Prevention of Surgical Site Infections: Considerations in

Measuring Effectiveness

Michele L. Pearson, MD

Division of Healthcare Quality Promotion

National 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

Staphylococcus aureus

17%

Coagulase neg. staphylococci

12%

Escherichia coli 10%

Enterococcus spp. 8%

Pseudomonas aeruginosa

8%

Staphylococcus aureus

20%

Coagulase neg. staphylococci

14%

Escherichia coli 8%

Enterococcus spp. 12%

Pseudomonas aeruginosa

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 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 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 Shower Cruse, 1973 2.3% 1.3% Ayliffe, 1983 4.9% 5.4% Rooter, 1988 2.4% 2.6%

Pre-operative Antiseptic Showers/Baths

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

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 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

1999-2004 1970-2004 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

Years

SS

Is p

er

100

op

era

tio

ns

Low risk

Medium low risk Medium high risk High 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 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%

What Is NHSN?

NNIS

NaSH

DSN

Integration of CDC’s three patient 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 SYSTEM

CATEGORY EVIDENCE PRACTICE

IA/IB STRONG RECOMMENDED

IC LACKING REQUIRED BY REGULATION

II GOOD SUGGESTED

NO REC INSUFFICIENT UNRESOLVED

CONTRADICTORY

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! 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