A fluid titration system has an optical sensor, a physiological monitor, a titration controller and an infusion device. The optical sensor transmits multiple wavelengths of light into a tissue site of a person and detects the optical radiation after attenuation by pulsatile blood flowing within the tissue site. The physiological monitor receives a resulting sensor signal and derives a plethysmograph that corresponds to the pulsatile blood flow. The monitor also calculates a plethysmograph variability measure that is responsive to changes in perfusion at the tissue site. A titration controller generates a fluid control output according to the variability measure. The infusion device administers a liquid solution via an intravenous (IV) connection to the person according to the fluid control output so as to regulate at least one of a fluid flow start, rate and stop.