by Dennis Ernst • September 05, 2018
Skin puncture or venipuncture? That's one of the first questions every healthcare professional with specimen collection responsibilities must answer when approaching every patient. What goes into your decision-making process?
For most patients, the volume of blood required mandates a venipuncture. But for many others, it's the collector's choice. What factors must be considered when making the decision? Those pertaining to specimen quality were covered last month in Part I in this series. This month we look at the pros and cons of each method of specimen collection as they pertain to patient and collector safety.
Stability and collector safety
Because venipunctures require precise placement of the needle in the vein throughout the procedure, patient stability is critical to its success. Patients who are apprehensive (e.g., needle-phobic patients, pediatric patients, etc.) may be collected more successfully by skin puncture, provided the volume of blood required is minimal. Although skin punctures may be more painful than a properly performed venipuncture, stabilizing the puncture site after the piercing the skin is less critical to the success of the procedure. Collectors must carefully weigh the benefits of minimizing venipuncture pain against the potential for patients to move their arm during the procedure, and determine which procedure is most likely to be successful.
Table 1: Venipuncture Pros and Cons
|direct access to the circulatory system||greater likelihood of sustaining an accidental needlestick|
|potentially less traumatic to the patient||greater potential for patient injury|
|the ability to draw larger volumes of blood||potential for hemoconcentration to affect test results|
|faster than obtaining capillary blood||increased potential for hematoma formation|
|less likely to be contaminated by tissue fluid||requires greater patient stability|
|less likely to be hemolyzed||multiple venipunctures precipitate iatrogenic anemia|
|difficulty detecting nerve damage in infants|
In addition, because venipunctures to patients whose arms are not properly immobilized put the collector at risk of sustaining an accidental needlestick, collectors should consider the potential when deciding which procedure to perform. Capillary punctures or incisions are less likely to result in accidental exposures regardless of patient stability since OSHA mandates the use of retractable skin puncture and incision devices. Such devices do not expose the collector to the contaminated sharp.
However, the pros and cons of performing a skin puncture bear no less consideration. Table 2 lists the benefits and detriments.
Capillary procedures may also be safer for patients at risk of developing iatrogenic anemia (anemia induced by diagnostic blood sampling). Newborns and geriatric patients are most vulnerable to red blood cell depletion should the cumulative volume of blood drawn by venipuncture be excessive. Collectors who consider iatrogenic anemia as a potential complication when selecting the method of specimen collection reduce this risk and enhance the quality of care the patient receives.
One of the most important factors to keep in mind when deciding which procedure to perform is the likelihood that the procedure could injure the patient. Since venipuncture to the antecubital area, specifically to the basilic vein, can involve underlying nerves and the brachial artery, collectors should weigh the potential for injury to these structures, especially in patients with hard-to-find veins. In newborns, the risk of complications from nerve injury when performing a venipuncture is even greater than for older children and adults. In an older patient, the pain associated with the needle coming in contact with a nerve is obvious. In newborns, reactions to extreme pain are difficult to differentiate from reactions to mild pain. Therefore, collectors performing venipunctures on newborns do not have the benefit of the same differential pain response that signals nerve involvement as in older patients, and are less likely to terminate a venipuncture immediately when a nerve is involved. The loss of the ability to differentiate pain in infants can lead to the potential for a permanent nerve injury.
Table 2: Skin Puncture Pros & Cons
|patient stability less critical||hemolysis more likely|
|requires less precision||specimen clotting more likely|
|minimizes iatrogenic anemia||more painful to the patient|
|patient injury less likely||yields smaller volumes of blood|
|decreased risk of accidental needlestick||potential for tissue fluid contamination|
|may take longer to complete|
An additional patient safety consideration is the likelihood of hematoma formation. When blood leaks from a vein into the surrounding tissue during or after a venipuncture, the potential for more than unsightly bruising exists. Hematoma formation can exert pressure on the nerves that pass through the antecubital area and lead to Complex Regional Pain Syndrome, Type II. If hemorrhaging is severe, other complications can develop. Capillary sampling does not risk complications from hematoma.
Since the risk of complications from skin punctures is minimal in comparison to venipunctures, the safety of the patient should be considered with all the other variables discussed when determining the most appropriate blood collection procedure. Collectors should be mindful of this risk along with the other variables discussed in this series in order to make a professional judgment as to which procedure is in the best interest of the patient in terms of safety and specimen quality. Continuing education on these and other specimen collection issues is critical to providing accurate results and quality patient care.
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