1. Prevention of Surgical Site Infections: Considerations in Measuring Effectiveness
Michele L. Pearson, MD
Division of Healthcare Quality Promotion
National Center for Infectious Diseases

2. Objectives
Provide overview of epidemiology of surgical site infections (SSI)
Discuss SSI prevention strategies
Highlight current surveillance systems for SSI
Provide overview of HICPAC/CDC process for developing recommendations for prevention healthcare-associated infections

3. Public Health Importance of Surgical Site Infections
In U.S., >40 million inpatient surgical procedures each year; 2-5% complicated by surgical site infection
SSIs second most common nosocomial infection (24% of all nosocomial infections)
Prolong hospital stay by 7.4 days
Cost $400-$2,600 per infection (TOTAL: $130-$845 million/year)

4. CDC Definition of Surgical Site Infections
SSI level classification
Incisional SSI
- Superficial incisional = skin and
subcutaneous tissue
- Deep incisional = involving deeper soft tissue
Organ/Space SSI
- Involve any part of the anatomy (organs
and spaces), other than the incision, opened or manipulated during operations

5. Cross Section of Abdominal Wall Depicting CDC SSI Classifications

6. Source of SSI Pathogens
Endogenous flora of the patient
Operating theater environment
Hospital personnel (MDs/RNs/staff)
Seeding of the operative site from distant focus of infection (prosthetic device, implants)

7. Microbiology of SSIs 1986-1989 (N=16,727) 1990-1996 (N=17,671)
Staphylococcus
aureus
17%
Coagulase neg.
staphylococci
12%
Escherichia
coli
10%
Enterococcus
spp. 8%
Pseudomonas
aeruginosa
Staphylococcus
aureus
20%
Coagulase neg.
staphylococci
14%
Escherichia
coli 8%
Enterococcus
spp.
12%
Pseudomonas
aeruginosa

8. Microbiology of SSIs Unusual pathogens
• Rhizopus oryzea - elastoplast adhesive bandage
• Clostridium perfringens - elastic bandages
• Rhodococcus bronchialis - colonized health care personnel
• Legionella dumoffii and pneumophila - tap water
• Pseudomonas multivorans - disinfectant solution
Cluster of unusual SSI pathogens  formal epidemiologic investigation

9. Pathogenesis of SSI
Relationship equation Dose of bacterial contamination x Virulence Resistance of host SSI Risk

10. SSI Risk Factors Age Obesity Diabetes Malnutrition
Prolonged preoperative stay
Infection at remote site
Systemic steroid use
Nicotine use
Hair removal/Shaving
Duration of surgery
Surgical technique
Presence of drains
Inappropriate use of antimicrobial prophylaxis

11. Perioperative Preventive Measures

12. Role of Antimicrobial Prophylaxis (AP) in Preventing SSI
Refers to very brief course of an antimicrobial agent initiated just before the operation begins
Should be viewed as an adjunctive preventive measure
Appropriately administered AP associated with a 5-fold decrease in SSI rates

13. Importance of Timing of Surgical Antimicrobial Prophylaxis (AP)
Prospective study of 2,847 elective clean and clean-contaminated procedures
Early AP (2-24 hrs before incision): 3.8% Postop AP (3-24 hrs after incision): 3.3% Periop AP (< 3 hrs after incision): 1.4% Preop AP (<2 hrs before incision): 0.6%
Classen, 1992 (NEJM 326: )

14. Impact of Prolonged Surgical Prophylaxis
DESIGN: Prospective
POPULATION: CABG patients (N=2641)
Group 1: pts who received < 48 hours of AP
Group 2: pts who received > 48 hrs of AP

15. Impact of Prolonged Surgical AP
OUTCOMES
• Incidence of SSI
• Isolation of a resistant pathogen
RESULTS: 43% of patients received AP > 48 hr
SSI Incidence
• <48 hrs group: 8.7% (131/1502) vs
• >48 hrs group: 8.8% (100/1139), p=1.0 Antimicrobial resistant pathogen
• OR 1.6 (95% CI )

16. Enhanced Perioperative Glucose Control in Diabetic Patients
DESIGN: Prospective, sequential study
POPULATION: Diabetic patients undergoing cardiac surgery (N=2467) during
Controls: pts who received intermittent subQ insulin (SQI)
Treated: pts who received continuous intravenous (IV) insulin
Furnary AP; Ann Thorac Surg, 2000

