الفهرس 
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Abstract
Total body water in adult ,male ( 70kg ) averages 40 liters ,classified into ICF ( 25 liters ) and ECF ( 15 liters ). ECF is classified into interstitial fluid (12 liters) and intravascular fluid (3 liters). Osmolality is the numbers of osmoles/kg of solvent, the major osmotic solutes of ICF are potassium, magnesium, phosphorous and proteins, while the major osmotic solutes of ECF are sodium and proteins, while the major osmotic solutes of ECF are sodium, and its accompanying anions.
Perioperative fluid loss is classified into abnormal losses either sensible or insensible, internal or external and existing deficits. Hypovolemia is associated with alterations in blood flow that are inadequate to fulfill the nutritive role of the circulation. The body tries to compensate for perfusion deficits by redistribution of flow to vital organs. Activation of sympathetic nervous system and the Renin angiotensin-aldosterone system are compensatory mechanisms to maintain peripheral perfusion. Various circulating vasoactive substances and inflammatory mediators are also released.
Fluid replacement for shock is the most important way of treatment. Fluid therapy consists of infusion of crystalloids, colloids or combination of both. Crystalloid fluids include: isotonic saline, lactated ringer’s, dextrose and hypertonic saline are used mainly as first line in transfusion of hypovolemic patients. But as crystalloids don’t cause marked volemic effects and can be easily filtered from the circulation. We cannot depend on them alone.
Colloids are fluids, which, because of their oncotic pressure are confined mainly to the intravascular space causing plasma expansion. Colloid fluids are either: blood derivatives (albumin and plasma protein fraction), synthetic colloids (dextran, gelatin and hydroxyethyl starch) or oxygen carrying solutions (perfluorochemical emulsions and hemoglobin based oxygen carriers). Each type has its own advantages and disadvantages.
The comparison between the usage of colloids and crystalloids in treatment of hypovolaemic shock concluded that the volume therapy with colloids requires less volume and achieve better filling of circulation compared to crystalloids.
The goal of intraoperative fluid management is to maintain fluid homeostasis by providing the appropriate amount of parenteral fluid to maintain adequate intravascular volume and constant haemodynamics during anaesthesia and surgery. Intraoperative fluid therapy include replacement of fluid deficit due to preoperative fasting; maintenance fluid to compensate for losses in urine, sweat and insensible loss; intraoperative translocated fluid; variable blood losses and other losses as gastric secretion and peritoneal fluids.
To know the degree of blood loss or hypovolemia and whether the resuscitation trials are effective the patient must be monitored. Monitoring is very important to detect the hydration state of the patient and adequacy of fluid replacement. Monitoring of changes in cardiovascular dynamics can be done by measurement of arterial blood pressure, pulse rate, central venous pressure and urine output. Oxygenation of the tissues can be monitored by pulse oximetry.
These monitors are:
Clinical methods: arterial blood pressure, heart rate and urine output.
Laboratory methods: hematocrit, blood volume, gastric tonometry and glomerular filtration rate.
Invasive measures: central venous pressure, pulmonary artery and pulmonary artery occlusion pressure.
Blood conservation has assumed a special importance in recent years. The techniques used to conserve blood including reduction of intraoperative blood loss; autologous blood transfusion and acute normovolaemic hemodilution and use of oxygen-carrying blood substitutes.