hemoglobineemia

Hemoglobinemia refers to the presence of free hemoglobin in the plasma. Normally, hemoglobin is contained within red blood cells. When red blood cells are destroyed, a process called hemolysis, their contents including hemoglobin are released into the bloodstream. Hemoglobinemia can occur in various clinical situations, often as a result of intravascular hemolysis.

This condition can be caused by a number of factors. Acute hemolytic anemias, such as those induced by certain infections, toxins, or autoimmune reactions, are common culprits. Mechanical damage to red blood cells, such as that occurring in prosthetic heart valves or during cardiopulmonary bypass, can also lead to hemoglobinemia. Certain genetic disorders affecting red blood cell membranes, like hereditary spherocytosis or paroxysmal nocturnal hemoglobinuria, predispose individuals to increased hemolysis and thus hemoglobinemia.

The clinical significance of hemoglobinemia is tied to the fate of free hemoglobin. Once released into the plasma, hemoglobin can bind to haptoglobin, a protein that scavenges free hemoglobin. When the capacity of haptoglobin is exceeded, free hemoglobin can circulate and interact with various tissues. Hemoglobin can be filtered by the kidneys, and high levels can lead to hemoglobinuria, potentially causing acute kidney injury. Furthermore, free hemoglobin can generate reactive oxygen species, contributing to oxidative stress and inflammation. The detection of hemoglobinemia is typically done through laboratory tests that measure plasma hemoglobin levels. Management focuses on addressing the underlying cause of hemolysis.