Fluid and Electrolyte Management Presented by :sajedesadeghzade
Total Body Water • Water constitutes approximately 50 to 60% of total body weight. • Lean tissues such as muscle and solid organs have higher water content than fat and bone. • The highest percentage of TBW is found in newborns, with approximately 80% of their total body weight comprised of water
Fluid Compartments • TBW is divided into three functional fluid compartments: plasma, extravascular interstitial fluid, and intracellular fluid. • Intracellular water makes up approximately 40% of an individual's total body weight, with the largest proportion in the skeletal muscle mass.
Composition of Fluid Compartments • The ECF compartment is balanced between sodium, the principal cation, and chloride and bicarbonate, the principal anions. • The intracellular fluid compartment is comprised primarily of the cations potassium and magnesium, and the anions phosphate and proteins.
Normal Exchange of Fluid and Electrolytes • The healthy person consumes an average of 2000 mL of water per day : • 75% from oral intake and the rest extracted from solid foods • Daily water losses include : • 800 to 1200 mL in urine • 250 mL in stool • 600 mL in insensible losses (the skin (75%) and lungs (25%)) • To clear the products of metabolism, the kidneys must excrete a minimum of 500 to 800 mL of urine per day, regardless of the amount of oral intake.
Disturbances in Fluid Balance • Extracellular volume deficit is the most common fluid disorder in surgical patients • Acute volume deficit is associated with cardiovascular and central nervous system signs • chronic deficits display tissue signs, such as a decrease in skin turgor and sunken eyes • Increase BUN • Urine osmolality > Plasma osmolality • Urine Na > 20 mEq/L
Disturbances in Fluid Balance • The most common cause of volume deficit in surgical patients is a loss of GI fluids • sequestration secondary to soft tissue injuries, burns, and intra-abdominal processes such as peritonitis, obstruction, or prolonged surgery can also lead to massive volume deficits. • Extracellular volume excess may be iatrogenic or secondary to renal dysfunction, congestive heart failure, or cirrhosis.
Hyponatremia • A low serum sodium level occurs when there is an excess of extracellular water relative to sodium. Extracellular volume can be high, normal, or low • In most cases of hyponatremia, sodium concentration is decreased as a consequence of either sodium depletion or dilution
Excess of Solute Hyponatremia • untreated hyperglycemia or mannitoladministration • When hyponatremia in the presence of hyperglycemia is being evaluated, the corrected sodium concentration should be calculated For every 100 mg/dL increase in plasma Glucose above normal the plasma Na should decreased by 1.6 mEq/L • extreme elevations in plasma lipids and proteins can cause pseudohyponatremia
Hypervolemic Hypernatremia • iatrogenic administration of sodium-containing fluids • mineralocorticoid excess : • Hyperaldosteronism • Cushing syndrom • Congenital adrenal hypreplasia • Urine Na > 20 mEq/L and urine osmolality > 300 mosm/L
Normovolemic Hypernatremia • renal causes : • diabetes insipidus • Diuretic use • Renal disease • Non renal causes : • Water loss from GI • Water loss from skin
Hypovolemic Hypernatremia • Same causes as normovolemic hyponatremia • Urine Na < 20 mEq/L • Urine Osmolality < 300 mOsm/L
Hyperkalemia • Serum K > 5 mEq/L • excessive potassium intake • increased release of potassium from cells • impaired potassium excretion by the kidneys
Sign and Symptoms of Hyperkalemia • GI symptoms include: • nausea, vomiting, intestinal colic, and diarrhea. • Neuromuscular symptoms range from weakness to ascending paralysis to respiratory failure • Early cardiovascular signs may be apparent ECG changes and eventually lead to hemodynamic symptoms of arrhythmia and cardiac arrest
Hypokalemia • inadequate potassium intake • excessive renal potassium excretion • potassium loss in pathologic GI secretions
Hypokalemia • The change in potassium associated with alkalosis can be calculated by the following formula: • K decrease by 0.3 mEq/L for every 0.1 increase in pH