Monitoring Noninvasively for Infusion and Transfusion Optimization

Inclusion Criteria: * 18 years or older at the time of consent. * Ability to provide written informed consent. * Scheduled for non-urgent major surgery with general anesthesia * At least one finger available and accessible for performing non-invasive pleth variability index (PVi) and hemoglobin (SpHb) monitoring. * The Attending surgeon, attending anesthesiologist and the clinical care team agree with enrollment in the study, including the restrictions on monitoring procedures defined in the control group. Exclusion Criteria: * Untreated or uncontrolled hypertension defined as mean arterial pressure (MAP) greater than 120 mmHg, despite medications. * Chronic kidney disease with glomerular filtration rate \<30 ml/min/1.73 m2 or requiring renal-replacement therapy for end-stage renal disease. * Surgeries where no bleeding is expected to occur (i.e., total knee surgery where blood loss is prevented by use of tourniquet). * Surgeries performed in the prone position. * Acute cardiovascular event, including acute or decompensated heart failure and acute coronary syndrome. * Aortic pathology that could lead to misinterpretation of hemodynamic variables (e.g. intra- aortic balloon pump, thoracic aorta aneurysm). * Renal vascular surgery. * Preoperative sepsis. * Circulatory shock. * Preoperative vasoactive substance infusion before study entry. * Concurrent participation in any interventional study. * Pregnant or lactating women. * Patients who refuse to receive blood transfusion(s). * Patients with Do Not Resuscitate (DNR) orders. * Open chest surgeries. * Prisoners * Patients for whom monitoring of CO, SV, PPV, and/or SVV to guide GDT or similar intra-operative fluid management, including continuous SpHb monitoring, would be standard of care. * Patients have skin abnormalities affecting the digits such as psoriasis, eczema, angioma, scar tissue, burn, fungal infection, substantial skin breakdown, nail polish or acrylic nails that would prevent the proper fit and application of the sensors. * Cardio-pulmonary bypass (CPB) surgery.