Intravenous Fluids

Intravenous Fluids

Two categories of fluid are available for plasma volume expansion- crystalloids & colloids. In most patients the proper administration of crystalloid solutions will adequately replace the perioperative fluid deficits and losses, there by maintaining an acceptable level of vital organ perfusion. Physiologic saline (e.g., 0.9%NaCl) and balanced salt solutions are often preferred because they are relatively safe and inexpensive. There are certain patients that may require supplemental infusions of red blood cells or colloid solutions to attain this end. Patients with large blood or other fluid losses, patients in hypovolemic shock, and those patients designed critically ill are often considered candidate for receiving blood product therapy.

Crystalloids

Are fluid that contains water and electrolytes. Crystalloid solutions are sufficient to maintain normal body fluid composition in the majority of patients. The replacement requirement is 3 folds the volume of blood lost because administered crystalloid distribute in a ratio 1:4 like extracellular fluid, which is composed of about 3 liter intravascular (plasma) and about 12 liter extravascular (i.e., about 20% should remain in the intravascular space). The common crystalloids are listed on ANNEX 2

Normal saline and lactated Ringer's are preferred for fluid replacement during anesthesia and surgery. Dextrose containing solution should not be routinely used. Five percent dextrose functions as free water not recommended for a surgical patient, but are most often used in the prevention of hypoglycemia in diabetic patients who have had insulin administered.

Colloids

An intravenous fluid that expands the intravascular space. Colloids remain in the intravascular space for longer periods than do crystalloids. Smaller quantities of colloids are required to restore circulating blood volume. They are significantly more expensive to use than crystalloids even though smaller absolute volumes are required. It is usually acceptable to predict (approximation) 1-ml plasma volume expansion for each 1 ml of administered colloid. It is generally agreed that when volume resuscitation must be rapidly accomplished and intravenous access is a limiting factor, colloid supplementation is indicated. Dextran, hetastarch and albumin are common colloids

• Dextran: The dextran solutions provide reliable plasma volume expansion resulting from a colloidal osmotic effect (i.e., a fluid translocation from the interstitial to the intravascular compartments). Each gram of dextran may retain as much as 25 ml of water with in the intravascular compartment; at least for a short period. Dextran may interfere with the cross matching of blood and coagulation. Anaphylactic reactions ranging from mild cutaneous eruptions to shock may occur.
• Hetastarch: a highly molecular weight hydroxyethyl starch (HES), synthetic colloids that structurally resemble glycogen, in patients with hypovolemia, hetastarch appears to produce a significantly greater increase in plasma colloid oncotic pressure. Hetastarch has a negligible effect on the typing and cross matching of blood.
• Albumin: is a natural blood colloid with a normal serum concentration of 3.5 to 5.0 g/dl in adults. Parenteral albumin preparations are often used to normalize both plasma volume and colloid oncotic pressure. Electrolyte