Schwartz Surgical Infection Ppt 3p4r46

Surgical Infection Schwartz’s principle of surgery 10th edition (chapter 6)

Introduction • Sepsis is both the presence of infection and the host response to infection (systemic inflammatory response syndrome, SIRS). • Sepsis is a clinical spectrum, ranging from sepsis (SIRS plus infection) to severe sepsis (organ dysfunction), to septic shock (hypotension requiring vasopressors). • Outcomes in patients with sepsis are improved with an organized approach to therapy that includes rapid resuscitation, antibiotics, and source control.

introduction • Source control is a key concept in the treatment of most surgically relevant infections. • Infected or necrotic material must be drained or removed as part of the treatment plan in this setting. • Delays inadequate source control are associated with Worsened outcomes

Pathogenesis of Infection • Host Defenses skin or subcutaneous tissue are common. The mammalian host possesses several layers of endogenous defense mechanisms that serve to prevent microbial invasion, limit proliferation of microbes within the host, and contain or eradicate invading microbes. • Infection is defined by the presence of microorganisms in host tissue or the bloodstream. At the site of infection the classic findings of rubor, calor, and dolor in areas such as the skin or subcutaneous tissue are common

Relationship between infection and systemic inflammatory response syndrome (SIRS). Sepsis is the presence both of infection and the systemic inflammatory response, shown here as the intersection of these two areas. Other conditions may cause SIRS as well (trauma, aspiration, etc.). Severe sepsis (and septic

Criteria systemic inflammatory response syndrome General variable • Fever (core temp > 38,3oC) • Hypothermia (core temp < 36oC) • Heart rate > 90 bpm Altered mental status • Significant edema or positive fluid balance (>20 mL/kg over 24 h) • Hyperglycemia in the absence of diabetes Inflammatory variable • • • • •

Leukocytosis (WBC >12,000) Leukopenia (WBC <4000) Bandemia (>10% band forms) Plasma C-reactive protein >2 s.d. above normal value Plasma procalcitonin >2 s.d. above normal value

Criteria systemic inflammatory response syndrome Hemodynamic variable • Arterial hypotension (Systolic Blood Pressure <90 mm Hg, MAP <70, or Systolic Blood Pressure decrease >40 mmHg)

Organ dysfunction variables • • • • • • •

Arterial hypoxemia Acute oliguria Creatinine increase Coagulation abnormalities Ileus Thrombocytopenia Hyperbilirubinemia

Tissue perfusion variables • Hyperlactatemia • Decreased capillary filling

Microbiology Of Infectious Agents • Bacteria are responsible for the majority of surgical infections. Specific species are identified using Gram’s stain and growth characteristics on specific media. • Bacteria are classified based upon a number of additional characteristics, including morphology (cocci and bacilli), the pattern of division (e.g., single organisms, groups of organisms in pairs [diplococci], clusters [staphylococci], and chains [streptococci]), and the presence and location of spores

Microbiology Of Infectious Agents • Fungi Fungi typically are identified by use of special stains (e.g., potassium hydroxide (KOH), India ink, methenamine silver, or Giemsa). Initial identification is assisted by observation of the form of branching and septation in stained specimens or in culture. • Viruses Viral infection was identified by indirect means (i.e., the host antibody response).

Common pathogen in surgical patient:

Surgical Site Infections (SSIs) • Infections of the tissues, organs, or spaces exposed by surgeons during performance of an invasive procedure. • SSIs are classified into incisional and organ/space infections, and the former are further sub classified into superficial (limited to skin and subcutaneous tissue) and deep incisional categories. • The development of SSIs is related to three factors : (a) the degree of microbial contamination of the wound during surgery, (b) the duration of the procedure, and (c) host factors such as diabetes, malnutrition, obesity, immune suppression, and a number of other underlying disease states.

Surgical wounds • Classified based on the presumed magnitude of the bacterial load at the time of surgery: • Clean wounds (class I) include those in which no infection is present; only skin microflora potentially contaminate the wound, and no hollow viscus that contains microbes is entered. • Class I D wounds are similar except that a prosthetic device (e.g., mesh or valve) is inserted.

• Clean/contaminated wounds (class II) include those in which a hollow viscus such as the respiratory, alimentary, or genitourinary tracts with indigenous bacterial flora is opened under controlled

• Contaminated wounds (class III) include open accidental wounds encountered early after injury, those with extensive introduction of bacteria into a normally sterile area of the body due to major breaks in sterile technique (e.g., open cardiac massage), gross spillage of viscus contents such as from the intestine, or incision through inflamed, albeit nonpurulent tissue. • Dirty wounds (class IV) include traumatic wounds in which a significant delay in treatment has occurred and in which necrotic tissue is present, those created in the presence of overt infection as evidenced by the presence of purulent material, and those created to access a perforated viscus accompanied by a high degree of contamination.

PREVENTION AND TREATMENT OF SURGICAL INFECTIONS • General Principles

Maneuvers to diminish the presence of exogenous (surgeon

and

operating

room

environment)

and

endogenous (patient) microbes are termed prophylaxis, and consist of the use of mechanical, chemical, and antimicrobial modalities, or a combination of these methods.

PREVENTION AND TREATMENT OF SURGICAL INFECTIONS • Source Control

The primary precept of surgical infectious disease therapy consists of : • drainage of all purulent material • debridement of all infected • devitalized tissue, and debris, or removal of foreign bodies at the site of infection • plus remediation of the underlying cause of infection.

Principles relevant to appropriate antibiotic prophylaxis for surgery: • select an agent with activity against organisms commonly found at the site of surgery • the initial dose of the antibiotic should be given within 30 minutes prior to the creation of the incision • the antibiotic should be redosed during long operations based upon the half-life of the agent to ensure adequate tissue levels • the antibiotic regimen should not be continued for more than 24 hours after surgeryfor routine prophylaxis

Principle using antimicrobial agent for therapy of serious infection: • identify likely sources of infection • select an agent (or agents) that will have efficacy against likely organisms for these sources • inadequate or delayed antibiotic therapy results in increased mortality, so it is important to begin therapy rapidly with broader coverage • when possible, obtain cultures early and use results to refine therapy • if no infection is identified after 3 days, strongly consider discontinuation of antibiotics, based upon the patient’s clinical course, • Discontinue antibiotics after an appropriate course of therapy

conclusion • The incidence of surgical site infections can be reduced by: • • • •

appropriate patient preparation timely perioperative antibiotic istration maintenance of perioperative normothermia and normoglycemia appropriate wound management.

• The keys to good outcomes in patients with necrotizing soft tissue infection are early recognition and appropriate debridement of infected tissue with repeated debridement until no further signs of infection are present.

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