Perioperative Infections and Antibiotics

Antibiotics are a critical tool in a physician’s arsenal when used appropriately. Although source control — physical measures used to control a focus of infection — remains an absolute priority, appropriate and judicious antibiotic use is an important adjunct in the treatment of infections. In this section, we provide basic information on diagnosis and management of perioperative infections, antibiotic treatment, and a summary table of key takeaways.

• Diagnosis

• Management

• Antibiotics

• Key Takeaways

Diagnosis

Diagnosing an infection requires consolidating information from both clinical assessment and laboratory evaluation. Early diagnosis and treatment are important to achieve improved outcomes. Common infections following surgery include wound infections, pneumonias, and urinary tract infections (UTIs).

Clinical Assessment

• A careful history should be obtained to identify infection risks (e.g., recent travel, immunosuppression, injection drug use, recent/frequent hospitalization, previous microbiology culture results).

• A clinical exam should include cardiopulmonary evaluation, surgical-site inspection, examination of areas of pain or tenderness (don’t forget to check the patient’s sacrum for wounds or decubitus ulcers).

• A variety of clinical signs may indicate an infection:

  • most common clinical signs: fevers (>38°C), hypotension, tachycardia, hypoxia

  • subtle signs: new-onset atrial fibrillation, delirium, and hypothermia

Laboratory Assessment

Laboratory tests include leukocyte count with differential, lactate level, glucose level, and metabolic base deficit.

• most common laboratory signs: new leukocytosis with neutrophilic predominance, worsening lactic acidosis

  • New leukocytosis immediately after any surgery, procedure, or trauma is normal and expected, but it should downtrend within 24-72 hours.

  • Persistent or rising leukocytosis after a period of normalization should be concerning for developing infection.

Imaging

Consider imaging to assist in workup (chest x-ray, ultrasound, computerized tomography).

• When obtaining a CT scan in patients with possible intra-abdominal infection, intravenous (IV) and per oral (PO) contrast can increase the diagnostic yield by highlighting tissue planes and spaces. In patients with contraindications or risks for IV or PO contrast, discuss clinical concerns with the surgical team and radiology before ordering scans.

Management

Source control — the definitive control of the infection through drainage or debridement — is the most important aspect of perioperative infection management. However, source control is not always feasible depending on the location of the collection, the stability of the patient, and the patient’s ability to heal. Antibiotics serve as an important management adjunct but should not be used in isolation.

Resuscitation

Fluids, fluids, fluids (see the Critical Care rotation guide and Fluids and Electrolytes in this rotation guide ).

• Physiologically, sepsis leads to vasodilation and leaky capillaries with resulting third spacing of fluids.

• Start with up to 20 cc/kg of crystalloid solution (e.g., lactated Ringer solution).

• If hypotension is severe or continues despite initial fluid resuscitation, the patient may require intensive care unit (ICU) admission and initiation of vasopressors (e.g., norepinephrine).

• Albumin is only indicated in select cases (cirrhosis, hepatorenal syndrome).

Source Control

• Surgical debridement is often necessary to treat wound infections, necrotizing skin and soft-tissue infections, abscesses, or free perforations of the gastrointestinal (GI) tract.

• Infected wounds cannot typically be closed initially and may require wound care or a temporary closure device to assist in wound healing. Placement of drains by interventional radiology or surgery is helpful for treating intra-abdominal or pelvic abscesses or when debridement is prohibitively morbid.

  • Wound-closure devices

    • Wound vacuum-assisted closure (VAC) dressings (see Wound Care below)

    • AbThera^TM (a negative pressure temporary abdominal closure that protects abdominal contents while suctioning fluids and drawing together the fascia)

Wound Care

The three major forms of dressings are wet-to-dry, packing, and wound vacuums.

• Wet-to-dry dressings are typically used for open wounds and allow for mechanical debridement of a wound by applying saline-moistened (not soaked) gauze, allowing the gauze to dry, and then removing the gauze at least once or twice a day.

• Packing is particularly helpful for abscess cavities to keep them open and draining while the wound heals by secondary intention (from the bottom up). Packing tape (regular, iodinated, or Mesalt®), wet-to-dry gauze, or diluted betadine-soaked gauze can be used for packing, depending on the size of the wound.

