Surgical Site Infection Prevention in Cardiac Surgery: Evidence-Based Strategies

Surgical site infections (SSIs) remain a significant cause of morbidity, mortality, and increased healthcare costs following cardiac surgery. Despite advances in surgical techniques and perioperative care, SSIs, particularly deep sternal wound infections (DSWIs) and mediastinitis, continue to challenge cardiac surgical teams worldwide. Implementing comprehensive, evidence-based prevention strategies is crucial to minimize the risk of these devastating complications. This article reviews the key components of SSI prevention bundles in cardiac surgery, focusing on preoperative, intraoperative, and postoperative measures.

Understanding Surgical Site Infections in Cardiac Surgery

Classification and Impact

Defining the scope of the problem:

Surgical site infections (SSIs) following cardiac surgery are classified based on the depth of tissue involvement, with significant implications for patient outcomes and healthcare resource utilization:

Superficial Incisional SSI:
– Involves only skin and subcutaneous tissue of the incision.
– Typically occurs within 30 days of the operation.
– Diagnosis requires at least one of the following:
Purulent drainage from the superficial incision.
Organisms isolated from aseptically obtained culture of fluid or tissue from the superficial incision.
At least one sign or symptom of infection (pain, tenderness, localized swelling, redness, heat) and incision deliberately opened by surgeon, unless culture-negative.
Diagnosis of superficial incisional SSI by surgeon or attending physician.
– Generally managed with local wound care and sometimes oral antibiotics.
– Lower morbidity compared to deeper infections but can impact recovery and patient satisfaction.

Deep Incisional SSI:
– Involves deep soft tissues (e.g., fascial and muscle layers) of the incision.
– Occurs within 30 or 90 days after the operative procedure (depending on presence of implant) and involves deep tissues.
– Diagnosis requires at least one of the following:
Purulent drainage from the deep incision but not from the organ/space component of the surgical site.
A deep incision spontaneously dehisces or is deliberately opened by a surgeon and is culture-positive or not cultured when the patient has at least one sign or symptom of infection.
An abscess or other evidence of infection involving the deep incision is found on direct examination, during reoperation, or by histopathologic or radiologic examination.
Diagnosis of deep incisional SSI by surgeon or attending physician.
– Often requires surgical debridement and parenteral antibiotics.
– Associated with increased length of stay and healthcare costs.

Organ/Space SSI (Mediastinitis/Deep Sternal Wound Infection – DSWI):
– Involves any part of the anatomy (e.g., organs or spaces), other than the incision, which was opened or manipulated during an operation.
– Specifically, in cardiac surgery, this refers primarily to mediastinitis or DSWI.
– Occurs within 30 or 90 days (depending on implant) and involves the organ/space.
– Diagnosis requires at least one of the following:
Purulent drainage from a drain placed through a stab wound into the organ/space.
Organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space.
An abscess or other evidence of infection involving the organ/space found on direct examination, during reoperation, or by histopathologic or radiologic examination.
Diagnosis of organ/space SSI by surgeon or attending physician.
– Most severe form of SSI after cardiac surgery.
– Associated with significantly increased morbidity, mortality (up to 25-50% in some series), prolonged hospitalization, multiple reoperations, and substantial healthcare costs.
– Often requires extensive surgical debridement, vacuum-assisted closure, and potentially flap reconstruction.

Impact of SSIs:
– Increased Mortality: DSWI is associated with a 2- to 4-fold increase in operative mortality.
– Prolonged Hospitalization: Patients with SSIs, especially DSWI, experience significantly longer hospital stays.
– Increased Costs: Treatment of DSWI can increase hospital costs by several hundred thousand dollars per patient.
– Reduced Quality of Life: Pain, prolonged recovery, cosmetic defects, and psychological distress impact patient well-being.
– Long-Term Complications: Chronic pain, sternal instability, and recurrent infections can occur.

Understanding these classifications and the profound impact of SSIs underscores the critical importance of implementing robust prevention strategies across the entire perioperative continuum.

