The investigators propose to determine esophageal Doppler goal-directed fluid requirements in lean, overweight, obese, and morbidly obese patients with the goal of developing a body mass index (BMI)-specific fluid replacement strategy. Specifically, th investigators will test the hypothesis that perioperative fluid requirements on a per-kg basis varies as a function of BMI. Individuals scheduled for elective, open abdominal surgeries, vaginal hysterectomies or genital prolapse repair will be eligible to participate