Fluid and Electrolyte Disorders

Adipose tissue

-The greater the amount of adipose tissue, the lower the percentage of water

Extracellular fluid (ECF): • outside the cells • comprises 20% of total body weight 

• intravascular space (vascular compartment)-arteries, veins, and capillaries (plasma) 

-Primarily saline (sodium chloride, bicarbonate, and protein)

Intracellular fluid (ICF): • within the cells • comprises 40% of total body weight

• Interstitial space-area surrounding cells

-Primarily water

Cell membranes separate: • intracellular compartments • extracellular compartments 

Capillary membranes separate: • intravascular space • interstitial space 

-Solutes (substances dissolved in water) and water move in both directions through semipermeable membranes.

Osmosis: The movement of fluid through a semipermeable membrane from an area of low solute concentration to an area of higher solute concentration until equilibrium is reached.

Diffusion: The movement of ions and molecules across a semipermeable membrane, from an area of high concentration to an area of lower concentration, until equilibrium is reached.

Filtration: The movement of water and solutes from an area of higher hydrostatic pressure to an area of lower pressure as in glomerular filtration.

Active Transport • Moves substances from an area of low concentration to an area of higher concentration • Requires energy • Example: Sodium-potassium pump

Osmolality Osmolality is the concentration of a solution expressed in osmoles of solute particles per kilogram of solvent. 

-Normal serum osmolality: 275-295 mOsm/kg

-Affects tonicity (normal tension of tissues) 

Osmotic pressure: 

• The pressure needed to prevent osmosis through a semipermeable membrane 

• Occurs between a solution and a pure solvent. 

• Is proportional to the osmolality of the solution 

Isotonic (iso-osmolar) solutions: Have the same osmotic pressure as blood Examples 

• Normal saline (NS or 0.9% NaCl) 

• Lactated Ringer's solution 

• 5% dextrose in water (D,W)

Hypotonic Solutions 

-Lower osmotic pressure than blood 

Examples: • ½ Normal saline (½ NS or 0.45% NaCl) • 2.5 dextrose in water (D2sW)

Hypertonic solutions 

-Higher osmotic pressure than blood

-Ex: 5% dextrose in normal saline (D,NS) • 5% dextrose in lactated Ringer's solution (DSLR)

Balancing Fluid 

-Volume In a healthy person, fluid intake and output are nearly equal. 

The body balances fluid volume through: 

• Thirst: 

• Kidneys: release Renin to combine Angiotensin to form 1 then lungs to 2 to adrenal cortex to release Aldosterone for sodium and water into ECF

• Renin-angiotensin-aldosterone system: ^

• Antidiuretic hormone (ADH or vasopressin): Posterior Pituitary Gland, increased osmolality and water retention 

• Atrial natriuretic peptide (ANP): Atria and decrease fluid retention by blocking aldosterone and renin secretion 

Hypovolemia 

Fluid volume deficit or hypovolemia is a diminished blood volume. 

Causes may include: • Fluid loss • Reduced fluid intake • Fluid shift out of vascular space 

Conditions that can result in hypovolemia: • Fluid loss • Hemorrhage • Frequent urination • Vomiting • Diarrhea • Fistulas • Fever • Excessive nasogastric suctioning

Hypovolemia 

Causes of hypovolemia (continued): 

Reduced fluid intake • Dysphagia (difficulty swallowing) • Unconscious states • Lack of fluids • Lack of supplemental water when receiving concentrated tube feedings • Reduced ability to sense taste (older adults) 

Fluid shift out of the vascular space • Burns • Acute intestinal obstruction • Pancreatitis • Crushing injuries

Clinical manifestations

• Hypotension • Tachycardia • Thirst • Poor skin turgor • Dry mucous membrane • Decrease in urinary output • Flattened neck veins • If severe, shock

Treatment 

• Oral or parenteral fluids • Blood or blood products, if due to hemorrhage • Antidiarrheals if the loss is from diarrhea • Antiemetics if the loss is from vomiting • Vasopressors (vasoconstriction) may be ordered if the patient is in hypovolemic shock

Hypervolemia 

-Edema: localized or generalized 

-third spacing: Ascites (serous fluid in peritoneal cavity) and Pleural effusion (in pleural space that cause compression of lung = shortness of breath and increased work of breathing 

Causes

• Kidney failure 

• Heart failure 

• Cirrhosis: end stage of liver disease 

• Nephrotic syndrome:edema, albuminuria, decreased plasma albumin, doubly refractile bodies in urine, and increased blood cholesterol 

-Cushing disease: hyperaldosteronism 

-Renal disease 

Signs

• Dyspnea • Crackles • Tachypnea • Bounding, rapid pulse • Hypertension • Distended neck veins • Edema • Ventricular gallop • Clammy skin

Treatment 

• Identify and treat the underlying cause. • Restrict sodium and water fluid intake. • If severe, then oxygen therapy, morphine, intravenous diuretics, and mechanical ventilation

Electrolytes 

• The principal extracellular electrolytes are sodium, calcium, and bicarbonate; sodium being the dominant extracellular cation

• The principal intracellular electrolytes are potassium, magnesium, and phosphorus; potassium being the dominant intracellular cation.