Risk Factors

Identifying vulnerable patients:

Numerous patient-related and procedure-related factors contribute to the risk of developing SSIs after cardiac surgery. Identifying and modifying these risk factors where possible is a key component of prevention:

Patient-Related Risk Factors:
– Diabetes Mellitus:
Poor glycemic control (hyperglycemia) impairs immune function and wound healing.
Both preoperative and postoperative hyperglycemia increase SSI risk.
Diabetic patients have a 2- to 4-fold higher risk of DSWI.
– Obesity:
Body Mass Index (BMI) > 30 kg/m² is a significant risk factor.
Increased adipose tissue leads to poor vascularity, larger incisions, and higher bacterial load.
Difficulty with sternal closure and increased tension on the wound.
– Nasal Carriage of Staphylococcus aureus:
S. aureus is the most common pathogen causing SSIs in cardiac surgery.
Preoperative nasal colonization increases the risk of subsequent infection.
Both methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) strains are implicated.
– Chronic Obstructive Pulmonary Disease (COPD):
Impaired respiratory function increases risk of postoperative pulmonary complications.
Chronic steroid use associated with COPD impairs wound healing.
Coughing can increase stress on the sternal closure.
– Renal Failure:
Particularly dialysis-dependent renal failure.
Associated with immunosuppression, malnutrition, and altered wound healing.
– Peripheral Vascular Disease (PVD):
Indicates systemic atherosclerosis and potentially impaired wound perfusion.
Often associated with other comorbidities like diabetes.
– Immunosuppression:
Use of corticosteroids, chemotherapy, or immunosuppressants for transplantation.
Conditions like HIV/AIDS.
Impaired host defenses against infection.
– Malnutrition:
Low serum albumin levels (<3.5 g/dL) indicate poor nutritional status.
Impaired wound healing and immune function.
– Smoking:
Nicotine causes vasoconstriction, reducing tissue oxygenation.
Impairs fibroblast function and collagen synthesis.
Increased risk of pulmonary complications.
– Advanced Age:
Often associated with multiple comorbidities and frailty.
Potential decline in immune function and healing capacity.
– Female Sex:
Some studies suggest a slightly higher risk, potentially related to adipose tissue distribution or hormonal factors.
– Congestive Heart Failure (CHF):
Poor tissue perfusion and edema can impair wound healing.

Procedure-Related Risk Factors:
– Use of Bilateral Internal Mammary Arteries (BIMA):
Harvesting both IMAs can impair sternal blood supply, particularly in diabetics.
Increased risk of sternal dehiscence and infection.
– Prolonged Operative Time:
Longer duration of surgery increases tissue exposure and potential contamination.
Often associated with more complex procedures.
– Prolonged Cardiopulmonary Bypass (CPB) Time:
CPB induces a systemic inflammatory response and potential immunosuppression.
Longer bypass times correlate with increased infection risk.
– Emergency Surgery:
Limited time for preoperative optimization.
Often associated with hemodynamic instability and increased complexity.
– Reoperation:
Scar tissue, adhesions, and altered anatomy increase technical difficulty.
Potential for residual bacterial contamination from previous procedures.
– Excessive Use of Electrocautery:
Can cause tissue necrosis and impair healing.
– Poor Sternal Closure Technique:
Inadequate stabilization can lead to sternal dehiscence and subsequent infection.
– Blood Transfusions:
Associated with immunomodulation and increased infection risk.
– Postoperative Hypothermia:
Impairs immune function and wound healing.

Recognizing these risk factors allows for targeted preoperative optimization and heightened intraoperative and postoperative vigilance in high-risk patients, forming a crucial part of SSI prevention strategies.

Preoperative Prevention Strategies

Patient Optimization

Preparing the patient for surgery:

Optimizing the patient’s condition before cardiac surgery is a fundamental step in minimizing SSI risk. This involves addressing modifiable risk factors and ensuring the patient is in the best possible state for the procedure:

Glycemic Control:
– Target preoperative HbA1c levels (e.g., <7% or <8% depending on guidelines).
– Intensive management of hyperglycemia in the days leading up to surgery.
– Consultation with endocrinology for complex diabetic management.
– Education on diet and medication adherence.

Smoking Cessation:
– Strong recommendation to quit smoking at least 4 weeks before surgery.
– Provides time for improvement in pulmonary function and tissue oxygenation.
– Counseling, nicotine replacement therapy, and support programs.
– Even short-term cessation can offer benefits.

Nutritional Support:
– Screening for malnutrition using tools like NRS-2002 or MUST.
– Measurement of serum albumin and prealbumin levels.
– Consultation with nutritionists or dietitians for malnourished patients.
– Oral nutritional supplements or, in severe cases, enteral/parenteral nutrition preoperatively.
– Optimization may require delaying elective surgery.

Management of Obesity:
– Preoperative weight loss is ideal but often impractical for urgent cardiac surgery.
– Focus on optimizing associated comorbidities (diabetes, hypertension).
– Education on postoperative mobility and wound care.
– Consideration of specialized bariatric equipment if needed.

