Capillary punctures require different devices than the typical venipuncture equipment. They include lancets, microcontainer tubes, microhematocrit tubes and sealants, and warming devices. Improper use of these devices may contribute to improper specimens and pre-analytical errors.
Lancets are incision devices meant to puncture or cut the skin to obtain capillary blood. They are specifically designed to be used for finger or heel puncture. Both types of devices are required to have the OSHA safety features, which include the use of a retractable blade or needle to reduce the risk of sharps injury. Most recently, laser lancets have become available on the market for use on the fingers of adults and children five years or older. They perforate the skin with a laser instead of a sharp blade or needle. This, in turn, eliminates the risk of accidental sharps injuries.
Microcontainer tubes are specially designed small plastic tubes used to collect minute volumes of blood via capillary puncture. They are coated with different additives and color-coded to represent the additive, just like the regular collection tubes. Some also have markings indicating the volume in µL, and some come fitted with capillary tubes or scoops to help with specimen collection.
Microhematocrit tubes are glass or plastic capillary tubes used for blood collection and hematocrit determination. They can be coated with anticoagulant or plain depending on the intended use. Plastic or clay sealants are commonly used to form a tight leak-proof seal used during centrifugation.
Warming devices, also known as heel warmers, are used to help increase the arterial blood flow at the puncture site. In doing so, the blood obtained more closely resembles arterial blood than venous blood. There are several manufacturers on the market which produce these warmers, but if one is not available, a towel dampened with warm water can be used to the same effect. Care must be taken so the water is not too hot to burn the patient.
