Conventional Fluid Management vs Plethysmographic Variability Index -Based Goal Directed Fluid Management

All patients in supine position will receive breathing 100% oxygen, induction of anaesthesia will be achieved using propofol (2 mg/Kg), 1-2 mcg/kg of fentanyl and atracurium (0.5 mg/Kg). Endotracheal tube will be inserted after 3 minutes of mask ventilation. Patients who will experience prolonged airway instrumentation due to a difficult intubation will be excluded from further data analysis because of excessive stimulation. Then mechanical ventilation will be performed using a tidal volume of 6-8 mL/kg of ideal body weight at an inspiratory to expiratory ratio of 1:2 without positive end-expiratory pressure. The ventilatory frequency will be adjusted to maintain an end-tidal carbon dioxide tension of 35-40 mmHg. Anaesthesia will be maintained by isoflurane (1-1.5%), atracurium 10 mg intravenous increments every 20 minutes and morphine 0.1 mg/kg intravenous will be given as a long acting analgesia.

Ringer solution at the dose of 5 ml/kg/h infused throughout the surgical procedure by taking the parameters such as Heart rate (HR), mean arterial pressure (MAP) and urine output, Hypotension was defined as a condition in which the MAP was below 30% of the baseline MAP of the patient. In this case, bolus of 250 ml crystalloids (0.9% NaCl) was given and in case of hypotension persistence, 5 mg I.V. ephedrine administered and repeated every 5 min till the MAP increased over 70% of baseline.

After the induction of anesthesia, Ringer solution infused at the dose of 2 ml/kg/h started as a basal rate of infusion. If the PVI was higher than 13% for more than 5 min, a 250-ml bolus of crystalloids administrated. If the PVI was still higher than 13% after the bolus, it was repeated every 5 min until the PVI was less than 13% and if MAP was below 30% of the baseline MAP of the patient 5 mg iv ephedrine was applied and repeated every 5 min to keep the MAP increased over 70% of baseline. In the cases where PVI was less than \< 13% and if MAP was below 30% of the baseline MAP of the patient 5 mg iv ephedrine was applied and repeated every 5 min to keep the MAP increased over 70% of baseline. Then the patient was turned to prone position and the same steps according to Massimo readings were repeated.