Surgical Site Infections: Known Risk Factors

Surgical Site Infections: Known Risk Factors

Lena M. Napolitano MD, FACS, FCCP, FCCMProfessor of Surgery, Chief, Acute Care Surgery

Chief, Surgical Critical Care Associate Chair, Department of Surgery

University of MichiganAnn Arbor, Michigan

Surgical Site Infections (SSI)Epidemiology

• Incidence: 2.6% of all operations• Third most common nosocomial infection

(14%–25%)• Most common nosocomial infection among

surgical patients (38%)• 7.3 mean additional postoperative days at

an additional cost of $3,152 per patient

Wilson. Am J Surg. 2003;186:35S-41S.Mangram et al. Infect Control Hosp Epidemiol. 1999;20:250-278.

Surgical Site Infection (SSI)

• Laparotomy for intestinal resection for Crohn’s disease

• SSI at laparotomy site• Wound opened fully• Wound debridement• IV antibiotics

SSI: Laparoscopic Ventral Hernia Repair

• Recurrent ventral hernia

• Prior mesh repair with postop SSI

• Diabetic, CRI• Required mesh

removal

SSI: Laparoscopic Ventral Hernia Repair

• Mesh removal, I&D

• V.A.C. dressing• Partial closure• LOS 12 days

I&D = incision and drainage; LOS = length of stay;V.A.C. = Vacuum-Assisted Closure.

CDC Classification of SSI(within 30 days of OR, 1 year if implant)

• Incisional– Superficial

• involve only skin and subcutaneous tissue

– Deep• involve deep

soft tissues• Organ/space

– involving any part of anatomy other than incision opened or manipulated

Mangram et al. Guideline for Prevention of Surgical Site Infection. 1999, with permission.

Subcutaneous tissue

Deep soft tissue (fascia and muscle)

Organ/space

SkinSuperficial incisional SSI

Organ/space SSI

Deep incisional SSI

National Nosocomial Infections Surveillance System (NNIS)

3

2

1

0

Wound Class

Dirty-infected

Contaminated:Open, fresh, traumatic woundsinfected urine, bile

gross spillage from GI tract

Clean-contaminated:GI/GU tracts entered in a controlled manner

Lower

Higher

Clean

SSI RiskClassification

SSI – Risk StratificationNNIS Project (CDC)

• 3 independent variables associated with SSI risk:– ASA score > 2

• 1 to 5, from 1=“normal, healthy” to 5=“patient not expected to survive for 24 hours with OR without operation

– Contaminated or dirty/infected wound classification

• Clean, clean-contaminated, contaminated, dirty– Length of operation > 75th percentile

of the specific operation being performed

NNIS. CDC. Am J Infect Control. 2001;29:404-421.

ASA = American Society of Anesthesiology

NNIS = National Nosocomial Infection Surveillance

SSI: Wound Class versus NNIS Class

13.0%6.8%2.9%1.5%2.8%All

12.8%8.1%3.1%N/A7.1%Dirty infected

13.2%6.8%3.4%N/A6.4%Contaminated

N/A9.5%4.0%2.1%3.3%Clean contaminated

N/A5.4%2.3%1.0%2.1%Clean

NNIS 3NNIS 2NNIS 1NNIS 0AllWound Class

NNIS. CDC. Am J Infect Control. 2001;29:404-421.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Incidence of Surgical Site

Infection

Thoracic Hemiorraphy Mastectomy VascularType of Operation

012 to 3

Percent of SSI by type of operation and number of NNIS risk data, January 1992 to June 2004. Patients with 2 or 3 risk factors are combined, as there

was no difference between 2 or 3 risk factors for these particular procedures.Am J Infect Control 2004;32:470-485.

Risk Factors for SSI

Mangram et al. Infect Control Hosp Epidemiol. 1999;20:250-278.

