The Sensitivity of Goal Plethysmography Variability Index (PVI) Directed Pre-anesthesia Intravenous Fluid Infusion in the Prevention of Spinal Anesthesia Induced Hypotension in Elective Caesarian Section: Prospective Observational Study

* This prospective observational study will be carried out on all pregnant women who will undergo elective cesarean section in obstetric department in Tanta university hospitals under spinal anesthesia over four month duration that starts immediately after obtaining ethical committee approval, an informed written consent will be included with the consent for spinal anesthesia for cesarean section, all patients data will be confidential and will be used for the current study only. * Inclusion criteria: Pregnant women which are listed to undergo elective caeserian section for single viable baby under spinal anesthesia. * Exclusion criteria: * Patients with pregnancy less than 36 weeks or more than 40 weeks * Patients with hypertension , pre-eclampsia , eclampsia. * Patients with diabetes * Patients with cardiovascular disease and /or arrhythmia. * Patients with placenta previa, accreta, percreta. * Obese patients with BMI >36 * Polyhydramnious patients * On arrival of patients to pre-anaesthesia preparation room, we will allow patients to rest in supine position with 15 degree left tilt by pillow wedge under right hip, after allowing patient to rest for five minutes, measures are recorded: ECG , heart rate, non invasive blood pressure, pulse oximeter applied on the index finger of the limb not attached to the blood pressure cuff, pulse oximetry and Plethysmography variability index (PVI) and perfusion index (PI) will be taken by (Massimo radical 7, Massimo corp. USA). Measures will be recorded every 5 minutes preoperative. Patients with PVI <15 are excluded from the study. Patients with PVI > 15 are started on intravenous infusion of warm ringer lactate solution via suitable pore intravenous cannula to reach target of PVI <15 or a total 1 liter of ringer lactate. The patients in which the PVI is corrected by fluid to level below 15 will be Group (C) or corrected group. Patients in which intravenous fluid administration did not result any change in PVI or changed but still higher than 15 will be Group (NC) or non corrected group. After preoperative preparation patient is shifted to operating theater, with all monitors applied. She will receive spinal block at lumbar 3-4 space with hyperbaric bupivacaine 8 mg plus 25 mic fentanyl. After giving anesthesia and positioning for surgery with a left lateral tilt of 15 degrees, supplemental oxygen at rate of 4 liter/minute is applied. Measurements will be taken every minute till delivery of the baby, and if the blood pressure is decreased below 20% of the baseline level before anesthesia, patients will be given incremental doses of ephedrine sulfate 0.1 mg /kg till blood pressure normalized above 80% of pre-anesthesia level. All measurements will be recorded in tables and subjected to statistical analysis.