Optimization of Comorbidities:
– Management of heart failure to achieve euvolemic state.
– Treatment of active infections elsewhere in the body before elective surgery.
– Optimization of renal function where possible.
– Management of COPD, including potential pulmonary rehabilitation.

Medication Review:
– Discontinuation of immunosuppressants if possible and appropriate.
– Careful management of anticoagulants and antiplatelet agents.
– Assessment of steroid use and potential need for stress-dose coverage.

Preoperative Showering:
– Instructing patients to shower or bathe with an antiseptic agent (e.g., chlorhexidine gluconate – CHG) the night before and/or morning of surgery.
– Reduces skin bacterial burden.
– Multiple applications may be more effective.

Addressing these factors requires a coordinated effort involving the surgical team, primary care physicians, specialists, and the patient. While not all risk factors are modifiable, optimizing those that are can significantly contribute to reducing SSI rates.

Decolonization Protocols

Reducing the bacterial reservoir:

Nasal carriage of Staphylococcus aureus is a major risk factor for SSIs after cardiac surgery. Preoperative decolonization protocols aim to reduce or eliminate this bacterial reservoir:

Screening for S. aureus Carriage:
– Nasal swabs obtained preoperatively (e.g., at pre-admission testing).
– Testing for both MSSA and MRSA using culture or rapid PCR methods.
– Allows for targeted decolonization therapy.
– Universal decolonization (treating all patients regardless of screening results) is an alternative strategy used by some centers.

Decolonization Regimens:
– Mupirocin Nasal Ointment:
Applied intranasally twice daily for 5 days preoperatively.
Effective in reducing S. aureus colonization.
Resistance can emerge with widespread use, necessitating surveillance.
– Chlorhexidine Gluconate (CHG) Body Washes:
Used in conjunction with mupirocin.
Daily showers or wipes for several days preoperatively and potentially postoperatively.
Reduces overall skin bacterial burden.
– Combination Therapy:
Studies suggest the combination of nasal mupirocin and CHG bathing is most effective.

Targeted vs. Universal Decolonization:
– Targeted Approach: Treat only patients identified as carriers.
Requires reliable screening infrastructure.
May reduce overall antibiotic/antiseptic pressure and resistance development.
– Universal Approach: Treat all cardiac surgery patients.
Simplifies logistics, eliminates need for screening.
Ensures treatment even if screening is missed or results are delayed.
May lead to unnecessary treatment and potentially increased resistance.
Often preferred in high-risk populations or settings with high carriage rates.

Timing and Duration:
– Optimal duration of preoperative treatment is typically 5 days for mupirocin.
– Shorter courses may be used in urgent settings, but efficacy is less established.
– Postoperative application may provide additional benefit but requires further study.

Considerations for MRSA Carriers:
– Standard mupirocin/CHG protocol is generally effective.
– Some centers add vancomycin to the standard preoperative antibiotic prophylaxis regimen for known MRSA carriers.

Implementing decolonization protocols requires clear institutional guidelines, patient education, and mechanisms to ensure adherence. These protocols have been shown to significantly reduce S. aureus SSIs in cardiac surgery patients.

Intraoperative Prevention Strategies

Antibiotic Prophylaxis

Timing and selection are key:

Appropriate administration of prophylactic antibiotics is a cornerstone of SSI prevention in cardiac surgery:

Choice of Antibiotics:
– Primary recommendation: First- or second-generation cephalosporins (e.g., Cefazolin).
Effective against common skin flora, including MSSA and Streptococci.
Favorable safety profile and cost-effectiveness.
– Alternative for beta-lactam allergy: Vancomycin or Clindamycin.
Vancomycin provides coverage against MRSA but requires slower infusion.
Clindamycin covers gram-positives but lacks gram-negative coverage.
– Consideration for MRSA coverage:
Addition of Vancomycin for known MRSA carriers or in high-prevalence settings.
Routine addition of Vancomycin is controversial and may increase risk of VRE.

Timing of Administration:
– First dose should be administered within 60 minutes before surgical incision.
Allows adequate tissue concentration at the time of incision.
For Vancomycin or fluoroquinolones, infusion should start within 120 minutes before incision due to longer infusion times.
– Timing is critical for efficacy.

Redosing During Prolonged Procedures:
– Intraoperative redosing is necessary for procedures longer than two half-lives of the antibiotic or with excessive blood loss.
– Cefazolin typically redosed every 4 hours (or based on weight/renal function).
– Vancomycin redosing is generally not required due to its longer half-life.
– Redosing ensures adequate antibiotic levels throughout the operation.

