Corresponding Bundle Element:

Blood cultures obtained prior to antibiotic administration.

Related Measures

Timing of Blood Cultures

Background:

The incidence of sepsis and bacteremia in critically ill patients has been increasing in the past two decades. [8,9]  Thirty percent to 50 percent of patients presenting with a clinical syndrome of severe sepsis or shock have positive blood cultures. Therefore, blood should be obtained for culture in any critically ill septic patient. 

Collecting blood cultures prior to antibiotic administration offers the best hope of identifying the organism that caused severe sepsis in an individual patient.  Failure to check blood cultures prior to antibiotic infusion will perhaps affect the growth of any blood borne bacteria and prevent a culture from becoming positive later. 

Collection Strategy:

Two or more blood cultures are recommended. [1]  In patients with suspected catheter-related infection, a pair of blood cultures obtained through the catheter hub and a peripheral site should be obtained simultaneously.  If the same organism is recovered from both cultures, the likelihood that the organism is causing the severe sepsis is enhanced. In addition, if the culture drawn through the vascular access device is positive much earlier than the peripheral blood culture (i.e., > 2 hours earlier), it may offer support that the vascular access device is the source of the infection. [2]  Volume of blood may also be important. [3]

Indications:

Fever, chills, hypothermia, leukocytosis, left shift of neutrophils, neutropenia, and the development of otherwise unexplained organ dysfunction, e.g., renal failure or signs of hemodynamic compromise, are specific indications for obtaining blood for culture.  Blood cultures should be taken as soon as possible after the onset of fever or chills.

While it remains difficult to predict bacteremia in patients with sepsis [4], a number of clinical and laboratory parameters are independently correlated with the presence of bacteria in the blood of patients when infection is suspected. These include chills, hypoalbuminemia, the development of renal failure, and a diagnosis of urinary tract infection [4,5]; other criteria are new fever, hypothermia, leukocytosis and left shift of neutrophils, neutropenia, and signs of hemodynamic compromise. [6]  Peaking fever appears to be more sensitive than leukocytosis to predict bacteremia [7]; however, fever and low-grade bacteremia can be continuous, such as in endocarditis.

References:

1. Weinstein MP, Reller LP, Murphy JR, et al. The clinical significance of positive blood cultures: A comprehensive analysis of 500 episodes of bacteremia and fungemia in adults. I. Laboratory and epidemiologic observations. Reviews of Infectious Diseases. 1983;5:35–53.
2. Blot F, Schmidt E, Nitenberg G, et al. Earlier positivity of central venous versus peripheral blood cultures is highly predictive of catheter-related sepsis. Journal of Clinical Microbiology. 1998; 36:105–109.
3. Mermel LA, Maki DG. Detection of bacteremia in adults: Consequences of culturing an inadequate volume of blood. Annals of Internal Medicine. 1993;119:270–272.
4. Bates DW, Sands K, Miller E, et al. Predicting bacteremia in patients with sepsis syndrome. Journal of Infectious Diseases. 1997;176:1538–1551.
5. Leibovici L, Greenshtain S, Cohen O, et al. Bacteremia in febrile patients: A clinical model for diagnosis. Archives of Internal Medicine. 1991;151:1801–1806.
6. Smith-Elekes S, Weinstein MP. Blood cultures. Infectious Disease Clinics of North America. 1993;7:221–234.
7. Groeneveld AB, Bossink AW, van Mierlo GJ, et al. Circulating inflammatory mediators in patients with fever: Predicting bloodstream infection. Clinical and Diagnostic Laboratory Immunology. 2001;8:1189–1195.
8. Crowe M, Ispahani P, Humphreys H, et al. Bacteraemia in the adult intensive care unit of a teaching hospital in Nottingham, UK, 1985–1996. European Journal of Clinical Microbiology and Infectious Diseases. 1998;17:377–384.
9. Martin GS, Mannino DM, Eaton S, et al. The epidemiology of sepsis in the United States from 1979 through 2000. New England Journal of Medicine. 2003;348:1546–1554.

Content adapted extensively from:

• Dellinger RP, Carlet JM, Masur H, et al. Surviving Sepsis Campaign Guidelines for management of severe sepsis and septic shock. Critical Care Medicine. 2004;32:858-873.
• Bochud PY, Bonten M, Marchetti O, et al. Antimicrobial therapy for patients with severe sepsis and septic shock: An evidence-based review. Critical Care Medicine. 2004;32(Suppl.):S495–S512.
• Cohen J, Brun-Buisson C, Torres A, et al. Diagnosis of infection in sepsis: an evidence-based review.  Critical Care Medicine. 2004;32(Suppl):S466-94.