A phlebotomist needs to collect a PT (Prothrombin Time) from a patient with a difficult vein. Which of the following is the best tube for the draw?
Light green
Lavender
Royal blue
Light blue
The Correct Answer is D
Choice A reason:
The light green tube typically contains lithium heparin and is used for plasma determinations in chemistry. It is not suitable for coagulation studies, such as PT, because heparin is an anticoagulant that would interfere with the test results.
Choice B reason:
The lavender tube contains EDTA, which is an anticoagulant that binds calcium. While it is commonly used for complete blood counts (CBC) and other hematology tests, it is not appropriate for coagulation studies because the binding of calcium would affect the clotting process required for a PT test.
Choice C reason:
The royal blue tube can come with different additives or be additive-free, depending on the color of the closure. It is primarily used for trace element testing, toxicology, and nutrient determinations. The additives in a royal blue tube could potentially contaminate the sample and interfere with the PT test.
Choice D reason:
The light blue tube contains sodium citrate, which is the appropriate anticoagulant for coagulation studies like PT. Sodium citrate works by binding calcium in the blood, preventing clotting. The PT test measures the time it takes for a clot to form after re-calcification, making the light blue tube the correct choice for this test.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A reason:
When encountering a patient who appears motionless and cyanotic, the first action should be to assess their level of consciousness. Asking loudly if they are okay can help determine if the patient is responsive or unresponsive. If there is no response, this indicates that the patient may be unconscious and requires further immediate assessment and potential intervention.
Choice B reason:
The head-tilt-chin-lift maneuver is used to open the airway of an unresponsive patient who is not suspected of having a spinal injury. However, this is not the first step. Before performing any maneuvers, it is essential to determine the patient's level of consciousness and whether they are breathing.
Choice C reason:
Administering rescue breaths is part of the process of cardiopulmonary resuscitation (CPR), which is only initiated after confirming that the patient is unresponsive and not breathing normally. This step comes after checking for responsiveness and breathing.
Choice D reason:
Looking, listening, and feeling for breathing movements is part of the assessment to determine if the patient is breathing normally. This is done after establishing unresponsiveness but before initiating CPR. It is a critical step, but it follows after confirming that the patient does not respond to verbal stimuli.
Correct Answer is B
Explanation
Choice A reason:
Using a needle at a 45° angle does not typically result in collapsing the vein. A collapsed vein is more likely due to excessive vacuum pressure from the tube, a very small or fragile vein, or the tourniquet being too tight.
Choice B reason:
At a 45° angle, the needle is more likely to penetrate through the entire depth of the vein, especially if the vein is superficial. This can result in a failed venipuncture because the needle has entered and exited the vein, missing the opportunity to collect blood.
Choice C reason:
While a steep angle like 45° could cause the needle to miss the vein superficially, it is more likely that the needle would go through the vein at this angle rather than merely missing it superficially. A superficial miss is more likely with an angle that is too shallow.
Choice D reason:
Contacting the upper wall of the vein alone would not necessarily result in a failed venipuncture. However, at a 45° angle, the needle could easily slip through the vein entirely after contacting the upper wall, especially if the vein is not anchored well.
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