Fluid & Electrolytes PDF

Fluid and electrolytes Normal anatomy and physiology Water comprises 60% of the body weight of an average adult, the total body water is divided functionally into the extracellular (ECF = 20% of body weight) and the intracellular fluid spaces (ICF = 40% of body weight)...

Fluid and electrolytes Normal anatomy and physiology Water comprises 60% of the body weight of an average adult, the total body water is divided functionally into the extracellular (ECF = 20% of body weight) and the intracellular fluid spaces (ICF = 40% of body weight) Solute composition of fluid compartments Intracellular fluid The dominant cation is potassium in the ICF The major intracellular anion are protein and phosphate. Extracellular fluid The dominant cation is sodium in the ECF The major extracellular anion are bicarbonate and chloride. This difference in concentration of different ions between ICF and ECF is maintain by NA-k pump.  Functions of body fluid Regulates body temperature Moistens tissues in the eyes, nose and mouth Protects body organs and tissues Carries nutrients and oxygen to cells Lubricates joints Lessens burden on the kidneys and liver by flushing out waste products Dissolves minerals and nutrients to make them accessible to your body Insensible Water Loss which is invisible vaporization from the lungs and skin, assists in regulating body temperature. Normally, about 600 to 900 mL/day is lost. Accelerated body metabolism, which occurs with increased body temperature and exercise, increases the amount of water loss.  Fluid and Electrolyte Imbalances Imbalances are commonly classified as deficits or excesses. Fluid Volume Deficit Fluid volume deficit can occur with abnormal loss of body fluids (e.g., diarrhea, fistula drainage, hemorrhage, polyuria), inadequate intake, or a shift of fluid from plasma into interstitial fluid. Extracellular Fluid Volume Imbalances ECF volume deficit (hypovolemia) and ECF volume excess (hypervolemia) are common clinical conditions. ECF volume imbalances are typically accompanied by one or more electrolyte imbalances, particularly changes in the serum sodium level. EXTRACELLULAR FLUID IMBALANCES: CAUSES AND CLINICAL MANIFESTATION ECF Volume Deficit Causes ↑ Insensible water loss or perspiration (high fever, heatstroke) Diabetes insipidus Osmotic diuresis Hemorrhage GI losses: vomiting, NG suction, diarrhea, fistula drainage Overuse of diuretics Inadequate fluid intake Third-space fluid shifts: intestinal obstruction  EXTRACELLULAR FLUID IMBALANCES: CAUSES AND CLINICAL MANIFESTATION ECF Volume Excess Excessive isotonic or hypotonic IV fluids Heart failure Renal failure Primary polydipsia SIADH Cushing syndrome Long-term use of corticosteroid Clinical Manifestations Deficit Excess Restlessness, drowsiness, lethargy, confusion Headache, confusion, lethargy Thirst, dry mucous membranes Peripheral edema Decreased skin turgor, ↓ capillary refill Jugular venous distention Postural hypotension, ↑ pulse, ↓ CVP ↑ BP, ↑ CVP ↓ Urine output, concentrated urine Polyuria (with normal renal function) ↑ Respiratory rate Dyspnea, pulmonary edema Weakness, dizziness Muscle spasms Weight loss Weight gain Seizures, coma Seizures, com  Hypernatremia(Na+ >145 mEq/L) An elevated serum sodium, may occur with water loss or sodium gain. Because sodium is the major determinant of the ECF osmolality, hypernatremia causes hyperosmolality. In turn, ECF hyperosmolality causes a shift of water out of the cells, which leads to cellular dehydration. Causes Excessive Sodium Intake IV fluids: hypertonic NaCl, IV sodium bicarbonate Hypertonic tube feedings without water supplements Near-drowning in salt water. Inadequate Water Intake Unconscious or cognitively impaired individuals Excessive Water Loss (↑ sodium concentration) ↑ Insensible water loss (high fever, heatstroke, prolonged hyperventilation) Osmotic diuretic therapy Diarrhea Disease States. Diabetes insipidus Primary hyperaldosteronism Cushing syndrome Uncontrolled diabetes mellitus  Clinical Manifestations Restlessness, agitation, twitching, seizures, coma Intense thirst. Dry, swollen tongue. Sticky mucous membranes Postural hypotension, ↓ CVP, weight loss, ↑ pulse Weakness, lethargy. Treatment The primary goal of treatment of hypernatremia is to treat the underlying cause. Replacing water and electrolytes as needed. Fluid should be administrated over 48 hr aiming for serum sodium concentration of approximately 1mEq/L/h. If hypernatremia is rabidly corrected, the osmotic imbalance may cause cerebral edema and potentially sever neurological impairment. Choice the type of fluid replacement Hypernatremia with hypovolemia: isotonic 0.9 normal slain to restore euvolemia and to treat hyperosmolality. After adequate volume resuscitation with normal slain , 0.45% or 5% dextrose or both can be use to replace any remaining free water deficit. Mild volume deficit may be treated with 0.45% slain and 5% dextrose.  