Influence of the timing and quantity of administration of crystalloid fluid on tissue oxygenation in parturients undergoing cesarean section under spinal anesthesia

Parturients were randomized into one of three groups with closed envelope method. All random numbers will conceal in sealed envelopes and assigned to a patient when entering the operating room by one anesthesiologist. Sequentially-numbered sealed opaque envelopes containing group allocation will open by the anesthesiologist responsible for fluid transfusion. First group: preload (applying fluid loading before administering the intrathecal local anesthetic) 20 ml/kg intravenous infusion Ringer's Lactate solution group (n=20), second group: preload 15 ml/kg intravenous infusion Ringer's Lactate solution group (n=20) (CONTROL GROUP) third group: coload (applying fluid loading at the after of administering the intrathecal local anesthetic) 15 ml/kg intravenous infusion Ringer's Lactate solution group (n=20). Ringer's Lactate preload solution administered during 20–25 min, prior to commencing the induction of the spinal anaesthesia. Ringer's Lactate Coload solution over 20-25 min as soon as CSF was tapped. Patients were fasted over-night for at least 6-8 h. The patients did not receive intravenous fluid prior to entering the study. All patients will be monitored and the basal vital functions (HR, SpO2, NIBP and StO2) will be recorded with admission into the OR. All patients will placed into a sitting position and spinal anesthesia will be performed with a median approach, at a level of L3-L4, with a 25 G Quincke type spinal needle and 2.0 ml hyperbaric bupivacaine. After succesful administration of anesthesia, all patients will be placed into supine position, monitored and administered oxygene via a venturi mask after administration of spinal anesthesia until the completion of surgery in inspirated fractions (21%,) and all vital functions will be recorded (HR, SpO2, NIBP and StO2) after spinal anesthesia (in minute 1, 3 and 5), with the beginning of surgery (in minute 5, 10, 15, 20, 25, 30 and 40), after the end of surgery (in minute 5, 10, 15, 30 and 60) and in the 24th hour postoperatively Beside this, hemoglobin levels will be evaluated preoperatively, during surgery and postoperatively in the 30th and 60th minute, by a noninvasive continuous monitoring device. Spinal block levels, duration of surgery, APGAR scores, vasopressor consumption will be recorded.