Venipuncture is a common medical procedure involving the collection of blood from a vein. It is frequently performed for diagnostic purposes, allowing healthcare providers to obtain blood samples for laboratory analysis to assess an individual’s health status. It also serves to monitor various health conditions and can be part of therapeutic treatments or blood donation.
Patient Preparation and Safety Supplies
Before and during a blood draw, specific supplies are used to prepare the patient and maintain a sterile, safe environment. Gloves are a foundational safety measure, acting as a barrier to prevent the healthcare worker’s exposure to bloodborne pathogens and minimizing the transfer of microorganisms to the patient. Many professionals prefer nitrile gloves due to their tactile sensitivity and because they are latex-free, which is safer for individuals with latex allergies.
A tourniquet is then applied to the upper arm, typically a few inches above the venipuncture site. This elastic band temporarily restricts venous blood flow, causing veins to become more distended and visible, making them easier to locate and access. It is important to remove the tourniquet once blood flow is established, generally within one minute, to prevent potential changes in blood composition that could affect test results.
The venipuncture site is cleaned with an antiseptic wipe, such as one containing alcohol or chlorhexidine, to reduce the risk of infection by eliminating surface bacteria. Following blood collection, sterile gauze pads or cotton balls are applied to the puncture site with gentle pressure to help stop bleeding and promote clot formation. An adhesive bandage or medical tape is then used to cover and protect the site. Hypoallergenic bandage options are available for patients with sensitive skin to minimize irritation.
Blood Collection Devices
The core of venipuncture involves specialized devices designed for drawing blood safely and efficiently. Needles come in various types and sizes; straight needles are commonly used for routine blood draws and when multiple samples are required from a single venipuncture.
Winged infusion sets, often called “butterfly” needles, are preferred for patients with small, fragile, or difficult-to-access veins, such as infants, elderly individuals, or those undergoing specific medical treatments, offering increased flexibility during insertion. Needle size is indicated by a gauge number, where a higher number signifies a thinner needle.
For most routine venipuncture, 21-gauge needles are typical, while 22- or 23-gauge needles are used for smaller veins. Larger gauges (e.g., 16-18 gauge) are reserved for procedures like blood donation where rapid flow is necessary. All needles are designed for single-use to ensure patient safety and prevent contamination.
A tube holder, also known as a needle holder or adapter, connects the venipuncture needle to the blood collection tubes. These clear, plastic devices allow for visual confirmation of blood flow into the tube and are designed for single-use to maintain hygiene. While the Vacutainer system is standard, syringes can also be used for manual blood collection, particularly in situations involving very fragile veins.
The most common system utilizes Vacutainer tubes, which are sterile, pre-evacuated tubes that draw a precise volume of blood due to their internal vacuum. These tubes are color-coded, with each color indicating the presence of specific additives that prevent clotting (anticoagulants) or promote it (clot activators) and preserve the blood sample for particular laboratory tests. Common examples include:
- Lavender or purple-topped tubes contain EDTA, an anticoagulant used for complete blood counts (CBC) and other hematology tests.
- Light blue-topped tubes contain sodium citrate and are designated for coagulation studies, assessing the blood’s clotting ability.
- Red or gold-topped tubes often contain clot activators, allowing the blood to clot for serum separation, which is necessary for chemistry and immunology tests.
- Green-topped tubes typically contain heparin for plasma chemistry determinations.
- Gray-topped tubes with sodium fluoride are used for glucose testing.
Post-Procedure Essentials
After the blood is collected, specific equipment is used for proper disposal and sample management. Sharps containers are rigid, puncture-resistant, and leak-proof, designed for the safe disposal of used needles, syringes, and other sharp medical instruments. These containers, often red or yellow and marked with a biohazard symbol, prevent needlestick injuries to healthcare workers and reduce the risk of exposure to bloodborne pathogens.
Specimen labels are applied to each blood collection tube immediately after the draw. These labels contain patient information, such as name, date of birth, and unique identification numbers, along with details about the collected sample and requested tests. Accurate labeling ensures the correct sample is processed for the right patient and tests, leading to reliable diagnostic results and appropriate medical treatment.