Prevention of Surgical Site Infections: Considerations in

Measuring Effectiveness

Michele L. Pearson, MDDivision of Healthcare Quality PromotionNational Center for Infectious Diseases

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

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)

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

CDC Definition of Surgical Site Infections

Cross Section of Abdominal Wall Depicting CDC SSI Classifications

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)

Microbiology of SSIs

Staphylococcusaureus

17%

Coagulase neg.staphylococci

12%

Escherichiacoli10%

Enterococcusspp.8%

Pseudomonasaeruginosa

8%

Staphylococcusaureus

20%

Coagulase neg.staphylococci

14%

Escherichiacoli8%

Enterococcusspp.12%

Pseudomonasaeruginosa

8%

1986-1989(N=16,727)

1990-1996(N=17,671)

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

Pathogenesis of SSI

• Relationship equation Dose of

bacterial contamination x Virulence

Resistance of host

SSI Risk

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

Perioperative Preventive Measures

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

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 326:281-286)

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

Impact of Prolonged Surgical AP• OUTCOMES

• Incidence of SSI• Isolation of a resistant pathogen

• RESULTS: 43% of patients received AP > 48 hrSSI 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 1.1-2.6)

Enhanced Perioperative Glucose Control in Diabetic Patients

• DESIGN: Prospective, sequential study

• POPULATION: Diabetic patients undergoing cardiac surgery (N=2467) during 1987-1997

Controls: pts who received intermittent subQ insulin (SQI)

Treated: pts who received continuous intravenous (IV) insulin

Furnary AP; Ann Thorac Surg, 2000

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: 0.8% (12/1499), p=0.01 Furnary AP; Ann Thorac Surg, 2000

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

Most studies examine effects on skin colony counts antiseptic showering decreases colony counts

Few studies examine effect on SSI rates

No Shower ShowerCruse, 1973 2.3% 1.3%

Ayliffe, 1983 4.9% 5.4%

Rooter, 1988 2.4% 2.6%

Pre-operative Antiseptic Showers/Baths

Seropian, 1971Method of hair removal

Razor = 5.6% SSI ratesDepilatory = 0.6% SSI ratesNo hair removal = 0.6% SSI rates

Timing of hair removalShaving immediately before = 3.1% SSI ratesShaving 24 hours before = 7.1% SSI ratesShaving >24 hours before = 20% SSI rates

Pre-operative Shaving/Hair Removal

CENTERS FOR DISEASE CONTROL

AND PREVENTION

Multiple studies show

- Clipping immediately before operation associated with lower SSI risk than shaving or clipping the night before operation

Pre-operative Shaving/Hair Removal

Surgical Attire

• Scrub suits

• Cap/hoods

• Shoe covers

• Masks

• Gloves

• Gowns

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

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

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%

Status of SSI Surveillance

CDC Surveillance SystemsNNIS 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

1999-20041970-2004 1996-present

Characteristics of NNIS Hospitals, 2000

300 hospitals 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

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)

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

Surgical Site Infection (SSI) Rates By Risk Category, NNIS System, 1986-1999

0

4

8

12

16

1986

-90

1992

1993

1994

1995

1996

1997

1998

1999

Years

SS

Is p

er 1

00 o

per

atio

ns

Low risk

Mediumlow riskMediumhigh riskHigh risk

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

CENTERS FOR DISEASE CONTROL

AND PREVENTION

Challenges to Surveillance for SSIsChallenges to Surveillance for SSIs

AdmissionsPatient-daysLength of StayInpatient Surgical ProceduresNosocomial Infection Rate per 1,000 Patient-days

1975 37,700,000299,000,000

7.9 days 18,300,000

7.2

1995 35,900,000190,000,000

5.3 days 13,300,000

9.8

Change 5%36%33%27%

36%

What Is NHSN?

NNIS

NaSH

DSN

Integration of CDC’s threepatient and healthcare personnel

surveillance systems

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

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

How do we develop policy?

Healthcare Infection Control Practices Advisory Committee

(HICPAC)

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

CDC/HICPAC

GUIDELINE SCOPE• TARGET AUDIENCE:

• clinicians • infection control professionals • public health officials • regulators

• TARGET SETTINGS: • Inpatient• Outpatient• Home care• Long term care

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.

CDC/HICPAC Guideline

RATING SYSTEMCATEGORY EVIDENCE PRACTICE

IA/IB STRONG RECOMMENDED

IC LACKING REQUIRED BY REGULATION

II GOOD SUGGESTED

NO REC INSUFFICIENT UNRESOLVEDCONTRADICTORY

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)

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

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

PREVENTION IS PRIMARY!

PREVENTION IS PRIMARY!

Protect patients…protect healthcare personnel…

promote quality healthcare!Division of Healthcare Quality Promotion

Division of Healthcare Quality Promotion (DHQP) website

http://www.cdc.gov/ncidod/hip/default.htm

To obtain HICPAC guidelines visit the