Final answer:
A phlebotomist should stop the blood collection if a vein collapses, apply a warm compress, not use a partially filled collection bag for transfusion, potentially draw from another vein, monitor the patient, and document the incident.
Step-by-step explanation:
When a phlebotomist encounters a collapsed vein during a blood donation, they should firstly stop the donation process to prevent further injury to the vein. They may apply a warm compress to help the vein recover and reestablish blood flow. If the collection bag only fills halfway, the standard procedure is not to use the partially filled bag for transfusion. It's important for the phlebotomist to monitor the patient for any adverse reactions and provide care as needed. Depending on the situation, they may attempt to draw blood from a different vein after ensuring the patient is comfortable and willing to continue. Additionally, documenting the episode and any actions taken is crucial for health records and future reference.