Fluid and Electrolyte Disorders

Adipose tissue

A type of body fat that stores energy; an increase in adipose tissue results in a lower percentage of water in the body.

Extracellular fluid (ECF)

Fluid outside the cells, comprising 20% of total body weight

-Intravascular spaces: arteries, veins, and capillaries

-Saline (Sodium chloride, bicarbonate, and protein)

Intracellular fluid (ICF)

Fluid within the cells, comprising 40% of total body weight

-Water

-Intersitial space area surrrounding cells

Osmosis

Movement of fluid through a semipermeable membrane from an area of low solute concentration to an area of higher concentration.

Diffusion

Movement of ions and molecules across a semipermeable membrane from high to low concentration.

Filtration

Movement of water and solutes from an area of higher hydrostatic pressure to lower pressure.

Active Transport

Movement of substances from low concentration to high concentration, requiring energy.

Ex: Sodium-potassium pump

Osmolality

measures the number of milliosmoles per kilogram of water, or the concentration of molecules per weight of water.

*preferred measure to evaluate the concentration of plasma, urine, and body fluids.

•1L = 1 kg of weight

Osmolarity

measures the total milliosmoles per liter of solution, or the concentration of molecules per volume of solution (mOsm/L).

Osmotic pressure

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 solutions

Solutions with the same osmotic pressure as blood

-normal saline (NS/0.9 % NaCl)

-lactated ringer’s solution

-5% dextrose in water (D,W)

Hypotonic solutions

Solutions with lower osmotic pressure than blood

• ½ Normal saline (½ NS or 0.45% NaCl)

• 2.5 dextrose in water (D2sW)

Hypertonic solutions

Solutions with higher osmotic pressure than blood.

-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

Diminished blood volume due to loss of fluids or reduced fluid intake.

-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

More causes of Hypovolemia

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 of hypovolemia

• Hypotension

• Tachycardia

• Thirst

• Poor skin turgor

• Dry mucous membrane

• Decrease in urinary output

• Flattened neck veins

• If severe, shock

Treatment of Hypovolemia

• 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

Excess fluid volume, can lead to edema and third spacing.

-Edema: localized or generalized 

-third spacing: Intravenous fluid shifts out of circulation in the blood and into the space between cells in organs and tissues

Ascites - serous fluid in peritoneal cavity

Pleural effusion - in pleural space that cause compression of lung = shortness of breath and increased work of breathing

Causes of Hypervolemia

• 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 and Treatment of Hypervolemia

• 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

Low sodium levels in the blood, defined as less than 135 mEq/L.

-Chloride: Sodium often combines with this anion 

-Normal serum sodium: 139-144 mEq/L

-Aldosterone and ADH: Hormones 

-Kidneys: Sodium excretion 

Hyponatremia causes

• 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

Manifesions of Hyponatremia

water shifting into cells, especially brain cells.

Manifestations: • Apprehension • Headache • Personality changes • Coma

Treatment of Hyponatremia

-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

High sodium levels in the blood, defined as greater than 145 mEq/L.

Causes of Hyperatremia

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

Manifesions 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

Treatment of Hypernatremia

• 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.

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

Low serum potassium level, defined as less than 3.5 mEq/L.

Causes of Hypokalemia and symptoms

• Alcohol misuse disorder

• Alkalosis

• Anorexia nervosa

• Cushing syndrome

• Diuretic agents

• Hyperalimentation

• Prolonged vomiting/diarrhea

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

Symptoms

• Apnea

• Hypotonic bowel sounds

• Muscle fatigue

Electrocardiogram (ECG) changes: • Flattened T wave • Prolonged PR interval • Large U wave

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 

Hyperkalemia

High serum potassium level, defined as greater than 5.0 mEq/L.

Causes of Hyperkalemia and manifestations

• Acidosis

• Burns

• Crushing injuries

• Hypoaldosteronism (primary adrenal insufficiency) like Addison’s disease

• Rapid IV administration

• Kidney failure

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

• Abdominal pain • Tingling fingers

ECG changes:

• Tall peaked T wave

• Widening QRS complex

• Ventricular fibrillation

• Cardiac arrest

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

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

Hypocholremia

Low serum chloride level, defined as less than 98 mEq/L.

Causes and manifestation of Hypocholremia

• Excessive vomiting

• Gl suctioning

• Excessive ingestion

• Decreased excretion

-Clinical manifestation:

• Metabolic alkalosis

• Hypertonicity of muscles

• Depressed respiration

• If severe, tetany

Care of a patient with hypochloremia

• Identify and treat the underlying cause.

• Replacement therapy 

Hypercholremia

High serum chloride level, defined as greater than 106 mEq /L.

Clinical manifestation of hyperchloremia

• Metabolic acidosis

• Stupor (lack of critical mental function)

• Deep, rapid respirations

• Weakness

• If severe, coma

Care of a patient with hyperchloremia

• Treat metabolic acidosis.

• Sodium bicarbonate IV

• Lactated Ringer's solution IV FEB

Calcium

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 through: • Dietary intake • Vitamin D

• Parathyroid hormone (PTH) regulates absorption and excretion

• Calcitonin

• Inverse relationship with phosphate 

Hypocalcemia

Serum calcium level < 8.5 mg/dL 

Causes and manifestation of Hypocalcemia

• 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 (face) • Trousseau sign (BP cuff)

• Tetany

• Seizures

• Decreased myocardial contractility

• Poor clotting

• ECG with shortened QT interval

Treatment of hypocalcemia

• Oral replacement: Dietary supplement of calcium with vitamin D

• IV calcium replacement

• Calcium gluconate

• Calcium chloride

Hypercalcemia

Serum calcium level > 10.5 mg/dL

Causes and manifestation of Hypercalcemia

• 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, short ST segment and QT intervel

• Confusion

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

Low serum phosphorus level, defined as less than 2.5 mg/dL.

Causes and Manifestions of Hypophosphatemia

-Selected causes: • Alkalosis

• Diabetic ketoacidosis

• Hyperalimentation

• Hyperparathyroidism

• Phosphate-binding antacids (aluminum and calcium) 

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

Treatment for hypophosphatemia

• Identifying and treating the underlying causes

• Replacement therapy either PO or IV, depending on severity.

Hyperphosphatemia

High serum phosphorus level, defined as greater than 4.5 mg/dL.

Causes and Manifestions of Hyperphosphatemia

-Selected causes: • Kidney failure

• Hypoparathyroidism

• Chemotherapy

• Large intake of calcium

• Excessive use of phosphate laxatives or enemas

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

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

Low serum magnesium level, defined as less than 1.8 mg/dL.

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

ECG: Prolong QT intervel

Treatment for hypomagnesemia

Replacement therapy 

Hypermagnesemia

High serum magnesium level, defined as greater than 3.0 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 T wave

• Complete heart block

• Cardiac arrest

Treatment for hypermagnesemia

• Eliminating ingestion

• Calcium