17. Enhanced Perioperative Glucose Control in Diabetic Patients
OUTCOMES
• Blood glucose <200 mg/dl in first two days postop
• Incidence of deep sternal SSI
RESULTS
• SQI group: 2.0% (19/968) vs
• IVI group: % (12/1499), p=0.01
Furnary AP; Ann Thorac Surg, 2000

18. Supplemental Perioperative O2
DESIGN: Randomized controlled trial, double blind
POPULATION: Colorectal surgery (N=500)
INTERVENTION: 30% vs 80% inspired oxygen during and up to hours after surgery
RESULTS: SSI incidence 5.2% (80% O2) vs 11.2% (30% O2), p=0.01
Greif, R, et al , NEJM, 2000

19. Pre-operative Antiseptic Showers/Baths
Most studies examine effects on skin colony counts
antiseptic showering decreases colony counts
Few studies examine effect on SSI rates
No Shower Shower
Cruse, % %
Ayliffe, % %
Rooter, % %

20. Pre-operative Shaving/Hair Removal
Seropian, 1971
Method of hair removal
Razor = 5.6% SSI rates
Depilatory = 0.6% SSI rates
No hair removal = 0.6% SSI rates
Timing of hair removal
Shaving immediately before = 3.1% SSI rates
Shaving  24 hours before = 7.1% SSI rates
Shaving >24 hours before = 20% SSI rates

21. CENTERS FOR DISEASE CONTROL
Pre-operative Shaving/Hair Removal
Multiple studies show
- Clipping immediately before operation associated with lower SSI risk than shaving or clipping the night before operation
CENTERS FOR DISEASE CONTROL
AND PREVENTION

22. Surgical Attire
Scrub suits
Cap/hoods
Shoe covers
Masks
Gloves
Gowns

23. Surgical Technique Removing devitalized tissue
Maintaining effective hemostasis
Gently handling tissues
Eradicating dead space
Avoiding inadvertent entries into a viscus
Using drains and suture material appropriately

24. Parameters for Operating Room Ventilation*
Temperature: 68o-73oF, depending on normal ambient temp
Relative humidity: 30%-60%
Air movement: from “clean to less clean” areas
Air changes: >15 total per hour >3 outdoor air per hour
*American Institute of Architects, 1996

25. Role of Laminar Air Flow (Ultraclean Air) in Preventing SSI
Most studies involve only orthopedic operations
Lidwell et al: 8,000 total hip and knee replacements ultraclean air: SSI rate 3.4% to 1.6% antimicrobial prophylaxis (AP): SSI rate 3.4% to 0.8% ultraclean air + AP: SSI rate 3.4% to 0.7%

26. Status of SSI Surveillance

27. CDC Surveillance Systems
NNIS
DSN
NaSH
Nosocomial infections in critical care and surgical patients
Bloodstream and vascular access infections in dialysis outpatients
Exposure to bloodborne pathogens; TB skin testing and exposure; Vaccine: history, receipt, and adverse events
1996-present

28. Characteristics of NNIS Hospitals, 2000
58% are MAJOR TEACHING
10% are Graduate Teaching
15% are Limited Teaching
16% are Non Affiliated Hospitals
Bed Size
Median: 360 beds
No facilities < 100 beds

29. Variables Collected in Surgical Patient Component, NNIS
Age
Sex
ASA score
Wound class
Trauma-related
Type of anesthesia
Emergency vs elective
Duration of surgery
Length of postoperative stay
Infection site (skin/soft tissue, organ space)
Pathogen
Mortality
Hospital demographics (bed-size, affiliation)

30. SSI Risk Index
From the U.S. National Nosocomial Infections Surveillance (NNIS) system
American Society of Anesthesiologists (ASA) score
1 to 5, from 1=“normal, healthy” to 5=“patient not expected to survive for 24 hours with OR without operation
Wound Class
Clean, clean-contaminated, contaminated, dirty
Duration of surgery

31. Surgical Site Infection (SSI) Rates By Risk Category,
NNIS System, 16 12
Low risk
Medium
SSIs per 100 operations 8
low risk
Medium
high risk 4
High risk
1992
1993
1994
1995
1996
1997
1998
1999
Years

32. SSI Definitions: Period of Surveillance
Infection occurs within 30 days after the operative procedure if no implant is left in place or within 1 year if implant is in place and the infection appears to be related to the operative procedure

