Which patient is most likely to require a transfusion of RBCs after cardiac surgery?

The scenario involving a patient actively bleeding with a hematocrit of 24% is the most likely candidate for requiring a transfusion of red blood cells (RBCs) after cardiac surgery. Active bleeding significantly decreases blood volume and can lead to hypovolemic shock, necessitating intervention to restore adequate circulating blood volume and oxygen-carrying capacity.

In this case, the combined factors of ongoing bleeding and a low hematocrit level indicate that the patient is not only losing blood but also has insufficient red blood cells to meet the body's oxygen demands. Immediate transfusion of RBCs would help correct these deficits and prevent complications associated with decreased oxygen delivery to vital organs.

Other options present scenarios where transfusion may be considered but do not present as immediate or critical a need. A stable patient with a hematocrit of 22% may not necessarily need transfusion if they are asymptomatic and stable; their condition might be monitored instead. A patient with a hemoglobin of 9 g/dL may also require a transfusion, but the decision would typically depend on symptoms and additional clinical context. Lastly, the 78-year-old patient with prolonged bypass time and a hematocrit of 26% could be at risk due to age and the