections, SSI was the most predominant (50.6%); 26.6% were incisional, and 24% were organ or space.
• Median length of hospital stay was 16 days for patients without SSI vs. 20 days for patients with SSI.
• Several variables were identified as statistically significant: age older than 50 years, male sex, ASA III to V, contaminated or dirty-infected surgeries, a preoperative stay above the 75th percentile of 16 days, prior radiotherapy, presence of remote infection at admission, antimicrobial prophylaxis not as recommended by protocol, surgical duration longer than the cut point of 280 minutes, presence of drains, and recent weight loss. Prior chemotherapy and emergency surgery were not associated with increased risk for SSI.
• Six independent risk factors were identified: contaminated and/or infected surgery, operating time more than 280 minutes, male sex, previous radiotherapy, ASA III to V, and inadequate antimicrobial prophylaxis.

Conclusions

• Only six of risk factors contributed independently to the SSI complication: contaminated and infected operations, operating time more than 280 minutes, male sex, prior radiotherapy, ASA III to V, and inadequate antimicrobial prophylaxis.
• Radiation therapy can cause a variety of dose related systemic and local side effects that will impair the ability of the patient and irradiated tissues to resist infection.

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¹ ASA score ranges from 1 to 5, 1 being a perfectly healthy individual and 5 being a patient not expected to survive the next 24 hrs.

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