Patient FactorsEnvironmental Factors

Treatment Factors

Risk Factors for SSI:Patient Factors

• Diabetes• Under-nutrition• Extremes of age• Skin or nasal carriage of staphylococci• Obesity• Ascites• Peripheral vascular disease (especially for lower extremity surgery)• Postoperative anemia• Prior site irradiation• Recent operation• Remote infection• Skin disease in the area of infection (e.g. psoriasis)• Chronic inflammation• Hypocholsterolemia• Hypoxemia• Corticosteroid therapy (controversial)

SSI: Reanalysis of Risk Factors• 5031 noncardiac surgery patients (1995 – 2000)• NSQIP prospective data collection• All preoperative risk factors evaluated as independent

predictors of SSI• SSI occurred in 162 (3.2% of study cohort)• Gram-positive organisms most common• Risk factors for SSI by multiple logistic regression

analysis:– Diabetes (IDDM and NIDDM)– Weight loss (within 6 months)– Ascites– Low postoperative hematocrit

Napolitano LM et al. J Surg Res. 2002 Mar;103(1):89-95.

Abdominal Hernias: Risk Factors for SSI

• 487 abdominal wall hernia patients (1995 – 2000)• NSQIP prospective data collection• SSI occurred in 4.3% of study cohort• Recurrent hernia in 15.1%• Risk factors for SSI by multiple logistic regression

analysis:– Low preoperative serum albumin– COPD– Steroid use

Napolitano LM et al. J Surg Res. 2003 May;111(1):78-84.

Risk Factors for SSI:Patient Factors

• Diabetes• Under-nutrition• Extremes of age• Skin or nasal carriage of staphylococci• Obesity• Ascites• Peripheral vascular disease (especially for lower extremity surgery)• Postoperative anemia• Prior site irradiation• Recent operation• Remote infection• Skin disease in the area of infection (e.g. psoriasis)• Chronic inflammation• Hypocholsterolemia• Hypoxemia• Corticosteroid therapy (controversial)

Nasal Mupirocin and SSI• 4030 patients enrolled, 3864 ITT• Prospective randomized double-

blind placebo controlled trial, intranasal mupirocin

• 891 patients (23.1%) had S aureusin anterior nares

• 444 mupirocin, 447 placebo• S aureus SSI: 2.3% mupirocin vs.

2.4% placebo• Among patients with nasal carriage

of S aureus, nosocomial S aureusinfections occurred in 4% of mupirocin pts vs. 7.7% placebo (OR 0.49, 95% CI 0.25-0.92, P = .02)

ITT = intent to treat.Perl et al. N Engl J Med. 2002;346:1871-1877.

1

1.5

2

2.5

3

Mupirocin Placebo

SSI

0

2,5

5

7,5

10

Mupirocin Placebo

S.aureus

P = NS

P = .02

Mupirocin and SSI• Prospective randomized study, n=395, Japan• Abdominal digestive surgery• Mupirocin 30 mg intranasal preoperative – 3 days,

no placebo control• All postoperative infections evaluated• 21 gram-positive SSI (10 vs 11)• Pneumonia decreased (0 vs 5, P = .028),

4 of 5 patients with MRSA in culture• Intranasal mupirocin had no significant impact on

SSI after digestive surgery

Suzuki et al. Br J Surg. 2003;90:1072-1075.

Mupirocin and SSI: Orthopedic Surgery

• University of Leeds, UK• Perioperative nasal

mupirocin for 5 days• Shower or bath with 2%

triclosan preoperative• Point prevalence nasal

MRSA carriage decreased (P < .001) at six-month intervals post-intervention

Wilcox et al. J Hosp Infect. 2003;54:196-201.

3.36 months after

MRSA SSI per 1000 CasesTime Period

4

23

12 months later

6 months prior

8%10%7%20%23%38%

beforeImmediately

after 6 months 6 months 6 months 6 months

Risk Factors for SSI:Environmental Factors

• Inadequate disinfection/sterilization• Inadequate skin antisepsis• Hair removal with shaving• Inadequate ventilation• Contaminated medications



Mitka. JAMA. 2000;283:44-45.

