Blood and blood component therapy

Significant hemorrhage may be defined as that degree of bleeding that either produces signs and symptoms of hemodynamic instability or that is likely to produce such if left untreated. Signs and symptoms of hemodynamic instability include dizziness, tachycardia, hypotension, and oliguria. Although the most useful laboratory indicator of significant blood loss is a marked drop in hemoglobin and hematocrit, initial measurements may not be indicative of actual blood loss because equilibration of volume may take several hours to occur. Hemorrhage severe enough to require transfusion may result following the loss of 750-1,000 mL in nonpregnant women. Most gravidas with uncomplicated term pregnancies, however, will expand their blood volume an average of 50%, and thus, greater blood loss is required to produce symptomatic anemia. Although whole blood is ideal for blood replacement in a woman with ongoing hemorrhage, crystalloids and packed red blood cells are generally utilized for volume expansion and improvement in oxygen-carrying capacity because of the limited availability of whole blood. Packed red blood cells may be expected to raise the hematocrit by approximately 3% per unit. Fresh frozen plasma contains all major clotting factors and is utilized for the treatment of coagulopathy. Various other components are available for specific coagulation defects. The major risks of blood component therapy are fatal transfusion reaction (approximately 1:100,000 units) and transfusion of various infections such as hepatitis B (1:63,000 U), hepatitis C (1:103.000 U), and human immunodeficiency virus (1:450,000-1:660,000 U). Thus, it is understandable that a woman and her health care provider may have significant apprehension when blood component therapy is indicated. However, it is of paramount importance not to delay such therapy when indicated because procrastination may place the woman's life at significant risk.