Summary

In study session VI you have learnt

• Water is the major component of all fluid compartments within the body. Total body water represents approximately 60% of body weight in an average adult. The compartments are separated by water permeable cell membranes. In the adult, the intracellular fluid volume represents two thirds of total body water, and extracellular fluid volume represents one third.
• The presence of a volume over load or deficit is best determined by the history and physical examination. If possible, correct the problem before anesthesia.
• Hypovolemia refers to any condition in which the extracellular fluid volume is reduced (low blood volume), and results in decreased tissue perfusion.
• Cardiovascular and central nervous system sign predominate during the acute phase of ECF loss. You have to categorize stages of hypovolemia before initiating management
• Management of fluid deficit includes treating the underlining causes, poly ionic balanced salt solution (lactated Ringer's is preferable).
• Hypervolemia is almost always an increase of extracellular volume with peripheral edema, ascites, or other fluid collection.
• The perioperative plan is basically composed of normal maintenance fluid requirements, pre anesthetic fluid deficit and replacing ongoing losses due to the surgical disease (surgical trauma). Adjusting the type & quantity of fluids in accordance with the basal function of vital organ system has great importance.
• A maintenance fluid is a constant loss of water & electrolytes from the body for basal metabolism and it counter balance these ongoing sensible & insensible losses. One can estimate the maintenance fluid requirements of patients of all ages using the "4-2-1'' rule
• Whenever possible, volume problems should be corrected prior to anesthesia. Electrolyte abnormalities should be corrected before anesthesia is induced that will prevent possible adverse reaction.
• Intra operative fluid losses (Fluid loss associated with surgery) develop rather quickly & should be replaced in an immediately
• The most significant fluid loss during surgery is the distributional volume deficit frequently termed ''third spacing''. Insensible losses which increase with fever, an elevated ambient temperature, perspiration and high flow of non humidified gasses may loss hypotonic fluids.
• Intraoperative blood loss is a relatively frequent occurrence, but it remains difficult to quantify. Depending the amount of blood lost, the preoperative blood lost, the preoperative hemoglobin concentration, and the patient's tolerance to a reduced red cell mass. A volume of 3 to 4 ml of isotonic or balanced salt solution should be infused for each 1 ml of blood loss.
• Sequestration or third spacing of ECF continues after surgery. These edema fluid remains sequestrated for 1-3 days & then mobilized in to the functional ECF compartment.
• Two categories of fluid are available for plasma volume expansion- crystalloids & colloids. In most a patient 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.
• Crystalloids are fluid that contains water & electrolytes. The replacement requirement is 3-4 folds the volume of blood lost.
• Colloids tend to remain in the intravascular space for longer periods than do crystalloids. Smaller quantities of colloids are required to restore circulating blood volume.
• Electrolyte imbalance should be corrected before anesthesia.