Preventing Surgical Infection Is More Important Than Ever

• The advent of antibiotic-defying pathogens reinforces the need for vigilance regarding strict sterile technique in the operating suite for prevention of SSI

SSI Preventive Strategies

• Hand Hygiene– Single most important method to limit cross

transmission of nosocomial pathogens• Strict sterile technique in OR• Strict infection control practices

Alcohol based hand hygiene solutions

Quick Easy to use

Very effective antisepsis due to bactericidal properties of alcohol

Infection Control



Chlorhexidine Prep• Kills more bacteria than all iodophors• Rapid activity against gram-positive and

gram-negative bacteria • Persistent antibacterial activity— prevents regrowth

of microorganisms on the skin for at least 48 hours • One application of ChloraPrep exceeds FDA criteria

for a patient preoperative skin preparation antiseptic • Unlike povidone iodine, ChloraPrep (CHG) remains

active in the presence of blood, serum, and other protein-rich biomaterials

• 50% reduction in the incidence of catheter-related bloodstream infections compared to povidone iodine (as shown in randomized, controlled trials)

Chlorhexidine Prep• Prospective study, n=125, foot/ankle surgery• Randomized to 3 preps

– DuraPrep (0.7% iodine, 74% isopropyl alcohol)– Techni Care (3% chloroxylenol)– Chlora Prep (2% chlorhexidine, 70% alcohol)

• Quantitative cultures from surgical site• ChloraPrep most effective in bacterial elimination

Ostrander et al. J Bone Joint Surg Am. 2005;87:980-985.



Pre-operative shaving• Shaving the surgical site with a razor induces

small skin lacerations– potential sites for infection– disturbs hair follicles which are often colonized

with S. aureus– Risk greatest when done the night before– Patient education

• be sure patients know that they should not do you a favor and shave before they come to the hospital!

What worked to eliminate razors in the preoperative patients?

• Many hospitals physically removed razors from the operating rooms and holding areas

• Clippers had to be readily available and training provided

• Patient education regarding no shaving of surgical site preoperatively

Risk Factors for SSI:Treatment Factors

• Inadequate antibiotic prophylaxis• Hypothermia• Prolonged operative time• Emergency procedure• Open vs. laparoscopic surgery• Hyperglycemia• Drains• Prolonged preoperative hospitalization• Supplemental Oxygen



Classen, et al. N Engl J Med. 1992;328:281.

Perioperative AntibioticsTiming of Administration

0

1

2

3

4

≤-3 -2 -1 0 1 2 3 4 ≥5

Hours from Incision

Infe

ctio

ns (%

)

14/369

5/6995/1009

2/180

1/81

1/411/47

15/441

Risk of SSI and Timing of Antimicrobial Prophylaxis

*p<0.0001 as compared to preoperative group.Classen DC, et al. The timing of prophylactic administration of antibiotics and the risk of surgical-wound infection. N Engl J Med 1992;326:281-286.

More than 2 h after skin

incision

Within 2 h after skin incision

(≤ 2 h before skin incision

> 2 hrs preop

Definition

44 (1.50)2847All

5.8*(2.4-13.8)

5.8* (2.6-12.3)

16* (3.30)488Postoperative

2.1(0.6-7.4)

2.4(0.9-7.9)

4 (1.40)282Perioperative

1.010 (0.59)1708Preoperative

4.3*(1.8-10.4)

6.7*(2.9-14.7)

14 (3.80)369Early

OR(95% CI)

RR(95% CI)

SSIn (%)

Patients(n)

Timing

Principles of Antibiotic Prophylaxis

Mangram et al. Infect Control Hosp Epidemiol. 1999;20:250-278.

Preoperative administration, serum levels adequate throughout procedure with a drug active

against expected microorganisms.

High Serum Levels1. Preoperative timing2. IV route3. Highest dose

of drug

During Procedure1. Long half-life2. Long procedure–

redose3. Large blood

loss–redose

Duration1. None after wound

closed2. 24 hours

maximum

www.medqic.org/sip

Bratzler et al. Arch Surg. 2005;140:174-182.

