Template:Featured Article/2007-06-27

=Cardiac Disease in Pregnancy=

Physiology of Labor and Delivery

 * 1) Hemodynamics are altered substantially during labor and delivery secondary to anxiety, pain, and uterine contractions.  Oxygen consumption increases threefold, and cardiac output rises progressively during labor owing to increases in both stroke volume and heart rate.  Blood pressure is higher in the lateral position.  Both the systolic and diastolic blood pressure increase markedly during contractions with a greater augmentation during the second stage.  The form of anesthesia impacts the blood pressure.
 * 2) By the time of delivery the Cardiac output (CO) has increased by 50%, the plasma volume has increased by 40% and the red cell mass has increased by 25 to 30%.
 * 3) The work of labor may increase the CO by 60% over the baseline level.
 * 4) During the second stage of labor the patient is on her back there is venous stasis, heart rate increases to > 120/min and the BP may be > 150 mm Hg.
 * 5) Immediately following delivery, the uterus contracts and delivers a sudden bolus of 500-750 cc of blood to the circulatory system which may result in pulmonary edema in the patient with heart disease.

Hemodynamic effect of cesarean section:
To avoid the hemodynamic changes assocaited with vaginal delivery, cesarean section is frequently recommended for women with cardiovascular disease. This form of delivery can also be associated with hemodynamic fluctuations related to intubation, analgesic as well as anesthetic use. There can be a greater extent of blood loss as well as relief of caval compression.

Hemodynamic changes postpartum:
There can be a temporary increase in venous return immediately after delivery due to relief of caval compression in addition to blood shifting from the contracting uterus into the systemic circulation. This change and effective blood volume occurs despite blood loss during delivery and can result in a substantial rise in ventricular filling pressures, stroke volume, and CO that may lead to clinical deterioration.

Both heart rate and CO returned to prelabor values by one hour after delivery and the blood pressure and stroke volume at 24 hours after delivery.

Hemodynamic adaptation of pregnancy persists postpartum and gradually returns to prepregnancy values within 12-24 weeks after delivery.

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