Fluid and Electrolyte Management Presented by :sajede sadeghzade

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 mannitol administration

• 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

Sign and Symptoms of Hyponatremia

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

GOOD LUCK