To reduce preventable surgical morbidity and mortality by 25% by 2010

www.medqic.org/scip

National Data Collection

• State-level baseline description from random sample of 788 cases per state, 2,965 hospitals

• Data collected from records by two professional clinical data abstraction centers

• Abstraction tool for hospitals is available and is JCAHO compatible

Bratzler DW et al. Arch Surg. 2005;140:174-182.

Surgical Infection Prevention (SIP):Results

205 (0.52)1,817 (4.7)

2 (0.01)1,461 (3.74)1,432 (3.66)

36 (0.09)

General ExclusionsSurgery of interest not performedInfection present pre-operativelyMissing antibiotic dates and timesPatient on antibiotics prior to admissionPatient on antibiotics for more than 24 hours pre-opOther

39,086 (100)Number of cases reviewedN (%)

34,133 (87.3)Cases eligible for analysis


Surgical Infection PreventionPerformance Stratified by Surgery1

55.7 (54.8-56.6)All Surgeries (11,220)

54.8 (51.4-58.3)Hysterectomy (432)46.0 (43.5-48.4)Colon (732)59.7 (58.3-61.2)Hip/knee (2,694)47.0 (44.0-49.9)Vascular (1,116)58.5 (56.8-60.2)Cardiac (3,287)

Antibiotic within 1 hour2

% (95% CI)Surgery (N)

1 All results are weighted to reflect adjustment based on the state-specific sampling scheme.2 Reflects data for only 11 220 cases that had an explicitly documented incision time.

These results include patients who received vancomycin between one and two hours before the incision (N=213).

Cases were excluded from this performance measure if there was insufficient data to determine the time interval between prophylactic antimicrobial dose and surgical incision (N=22,902). In addition, patients undergoing colon surgery who received oral antimicrobials only for prophylaxis were excluded from the denominator (N=11).


Antibiotic Timing Related to Incision

2.7 1.24.3

20.3

56

2.8 1.4 0.9 0.9

9.6

0

10

20

30

40

50

60

> 240

240-1

8118

0-121

120-6

1

60-0

0-60

61-12

012

1-180

181-2

40

> 240

Minutes Before or After Incision

Perc

ent

Inci

sion



92.6 (92.3-92.8)All Surgeries (33,229)

90.2 (89.0-91.3Hysterectomy (2,395)75.8 (74.6-77.0)Colon (4,855)97.2 (96.7-97.5)Hip/knee (14,996)91.5 (90.5-92.5)Vascular (3,140)95.1 (94.7-95.6)Cardiac (7,843)

Correct Antibiotic% (95% CI)Surgery (N)

1 All results are weighted to reflect adjustment based on the state-specific sampling scheme.

Antimicrobials were considered “prophylactic” if they were given before surgery, given intraoperatively, or given within 24 hours after the end of surgery.

Cases were excluded from this performance measure if no antimicrobials were administered, if no antimicrobials administered were considered “prophylactic,” or if there was insufficient data to make the determination on timing (N=336). In addition, because there are no published guidelines for antimicrobial selection for beta-lactam allergic patients undergoing colon surgery or hysterectomy, cases with a documented beta-lactam allergy that did not pass the performance measure for these two operations were excluded from the denominator (N=568).



40.7 (40.2-41.2)

77.9 (76.3-79.5)40.8 (39.5-42.2)36.7 (35.9-37.4)45.2 (43.4-47.0)34.4 (33.4-35.5)

Antibiotic Stopped within 24 hours

% (95% CI)

40.4

21.457.039.042.740.9

Median Time to Discontinuation

(Hours)

All Surgeries (32,603)

Hysterectomy (2,569)Colon (4,911)Hip/knee (14,575)Vascular (2,913)Cardiac (7,635)Surgery (N)

1 All results are weighted to reflect adjustment based on the state-specific sampling scheme.

Antimicrobials were considered “prophylactic” if they were given before surgery, given intraoperatively, or given within 24 hours after the end of surgery.

Cases were excluded from this performance measure if no antimicrobials were administered, if no antimicrobials administered were considered “prophylactic,” or if there was insufficient data to make the determination of timing (N=344). Any patient with documentation in the medical record of an infection during surgery or within 48 hours after the end of surgery was excluded fromthe denominator (N=634). In addition, patients who underwent more than one surgical procedure of interest during the hospitalization were excluded from the denominator (N=552).


