Infusion of intravenous fluids is mandatory especially in major and prolonged surgeries. However, there is no available optimum ideal type of fluid nor a fixed amount suitable for transfusion but it must be individualized for every patient to minimize the side effects of fluids.

Ringer's lactate as an example of crystalloids, causes a transient hypercoagulable state after its infusion, disappears in less than 6 hours of infusion and the coagulation profile returns to its state before Ringer's.

Voluven (Hydroxyehthyl starch 130/0.4) a colloid causes a hypocoagulable state after its infusion, and its effect is prolonged to more than 6 hours after infusion.

The effects of hydroxyethyl starch are not dose-dependent, but they can be remarkable even with mild to moderate amount of blood dilution applying nearly a restrictive fluid transfusion strategy and a goal-directed fluid therapy mode.

The amount of needed crystalloids is much more than that of colloids to maintain patients hemodynamically stable.

When considering the optimum fluid of choice to achieve hemodynamic stability and the least morbidity, colloids have a theoritical and intuitive advantage. Being composed of molecules >35 kDa, colloids have traditionally been thought to have greater fluid efficacy (i.e. they remain in the intravascular space for longer ,thus contributing a greater effect on cardiac output) compared with crystalloids. These theoritical benefits of colloids led to their routine use in goal-directed therapy (GDT).

Studies in healthy volunteers have demonstrated that crystalloids tend to expand the intravascular volume by about 20% of the infused volume ;however when physiological endpoints have been used in clinical studies , the fluid efficacy of crystalloids increases up to 60%. This discrepancy may be explained by a number of factors, including the time taken for fluid to equilibrate throughout the extracellular fluid , the vaodilating effect of anethetic-indused hypotension on vascular capacitance, and the impairment of fluid elimination because of the surgical stress response.

While colloid has been the default fluid choice in most GDT studies to date, recent evidence from both the perioperative anesthestic setting and from intensive care have raised concerns that these agents may produce adverse effects on renal function and coagulation . recent studies have sought to compare the use of crystalloid solutions with colloids for GDT.

Inclusion Criteria:

• age between 18 to 75 years
• undergoing elective colorectal surgery

Exclusion Criteria:

• refusal by the patient
• patient with cardiac disease
• hepatic disease
• renal disease
• blood disease
• patient on regular anticoagulant drug

patient undergoing elective colorectal surgery