• Wound vacuums or negative pressure wound therapy (NPWT), first developed in the 1990s, rely on negative pressure to keep wounds clean and aid in granulation and contraction to decrease the wound burden.

  • The suction feature of wound vacuums is critical. Surgeons or wound care specialists should be notified if the wound vacuum is no longer maintaining suction.

Antibiotics

Answers to the following questions are important to determine when treating patients with surgical infections with antibiotics (see The Surgical Infection Society Revised Guidelines on the Management of Intra-Abdominal Infection):

What is the type of infection and the type of antibiotic?

If the patient needs empiric therapy prior to receiving culture results:

• Intra-abdominal infection: Ensure coverage of colonic flora, most commonly gram-negative rods (e.g., Escherichia coli) and anaerobes (e.g., Bacteroides fragilis).

• Upper gastrointestinal perforations (esophageal, gastric, and duodenal): Add antifungal coverage to above coverage given Candida spp. are part of normal flora.

  • Antifungal treatment is also indicated in the setting of fungemia (fungal growth detected in blood cultures or in aspirates from fluid collections).

• Pneumonia: Consider the underlying cause and whether it could be ventilator-associated, hospital-acquired vs. community acquired, or aspiration pneumonia and treat accordingly (see Pneumonia in the Adult Infectious Diseases rotation guide).

• Intra-abdominal infections: Treat with single-agent regimen of piperacillin-tazobactam every 6 hours or metronidazole IV or PO every 12 hours in combination with ceftriaxone IV once daily, depending on the local or institutional antibiogram.

• Clostridioides difficile infection: Treatment regimen is dependent on the severity of infection and whether it is an initial or recurrent episode.

  • 2021 Infectious Diseases Society of American guidelines recommend the use of fidaxomicin over vancomycin for both initial and recurrent episodes of C. difficile infection (see the Infectious Diseases rotation guide).

How should antibiotics be administered?

• Review of institutional or local antibiogram is strongly recommended to adjust medications to address local/regional resistance patterns.

• Develop a strong relationship with the clinical pharmacist to ensure that the medications chosen are appropriate for the clinical syndrome and are dosed appropriately (e.g., for renal dysfunction or obesity).

• Oral antibiotics are appropriate when a patient can tolerate oral intake without vomiting, the patient is clinically improving, and an oral option with good bioavailability is available.

  • The choice of antibiotic ideally is culture directed, but empiric options for typical abdominal infections include single-agent therapy with amoxicillin-clavulanate two to three times daily or metronidazole two times daily with levofloxacin once daily or ciprofloxacin twice daily.

• If the patient is not septic, attempt to hold initiation of antibiotics until deep cultures can be obtained (e.g., abdominal drain placement) to avoid reduced culture yield.

• In a septic patient, start broad antibiotic/antifungal coverage but attempt to narrow as soon as culture results are known.

  • In a septic patient with limited IV access, prioritize the antibiotic with broadest coverage first (unless a specific source is strongly suspected, [e.g., vancomycin for suspected methicillin-resistant Staphylococcus aureus (MRSA)]).

What is the duration of therapy?

Pick an end date to avoid antibiotic resistance and promote antimicrobial stewardship.

• After the confirmation of source control, studies indicate that short-course therapy can be sufficient in some cases. In a well-designed randomized, controlled trial, an average of 4 days of antibiotics after a source-control procedure (e.g., debridement or drain) was noninferior to longer courses. However, these data are only pertinent to intra-abdominal infections in immunocompetent patients in whom source control is thought to be achieved; clinical judgment must be used for patients who do not fit these criteria.

When should an infectious diseases consult be called?

• diagnostic uncertainty

• complex scenarios (immunocompromised patients, resistant organisms, treatment failure)

• no response to initial therapy

Risks Associated with Antibiotic Use

Antibiotics do not come without risk. Adverse effects during treatment include the following:

• acute kidney injury

• C. difficile infection

• antibiotic resistance

• drug interactions

• allergic reactions/anaphylaxis

Other Surgical Uses of Antibiotics

• perioperative prophylaxis: reduce the risk of surgical-site infections

• colonoscopy preparation: Nichols and Condon prep for colonoscopies (neomycin or erythromycin at 2:00 p.m., 3:00 p.m., and 10:00 p.m. the day prior to procedure)

Key Takeaways