Blood Specimen Collection Blood Cultures (Ambulatory)
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Signs and symptoms of nerve injury to the arm include severe, unusual, or shooting pain; tingling; numbness; or a tremor. If the patient complains of any of these during venipuncture, withdraw the needle immediately.undefined#ref12">12
Draw specimens for blood cultures before administering antibiotics.
Take precautions with a patient who takes medications that increase the risk for bleeding.9
Don appropriate personal protective equipment (PPE) based on the patient’s signs and symptoms and indications for isolation precautions.
Although recommendations are that trained phlebotomy personnel collect peripheral blood culture specimens by venipuncture to minimize collection errors, other health care team members may be responsible for specimen collection. Health care team members should be familiar with the organization’s practice and the state’s nurse practice act regarding venipuncture, blood specimen collection, and delegation.
A blood culture specimen set requires that 20 to 30 ml of blood be obtained at one time from one location.1 Blood culture specimens should be drawn when the patient is experiencing signs and symptoms of bloodstream infection, including fever or chills, and before the administration of antibiotics to increase the likelihood of obtaining a true-positive result. If the patient has been receiving antibiotics at the time the blood cultures are obtained, the laboratory should be notified because an additive can be applied to the blood culture medium to negate the antibiotic’s effect.11 Typically, two sets of blood cultures are ordered, and each set (Figure 1) contains one aerobic bottle and one anaerobic bottle. Orders regarding the spacing of the specimens may vary among practitioners and organizations.
Blood culture specimens are usually drawn using either a needle and syringe or a vacuum-extraction collection system that draws blood into vacuum-sealed blood culture bottles. In both cases, a hollow-bore needle is inserted into the lumen of a patient’s vein to obtain the blood culture specimen. Straight needles from vacuum-extraction collection systems are not used with blood culture bottles. Instead, winged-butterfly needles with a short length of tubing may be approved by the organization for use. Caution should be taken to avoid contaminating the patient’s skin or equipment to minimize the risk of false-positive test results, which can lead to inappropriate antibiotic use. False-positive results may expose patients to additional laboratory tests and increased length of stay.
The correct amount of blood required by the laboratory must be extracted into each blood culture bottle to ensure accurate test results and decrease the patient’s risk of anemia.7 If more than one blood specimen is to be drawn during a single venipuncture, specimens for blood cultures should be drawn first to maintain asepsis and prevent contamination with additives from laboratory tubes.
Because limited venous access may be a life-threatening complication of venipuncture, maintaining the patient’s vein’s integrity is essential. A patient with veins that may collapse or become injured from the vacuum or a patient whose veins may be difficult to locate because of unusual anatomy, trauma from repeated phlebotomy, or edema may also require an alternative method of blood specimen collection. Vascular visualization technology, such as ultrasound, infrared light technology, or transillumination devices, may be necessary to identify vasculature and can be used for difficult access.3
Tourniquets should be used with caution. If a tourniquet is deemed necessary, the nurse should not apply the tourniquet for longer than 1 minute.7 Prolonged tourniquet application can cause stasis and hemoconcentration.7 Infection control standards require that tourniquets be single use.6 Staphylococcus aureus contamination from reused tourniquets is a common finding.15
Venipuncture can be painful, and the patient may experience anxiety or fear before the procedure. For some patients, just the appearance of a needle is frightening, especially to a pediatric patient. A calm approach and skilled technique may help limit the patient’s aversion to venipuncture. The application of a vapocoolant spray has been shown to be effective in reducing pain during venipuncture.16 Anxiety may be assuaged by communicating with the patient about how to help relieve the patient’s concerns.
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Rationale: Three blood culture samples should be drawn at least 1 hour apart beginning at the earliest signs of sepsis.11
Rationale: Resin can be added to the culture medium to negate the antibiotic effect.11
If cultures are needed while the patient is receiving antibiotic therapy, obtain the blood culture specimen shortly before the next antibiotic dose.11
Rationale: A low, supported position and an empty mouth reduce the risk of injury if the patient experiences lightheadedness or a seizure or faints from vagal stimulation.
Be prepared to manage venipuncture-associated vasovagal reactions for a patient who is at risk.
Do not draw blood if there is a discrepancy between the laboratory requisitions or labels and the patient’s identity.
Rationale: Correct patient positioning helps stabilize the patient’s arm.
Consult with the clinical team leader, per the organization’s practice, about stopping the IV infusion for 30 seconds to 2 minutes before obtaining the blood specimen (as applicable).7
Rationale: A tourniquet blocks venous return to the heart from the arm, causing the veins to dilate for easier access.
Avoid using a tourniquet for a patient who has a history of bleeding, is easily bruised, has fragile skin, or has diminished circulation; however, if a tourniquet must be used, apply it loosely.
Do not keep the tourniquet on the patient longer than 1 minute before the procedure is performed.7 Prolonged tourniquet application causes stasis, hemolysis, and hemoconcentration because of changes in the vascular endothelium from increased venous pressure and hypoxia.7
Rationale: A patent, healthy vein is elastic and rebounds on palpation. A thrombosed vein is rigid, rolls easily, and is difficult to puncture.15
Do not use a vein that feels rigid or cordlike or one that rolls when palpated.
Rationale: Warming increases arterial blood flow, making veins more prominent.