Duration of Prophylaxis:
– Antibiotics should generally be discontinued within 24 hours after the end of surgery.
– Some guidelines suggest up to 48 hours for cardiac surgery, particularly if chest tubes remain.
– Prolonged prophylaxis beyond 48 hours has not shown benefit and increases risk of resistance and side effects (e.g., C. difficile infection).

Weight-Based Dosing:
– Adjusting antibiotic doses based on patient weight (especially for obese patients) is crucial to achieve adequate tissue concentrations.
– E.g., Cefazolin dose may need to be increased to 2g or 3g for patients >80kg or >120kg, respectively.

Proper antibiotic prophylaxis requires adherence to established protocols regarding selection, timing, redosing, and duration, tailored to patient factors like allergies and weight.

Surgical Technique and Environment

Maintaining sterility and minimizing tissue trauma:

Meticulous surgical technique and maintaining a sterile operating room environment are fundamental to preventing intraoperative contamination:

Operating Room Environment:
– Strict adherence to sterile protocols by all personnel.
– Minimizing OR traffic and conversation.
– Maintaining positive pressure ventilation with appropriate air filtration (HEPA filters).
– Regular environmental cleaning and disinfection.
– Proper temperature and humidity control.

Skin Preparation:
– Use of an alcohol-based antiseptic agent (e.g., chlorhexidine-alcohol) for skin preparation unless contraindicated.
– Allowing adequate drying time before incision.
– Proper draping to isolate the surgical field.

Hair Removal:
– Avoid shaving with razors, as it causes micro-abrasions.
– If hair removal is necessary, use electric clippers immediately before the operation.
– Clipping outside the operating room is preferred.

Surgical Technique:
– Gentle tissue handling to minimize devitalization.
– Judicious use of electrocautery.
– Maintaining adequate hemostasis to prevent hematoma formation (a nidus for infection).
– Minimizing operative time where possible without compromising safety.
– Use of wound protectors or impervious drapes to shield wound edges.
– Irrigation of the surgical site before closure (evidence for antiseptic irrigation is mixed).

Sternal Closure:
– Ensuring stable sternal approximation.
– Use of appropriate wire gauge and number based on patient factors (e.g., obesity, osteoporosis).
– Techniques like figure-of-eight wiring or sternal plating in high-risk patients.
– Ensuring wires are not overly tightened to avoid tissue necrosis.

Instrument Sterilization:
– Strict adherence to protocols for cleaning, disinfection, and sterilization of surgical instruments.
– Regular monitoring of sterilization equipment efficacy (e.g., biological indicators).
– Avoiding flash sterilization for routine instruments.

Double Gloving:
– May reduce risk of contamination from glove perforations, although evidence is not definitive.

Attention to these details throughout the intraoperative period is crucial for minimizing the introduction of pathogens into the surgical site.

Postoperative Prevention Strategies

Wound Care and Monitoring

Vigilance after surgery:

Postoperative care focuses on protecting the incision, monitoring for early signs of infection, and continuing relevant preventive measures:

Wound Dressing:
– Application of a sterile dressing at the end of the operation.
– Keeping the incision covered with a sterile dressing for 24-48 hours postoperatively.
– Use of occlusive dressings may offer additional protection.
– Changing dressings using aseptic technique if they become wet or soiled.

Incision Care:
– Patient education on proper hand hygiene before touching the incision area.
– Instructions on showering (timing varies by institutional protocol, often after 48 hours if incision is healing well).
– Avoiding soaking the incision (no baths, hot tubs, swimming) until fully healed.
– Monitoring for signs of infection: increasing redness, swelling, warmth, pain, or purulent drainage.

Glycemic Control:
– Maintaining strict postoperative glycemic control (e.g., blood glucose <180 mg/dL).
– Use of continuous insulin infusions may be necessary in the early postoperative period.
– Transition to subcutaneous insulin regimens as patient recovers.
– Crucial for optimal immune function and wound healing.

Normothermia:
– Maintaining normothermia in the postoperative period.
– Active warming measures if necessary.
– Hypothermia can impair immune function.

Sternal Precautions:
– Educating patients on sternal precautions (e.g., avoiding lifting heavy objects, using arms for support when moving) for 6-8 weeks.
– Helps maintain sternal stability during healing.
– Use of sternal vests or supports in high-risk patients.

Early Mobilization:
– Encouraging early ambulation improves circulation and pulmonary function.
– Reduces risk of general postoperative complications.

