During which procedure is an autotransfusion machine most likely utilized?

An autotransfusion machine is most commonly utilized during a splenectomy, which involves the surgical removal of the spleen. This procedure can lead to significant blood loss due to the rich vascular supply of the spleen. The use of an autotransfusion machine allows the surgical team to collect, process, and reinfuse the patient's own blood, which is more beneficial than using allogeneic blood transfusions. This can help manage the patient’s blood volume more effectively during surgery, reduce the risk of transfusion reactions, and decrease recovery time.

In contrast, the other procedures listed—appendectomy, cholecystectomy, and herniorrhaphy—typically involve far less blood loss and do not usually necessitate the use of an autotransfusion machine. Hence, the likelihood of needing this technology is significantly lower in those surgeries.