Treatment Hypernatremia with euvolemia Water ingestion or IV 5% dextrose. Hypernatremia with hypervolemia: Include 5% dextrose solution to reduce hyperosmolarity. Loop diuretic may be necessary to promote natriuresis and lower body sodium. In sever cases with kidney disease hemodialysis may be necessary to correct the excess total body sodium and water Laparotory finding Serum electrolytes. Serum creatinine ,osmolarity, and urine sodium. History and physical examination. Adrenal function assessment. Hyponitremia Sodium concentration inversely relayed to total body water. Hyponatremiaoccur when there is excess in extracellular water relative to sodium. it could be hypovol., normovol. Hypervol. Excess extracellular water result in A-Dilutional hyponatremia. Causes:- 1 excessive oral water intake. 2 iatrogenic excess IVF. 3post operative due to excess ADH secretion. Which increase water reabsorption from kidney. 4Drugs, like anti psychotic , tricyclic anti depressant, angiotensin enzyme inhibitors.  Hyponitremia Serum sodium concentration less than 135 mEq/l Most causes is related to water imbalance and abnormal water handling. Usually reflect excess water retention relative to sodium rather than sodium deficiency. Hypotonic fluid commonly cause hyponatremia in hospitalized patient. Isotonic and hypertonic hyponatremia Carful history and laboratory test Seen with sever hyperlipidemia,hyperproteinemia this will interfere with measurement of serum sodium causing pseudohyponitremia. Hypertonic hyponatremia Occure in hyperglycemia and mannitol infusion for increase intracranial pressure Translocation of water lower serum sodium conc. Serum sodium conc fall 2 mEq/l for each 100mg/dl raise in glucose.  Treatment in the absence of renal disease the goal of serum sodium is 130 meq/l 1 -correct hypovolemia if presents. 2-restore normal sodium by giving normal salin 3- in sever hyponatremia 3% saline used. Syndrome of inappropriate antidiuretic hormone ADH release (SIADH) unsuppressed release of antidiuretic hormone (ADH) from the pituitary gland. Etiology secondary to another disease process elsewhere in the body. (ectopic ADH production) Hereditary SIADH, Nephrogenic SIADH, Drugs(carbamazepine, oxcarbazepine, chlorpropamide, cyclophosphamide) Surgical procedures. Hormone administration: vasopressin. Virus (HIV) infection Volume Regulation An acute drop in blood pressure as sensed by " volume receptors causes ADH release (along with other hormones like rennin and epinephrine), which generates free water absorption from the kidneys.  Osmoregulation The most important and primary function of ADH is to maintain the plasma tonicity, primarily by an alteration in water balance. A decrease in tonicity prevents ADH release and prevents water retention, while increase in tonicity causes ADH release. In patients with SIADH, levels of ADH are high even in the presence of decreased plasma osmolality and/or hyponatremia. Clinical manifestations of SIADH can be due to hyponatremia and decreased ECF osmolality, which causes the water to move into the cells causing cerebral edema. Evaluation There is no single test to diagnose SIADH. Patients usually present with hyponatremia with normal volume status. Serum sodium less than 135mEq/L Serum osmolality less than 275 mOsm/kg Urine sodium greater than 40 mEq/L Urine osmolality greater than 100 mOsm/kg The absence of clinical evidence of volume depletion - normal skin turgor, blood pressure within the reference range.  treatment Correction sodium levels Correction of underlying abnormalities Restriction of oral water intake with the goal of less than 800 mL/day. If hyponatremia is persistent, sodium chloride in the form of oral salt tablets or intravenous saline. Loop diuretics such as furosemide.