Pulse wave analysis by digital photoplethysmography to record maternal hemodynamic effects of spinal anesthesia, delivery of the baby, and intravenous oxytocin during cesarean section

Objective: To investigate changes in maternal ECG ST index, blood pressure (BP), cardiac left ventricular (LV) ejection function and vascular tone/stiffness in large and small arteries occurring during elective cesarean section (CS) in spinal anesthesia. Material and methods: Twenty-six women were monitored with photoplethysmographic digital pulse wave (PW) analysis (DPA) before and after spinal anesthesia, after delivery of the baby, after 5IU oxytocin bolus IV, and 5min later. Statistics with Wilcoxon matched-pairs signed-rank and Friedman tests at a p<0.05 were performed. Results: Spinal anesthesia resulted in significantly decreased BP, increased ST index and LV ejection time, and small-artery vasodilation. Delivery of the baby resulted in global vasoconstriction and increases in systolic BP and heart rate (HR). Oxytocin lowered BP, HR and ST index, increased LV ejection power and caused both large- and small-artery vasodilation. ST index and BP recovered after 5min, but low HR and low vascular tone persisted. Conclusions: Spinal anesthesia and oxytocin caused arterial vasodilation and cardiac affection. Oxytocin caused a decrease in HR despite a fall in BP, indicating a direct negative chronotropic effect. Delivery of the baby caused momentous cardiovascular changes, possibly due to maternal emotions and auto-transfusion of blood from the uterus.