NURS 2373 Basic Pathophysiology Fluid & Electrolytes

Intracellular fluid (ICF)

Fluid that is inside the cell; makes up about 2/3 of total body fluid

Extracellular fluid (ECF)

Fluid that is outside the cell; makes up about 1/3 of total body fluid; includes intravascular, interstitial, and transcellular fluid

Intravascular fluid

Extracellular fluid located inside blood vessels; also called the vascular compartment; reflected by "serum" blood tests

Interstitial fluid

Extracellular fluid in the space between cells and vessels

Transcellular fluid

Extracellular fluid in specialized spaces such as synovial cavities and the pericardial/pleural space; about 1% of body fluid

Total body water (TBW)

Total water content of the body, approximately 60% of body weight; varies with age, gender, and body fat (higher in infants, lower in obese individuals and the elderly)

Diffusion

Movement of particles from an area of greater concentration to an area of lesser concentration (example: alveolar-capillary gas exchange)

Osmosis

Movement of water across a semipermeable membrane from an area of lesser solute concentration to an area of greater solute concentration

Osmolality

Concentration of solutes per weight of water; used to describe fluids inside the body; normal value 275-295 mOsm/kg; includes glucose, HCO3, Na+, Cl-, and urea

Tonicity

The movement of water (osmotic pull) that affects cell size; classified as isotonic, hypotonic, or hypertonic

Isotonic solution

Solution with the same osmolality as body fluids; cell size stays the same (280 mOsm/kg)

Hypotonic solution

Solution with lower osmolality than body fluids; causes cells to SWELL as water moves into the cell (

Hypertonic solution

Solution with higher osmolality than body fluids; causes cells to SHRINK as water moves out of the cell (>280 mOsm/kg)

Capillary filtration pressure

Pressure that pushes water out of the capillary into the interstitial spaces

Interstitial hydrostatic pressure

Pressure from the tissues that opposes the movement of water out of the capillary

Capillary colloidal osmotic pressure

Pressure created by plasma proteins that pulls water back into the capillary

Tissue colloidal osmotic pressure

Pressure that pulls water out of the capillary into the interstitial spaces

Edema

Swelling, an increase in interstitial fluid volume, is evident when interstitial volume exceeds 2-3 L

Localized edema

Edema in only one location, usually related to allergic reaction or inflammation

Anasarca

Generalized edema throughout the body, usually related to excess vascular volume

Pitting edema

Visible manifestation of edema where pressure leaves an indentation in the skin

Lymphedema

Edema caused by obstruction of lymph flow, such as from malignancy of the lymph system

Third space accumulation

Accumulation of fluid outside the vascular compartment that is not the interstitial space; fluid is not available for metabolic processes (also called effusion)

Ascites

Third space fluid accumulation in the peritoneal cavity (abdomen)

Perfusion

Delivery of oxygen to tissues via arteries; dependent on vessel diameter, volume, and resistance

Baroreceptors

Sensors that detect pressure changes in arterial vasculature (such as decreases in volume) and activate other fluid regulatory mechanisms

Sympathetic nervous system (SNS) - fluid regulation

Activated by baroreceptors; results in vessel constriction and increased heart rate (tachycardia) to help regulate fluid/pressure balance

Renin-Angiotensin-Aldosterone System (RAAS)

Activated by decreased renal blood flow; renin leads to angiotensin I, then angiotensin II (potent vasoconstrictor), then aldosterone (causes retention of sodium and water, and excretion of potassium)

Renin

Enzyme released by the kidneys in response to decreased renal blood flow; converts angiotensinogen to angiotensin I

Angiotensin II

Potent vasoconstrictor formed from angiotensin I; also stimulates aldosterone release

Aldosterone

Hormone that causes retention of sodium and water and excretion of potassium by the kidneys

Antidiuretic hormone (ADH)

Hormone released by the posterior pituitary; activated by increased osmolality and decreased ECF volume; causes reabsorption of water from the kidneys

Atrial natriuretic peptide (ANP)

Hormone released in response to atrial stretch; causes vasodilation and excretion of fluid by the kidneys

Causes of edema

caused by increased capillary filtration pressure, decreased capillary colloidal pressure, increased capillary permeability, or lymphatic obstruction

Third spaces (transcellular)

