Physiologic and Anatomic Changes during Pregnancy

Pregnancy results in physiologic and anatomic changes that allow the mother to adapt to the greater metabolic requirements of pregnancy. These changes include the enlarging uterus, which results in compression of surrounding structures, and increased hormonal production, which exerts its effects on maternal physiology. Cardiac output increases to maintain higher uterine blood flow, and minute ventilation increases, which results in a chronic respiratory alkalosis. Plasma volume increases, which results in physiologic anemia of pregnancy and may contribute to gestational thrombocytopenia. An understanding of these and other changes that occur in pregnancy is important for the anesthesiologist because they have important implications for management of the parturient undergoing an anesthetic procedure. The goal of this chapter is to highlight some of the most salient features of physiologic changes that occur during pregnancy and to begin to offer some basic anesthetic management strategies. This review contains 6 tables, and 36 references. Key Words: airway changes during labor, cardiovascular changes during pregnancy, gastroesophageal reflux disease, gestational thrombocytopenia, hydronephrosis during pregnancy, left uterine displacement, physiologic anemia, ventilatory mechanics