Prevention of Surgical
Wound Infections
Presented by:
Daniel Sessler, MD
Department of OUTCOMES RESEARCH
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
Supplemental Oxygen
Normothermia
Transfusion
www.OR.org
Smoking
Normoglycemia
Fluid Management
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 Defense
Oxidative 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%
10
8
6
Atelectasis
4
(%)
2
0
30
80
FiO2 (%)
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)
200
PsqO2
(mmHg)
150
80% FiO2
100
30% FiO2
50
Intra-op
0
1
2
3
Post-op
4 0 1
Time (h)
2
3
Oxygen & Wound Infection
Effect of Infections
Number
Hospitalization
(days)
Infec t e d
Uninfec t e d
40
460
18 ± 9
11 ± 4
P
<0.00 1
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.
Wound Infection (%)
16
P = 0.001
12
8
4
0
Hypothermic
Normothermic
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
Blood Transfusion
Transfusion can save lives
• Appropriate triggers unknown
Associated with
complications
• Viral infection not major risk
Potential risk mechanisms
• Highly immunogenic
• Nitric oxide depletion
Koch, et al., 2006, Crit Care Med
Stroke
Cardiac Morbidity
Infection
Pulmonary Failure
Younger blood
Renal Failure
Older blood
1.0
1.5
2.0
2.5
Adjusted OR (95% CI)
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
Younger blood
Older blood
Younger blood
Older blood
Stored blood degrades over time, especially after 2 weeks
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
Younger blood
Older blood
Prolonged blood storage increases morbidity and mortality
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