Department of OUTCOMES RESEARCH

Prevention of Surgical Wound Infections

Presented by:

Daniel Sessler, MD

Disclosure Slide• I have no personal financial interest related to the presentation.

• I work with many companies that make temperature monitoring and management systems through grant and research support.

Infection Prevention

Prophylactic Antibiotics

Smoking

Supplemental Oxygen

Normoglycemia

Normothermia

Fluid Management

Transfusion

www.OR.org

Surgical Site Infections

Common• >500,000 surgical site infections per year in the States• 1-3% incidence overall; ≈10% after colon surgery

Serious• Increases hospital duration ≈1 week•Doubles ICU admission and mortality

Costly• $1.6 billion annually in the United States• 3.7 million excess hospital days yearly in the States

CMS priority• SCIP measure• Probable “pay-for-performance” measure

Decisive Period

All wounds become contaminated

Infections established within 2 h of contamination

•Interventions most effective during “Decisive Period”

Progression to infection determined by•Prophylactic antibiotics

•Host defense

Prophylactic Antibiotics

Effective only during the decisive period•Subsequent administration useless (or harmful)

Should be given within 1 hour before incision•Repeat after 4-6 hours for long operations

•Discontinue within 24-48 hours

Various guidelines for type of antibiotic•In practice, surgeons choose antibiotics

•Our mission is to give them — on time

Host DefenseOxidative killing by neutrophils•Primary defense against surgical pathogens

Oxygen is transformed to superoxide radical•Killing determined by tissue oxygen

Oxygen also•Promotes angiogenesis

•Improves scar formation

Measuring Tissue Oxygen

Tissue oxygenation ≠ saturation; much lower than arterial PO2

Tissue Oxygen Correlates with Infection

Hopf, et al., 1996, Arch Surg

Supplemental Oxygen

Supplemental Oxygen•Easy to provide•Inexpensive (a few cents/patient)

Recent utilization•Usually 30% in Europe•Essentially random concentrations in the States

Rationale for various concentrations unclear

Postoperative Atelectasis: 30% vs. 80%

Greif, et al. NEJM, 2000

Hypothesis: 80% O2 reduces wound infection risk

500 patients having elective colon resection •Standardized antibiotic, anesthetic, & fluid management•Intraoperative core temperature maintained at 36oC

Randomization•30% oxygen (balance nitrogen); PaO2 ≈ 120

•80% oxygen (balance nitrogen) ; PaO2 ≈ 350

Wound infections•Wounds evaluated daily by a blinded observer•Pus and positive culture required for diagnosis

Subcutaneous Oxygen Tension (n=30)

Oxygen & Wound Infection

Effect of Infections

Infections prolong hospitalization by a full week

Oxygen Confirmation

PROXI Trial

30% vs. 80% perioperative oxygen•Randomized, blinded•1,400 patients

Primary result•Wound infection rates nearly identical

Why results differ from previous trials unclear

Meyhoff, Lancet 2009

Temperature and Infection

Hypothermia•Decreases tissue oxygen•Impairs numerous immune functions

Hypothesis: normothermia reduces infection risk

200 patients having elective colon resection•Standardized antibiotic, anesthetic, & fluid management•Randomized to normothermia or ≈2°C hypothermia

Wound infections•Wounds evaluated daily by a blinded observer•Pus and positive culture required for diagnosis

Hypothermia & Wound Infection

Wound Infections: Melling, et al.

Surgical Care Improvement Project (SCIP)

Patients included (denominator)•Surgical procedure •General or neuraxial anesthesia ≥60 minutes•Not having documented intentional hypothermia

Criteria (numerator)•Active over-body intraoperative warming, or•Core temp ≥36°C within 30 min before anesth end time, or•Core temp ≥36°C within 15 min after anesth end time

Comments•A similar “pay-for-reporting” measure coming•“Core temperature” sites and devices undefined

Transfusion can save lives•Appropriate triggers unknown

Associated with complications•Viral infection not major risk

Potential risk mechanisms•Highly immunogenic•Nitric oxide depletion

Blood Transfusion

Koch, et al., 2006, Crit Care Med

Older blood

Younger blood

N=11,963. Transfusions increase morbidities and infection

Marik & Corwin, 2008, Crit Care Med

Transfusions double infection risk

Berezina, et al., 2002, J Surg Res

Older blood

Younger blood

Stored blood degrades over time, especially after 2 weeks

Younger blood Older blood

Older Blood Increases Infection Risk

Newer blood (≤14 days) N=2,872

Older blood (>14 days) N=3,130

P

Sepsis 2.8% 4% 0.01

Pneumonia 2.8% 3.6% 0.11

Deep sternal infection

0.87% 0.80% 0.76

Multi-organ failure

0.24% 0.73% 0.007

Koch, et al., NEJM 2008

Prolonged blood storage increases morbidity and mortality

Older blood

Younger blood

Smoking and Infection

Tissue oxygen decreases: 65 ± 7 to 44 ± 3 mmHg•Jensen, et al. Arch Surg, 1991

Tissue oxygen 40-50 mmHg —> infection•Hopf, et al. Arch Surg, 1997

"Pack-a-day" smokers hypoxic most of the time

Habitual smoking increases infection risk 23%•Neumayer, et al. J Am Coll Surg, 2007

Effect of smoking perioperative cessation unclear

Hyperglycemia and Infection

Tight control of glucose improves immunity

•Gallacher et al. Diabet Med 1995

Glucose control maintains neutrophil phagocytosis

•Athos et al. Anesth Analg 1999

Mortality reduced by intensive insulin therapy in critical care patients (including cardiac surgery)

•Van Den Berghe et al., NEJM 2001

IntraOp Glucose & Major Complications

Glucose Concentrations Randomized

Aggressive Fluid Management

Volume management for colon resection•30 vs. 50 ml/kg crystalloid

Tissue oxygenation in arm (n=56)•81 ± 26 vs. 67 ± 18 mmHg, P = 0.03•Arkilic, et al. Surgery 2003

Similar wound infection risk (n=255)•11.3 vs. 8.5%, P = 0.46•Kabon, et al. Anesth Analg 2005

Major limitations•Small study with low power•Fluid management not titrated to individual need

Doppler-Guided Fluid Management

Speeds hospital discharge

Reduces composite complications

But does not reduce wound infection risk

Key citations•Gan, et al. Anesthesiology 2002•Noblett, et al. Br J Surg 2006•Wakeling, et al. Br J Anaesth 2005

Summary 1

Prophylactic antibiotics:•Give one hour before incision

Supplemental oxygen:•Does not cause atelectasis•Effect on surgical wound infection controversial

Maintaining normothermia:•Decreases wound infection risk 3-fold•Reduces the duration of hospitalization 20%

Summary 2

Red cell transfusions•Nearly doubles infection risk•Older blood worse than younger blood

Smoking:•Habitual smoking slightly increases risk•Effect of perioperative cessation on infection uncertain

Maintaining intraoperative glucose•Does not appear helpful in non-cardiac surgery•Unclear if helpful in cardiac surgery

Aggressive hydration does not appear to reduce infection risk•Doppler guidance improves outcomes

Recommendations

Timely antibiotic administration

Consider giving 80% intraoperative oxygen

Maintain Normothermia•Forced-air•Fluid warming

Reduce red cell transfusions

Smoking•Not smoking lowers risk•Perioperative cessation might help

Euglycemia and aggressive hydration•Probably prudent, but not shown to reduce infection risk

Department of OUTCOMES RESEARCH