alterations in fluid and electrolytes Chapter 8

intracellular fluid compartment

makes up 2/3

extracellular fluid compartment

makes up 1/3

intracellular water of body weight

makes up 40%

extracellular water of body weight

makes up 20%

electrolyte

substances that dissociate in solution to form charged particles

what does ECF have lots of?

lots of sodium and chloride

what doesn’t ECF have lots of

little Potassium

what does ICF have lots of?

lots of potassium

what doesn't ICF have lots of?

little sodium and chloride

Osmosis

movement of water down its concentration gradient \n across a semipermeable membran

increase in ECF osmolarity

water leaves the cell

decrease in ECF osmolarity

water enters the cell

tonicity

tension or effect a solution with impermeable solutes exerts on cell size due to water movement across the cell membrane

what does water always move from?

low to high osmotic pressure

capillary filtration pressure (hydrostatic)

pushes water out of capillary and into tissue

capillary colloidal /osmotic pressure

pulls water into capillary from tissue

interstitial hydrostatic pressure

pushes water out of tissue and into capillary

interstitial colloidal osmotic pressure

pulls water into tissue and out of capillary

hydrostatic pressure

pushes fluid into something

colloidal osmotic pressure

pulls fluid into something

interstitial pressures

pushes fluid in and out of something

lymph system

accessory system where fluid is returned to the circulatory system

edema

palpable swelling produced by an increase in interstitial fluid volume

increased capillary filtration pressure

Increased vascular volume \n • Heart failure, kidney disease \n • Hormone-related sodium retention, pregnancy \n • Venous obstruction \n • Liver disease, pulmonary edema, venous \n thrombosis

decreased capillary colloidal pressure

Increased loss of plasma proteins (burns, \n glomerular basement membrane injury) \n • Decreased plasma protein production (liver \n disease, malnutrition, starvation

increased capillary permeability

Inflammation, allergic reactions \n • Tissue injury and burns

obstruction of lymph flow

Malignant obstruction \n • Removal of lymph nodes

manifestations of edema

life threatening : brain, lungs, and larynx

impairs movement and discomfort

tissue level : impairs diffusion of oxygen, nutrients, and waste which increases damage

pitting

fluid exceeds absorptive capacity

edema- assessment

daily weights, visual inspection, and pitting ed

edema treatment

elevation, diuretics, and albumin replacements if needed

third spacing

considerable enlargement of transcellular fluid compartment (fluid is trapped)

ascites

accumulation of fluid in peritoneal cavity

total body water

varies by body composition

increase in lean muscle mass and infants

decrease with age and obesity

sodium

normal levels: 135-145

primary loss through kidneys

big loss through vomitting and diarrhea

little loss through GI and skin

effective circulating volume

monitored by sensors in vascular system and kidneys

baroreceptors

respond to pressure-inducted stretch of vessel walls

mechanisms of water and sodium regulation

ADH

SNS

RAAS

ANP

high osmolarity leads to

increase thirst

release of ADH

low osmolarity leaves to

lack of thirst

decreased ADH release

hypodipsia

decrease in ability to sense thirst

polydipsia

excessive thirst

true thirst

loss of body water and resolves with fluid replacement

false thirst

occurs with chronic diseases, dry mouth, medications

psychogenic

compulsive-schizophrenia

what does ADH controls ?

resorption of water by the kidneys

diabetes insipidus

insufficiency of ADH

partial or total inability to concentrate the urine that increases plasma osmolarity resulting in hypertonic dehydration

\-enhanced water excretion

\-hypernatremia

\-serum hyperosmolarity

decrease in H2O and increase in osmolarity

syndrome of inappropriate antidiuretic hormone secretion

hypersecretion of ADH

\-enhanced renal water retention

\-hyponatremia

\-sereum hypo-osmolarity

low urine output, GI symptoms, dulled senses, mental changes

increase in H2O and decrease in osmolarity

isotonic

proportional changes in sodium with changes in water

hypotonic dilution or hypertonic concentration of extracellular fluid volume will?

cause water movement between ECF and ICF

isotonic fluid deficit

causes: volume loss( vomiting and diarrhea), third spacing, endocrine disturbances

compensatory mechanisms: increased thirst, increased ADH

manifestations:

Vascular dehydration - decrease skin turgor, dry mucous membrane, sunken eyeballs

decrease vascular volume- postural hypotension, weak rapid pulse

isotonic fluid volume excess

causes: decrease renal elimination (kidney disorder, heart and liver failure)

manifestations:

increased interstitial fluid volume: edema

increased vascular volume: bounding pulse, pulmonary edema ( shortness of breath, crackles, cough)

dispropriate changes in sodium or oxygen leaves to what?

