Diastolic Performance and Norepinephrine in Spinal-Induced Hypotension for Cesarean Delivery

Background and rationale: The best agent to prevent spinal-induced hypotension is still uncertain but norepinephrine showed fewer effects on heart rate and cardiac output. In septic patients norepinephrine has been shown to produce an "endogenous fluid challenge". Objective: We aim to assess if patients with impaired diastolic function (46% of pregnant women at term) are less able to maintain indexed cardiac output in response to norepinephrine infusion during spinal-induced vasoplegia. We also aim to assess if fetal wellbeing is related to maternal cardiac output during spinal anesthesia for cesarean delivery. Methods: We will assess by echocardiogram the diastolic function before surgery and will then start continuous non-invasive hemodynamic monitoring with a ClearSight® monitor (ClearSight®, Edwards Lifescience, Irvine, CA) and perform a fluid challenge to relate diastolic disfunction with fluid responsiveness. Hemodynamic monitoring will continue throughout the surgery. Norepinephrine infusion will start concomitantly to beginning of spinal anesthesia and will stop 5 minutes after uterotonic medication. Outcome: We aim to assess if patients with diastolic disfunction are less able to maintain cardiac output in response to norepinephrine infusion during spinal anesthesia induced vasoplegia. We also aim to assess if fetal wellbeing is related to maternal cardiac output during spinal anesthesia for cesarean delivery.)