Specimen Requirements

Patient Preparation:

1. See details under procedure.

2. Use ChloraPrep Kit to prepare site and prevent contamination of blood sample with skin flora.

Site Selection and Timing:

1. If possible, blood cultures will be obtained prior to initiating antibiotic therapy.
2. Every effort will be made to avoid drawing blood through indwelling intravenous or intra-arterial catheters unless blood cannot be obtained by venipuncture or unless the diagnosis of catheter sepsis is suspected.  Disinfection of IV site and/or buff cap is very important to obtain an uncontaminated specimen.
3. For patient comfort, one set of blood cultures may be obtained while starting I.V. therapy.
4. Draw blood cultures as close to rise in temperature as possible
5. Draw blood cultures 10 to 15 minutes apart.
6. The volume of blood is critical especially if the patient is on antimicrobial therapy.
a. For adult patients the aerobic and anaerobic vials are used with a volume of 8 to 10 mL of blood in each vial for optimum results.
b. Optimal results are obtained by drawing two sets of blood cultures (for a total of 32-40 mL of blood). If you are unable to obtain the optimum volume on adults, the minimum for adults is 3 mL in each bottle. If only 3 mL of blood are obtained, put all the blood in the aerobic bottle. If 5 mLs are obtained put 3 mLs in the aerobic bottle and 2 mLs in the anaerobic bottle. Anything above 6 mL is to be split equally.
7. For pediatric patients the minimum volume is 0.5 mL. If only 0.5 mLs are drawn, put all blood into the aerobic bottle. If more than 0.5 mLs are drawn, split between the two bottles, aerobic/anaerobic.
8. The vacuum in the vial may exceed 10 mLs the volume collected or transferred into the vials must be monitored by using the 5 mL graduation marks on the vial label. On occasion, the vacuum in the vials is not reliable, and one may fail to get a sufficient volume. If the bottles are overfilled, false positives may occur.

Site Preparation and Phlebotomy

1. Assemble collection and drawing supplies.
2. Aseptic technique is used at all times.
3. Explain the procedure thoroughly to the patient prior to blood draw. Make every effort to avoid any additional conversation during blood draw as aerosols created can contaminate the site. Encourage the patient to not talk or cough  in the direction of the draw site.
4. Pinch the barrel on the applicator of ChloraPrep to break the ampule and release the antiseptic. Do not touch the applicator tip. Press the applicator tip against the treatment area until liquid is visible on the skin.
5. Use repeated back-and-forth strokes of the applicator for a minimum of 30 seconds. Completely wet the treatment area with antiseptic. 
6. Allow the area to air dry for approximately 30 seconds. Do not blot or wipe away. Discard the applicator after a single use. One full minute of application and drying is necessary to insure that the blood cultures do not become contaminated.

7. Do not touch the venipuncture site after preparation and prior to the phlebotomy.
8. Insert the needle into the vein, and withdraw blood.  Do not change needles before injecting the blood into the culture bottles using a one handed technique. The favored technique for drawing blood cultures is to use a large syringe to draw the blood then transfer the blood to the blood culture bottles. It is important to keep the area disinfected and clean throughout the entire collection procedure.
9. Mix well to avoid clotting and label.
10. Document the draw site (left anticubital, right hand, etc.) on the bottles, if an RN draws the blood cultures, in the nursing notes in Point of Care.
11. Each set should be clearly labeled as to order of draw. The sets cannot be mixed up as this leads to confusion when trying to determine if a positive blood culture is real or a contaminant.
12. Use a new needle and repeat site preparation if the vein is missed initially and for the 2nd draw on patients >13 years old.
13. The inoculated vial should be transported to the laboratory as soon as possible.

Applications: Prompt and accurate isolation of the organisms causing septicemia remains one of the most important functions of the Microbiology Department. A sudden increase in a patients pulse rate and temperature, change in sensorium and the onset of chills, prostration and hypotension are some indications for obtaining a blood culture. Sensitivities are performed on all isolates when appropriate.

Specific recommendations for systemic and localized infections are as follows: In suspected acute sepsis, meningitis, osteomyelitis, arthritis or acute untreated bacterial pneumonia, obtain 2 blood cultures from 2 separate venipuncture sites before starting therapy.  For FUO (fever of unknown origin eg, occult abscesses, typhoid fever or brucellosis) obtain 2 separate blood cultures initially, 24 to 36 hours later obtain 2 more just before the expected temperature elevation (afternoon). The yield beyond 4 blood cultures is virtually nil.

Specific recommendations for suspected infective endocarditis are as follows:

1. Acute: Obtain 3 blood cultures with 3 separate venipunctures during the first 1 to 2 hours of evaluation and begin therapy.

2. Subacute: Obtain 3 blood cultures on day 1; if all negative then 24 hours later obtain 3 more. 

3. Undiagnosed patients who have received antimicrobial therapy in the week or 2 before admission, obtain 2 separate blood cultures on each of 3 consecutive days. In addition, blood cultures are complimentary to cultures of urine and CSF in the evaluation of neonates with suspected sepsis whose only clinical findings in addition to fever or hypothermia may be poor feeding and failure to thrive.

4. Young children, especially those 2 years or under, with pneumococcal and H. influenzae bacteremia may present as out patients with marked fever (>39.4° C) and leukocytosis (WBC >20,000) as their principle findings.

5. Lastly, nondescript complaints may result from bacteremia in elderly patients. Even a low-grade fever in such patients may signal subacute bacterial endocarditis, especially when accompanied by malaise, myalgia or stroke.