Sodium Regulation 

The body regulates sodium through: • Dietary intake • Excretion • Kidneys • Hormonal regulation • Aldosterone • Antidiuretic hormone (ADH or vasopressin)

Hyponatremia: <135 mEq/ L

Loss of sodium due to: 

• Excessive diuresis • Diuretic therapy • Sodium-losing nephritis • Excessive sweating, with nonsodium fluid replacement • Gastrointestinal (GI) fluid loss • Vomiting • Diarrhea • Fistula • Adrenocorticoid insufficiency 

Excess of water due to: • Excess oral fluids • Excess parenteral administration of dextrose and water solutions such as D,W • Syndrome of inappropriate antidiuretic hormone (SIADH) • Excessive intravenous (IV) administration

The manifestations of hyponatremia are due to water shifting into cells, especially brain cells. Manifestations: • Apprehension • Headache • Personality changes • Coma

Hypernatremia: >135 mEq/ L

Intake of excessive sodium due to: • Rapid infusion of hypertonic saline, sodium bicarbonate, or isotonic saline • Drinking salt water • Ingesting large amounts of salt without increasing water intake

Loss of water due to: 

• Diarrhea • Increase in insensible loss • Diabetes insipidus • Decreased water intake • Unavailability of water • Withholding water • Impaired thirst center

Manifestations of hypernatremia are due to intracellular dehydration and intravascular volume depletion.

• Thirst • Dry, sticky mucous membrane • Decreased skin turgor • Weak, rapid pulse • Decreased blood pressure • Oliguria or anuria • Imitability • Decreased reflexes • Disorientation • Hallucinations

Hyponatremia Treatment: 

• Identify and treat the cause. • Restrict fluid intake. • Administer hypertonic 3% sodium chloride solution slowly and with caution, and only in clinical areas where close monitoring can be maintained.

Hypernatremia Treatment: 

• Administer hypotonic solution, such as 0.45 NaCl or 0.3% NaCl. • If diabetes insipidus is the cause of hypernatremia, desmopressin or vasopressin may be ordered.

-Chloride: Sodium often combines with this anion 

-Normal serum sodium: 139-144 mEq/L

-Aldosterone and ADH: Hormones 

-Kidneys: Sodium excretion 

Potassium 

• Essential in creating the resting membrane potential in neuromuscular tissue • Transforms carbohydrates into energy • Changes glucose into glycogen • Helps build up amino acids into protein

The body regulates potassium through: • Dietary intake • Excretion • Kidneys • Hormonal regulation: Aldosterone The mineralocorticoids, primarily aldosterone, cause the kidneys to retain sodium and excrete potassium. 

Hypokalemia: Serum potassium level < 3.5 mEq/L 

• Alcohol misuse disorder • Alkalosis • Anorexia nervosa • Cushing syndrome • Diuretic agents • Hyperalimentation • Prolonged vomiting/diarrhea

Manifestations of hypokalemia are due to alterations in cardiovascular, skeletal, and gastrointestinal function.

Hypokalemia causes: • Apnea • Hypotonic bowel sounds • Muscle fatigue Electrocardiogram (ECG) changes with hypokalemia: • Flattened T wave • Prolonged PR interval • Large U wave

Hyperkalemia: Serum potassium level > 5.0 mEq/L

• Acidosis • Burns • Crushing injuries • Hypoaldosteronism (primary adrenal insufficiency) • Rapid IV administration • Kidney failure

Manifestations of hyperkalemia are related to potassium's influence on resting membrane potentials. 

• Abdominal pain • Tingling fingers ECG changes with hyperkalemia: • Tall peaked I wave • Widening QRS complex • Ventricular fibrillation • Cardiac arrest

Hypokalemia Care of the patient with hypokalemia includes: • Identifying the underlying cause and treating it • Replacement therapy, either by mouth (PO) or . intravenously (IV), depending on severity • Foods high in potassium: • Oranges • Banana • Cantaloupes • Prunes • Squash • Raisins • Dried beans • Potatoes • Sweet potatoes • Administering IV potassium with an IV pump • Checking policy regarding the rate of infusion 

Care of the patient with hyperkalemia includes: • Reducing intake of foods high in potassium • Stopping potassium-sparing diuretics • Administering sodium polystyrene sulfonate PO • Administering 50% glucose with insulin IV

Chloride 

• Maintains acid-base balance • Maintains osmotic pressure • Maintains acidity of gastric secretions

Chloride Regulation The body regulates chloride through: Dietary intake: • Excretion • Kidneys • Acid-base balance. 

