Antimicrobial therapy should be based on infection site, host defenses, antibiotic pharmacokinetics and pharmacodynamics, and local microbial susceptibility patterns.
Antibiotic use, especially of broad-spectrum drugs, is often inappropriate and may lead to microbial resistance. The Centers for Disease Control and Prevention (CDC) encourage the development of formal antibiotic stewardship programs to encourage the judicious use of antibiotics and minimize adverse events.
The term catheter-associated infection, which indirectly associates a bloodstream infection with the current or recent presence of a catheter, is designed for surveillance, whereas a catheter-related bloodstream infection is directly attributable to a catheter.
The optimal location to avoid a catheter-related infection is controversial, although most data favor subclavian placement. In hospitalized patients, peripherally inserted central catheter (PICC) lines have infection rates similar to those for central catheter placement in other locations.
Bacteria causing ventilator-associated pneumonia are similar to those in other hospitalized patients. The efficacy of “bundles” for their prevention is controversial.
Prophylactic antibiotics for surgery should be administered for all clean-contaminated and contaminated wounds as well as for hysterectomies and most invasive urologic procedures. With a few exceptions, they should be discontinued within 24 hours.
This chapter is intended to provide a general overview of principles of antimicrobial therapy and to address practices and issues that will likely be encountered by anesthesiologists perioperatively and in surgical intensive care units (ICUs). Discussed within this scope are the pharmacologic and clinical principles that underlie antimicrobial use, distinguishing between what is known from what is suggested by consensus but lacks definitive evidence and what needs further study. For more comprehensive information, there are many excellent textbooks devoted to infectious diseases.1,2 The focus is primarily on antibiotic and antifungal therapeutics, addressing only briefly human immunodeficiency virus (HIV) prophylaxis and drugs because this is a subject unto itself, generally relegated to infectious disease experts. More specific information on newer antibiotics, such as cyclic lipopeptides, glycylcyclines, ketolides, oxazolidinones, streptogramins, and newer fluoroquinolones, can be found in textbooks1,2 and review articles.3,4
GENERAL PRINCIPLES OF ANTIMICROBIAL THERAPY
It is important to recognize the different characteristics, antimicrobial spectra, and mechanisms of action among the various antibiotic classes (Table 16-1). For example, some antibiotic classes (eg, tetracyclines) are bacteriostatic, meaning they inhibit bacterial growth but generally require functional leukocytes to kill them. In contrast, bacteriocidal antibiotics, such as fluoroquinolones, directly kill bacteria. However, this distinction is sometimes blurred depending on the dose, the environment, and the particular bacteria.5 Another important difference among antibiotic classes is their mechanisms of action, especially the distinction between antimicrobials that directly affect cell wall synthesis and those that affect protein or nucleic acid synthesis. β–Lactams and vancomycin are examples of the former, whereas aminoglycosides, macrolides, glycylcyclines (eg, tigecycline), and fluoroquinolones are examples of the latter.