Discontinuation of Antibiotics

Patients were excluded from the denominator of this performance measure if there was any documentation of an infection during surgery or in the first 48 hours after surgery.

26.2

10

22.6

6.2 6.32.2 2.7

9.3

14.5

40.7

50.7

73.379.5

85.8 88 90.7

0

20

40

60

80

100

12 or le

ss

>12-2

4

>24-3

6

>36-4

8

>48-6

0

>60-7

2

>72-8

4

>84-9

6

> 96

Hours After Surgery End Time

Perc

ent

0

20

40

60

80

100

Cum

ulat

ive

Perc

ent

National SIP Project

Conclusion:

“Substantial opportunities exist to improve the use of prophylactic antimicrobials for patients undergoing major surgery.”


* Based on medical record abstraction from the charts of patients discharged in the 1st quarter of 2004. Benchmark rates were calculated for all hospitals in the US based on discharges during calendar year 2003 using the Achievable Benchmarks of CareTM

methodology (http://main.uab.edu/show.asp?durki=14527).

Surgical Infection PreventionNational Baseline Performance, Qtr. 1, 2004

64.1

91

44.3

91.998.8

84.2

0

20

40

60

80

100

Antibiotics w/in 1 hour Correct Antibiotic Antibiotic DCed w/in 24hours

Perc

ent

National Ave.* National Benchmark

Surgical Infection Prevention ProjectNational Performance – 4th Quarter, 2004

*Denominator for the aggregate is 5,210

91

42

28

650

100All Three Measures*

Abx in 1 hour

Guideline Abx

Abx DCed in 24 h

*Denominator for the aggregate is 5,210

•Based on medical record abstraction from the charts of patients discharged in the 2nd quarter of 2005. Benchmark rates were calculated for all HQA reporting hospitals (N=1487) in the US based on discharges during the 2nd quarter of 2005 using the Achievable Benchmarks of CareTM methodology (http://main.uab.edu/show.asp?durki=14527).

Surgical Infection PreventionHospital Voluntary Self-Reporting, Qtr. 2, 2005

80

90

67.2

96.5 98.994.7

0

20

40

60

80

100

Antibiotics w/in 1 hour Correct Antibiotic Antibiotic DCed w/in 24hours

Perc

ent

Average* Benchmark

Surgical Infection Prevention ProjectMedicare Quality Improvement Community

Bratzler et al. Clin Infect Dis. 2004;38:1706-1715.



Temperature Control

• Control:– routine

intraoperative thermal care

– mean temp 34.7°C on arrival to PACU

• SSI 19% (18/96)

• Treatment:– active warming to

maintain normothermia

– mean temp 36.6°C on arrival to PACU

• SSI 6% (6/104)• P = 0.009

Kurz A, et al. N Engl J Med. 1996.

Melling AC, et al. Lancet. 2001. (preop warming)

200 colorectal surgery patients



Laparoscopic Surgery and SSI• Decreased incidence of SSI• For biliary, gastric, and colon surgery, subtract

one risk factor if procedure done laparoscopically• Laparoscopic appendectomy: decreased SSI if no risk

factors, but no difference if one risk factor present



Perioperative Glucose Control• 1,000 cardiothoracic surgery patients• Diabetics and non-diabetics with hyperglycemia

Patients with a blood sugar > 300 mg/dL during or within 48 hours of surgery had more than 3X the likelihood of SSI!

Latham R, et al. Infect Control Hosp Epidemiol. 2001.



Supplemental Perioperative Oxygen to Reduce the Incidence of Surgical Wound Infection

• Double-blind randomized controlled trial

• 3 hospitals (2 in Austria, 1 in Germany)

• N = 500, colorectal resection (cancer, inflammatory bowel disease)

• July 1996–October 1998

• FiO2 0.8 vs 0.3 during and 2 hours postoperative

• SSI during 14 days postoperative

Greif et al. N Engl J Med. 2000;342:161-167

Greif et al. N Engl J Med. 2000;342:161-167.