If unable to locate an acceptable vein after reapplying the tourniquet, consider using transillumination, infrared light technology, or ultrasonography, per the organization’s practice, to help locate an appropriately perfused vein before attempting venipuncture.
Rationale: Combining different manufacturers or systems for blood specimen collection equipment may cause injury to the patient or yield incorrect test results. Incompatibility of components may cause failure of the process.
Do not use pediatric culture bottles for adult blood specimens because smaller volumes diminish the yield of pathogens.
Rationale: Needles that are 22 G or smaller minimize insertion-related trauma to the vein.4
Rationale: Safety devices can decrease the risk of needlestick injury by 75%.15
Vacuum-extraction system sheathed needles are considered sharps that are associated with needlestick injuries, and they must be disposed of in a sharps container that is within arm’s reach and is large enough to allow disposal of the entire device without detaching the needle.15 The sheathed needle’s flexible cover prevents blood from flowing when the needle is not engaged in a vacuum tube; however, the sheath does not prevent a needlestick injury if a finger inadvertently enters the collection barrel.
Use a new collection barrel for each patient. Do not detach the needle from the collection barrel for disposal after use.15
Keep the needle hub and the connection sites sterile.
Rationale: Puncturing the stopper before the needle is in the vein causes the culture bottle to lose its vacuum.
Do not contaminate the top of the bottle after it is prepared with alcohol.
Rationale: The rubber-sheathed needle housed in the collection barrel is used to puncture the rubber top of the vacuum bottle. When the rubber top is punctured, the vacuum in the bottle extracts blood from the syringe.
Do not contaminate the transfer device or the top of the bottle after it is prepared with alcohol.
Do not touch the site after preparation unless sterile gloves are worn.
If contamination occurs, discard the needle and the collection barrel or syringe in a sharps container and prepare a new venipuncture set.
Rationale: Gently stretching the patient’s skin helps stabilize the vein and prevents it from rolling during needle insertion.
Rationale: The smallest and sharpest point of the needle should puncture the skin first to reduce the chance of penetrating the sides of the vein during insertion. Keeping the bevel up causes less trauma to the vein. Entering the skin distal to the vein prevents unanticipated vein puncture, which may result in inadequate blood specimen retrieval and hematoma.
Rationale: Inserting the needle slowly prevents puncture through the opposite side of the vein.
To avoid false positive results when obtaining blood cultures via a venipuncture, discard a volume of blood, per the organization’s practice, before filling the blood culture bottles.7
Do not underfill or overfill the culture bottles because this can adversely affect the laboratory test results.
Observe the rapid flow of blood into the bottle. Failure of blood to appear indicates that the vacuum is lost or that the needle is not in the vein.
Avoid overfilling the culture bottle, which may cause a false-positive result.
If an insufficient amount of blood is drawn, inoculate the aerobic culture bottle with the required amount and then inoculate the anaerobic culture bottle with the remaining volume of blood.
Rationale: Inverting the blood collection tube gently ensures that the additives are properly mixed and prevents erroneous test results.
Do not shake the blood collection tube.
Rationale: Shaking may cause lysis of cells, resulting in inaccurate test results.
Rationale: Releasing the tourniquet before filling the last blood specimen tube reduces bleeding at the site when the needle is withdrawn.
Rationale: Applying pressure over the needle can cause discomfort and injury to the patient. Carefully removing the needle minimizes discomfort and vein trauma.
Rationale: Direct pressure minimizes bleeding and prevents hematoma formation. A hematoma may cause compression and nerve injury.
For a patient who has a bleeding disorder or who is undergoing anticoagulant therapy, hold pressure for several minutes, as needed, until the bleeding stops.
Rationale: Applying gauze with tape or a bandage keeps the venipuncture site clean and controls any final oozing.
Instruct the patient not to bend the arm of the venipuncture site.
Carefully evaluate the patient for the potential for venous collapse when using a syringe barrel that is 10 ml or larger.15 Consider that young children, older adults, and those who have received treatments that are damaging to the veins may not be able to withstand high pressure or may require a smaller syringe barrel.
Rationale: Releasing the tourniquet before the last of the blood is drawn reduces bleeding at the site when the needle is withdrawn.
Rationale: Applying gauze with tape or a bandage keeps the venipuncture site clean and controls oozing.
After skin antisepsis, the volume of blood is the next most important variable affecting the sensitivity of detection of bacteria and fungi in the blood.
Rationale: Transfer devices and sheathed needles are considered sharps that are associated with needlestick injuries, and they must be disposed of in a sharps container. The sheathed needle’s flexible cover prevents blood from flowing when the needle is not engaged in a vacuum tube; however, the sheath does not prevent a needlestick injury if a finger inadvertently enters the collection barrel.10
Do not recap needles or attempt to remove the needle from the collection barrel.10
Rationale: Unless ordered by the practitioner or per the laboratory’s practice, blood cultures should be obtained from at least two separate blood draws from two separate peripheral sites.7
Rationale: Mixing gently blends the medium and the blood.
Rationale: Decontamination prevents cross-contamination and reduces the risk for exposure to blood-borne pathogens.
Rationale: Documenting the patient’s response allows for improved care and planning for future venipunctures.
Chela, H.K. and others. (2019). Approach to positive blood cultures in the hospitalized patient: A review. Missouri Medicine, 116(4), 313-317.
*In these skills, a "classic" reference is a widely cited, standard work of established excellence that significantly affects current practice and may also represent the foundational research for practice.
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