unable to enrollment subjects due to early departure of study personele

The investigators hypothesize that continuously measuring stroke volume (SV) and cardiac output (CO) will 1) reveal hemodynamic instability in a timely manner and alert the physician promptly, 2) provide information for the physician to make the differential diagnosis as to whether the hemodynamic instability was due to vasodilatation or reduction of venous blood return, and 3) lead to appropriate and prompt treatment to improve patient outcome.

-determine the SV and CO and their kinetic change using ICON® to establish a hemodynamic profile of the patient under spinal anesthesia for cesarean section. To determine if using instantaneous measurements of SV and CO to guide patient management improves hemodynamic stability.

Inclusion Criteria:

• age 18-45;
• receiving spinal anesthesia or combined spinal and epidural anesthesia to undergo cesarean section

Exclusion Criteria:

• Patients who have major cardiovascular disease,preexisting of hypertension or gestational hypertension, preeclampsia and body mass index greater than 35kg/m2;
• Patients who have skin lesion at the place where the electrode is supposed to be applied;
• Emergency cesarean section patients.