A phlebotomist should instruct a patient to take which of the following actions when providing a sputum specimen?

Choice A reason:
The high pressure in the arterial system is not a factor in the filling of blood collection tubes during venipuncture. Arterial blood is not typically collected using evacuated tubes; these are used for venous blood collection, where the pressure is lower.

Choice B reason:
While the venous system does have pressure that aids in blood flow, it is not the high pressure that causes blood collection tubes to fill. Venous pressure is relatively low compared to arterial pressure, and on its own, it is not sufficient to fill the vacuum tubes used in venipuncture.

Choice C reason:
The positive pressure created by the tourniquet can help engorge the veins, making them easier to access, but it does not directly cause the blood collection tubes to fill. The tourniquet's role is to assist in vein visualization and palpation rather than in the filling of the tube.

Choice D reason:
The negative pressure within the tube is the correct factor that causes blood collection tubes to fill during venipuncture. When the needle punctures the patient's vein and then the tube stopper, the vacuum in the tube pulls blood into it until the vacuum is exhausted or the tube is filled. This is why it is essential not to allow the tube contents to contact the stopper, as backflow into the venous system can cause adverse reactions.

Choice A reason:
A sodium level test is important for managing and monitoring a patient's electrolyte balance, particularly in critical care settings. However, a DNR order indicates that the patient has chosen not to undergo CPR, not necessarily that their condition is the most critical at the moment. Therefore, while important, it may not be the most urgent sample to process.

Choice B reason:
Postoperative monitoring of hemoglobin and hematocrit levels is crucial for detecting possible hemorrhage and ensuring proper recovery. However, unless there is an immediate concern for acute blood loss or other complications, these tests may not be as urgent as a stat test from the emergency room.

Choice C reason:
A stat potassium level is typically ordered when there is an urgent need to assess a patient's potassium due to conditions that can rapidly affect heart rhythm and muscle function. In the emergency room setting, where patients often present with acute and life-threatening conditions, stat tests are prioritized to provide rapid results that can influence immediate clinical decisions.

Choice D reason:
Peak antibiotic levels are measured to ensure therapeutic efficacy and to avoid toxicity. While important for managing a patient's treatment, especially for those who are NPO (nothing by mouth), it may not be as time-sensitive as a stat test required for an acute emergency.