American Medical Certification Association (AMCA) Phlebotomy Practice Exam 2025 - Free Phlebotomy Practice Questions and Study Guide

Leaving a tourniquet on for too long can lead to hemoconcentration, which occurs when the blood in the veins becomes more concentrated due to the removal of plasma. This concentration can happen because the tourniquet restricts blood flow, causing the cells and proteins in the blood to become more densely packed as the liquid portion (plasma) is forced away from the area. This condition can significantly affect the results of laboratory tests, leading to potential misinterpretations of a patient's lab results.

While bruising, thrombosis, and hematoma can occur due to improper tourniquet application or other issues, they are not directly related to the duration for which the tourniquet is applied. Bruising is typically linked to damage to blood vessels during needle insertion, thrombosis refers to clot formation within a blood vessel, and hematoma is a localized collection of blood outside of blood vessels that can occur after a blood draw. Thus, hemoconcentration specifically arises from prolonged pressure caused by the tourniquet, making it the correct answer.