Antibiotic Duration:
– Discontinuing prophylactic antibiotics within 24-48 hours as per protocol.

Drain Management:
– Aseptic management of chest tubes and mediastinal drains.
– Prompt removal when drainage criteria are met.

Surveillance for Infection:
– Regular assessment of the surgical incision by clinical staff.
– Monitoring vital signs, white blood cell count, and inflammatory markers.
– Prompt investigation of any suspected infection.

Post-Discharge Follow-up:
– Clear instructions for patients on wound monitoring at home.
– Scheduled follow-up appointments for wound assessment.
– Providing contact information for concerns or questions.

Consistent application of these postoperative measures helps protect the healing wound and allows for early detection and management of any developing SSIs.

SSI Bundles and Quality Improvement

Systematic approach to prevention:

Implementing SSI prevention strategies effectively often involves bundling multiple evidence-based interventions together and integrating them into routine clinical practice through quality improvement initiatives:

SSI Prevention Bundles:
– Definition: A structured set of evidence-based practices that, when implemented collectively, improve outcomes more than implementing individual practices alone.
– Key Components Typically Included:
Appropriate hair removal (clipping, not shaving).
Preoperative CHG showering.
S. aureus screening and decolonization (mupirocin/CHG).
Appropriate antibiotic prophylaxis (selection, timing, redosing, duration).
Strict perioperative glycemic control.
Maintaining postoperative normothermia.
Meticulous surgical technique and sterile environment.
– Rationale: Addresses multiple risk factors simultaneously across the perioperative continuum.
– Implementation: Requires multidisciplinary collaboration, standardized protocols, checklists, and education.

Quality Improvement (QI) Initiatives:
– Data Collection and Surveillance:
Systematic tracking of SSI rates using standardized definitions (e.g., NHSN).
Stratification by procedure type and surgeon.
Monitoring adherence to bundle components.
– Feedback and Benchmarking:
Regular reporting of SSI rates and bundle compliance to clinical teams.
Comparison to internal targets and external benchmarks.
– Process Analysis and Improvement:
Identifying barriers to adherence.
Root cause analysis of infections that occur despite bundle use.
Iterative refinement of protocols based on data and feedback.
– Education and Training:
Ongoing education for all staff involved (surgeons, nurses, anesthesiologists, perfusionists, etc.).
Reinforcement of best practices.
– Leadership Support and Culture of Safety:
Institutional commitment to SSI prevention.
Empowering staff to speak up about potential breaches in protocol.
Celebrating successes and learning from failures.

Examples of Successful Programs:
– Numerous institutions have reported significant reductions in cardiac SSI rates (often >50%) after implementing comprehensive bundles and QI programs.
– Success often depends on consistent adherence to all bundle elements.

Challenges:
– Achieving high compliance rates across all bundle elements.
– Sustaining improvements over time.
– Adapting bundles to local context and emerging evidence.
– Resource allocation for screening, monitoring, and QI activities.

Using bundled interventions within a structured QI framework provides a powerful, systematic approach to reducing SSIs in cardiac surgery, requiring ongoing effort and commitment from the entire healthcare team.

Tıbbi Sorumluluk Reddi

Önemli Uyarı: This information is provided for educational purposes only and does not constitute medical advice. Surgical site infection prevention strategies are complex and require implementation by qualified healthcare professionals within established institutional protocols. The specific recommendations may vary based on patient populations, local epidemiology, and evolving evidence. This article is not a substitute for professional medical judgment, diagnosis, or treatment. Adherence to infection control guidelines is critical for patient safety in cardiac surgery.

Sonuç

Surgical site infections following cardiac surgery, particularly deep sternal wound infections, represent a major clinical challenge with severe consequences for patients and significant burdens on healthcare systems. Prevention requires a multifaceted approach encompassing the entire perioperative period. Key strategies include meticulous preoperative patient optimization, targeted decolonization protocols, appropriate antibiotic prophylaxis, rigorous intraoperative sterile technique, and vigilant postoperative care with strict glycemic control and wound monitoring.

The implementation of evidence-based SSI prevention bundles, integrated within a continuous quality improvement framework, has proven effective in significantly reducing infection rates. Success hinges on a multidisciplinary commitment, standardized protocols, consistent adherence monitoring, and a culture of safety. By systematically addressing patient-related and procedure-related risk factors, cardiac surgical teams can substantially mitigate the risk of SSIs, improving patient outcomes and enhancing the overall safety of these life-saving procedures.