Fluids & Electrolytes Lecture PDF

Fluids & electrolytes Presented by: Eiman Bakri Clinical Pharmacy, NUSU  Objectives Assess electrolyte abnormalities and recommend an appropriate pharmacologic treatment plan Discuss the appropriate role and risks of hypertonic and hypotonic saline R...

Fluids & electrolytes Presented by: Eiman Bakri Clinical Pharmacy, NUSU  Objectives Assess electrolyte abnormalities and recommend an appropriate pharmacologic treatment plan Discuss the appropriate role and risks of hypertonic and hypotonic saline Recommend an appropriate intravenous fluid regimen and monitoring parameters Distribution of total body fluid  Body Water Compartments and Electrolyte Composition Two thirds of the total body water resides in the cells (intracellular water) The extracellular water can be divided into different compartments—the interstitial fluid and the plasma The kidneys play an important role in maintaining a constant extracellular environment by regulating the excretion of water and various electrolytes  Potassium, magnesium, and phosphate are the major ions in the intracellular compartment, Whereas sodium, chloride, and bicarbonate are predominant in the extracellular space Water moves across the cell membrane from a region of low osmolality to one of high osmolality Differences between ECF and ICF in a 70 Kg adult male  Plasma Osmolality It is determined by the number of particles in solution Plasma osmolality reflects the osmolality of total body water The osmolality of body fluid is maintained between 280 and 295 mOsm/kg  Volume regulation Antidiuretic hormone (ADH) plays an important role in maintaining fluid balance in the body. Aldosterone is the main regulatory hormone for sodium homeostasis. Fluid Management Intravascular volume makes us go…  Fluid resuscitation Is indicated in patients with signs and symptoms of intravascular volume depletion. The goal of fluid resuscitation is to restore intravascular volume and prevent organ hypoperfusion Because intravascular volume depletion can cause organ dysfunction and death, prompt resuscitation is necessary  Signs and Symptoms of Intravascular Volume Depletion Tachycardia (HR > 100 beats/min) Hypotension (SBP < 80 mmHg) Orthostatic changes in HR or BP Increased BUN/SCr ratio > 20:1 Dry mucous membranes Decreased skin turgor Reduced urine output Dizziness Improvement in HR and BP after a 500-to 1000- mL fluid bolus  Crystalloids VERSUS Colloids The most commonly used Crystalloids are: Normal saline, Ringer lactate and Dextrose in water. Crystalloids like Na and Cl do not freely cross into cells, but they will distribute evenly in the EC space D5W is metabolized to water and carbon dioxide. Water can cross any membrane in the body; therefore, it is evenly distributed in TBF ▪ Colloids include: Packed red blood cells, Pooled human plasma (5% albumin, 25% albumin, and 5% plasma protein fraction) Semisynthetic glucose polymers (dextran) Hetastarch Colloids are too large to cross the capillary membrane; therefore, they remain primarily in the intravascular space Distribution of IV fluids  Crystalloids (0.9% sodium chloride or lactated Ringer solution) are recommended for fluid resuscitation in hypovolemia Colloids may be considered after fluid resuscitation with crystalloid (usually 4–6 L) has failed to achieve hemodynamic goals or after clinically significant edema limits the further administration of crystalloid Albumin (theoretically, 25% is preferred) may be consideredin conjunction with diuretics for patients with: Clinically significant edema (e.g., pulmonary edema causing respiratory failure) An albumin concentration less than 2.5 g/dL  The choice of replacement fluid to replenish the extracellular volume depends on the sodium status. The treatment goal is to achieve a positive fluid balance. In patients who are neither hypo- nor hypernatremic, normal saline should be used. In patients who are hypernatremic, half-isotonic saline or dextrose solutions should be used.  Maintenance Intravenous Fluids Maintenance intravenous fluids are indicated in patients who are unable to tolerate oral fluids. The goal of maintenance intravenous fluids is to prevent dehydration and maintain a normal fluid and electrolyte balance. Maintenance intravenous fluids are typically administered as a continuous infusion through a peripheral or central intravenous catheter.  Common methods of estimating the daily volume in children and adults Administer 100 mL/kg for first 10 kg + 50 mL/kg for the next 10–20 kg (i.e., 1500 mL so far) + 20 mL/kg for every kilogram greater than 20 kg = (~2500ml/day) Or Administer 20–40 mL/kg/day (for adults only).  Disorders in Osmoregulation ❖Hyponatremia: A patient may have hypotonic, isotonic, or hypertonic hyponatremia depending on plasma osmolality. ❖ According to volume status, hyponatremia is divided into: 1. Hypovolemic hypotonic hyponatremia 2. Hypervolemic hypotonic hyponatremia 3. Normovolemic hypotonic hyponatremia  Hypovolemic hypotonic hyponatremia can occur with volume depletion and extracellular fluid depletion Treatment involves sodium replacement to correct the deficit  Hypervolemic hypotonic hyponatremia is caused by excess water intake relative to sodium. It is also seen in patients with heart failure, liver or renal failure, and nephrotic syndrome. Water restriction is the mainstay of therapy.  Normovolemic hypotonic hyponatremia can be caused by syndrome of inappropriate antidiuretic hormone (SIADH). Persistent ADH secretion together with water ingestion results in hyponatremia. All fluids should be reduced. Diuretics furosemide or demeclocycline are treatment options  Disorders in Osmoregulation(cont) ❖Hypernatremia: Occur with: Normal total body sodium and pure water loss Low total body sodium with hypotonic fluid loss High total body sodium as a result of salt gain  Hypernatremia(cont) Management includes Correcting the underlying cause of the hypertonic state Replacing water deficits Administering adequate water to match ongoing losses  Clinical Use of Diuretics o Diuretics reduce sodium and chloride reabsorption in the renal tubules, thereby increasing urine volume. o Individual diuretics can be categorized according to their site of action in the renal tubules  Loop diuretics(e.g., furosemide, bumetanide, torsemide, ethacrynic acid) are the most potent diuretics. Thiazide diuretics and other sulfonamide diuretics (e.g., chlorthalidone) are less potent than loop diuretics. They can enhance reabsorption of calcium, so are useful in patients with kidney stones. Magnesium excretion is increased by thiazides.  Potassium-sparing diuretics (e.g. spironolactone, triamterene, amiloride) are less potent but offer the advantage of sparing potassium loss. Acetazolamide inhibits carbonic anhydrase. It has limited diuretic and natriuretic effects. ? Osmotic diuretics (e.g., mannitol, urea) are non resorbable solutes.  Clinical case Q.B., a 30-year-old male athlete who has had multiple bouts of diarrhea for the last several days, has been drinking a sports drink to keep himself from getting dehydrated. His vital signs include supine BP, 145/80 mm Hg, and pulse, 70 beats/minute; standing BP, 128/68 mm Hg, and pulse, 90 beats/minute. Respiratory rate (RR) is 12 breaths/minute, and he is afebrile. His skin turgor is mildly decreased and laboratory data are the following: Na, 128 mEq/L K, 3.0 mEq/L Cl, 100 mEq/L Bicarbonate, 17 mEq/L BUN, 27 mg/dL Creatinine, 1.2 mg/dL Urinary sodium and chloride were both less than 10 mEq/L.  Assess Q.B.’s electrolyte and fluid status. What is the etiology of Q.B.’s hyponatremia? How should Q.B.’s hyponatremia be treated?