Pericardial sac, peritoneal cavity, pleural cavity

what happens to intravascular pressure if the vessel is constricted and volume stays the same

increased pressure

what happens to intravascular pressure if the vessel dilates and the volume stays the same

decreased pressure

what happens to intravascular pressure if the volume of blood in the vessel increases and the diameter stays the same

increased pressure

what happens to intravascular pressure if the volume of blood in the vessel decreases and the diameter stays the same

decreased pressure

hypothalmus role in fluid balance / perfusion

contains thirst center, responds to cellular dehydration or decreased ECF volume (increased ECF osmolality), has osmoreceptors

baroreceptors

sense changes in pressure of arteries

SNS role in fluid balance / perfusion

activated by baroreceptors, results in constriction of blood vessels to increase pressure (and increase perfusion), also results in increased heart rate (tachycardia)

isotonic fluid deficit

hypovolemia, water and electrolytes lost in proportional amounts

hypovolemia

low fluid volume, fluid volume deficit, compromises perfusion

causes of hypovolemia (fluid volume deficit)

dehydration, decreaed fluid intake, increased fluid loss, third space accumulation of fluid (fluid is no longer in circulation)

manifestations of fluid volume deficit (hypovolemia)

weight loss, increased serum osmolality, low blood pressure (hypotension), fast heart rate (tachycardia), concentrated blood, poor skin turgor, sunken eyes, increased temperature, decreased urine output

fluid volume excess (hypervolemia)

water and electrolytes are retained in proportional amounts

causes of hypervolemia (fluid volume excess)

weight gain, high blood pressure (hypertension), bounding pulse, edema, shortness of breath (dyspnea), cough, crackles in lungs, diluted blood

normal sodium range

135-145 mEq/L

causes of hyponatremia (low sodium)

burns, excessive sweating, vomiting, diarrhea, certain drugs or medications, heart failure, liver disease, kidney failure

manifestations of hyponatremia (low sodium)

low serum osmolality, nausea, abdominal cramps, apprehension, coma, headache, lethargy, personality changes, confusion, muscle cramps/weakness

causes of hypernatremia (high sodium) >145

diarrhea, sweating, breathing fast (tachypnea), decreased water intake, drinking salt water

manifestations of hypernatremia (high sodium)

high serum osmolality, thirst, tachycardia, low blood pressure, dry mucous membranes, poor skin turgor, headache, agitation, restlessness, seizures, coma

will cells shrink or swell with hypernatremia (high sodium)

SHRINK - high osmolality of serum = hypertonic = fluid will shift out of the cells toward the fluid and shrink

will cells shrink or swell with hyponatremia (low sodium)

SWELL - low osmolality of serum = hypotonic = fluid will shift into the cells and swell

normal potassium range

3.5 - 5.0 mEq/L

causes of hypokalemia (low potassium)

GI loss-vomiting, diarrhea, suction, renal loss-medications, high aldosterone, low magnesium, skin loss, drugs, alkalosis

manifestations of hypokalemia (low potassium)

CARDIAC DYSRHYTHMIAS, metabolic alkalosis, low blood pressure (hypotension), confusion, weakness, fatigue, cramping, paralysis

causes of hyperkalemia (high potassium)

decreased renal excretion, kidney failure, low aldosterone, medications, high intake of potassium, burns, acidosis

manifestations of hyperkalemia (high potassium)

CARDIAC DYSRHYTHMIAS, metabolic acidosis, low blood pressure (hypotension), diarrhea, muscle weakness, paresthesias, paralysis

hypokalemia

Low potassium levels in the blood.

hyperkalemia

High potassium levels in the blood.

hypernatremia

High sodium levels in the blood.

hyponatremia

Low sodium levels in the blood.

hypercalcemia

High calcium levels in the blood.

hypocalcemia

Low calcium levels in the blood.

hypermagnesemia

High magnesium levels in the blood.

Hypomagnesemia

Low magnesium levels in the blood.

where should most calcium in the body be?

in the bones (99%)

causes of hypocalcemia (low calcium levels)

decreased intake, vitamin d deficiency, hypoparathyroidism, kidney disease, pancreatitis

manifestations of hypocalcemia (low calcium levels)

CARDIAC DYSRHYTHMIA, hypotension, *neuromuscular - paresthesias, muscle cramps, hyperreflexia, tetany, bone pain, fractures

causes of hypercalcemia (high calcium levels)

increased absorption, high vitamin d, hyperparathyroidism, CANCER/malignancies*, IMMOBILIZATION

manifestations of hypercalcemia (high calcium levels)

hypertension, lethargy, personality changes, stupor, coma, *neuromuscular - weakness, atrophy, ataxia

when you think about hypercalcemia, what causes do you think of most?

malignancies, immobilization, hyperparathyroidism

when you think about phosphorous abnormalities, what causes do you think of most?

kidney problems

when you think about magnesium imbalance, what manifestations do you think of most?

cardiac dysrhythmias, blood pressure changes, neuromuscular - reflexes, personality, confusion, coma

when you think about calcium imbalance, what manifestations do you think of most?

cardiac dyrhythmias, blood pressure changes, neuromuscular - cramps, reflexes, weakness, mental changes

when you think of potassium imbalance, what manifestations do you think of most?

CARDIAC DYSRHYTHMIAS

when you think of sodium imbalances, what manifestations do you think of most?

mental changes, neurological changes