Perioperative fluid therapy

General anesthesia of the surgical patient should provide reversible amnesia, analgesia, unconsciousness, muscle relaxation, and immobility. During the anesthetic period, every effort should be made to ensure homeostasis of the patient to minimize anesthetic complications and ensure a smooth and uneventful recovery. Many anesthetic drugs that provide these desirable qualities, however, adversely influence the hemodynamic status of the patient. 1-3 A principal consideration during anesthesia is to maintain microcirculatory organ perfusion and oxygen delivery to tissues to maintain cellular energy production. Perioperative fluid therapy is important to help maintain intravascular volume, optimize cardiac output (CO), and ensure that blood oxygen content (CaO 2 ) is adequate by ensuring an adequate concentration of hemoglobin (Hb). Oxygen delivery (DO 2 ) is determined by CaO 2 and CO: DO 2 = CaO 2 X CO Blood oxygen content is affected by blood oxygen saturation (SaO 2 ), Hb concentration, and the partial pressure of oxygen in arterial blood (PaO 2 ):