33. Challenges to Surveillance for SSIs
Admissions
Patient-days
Length of Stay
Inpatient Surgical Procedures
Nosocomial Infection Rate
per 1,000 Patient-days
1975
37,700,000
299,000,000
7.9 days
18,300,000
7.2
1995
35,900,000
190,000,000
5.3 days
13,300,000
9.8
Change
5%
36%
33%
27%
36%
CENTERS FOR DISEASE CONTROL
AND PREVENTION

34. Integration of CDC’s three patient and healthcare personnel
What Is NHSN?
Integration of CDC’s three
patient and healthcare personnel
surveillance systems
NNIS
NaSH
DSN

35. NHSN Premises Maintain the goals of predecessor systems
Minimize data collection and manual data entry burden
Streamline existing surveillance protocols
Increase capacity for capturing electronic data (e.g., Laboratory information systems, operating room, pharmacy, clinical, administrative databases)
Extensible web-based application
What is OT? Surgery? All entities can participate on a limited basis. Hospitals and outpatient dialysis.

36. Priority Areas for NHSN Development
Inclusion of process measures linked to outcomes
Surgical prophylaxis
Central line insertion practices
Completion of HCP Safety Component
NaSH  NHSN
Influenza pilot: vaccine coverage and use of antiviral medications

37. How do we develop policy?

38. Healthcare Infection Control Practices Advisory Committee (HICPAC)

39. Healthcare Infection Control Practices Advisory Committee MISSION
Advise the US Secretary of Health and the Director of CDC regarding the practice of infection control and strategies for surveillance, prevention and control of antimicrobial resistance, and related adverse events in healthcare settings

40. CDC/HICPAC GUIDELINE SCOPE
TARGET AUDIENCE:
• clinicians
• infection control professionals
• public health officials
• regulators
TARGET SETTINGS:
• Inpatient
• Outpatient
• Home care
• Long term care

41. Ranking Scheme for HICPAC Recommendations (2001)
CATEGORY IA. Strongly recommended for all hospitals and strongly supported by well-designed experimental or epidemiologic studies.
CATEGORY IB. Strongly recommended for all hospitals and viewed as effective by experts in the field and a consensus of HICPAC based on strong rationale and suggestive evidence, even though definitive scientific studies may not have been done.
CATEGORY IC. Required for implementation, as mandated by federal or state regulation or standard. CATEGORY II. Suggested for implementation in many hospitals. Recommendations may be supported by suggestive clinical or epidemiologic studies, a strong theoretical rationale, or definitive studies applicable to some but not all hospitals.
NO RECOMMENDATION; UNRESOLVED ISSUE. Practices for which insufficient evidence or consensus regarding efficacy exists.

42. CDC/HICPAC Guideline RATING SYSTEM
CATEGORY EVIDENCE PRACTICE
IA/IB STRONG RECOMMENDED
IC LACKING REQUIRED BY REGULATION
II GOOD SUGGESTED
NO REC INSUFFICIENT UNRESOLVED
CONTRADICTORY

43. Challenges/Issues Subject matter experts vs. methodologic experts
Resources for systematic reviews
Limited randomized trials
User needs vs available science (e.g., expansion to non-hospital settings)

44. PART II: Provides summary of practice recommendations
Healthcare Infection Control Practices Advisory Committee GUIDELINE FORMAT
PART I: Provides review and synthesis of available research on guideline topic and established scientific rationale for recommendations
PART II: Provides summary of practice recommendations
PART III: Provides performance indicators for institutions to monitor success in implementing recommended practices

45. Summary
Prevention of SSI require a multifaceted approach targeting pre-, intra-, and postoperative factors
Current surveillance systems do collect data on perioperative processes
Increasing shift of surgical procedures to outpatient settings and decrease in postoperative length of stay complicate surveillance efforts
Incidence is generally low; so studies would require large sample size
Some prevention practices (e.g. hand hygiene) would be difficult to study using traditional randomized controlled trial research design

46. PREVENTION IS PRIMARY! Protect patients…protect healthcare personnel…
promote quality healthcare!
Division of Healthcare Quality Promotion

47. Division of Healthcare Quality Promotion (DHQP) website
To obtain HICPAC guidelines visit the
Division of Healthcare Quality Promotion (DHQP) website