Bacterial Sepsis Workup
- Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD more...
Workup for sepsis may include the following:
Blood and urine studies, including appropriate cultures
Diagnostic imaging of the chest and abdomen/pelvis
Cardiac studies such as ECG and troponins, as indicated
Interventions such as paracentesis, thoracentesis, lumbar puncture, or aspiration of an abscess, as clinically indicated
Measurement of biomarkers of sepsis such as procalcitonin levels
Histologic examination is generally unhelpful, because sepsis does not cause diagnostic findings in various organs.
Complete blood cell count
A complete blood cell (CBC) count is usually not specific, because of the numerous conditions that mimic sepsis and produce leukocytosis with variable degrees of a left shift. Leukocytosis with a left shift is a nonspecific diagnostic finding that is as common in noninfectious states as in infection. Leukopenia, anemia, and thrombocytopenia may be observed in sepsis.
Obtain blood cultures in all patients upon admission to demonstrate the organism responsible for infection. Negative blood culture results are also necessary to include pseudosepsis in the differential diagnosis. Blood culture isolates might suggest the underlying disease process. Bacteroides fragilis suggests a colonic or pelvic source, whereas Klebsiella species or enterococci suggest a gallbladder or urinary tract source.
If central intravenous (IV) line sepsis is suspected, remove the line and send the tip for semiquantitative bacterial culture. If culture of the catheter tip yields positive results and demonstrates 15 or more colonies and if the isolate from the tip matches the isolate from the blood culture, an infection associated with the central IV line is diagnosed.
The rationale for nasal cultures is that nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is often viewed as a potential marker of subsequent risk for severe MRSA infection. However, a meta-analysis found nasal colonization with MRSA to be a poor predictor for the subsequent occurrence of MRSA lower respiratory tract infections and MRSA bloodstream infections that require antimicrobial treatment. Thus, caution should be exercised in interpreting nasal cultures in patients in the intensive care unit (ICU).
Buffy coat analysis of CBC may be useful in identifying certain infectious agents.
Although the yield is low, stained buffy coat smears, if positive, are the best available rapid tests for demonstrating organisms that cause bacteremia. If the stained buffy coat smear yields a positive result, it demonstrates the morphology of the bacteria that is causing the bacteremia, which provides rapid information on which to base empiric antimicrobial therapy.
If urosepsis is suspected, obtain a urine Gram stain, urinalysis, and urine culture. A systematic review found that in adult ICU patients, catheter-associated urinary tract infection was associated with significantly higher mortality and a longer stay.
Chest radiography is important to rule out pneumonia and diagnose other causes of pulmonary infiltrates, such as the following:
Pulmonary drug reactions
Primary or metastatic pulmonary neoplasms
Lymphangitic spread of malignancies
Large pleural effusions
Congestive heart failure (CHF)
Acute myocardial infarction (MI)
Acute respiratory distress syndrome – This condition should suggest an intra-abdominal source (eg, acute pancreatitis)
Abdominal Ultrasonography, CT, and MRI
Perform abdominal ultrasonography if biliary tract obstruction is suspected on the basis of the clinical presentation. However, abdominal ultrasonography is suboptimal for the detection of abscesses or perforated hollow organs. Ultrasonograms in patients with cholecystitis may show a thickened gallbladder wall or biliary calculi but no dilatation of the common bile duct (CBD). Stones in the biliary tract are visible in patients with cholangitis, but the CBD is dilated.
Use computed tomography (CT) or magnetic resonance imaging (MRI) of the abdomen if a nonbiliary intra-abdominal source of infection is suspected on the basis of the history or physical examination findings. These 2 imaging modalities are superior to ultrasonography in demonstrating all lesions, except those related to the biliary tract. Abdominal CT or MRI is also helpful in delineating intrarenal and extrarenal pathology. Gallium or indium scanning has no place in the initial workup of sepsis; patients with sepsis are acutely ill by definition, and rapid diagnostic tests (eg, CT or MRI of the abdomen and ultrasonography of the right upper quadrant) are time-critical, life-saving tools.
If an acute MI is likely, perform electrocardiography (ECG) and obtain cardiac enzyme levels. Remember that certain patients may present with a silent, asymptomatic MI, which should be included in the differential diagnosis of otherwise unexplained fever, leukocytosis, and hypotension. Silent MIs are common in elderly patients and in those who have recent undergone abdominal or pelvic surgical procedures. They are also common in individuals with alcoholism, diabetes, and uremic conditions.
Perform thoracentesis for diagnostic purposes in patients with substantial pleural effusion. Perform paracentesis in patients with gross ascites.
In some cases, a Swan-Ganz catheter may be useful in managing the fluid status of the patient and in assessing left ventricular dysfunction. However, routine use is not recommended.
A study from van Nieuwkoop et al examined the use of PCT levels in predicting bacteremia in a group of 581 patients, 136 of whom had bacteremia; PCT levels successfully identified 94-99% of the patients with bacteremia. Use PCT for blood cultures.
Heyland et al, in a systematic review of the economic value of PCT-guided reduction in antibiotic use in intensive care, found that with hospital mortality and length of stay unchanged, PCT testing to reduce antibiotic treatment broke even when daily antibiotics cost about $150 in Canadian dollars. The authors concluded that under some conditions, PCT testing could result in savings from reduced antibiotic use, but they were unable to exclude a possible 7% hospital mortality increase.
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|Associated With Sepsis (Fever ≥102°F)||Not Associated With Sepsis (Fever ≤102°F)|
|GI tract source
|GI tract source
Small bowel disorders
|GU tract source
Intra- or perinephric abscess
Urinary tract obstruction
Instrumentation in patients with bacteriuria
|GU tract source
Catheter-associated bacteriuria (in otherwise healthy hosts without genitourinary tract disease)
|Upper respiratory tract source
|Lower respiratory tract source
Community-acquired pneumonia (with asplenia)
|Lower respiratory tract source
Community-acquired pneumonia (in otherwise healthy host)
IV line sepsis
Infected prosthetic device
Acute bacterial endocarditis
Uncomplicated wound infections
Acute bacterial endocarditis
Myocardial/perivalvular ring abscess
Subacute bacterial endocarditis
|CNS = central nervous system; GI = gastrointestinal; GU = genitourinary; IV = intravenous.|
|Adapted from: Cunha BA, Shea KW. Fever in the intensive care unit. Infect Dis Clin North Am. Mar 1996;10(1):185-209.|
|Clinical Presentations Mimicking Sepsis||Hemodynamic Parameters Mimicking Sepsis|
|Myocardial infarction||Spinal cord injury|
|Diabetic (abdominal crisis) ketoacidosis|
|Systemic lupus erythematosus flare with abdominal crisis|
|Microbiologic||No definite source PLUS ≥1 abnormalities
Negative blood cultures excluding contaminants
|Proper identification/process/source PLUS ≥1 microbiologic abnormalities
Positive buffy coat smear result OR 2/3 or 3/3 positive blood cultures
Left ventricular dilatation
|Laboratory||⇑ WBC count (with left shift)
Normal platelet count
|⇑ WBC count (with left shift)
Respiratory alkalosis ±
Mental status changes ±
|CO = cardiac output; FSP = fibrin split products; GI = gastrointestinal; GU = genitourinary; PT/PTT = prothrombin time/partial thromboplastin time; PVR = peripheral vascular resistance; WBC = white blood cell.|