Surgical Intensive Care Medicine by John M. O'Donnell & Flávio E. Nácul

Author:John M. O'Donnell & Flávio E. Nácul
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

General Principles

Infection and Diagnosis

Fever is a common occurrence in the postoperative patient [1]. This can reflect developing infection but also may stem from a myriad of noninfectious sources [2], most frequently arising within 48 h of surgery. Differentiating these causes is essential to optimal care and serves to minimize excessive antibiotic use and its aftereffects. It must also be acknowledged that fever is a natural defense mechanism and is itself only rarely harmful [3].

In addition to the common infectious causes of postoperative fever—surgical site infection, central venous catheter infection, ventilator-associated pneumonia, urinary tract infection, Clostridium difficile-associated disease, and occasional cholecystitis, sinusitis, meningitis, or epidural catheter infection—fever may be associated with atelectasis, allergic drug reactions (frequently to beta-lactam antibiotics or phenytoin), infusion of blood products, pancreatitis, alcohol withdrawal, malignant hyperthermia, or neuroleptic malignant syndrome [4]. Serotonin syndrome , a potentially life-threatening combination of fever, agitation, and autonomic instability, may stem from the use of linezolid when combined with monoamine oxidase inhibitors, serotonin reuptake inhibitors (SSRIs), tramadol, or meperidine [5, 6]. These manifestations may be easily overlooked, given the sedative properties common to several of these drugs.

Similarly, abnormal chest radiographs may reflect pneumonia or can result from numerous noninfectious causes, such as pleural effusions, congestive heart failure, aspiration pneumonitis, pulmonary hemorrhage, or acute respiratory distress syndrome (ARDS) (see Chap. 25). A diagnosis of pneumonia is the single largest reason for antibiotic use in the ICU, yet clinical diagnosis may only be correct about half the time [7], driving unnecessary antibiotic consumption while risking adverse effects. Careful consideration of the diagnosis is thus imperative.

An early and aggressive diagnostic search for sources of infection helps to optimize anti-infective therapy [4, 8]. Knowing the site of infection is the most important determinant of drug choice and administration. Identifying a specific etiologic agent allows honing initial empiric therapy to the most effective, narrowest spectrum agent with the fewest side effects. The alternative strategy of rapidly initiating an aggressive, broad-spectrum regimen that “covers everything” often results in ballooning empiricism, treating symptoms without addressing the source. This delays effective, specific therapy, prolonging ICU length of stay and facilitating development of resistance.

Cultures should be obtained immediately when suspecting sepsis or significant infection, before initiating antibiotics. These should include peripheral blood cultures ; a blood culture from an intravascular catheter in place >48 h or suspected of contamination (generally limited to no more than three blood cultures in 24–48 h); urine with urinalysis; tracheal secretions if pneumonia is suspected (quantitative bronchoscopic or non-bronchoscopic bronchoalveolar lavage are preferable); deep wound cultures ; percutaneous drainage cultures if a collection is found; and stool detection of C. difficile if there is diarrhea. Pre-existing drainage catheters are often contaminated within 24–48 h; cultures from these sources should be approached with great caution. Cell counts, particularly from spinal fluid drains, may be invaluable.

Diagnostic imaging should be obtained expeditiously. A computed tomography (CT) scan often helps to differentiate pneumonia from pleural effusion or scar and may identify infarctions, occult abscesses, anastomotic leaks, fistulas, or fluid collections. Some of these may be amenable to CT- or ultrasound-guided percutaneous drainage and culture.

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