Final answer:
If no blood enters the tube during a venipuncture, reposition the needle, check the tourniquet, ensure correct tube attachment and active vacuum, or try another puncture site if necessary, maintaining safety and infection protocols.
Step-by-step explanation:
If no blood fills the tube after a venipuncture, a few adjustments might be necessary. Begin by slightly repositioning the needle. Sometimes, the needle may either pass through the vein or not fully penetrate it. A subtle redirection without withdrawing the needle completely can solve the issue. If there's still no blood return, you should then check if the tourniquet is properly placed and that it is not too tight or too loose. It is essential to ensure that the phlebotomy tube is also correctly attached and that the vacuum within is active.
However, if these attempts don't yield success, you may need to remove the needle and apply pressure to the puncture site to prevent bruising. Afterwards, assess the need for another venipuncture attempt, possibly on a different site or with a better-sized needle. Safety protocols must be followed at all times to prevent any infection or additional injury.