Anatomic and physiologic changes of pregnancy: anesthetic considerations.

Cardiovascular system One of the major alterations to the cardiovascular system seen in the pregnant patient is that of blood volume. During pregnancy, an increase is seen in plasma volume (up to 50%), red blood cell volume (up to 20%) and total blood volume (up to 35%). Healthy women in a normal first pregnancy increase their plasma volume from a nonpregnant level by approximately 1250 ml. In subsequent pregnancies, the increase is greater and may be as high as 1500 ml. Most of the rise takes place before 32-34 weeks gestation; thereafter, there is relatively little change. The increase is related to the size of the fetus, and there are particularly large increases in plasma volume associated with a multiple pregnancy.1