Whole-body impedance cardiography (ICGWB), a noninvasive procedure that provides continuous data on cardiac output, was used to assess hemodynamics and cardiovascular responses during elective cesarean section performed under spinal anesthesia in 10 healthy women with normal pregnancies. Five of these women were nulliparous. Two pregnant women with heart disease also were studied; one had aortic valve stenosis, and one had operated tetralogy of Fallot. Mean arterial pressure (MAP), heart rate (HR), stroke index (SI), cardiac index (CI), and systemic vascular resistance index (SVRI) were recorded during surgery, as anesthesia lightened, and 2 to 5 days postpartum.
There were significant changes in all hemodynamic parameters over time (Fig. 3). Preloading increased both MAP and HR, but did not alter SI or CI. Spinal anesthesia led to lower SVRI, and MAP was significantly lower than after preloading. The CI and SI, however, remained unchanged. SVRI increased significantly in hypotonic patients given an infusion of ephedrine. Immediately after delivery, CI increased 47% over baseline and 34% from predelivery values. Both HR and SI increased significantly, but the MAP was stable—presumably because of a 39% decrease in SVRI. These changes lasted approximately 10 minutes on average but continued for 30 minutes in one instance. When ephedrine was not infused, hemodynamic responses to delivery resembled those in hypotonic patients. Baseline hemodynamic values returned after spinal blockade resolved. MAP was below baseline in the early postpartum period. CI was stable and SVRI tended to decline. The woman operated on for tetralogy of Fallot had normal baseline hemodynamic values. In the woman with aortic valve stenosis, the CI and the SI did not increase after delivery and pulmonary edema developed, from which she recovered completely.
This experience indicates that ICGWB may provide a useful noninvasive means of monitoring hemodynamic changes during cesarean delivery.