0.0113 (5.2)28 (11.2)SSI - no. (%)

PValue

Patients Who Received

80% Oxygen(N=250)

Patients Who Received

30% Oxygen(N=250)Characteristic

Supplemental Perioperative Oxygen to Reduce the Incidence of Surgical Wound Infection

SSI and the Routine Use of PerioperativeHyperoxia in a General Surgical Population:

A Randomized Controlled Trial

• Double-blind randomized controlled trial• Cornell University• N = 165, general surgery, general anesthesia• September 2001–May 2003• FiO2 0.8 vs 0.35 during and 2

hours postoperative• Overall SSI incidence = 18.1% (14 days)• No significant difference

Pryor et al. JAMA. 2004;291:79-87.

Supplemental Perioperative Oxygen and the Risk of Surgical Wound Infection:


• Prospective, Randomized, Double Blind, Controlled Trial, n=300, age 18–80 years

• Elective colorectal surgery• 14 Spanish hospitals,

3/1/03 to 10/31/04• Randomized to 30% vs

80% FiO2

• FiO2 intraoperative and for 6 hours after surgery

Belda et al. JAMA. 2005;294:2035-2042

Belda et al. JAMA. 2005;294:2035-2042

Supplemental Perioperative Oxygen and the Risk of Surgical Wound Infection:


Belda et al. JAMA. 2005;294:2035-2042

Bacteriologic Etiology of Infection

42

3127

15

50

10

20

30

40

50

MRSA CNS VRE

Taylor M and Napolitano L. Surg Infect. 2004;5:180-187

Perc

enta

ge In

fect

ed P

atie

nts

%

79 infected pts of 772 vascular surgery pts over 2 years (1/2000-12/2001)

MSSA Enterocococus

S aureus

MRSA in Cardiac Surgery– All 3,443 CABG patients received antimicrobial

prophylaxis– June 1997 through December 2000– Sternal SSI developed in 122 (3.5%)

• 71 (58.2%) were superficial SSI • 51 (41.8%) were deep SSI

– Gram-positive cocci most frequently recovered (81%)– S aureus most frequently isolated pathogen (49%)– Bacteremia in 18%, associated with deep SSI

(P = .002) and identified only in patients with S aureus infection

Sharma et al. Infect Control Hosp Epidemiol. 2004;25:468-471.

MRSA in Orthopedic SSI

• Prospective study; London, UK; 12 months, 2000• 1.6% of total with MRSA infection/colonization• Higher risk for MRSA infection

– Hip surgery– Emergency surgery for femoral neck fracture– Presence of wound was associated with

higher risk for MRSA infection• MRSA increased hospital LOS (88 vs 11d)• 41% MRSA patients still carried MRSA on discharge

Tai et al. Int Orthop. 2004;28:32-35.

Risk Factors for MRSA SSI

• Nasal or wound colonization with MRSA• Prior infection with MRSA• Prior antibiotic use• Previous cSSTI

Preventing Surgical Site Infections

Focus on modifiable risk factors

Streptococcus

Staphylococcus

SSI: Benchmarking for Prevention

• Prevention is key!!!– Antimicrobial prophylaxis – OR ventilation– Aseptic strict technique– Barriers, no shaving (clipping)– Surgical prep, surgical techniques– Normothermia– Glucose control– Supplemental oxygen

Clinicians hold the solution!

Campaign to Prevent

Antimicrobial Resistance

Centers for Disease Control and PreventionNational Center for Infectious Diseases

Division of Healthcare Quality Promotion

12 Steps to Prevent Antimicrobial Resistance Among Surgical Patients

• Step 1: Prevent surgical site infections (SSI)– Monitor and maintain normal

glycemia– Maintain normothermia– Perform proper skin preparation

using appropriate antiseptic agent and, when necessary, hair removal techniques

– Think outside the wound to stop surgical site infections

Documents

Surgical Site Infections: Known Risk Factors