movement of oxygen between ICF and ECF

hyponatremia

greater than 135

water moves into cells

manifestations: salt loss ( lethargy, anorexia, limp muscles, stupor)

treatment: add sodium via hypertonic IV solution, loop diuretic to increase oxygen elimination

hypertonic translational

osmotic shift from ICF to ECF

hypotonic dilution

sodium and water loss

edema

hypernatremia

greater than 145

causes: water deficit, decreased oxygen intake, sodium administration

water moves out of cell

manifestations: dry skin, decrease tissue turgor, elevated body temperature

treatment: replacement fluids

potassium

most intracellular electrolyte

essential for normal cell functions: osmolarity and fluid balance, glycogen and glucose deposition in skeletal muscle and liver, nerve and skeletal muscle and cardiac function

mechanisms of regulation: kidney and transcellular shift between ECF and ICF

3\.5-5.0

renal regulation

ADH increases potassium which stimulates RAAS resulting in renal excretion

K+/H+ exchange

extracellular-intracellular shifts

sodium/postassium-ATPase pump

potassium.hydrogen exchange

\
Insulin, catecholamines, and β-adrenergic agonists \n increase cellular uptake via ↑ Na+/K+-ATPase pump \n activity

what is potassium vital to the regulation of?

resting membrane potential

opening sodium channels during action potential

rate of membrane repolarization

can have significant effects on cardiac, skeletal, and smooth muscle

hyperkalemia

decreases membrane excitability

hypokalemia

decreases resting membrane potential

hypokalemia causes what?

inadequate intake

excessive losses- renal, skin, and GI

redistribution between ICF and ECF compartments

(diarrhea, insulin, eating disorders)

hypokalemia manifestations

Impaired ability to concentrate urine – polyuria, polydipsia \n • GI – anorexia, N/V, constipation, abdominal distention, paralytic ileus \n • Neuromuscular – weakness, fatigue, muscle cramps, paresthesia, paralysis \n • Cardiovascular – postural hypotension, ECG changes, dysrhythmias \n • CNS – confusion, depression \n • Metabolic alkalosis

hypokalemia treatment

IV replacement ( must be slow) (if not could cause cardiac arrest)

hyperkalemia

causes: Decreased renal elimination – renal failure, Addison disease, K

\+-sparing diuretics, ACEi/ARBs \n • Excessive intake \n • Movement from ICF to ECF – tissue trauma, burns, seizures, acidosi

hyperkalemia manifestations

GI –N/V/D, cramping \n • Neuromuscular – weakness, dizziness, muscle cramps, paresthesia \n • Cardiovascular –ECG changes, bradycardia, ventricular fibrillation, cardiac \n arrest

hyperkalemia treatment

In emergent situations – IV insulin (plus glucose to prevent hypoglycemia), \n calcium, sodium bicarbonate \n • Insulin stimulates Na+/K+ pump – brings K+ into cells and pumps out Na+

\

calcium

Normal level is 8.5 to 10.5 mg/dL. \n • Functions: \n • Bone strength and stability. \n • Membrane potentials and excitability. \n • Contraction of all muscle types. \n • Clotting. \n • Second messenger in many hormone and \n neurotransmitter pathways

parathyroid hormone

Maintains blood calcium and phosphorous \n • Stimulates release of calcium and phosphorus \n from bone \n • ↑ renal resorption of calcium \n • ↑ GI calcium absorption \n • Requires activation of Vitamin D and magnesium \n • Vitamin D \n • Increases intestinal absorption of calcium \n phosphorous \n • Necessary for normal bone formation

hypocalcemia

greater than 8.5

nerves fire more easily bc Calcium stabilizes neuromuscular excitability, making them less sensitive to stimuli

decrease in calcium and increases excitability

cardiovascular effects: hypotension and prolonged QT interval

hypercalcemia

less than 10.5

Nerves are less able to fire → decreased excitability \n • Cardiovascular effects: hypertension, shortened QT interval

phosphorus

normal 2.5-4.5

Functions: \n • Bone and ATP formation \n • Glucose, fat, protein metabolism \n • In DNA, RNA, phospholipids \n • Acid-base buffer \n • RBC, WBC, platelet function

Magnesium

normal 1.3-2.1

Functions: \n • Cofactor in enzymatic reactions: \n • ATP generation \n • DNA replication \n • mRNA production and translation \n • Blocks K+ exit from cardiac cells \n • Smooth muscle relaxant