Final answer:
After a gray top tube is drawn in a blood collection sequence, none of the options listed (blood cultures, heparin tubes, or sodium citrate tubes) are typically collected next due to the importance of the order of draw to prevent contamination and test interference.
Step-by-step explanation:
The order of draw for blood collection tubes is critical to prevent cross-contamination between different additives used in blood collection tubes. A gray top tube typically contains sodium fluoride and potassium oxalate, which are used for glucose preservation and as an anticoagulant, respectively. After drawing a gray top tube, one should NOT collect a tube used for blood cultures (option A), as this requires a sterile collection process typically done first to avoid contamination. When it comes to heparin tubes (option B), these would not follow a gray top in the order of draw because heparin can interfere with chemistry tests; gray tops are generally drawn after tubes containing anticoagulants like heparin. Sodium citrate tubes (option C) are special coagulation tubes which, like heparin tubes, should be drawn before gray top tubes to avoid interference. Therefore, the correct answer here would be D. None of the above.