Hypochloremia: Serum chloride level < 95 mEq/L

• Excessive vomiting • Gl suctioning Causes of hyperchloremia: • Excessive ingestion • Decreased excretion

Clinical manifestation of hypochloremia: • Metabolic alkalosis • Hypertonicity of muscles • Depressed respiration • If severe, tetany 

Hyperchloremia: Serum chloride level > 105 mEq/L

Clinical manifestation of hyperchloremia: • Metabolic acidosis • Stupor • Deep, rapid respirations • Weakness • If severe, coma

Patient Care Care of a patient with hypochloremia: • Identify and treat the underlying cause. • Replacement therapy 

Care of a patient with hyperchloremia: • Treat metabolic acidosis. • Sodium bicarbonate IV • Lactated Ringer's solution IV FEB

Calcium 

Calcium is essential for: • Neuromuscular function • Transmission of nerve impulses • Contraction of skeletal and cardiac muscle • Clotting of blood • Maintenance of normal cell membrane permeability • Formation of bones and teeth

The body regulates calcium through: • Dietary intake • Vitamin D • Parathyroid hormone (PTH) regulates absorption and excretion • Calcitonin • Inverse relationship with phosphate 

Hypocalcemia: Serum calcium level < 8.6 mg/dL 

• Hypoparathyroidism • Surgical removal • Idiopathic • Thyroid cancers • Hyperphosphatemia • Malabsorption • Vitamin D deficiency • Excessive administration of citrated blood • Hypoalbuminemia

Clinical manifestation 

• Numbness, tingling of hands, toes, and around the mouth • Weakness • Emotional instability • Muscle cramping • Hypotension • Hyperactive deep tendon reflexes • Chvostek sign • Trousseau sign • Tetany • Seizures • Decreased myocardial contractility • Poor clotting • ECG with shortened QT interval

Hypercalcemia: Serum calcium level > 10.5 mg/dL

• Hypophosphatemia • Certain cancers • Thyrotoxicosis • Acromegaly • Kidney failure

Clinical manifestation

• Anorexia, nausea, and vomiting • Constipation • Hypertonicity of the muscles • Increase in cardiac contractility • Decrease in heart rate • Renal calculus • ECG with wide T wave • Confusion

Treatment of hypocalcemia: • Oral replacement: Dietary supplement of calcium with vitamin D • IV calcium replacement • Calcium gluconate • Calcium chloride 

Treatment for hypercalcemia: • Identify and remove the cause, if possible • IV fluids with diuretic

Phosphorus 

• Essential component of bone • Affects metabolism of carbohydrates, lipids, and protein • Component of adenosine triphosphate (ATP) and 2,3 DPG • Major buffer in maintaining acid-base balance

• Dietary intake • Excretion • Kidneys • Parathyroid hormone (PTH) secretion 

Hypophosphatemia: Serum phosphorus level < 2.5 mg/dL 

Hypetphosphatemia: Serum phosphorus level > 4.5 mg/dL

Selected causes of hypophosphatemia: • Alkalosis • Diabetic ketoacidosis • Hyperalimentation • Hyperparathyroidism • Phosphate-binding antacids (aluminum and calcium) 

Selected causes of hyperphosphatemia: • Kidney failure • Hypoparathyroidism • Chemotherapy • Large intake of calcium • Excessive use of phosphate laxatives or enemas

Examples of clinical manifestations of hypophosphatemia: • Hemolysis • Platelet dysfunction • Paresthesia • Seizure 

Examples of clinical manifestations of hyperphosphatemia: • Tetany • Hypotension • ECG with shortened QT interval

Treatment for hypophosphatemia: • Identifying and treating the underlying causes • Replacement therapy either PO or IV, depending on severity. 

Treatment for hyperphosphatemia: • Identifying and treating the underlying causes • Restricting intake • Calcium-based phosphate binders

Magnesium 

• Enzyme activity • Carbohydrates and protein metabolism • Synthesis of protein and DNA • Electrical activity of the heart, muscles, and nerves

• Dietary intake • Parathyroid hormone (PTH) regulates absorption and excretion • Influenced by calcium absorption • Excreted by the kidneys 

Hypomagnesemia: Serum magnesium level < 1.5 mg/dL 

• Diuretic therapy • SIADH • Small bowel bypass surgery • Hypercalcemia

Hypermagnesemia: Serum magnesium level > 2.5 mg/dL

• Decrease in kidney excretion • Increase in intake • Traumatic soft tissue injury

ECG changes 

• Ventricular extrasystole • Prolonged PR interval • Widening of QRS complex • Tall I wave • Complete heart block • Cardiac arrest

Treatment for hypomagnesemia: Replacement therapy 

Treatment for hypermagnesemia: • Eliminating ingestion • Calcium