Two Cut-Off Values of Plethysmographic Variability Index to Guide Intraoperative Fluid Therapy on Serum Lactate in Patients Undergoing Excision of Supra-Tentorial Brain Tumors

Inclusion Criteria: * Age above 18 years old. * Both sexes. * Patients scheduled for supra-tentorial brain tumor excision. Exclusion Criteria: * Arrhythmias. * Pulmonary hypertension. * Impaired cardiac contractility. * Impaired liver or kidney function. * Low lung compliance. * Body mass index above 40. * Intra-operative hemodynamic instability on vasopressors or inotropes. * Peripheral arterial occlusive diseases. * Hand injuries or burns that preclude the application of the Masimo device probe.