Surgical Site Infections and Sternal Complications

Surgical site infections are infections of the tissues involved in an operation, occurring within a defined window after surgery. In cardiac surgery the most serious form is deep sternal wound infection, which can extend into the mediastinum (mediastinitis) after median sternotomy and is a feared complication with substantial associated morbidity.

Definition

A surgical site infection is an infection occurring at or near a surgical incision within the postoperative period; in cardiac surgery, sternal wound complications range from superficial incisional infection to deep sternal wound infection with mediastinitis.

Scope

This topic covers surgical site infections after cardiothoracic surgery, with particular attention to sternal wound complications and mediastinitis following median sternotomy: how these infections are defined and classified, recognized risk factors, and the structure of prevention evidence. It is reference material on a clinical entity, describing how the condition is characterized rather than directing treatment.

Core questions

• How are surgical site infections defined and classified?
• What distinguishes superficial sternal infection from deep sternal wound infection and mediastinitis?
• Which factors increase the risk of sternal wound complications?
• How is prevention of surgical site infection structured in guidelines?

Key concepts

• Superficial, deep, and organ/space surgical site infection
• Deep sternal wound infection
• Mediastinitis after median sternotomy
• Perioperative glycaemic control
• Antimicrobial prophylaxis and skin preparation
• Risk factors (diabetes, obesity, bilateral internal mammary harvest)

Mechanisms

Surgical site infection develops when microorganisms — often from the patient's own skin flora — contaminate the wound and overcome host defences, with risk shaped by the surgical insult, tissue perfusion, and host factors such as hyperglycaemia and obesity. After median sternotomy, infection can track from the skin into the sternum and the underlying mediastinum, producing deep sternal wound infection and mediastinitis; impaired sternal healing and reduced blood supply contribute. Prevention strategies target these pathways: antimicrobial prophylaxis, skin antisepsis, normothermia and tissue oxygenation, and perioperative glycaemic control, which has been associated with lower rates of deep sternal wound infection in diabetic patients.

Clinical relevance

Classifying surgical site and sternal infections and their risk factors helps explain why specific perioperative prevention measures are emphasized and how outcomes are reported in cardiac surgery. This entry describes the entity and prevention evidence at a conceptual level; it does not prescribe antibiotic choice, glycaemic targets, or wound management for an individual patient, which are decisions for the responsible clinical team.

Epidemiology

Surgical site infection is among the more frequent healthcare-associated infections, and deep sternal wound infection, though relatively uncommon after cardiac surgery, carries high associated morbidity and mortality. Recognized risk factors include diabetes, obesity, and bilateral internal mammary artery harvesting, and prevention is addressed by national guidelines.

History

Standardized definitions of surgical site infection, including the superficial, deep, and organ/space categories, were established to support surveillance and prevention. In cardiac surgery, work in the 1990s linked perioperative glycaemic control to reduced deep sternal wound infection, and the CDC's 2017 guideline consolidated evidence-based prevention recommendations.

Debates

Internal mammary artery harvesting and sternal wound risk

Bilateral internal mammary artery grafting offers potential long-term graft benefits but has been associated with greater risk of sternal devascularization and deep wound infection, especially in higher-risk patients, making the trade-off a recurring surgical consideration.

Key figures

• Sandra I. Berríos-Torres
• Anthony P. Furnary

Seminal works

• berrios-torres-2017
• furnary-1999

Frequently asked questions

What is a deep sternal wound infection?

It is an infection that extends beyond the skin into the sternum and often the mediastinum after median sternotomy; when the mediastinum is involved it is called mediastinitis, a serious complication of cardiac surgery.

How are surgical site infections classified?

They are commonly categorized as superficial incisional, deep incisional, or organ/space infections, based on the depth and tissues involved, using standardized surveillance definitions.