PAT 201 - Week 6 Fluid and Electrolytes

distribution of body fluids

• body fluids divided into fluid compartments

• extracellular fluid composed of plasma interstitial fluid

• through semi-permeable cell membranes

• moves continuously between intracellular and extracellular compartments

intracellular compartment (ICF)

fluid that sits within the cell

extracellular component (ECF)

• fluid that sits outside the cell

• broken into two groups: interstitial fluid and blood plasma

interstitial fluid

fluid between cells

blood plasma

fluid within blood vessels (another term is intravascular fluid)

ions of extracellular fluid

Na+, Ca2+, Cl-, HCO3- (bicarbonate)

ions of intracellular fluid

K+, Mg2+, PO43- (phosphate), proteins

osmolarity formula

2(Na+) + 2(K+) + Glucose + Urea

Na+ value

135-145 (higher number because we have more sodium outside of cell)

K+ value

35-51 (lower because less potassium outside of cell)

what is found in plasma

• water (about 90-92%)

• plasma proteins

• electrolytes

• hormones waste products

• gases

aging and distribution of body fluids

• newborn (total body fluid is 70-80%)

• men have more water inside them than females

• individuals who carry fat have less body fluid

• infants have high body fluid, elderly have low → both these extremes are fragile when it comes to water

diffusion

particles move from an area of higher concentration to an area of lower concentration until they reach equilibrium

active transport

particles move from an area of lower concentration to an area of higher concentration; this requires energy (ATP)

osmosis

movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration

filtration

pressure pushes water and small dissolved substances across a membrane

• example: the kidneys reabsorb water and sodium back into the bloodstream

reabsorption

substances return to the blood

starling forces

hydrostatic and oncotic pressures that control the movement of fluid between capillaries and surrounding tissue

osmolallity

the concentration of dissolved particles (solutes) in a fluid; it affects how water moves between ICF and ECF

osmotic forces

forces created by differences in solute concentration that cause water to move across a semipermeable membrane toward the area with the higher solute concentration

sodium for the extracellular fluid

major cation outside cells

potassium for the intracellular fluid

major cation inside the cell

aquaporins

family of water channel proteins that provide permeability to water

water and waste

hydrostatic and osmotic pressure

• plasma does not cross the capillary membrane → because the capillary wall restricts their passage

• water and so many dissolved substances can cross the capillary wall

capillary hydrostatic pressure (pushes out)

pressure exerted by blood against capillary wall, pushes fluid out of capillaries into interstitial space

interstitial oncotic pressure (pulls out)

osmotic pull created by proteins in the interstitial fluid, tends to pull fluid out of capillaries into interstitial space

capillary oncotic pressure (pulls in)

osmotic pull created mainly by plasma proteins, especially albumin, in the blood; pulls fluid into capillaries from interstitial space

interstitial hydrostatic pressure (pushes in)

pressure exerted by interstitial fluid against the outside of capillaries; when positive it tends to push fluid into capillaries

pathophysiology of edema

• increases capillary hydrostatic pressure (think elevated pressure)

• decreased capillary oncotic pressure

• increases capillary membrane permeability (burns or inflammation)

• lymphatic channel obstruction (purpose of lymph is to drain the fluid in lymph vessels which reduces swelling)

edema

• manifestations: localized vs generalized dependent (peripheral), pitting vs non-pitting (lymphedema), third space, pulmonary edema (lots of fluid in lungs lead to SOB, crackles, ascites (edema in abdomen), cerebral edema (fluid in brain), weight gain

• evaluations: physical exam, weight gain, input/output

• treatment: treat the underlying condition (don’t just treat symptoms treat the cause of those symptoms), diuretics, elevating limbs, compression stockings, avoiding prolonged standing, restricting salt intake (it leads to drinking more water which leads to hydrostatic pressure and edema gets worse)

sodium

• primary extracellular fluid cation

• regulations osmotic forces

• aldosterone (Na+ increase) and natriuretic peptides (Na+ decrease)

aldosterone

• Na+ increase

• when blood pressure drops the process starts where this is formed and it starts to reabsorb water and sodium and blood pressure goes up

• the two roles is to reabsorb sodium and water and waste potassium

natriuretic peptides

• Na+ decrease

• it does the opposite from aldosterone

• when blood pressure is too high it starts informing the kidneys to pee out the water because there is too much water

chloride

• primary extracellular fluid anion

• follows Na+

• provides electroneutrality

renin-angiotensin-aldosterone system

• aldosterone

• increases excretion of potassium by the distal tubule of the kidney

natriuretic peptide system

• decreases tubular reabsorption

• natriuretic peptides do the opposite; when blood pressure is too high it starts informing the kidneys to pee out the water because there is too much

• promotes urinary excretion of sodium and water

• decreases BP

→ atrial natriuretic peptide

→ B-type peptide

→ urodilation (kidney)

ADH (antidiuretic hormone)

• hormone that helps the body retain water

• released form the posterior pituitary gland

• signals the kidneys to reabsorb more water back into the blood stream

• less water leaves the body thrugh urine

• helps maintain blood volume and blood osmolality

antidiuretic hormone system

there are two main types of receptors that help trigger ADH release:

1. osmolality receptors (osmoreceptors)

2. baroreceptors

osmolality receptors (osmoreceptors)

• signals posterior pituitary to release ADH

• increase water intake

baroreceptors

• stimulated from depleted plasma volume

• causes release of ADH

tonicity

predicts whether cells swell, shrink, or stay the same

osmolality

measures how concentrated a fluid is

isotonic

• same solute concentration inside and outside of the cell

• water moves in and out at equal rates

• no net water movement

• cell stays the same size

hypertonic

• higher solute concentration outside the cell

• water moves out the cell

• cell loses water and shrinks

hypotonic

• lower solute concentration outside the cell

• water moves into the cell

• cell gains water and swells (may burst)

normal adult Na+

136-145 mmol/L (136-145 mEq/L)

isotonic fluid loss

hypovolemia

isotonic fluid gain

hypervalemia

hypovolemia

pathophysiology

• loss of plasma or extracellular fluid, fluid volume is depleted

• hemorrhage severe wound drainage, excessive diaphoresis, diarrhea, urine+

manifestations

• weight loss, dry skin and mucous membranes, decreased urine output, urine colour becomes concentrated since all waste is mixed with water, increased hematocrit (concentration of RBC in the water around it)

evaluation

• rapid HR, flattened neck veins (not enough fluid there), normal or decreased BP, severe hypovolemic shock (medical emergency when BP drops and heart rate is high), elevated serum Na>145mmol/L

treatment

• give them fluids

• IV NS (0.9% normal saline), or RL (ringers lactate) or D5W (only contains glucose and water, good if patient is fasting)

hypervolemia

pathophysiology

• gain of plasma or extracellular fluid, fluid volume is increased

• excessive Na+ IV fluids, hypersecretion of aldosterone, corticosteroids kidney disease

manifestations

• weight gain, decreased hematocrit, decreased plasma protein (because it is diluted in all the water)

evaluation

• distended neck veins, increased BP, edema, pulmonary edema (capillary hydrostatic pressure), heart failure

treatment

• diuretics

hypernatremia

pathophysiology

• increased sodium, water deficit, hyperglycemia

• solution where you end up with way more sodium than normal

• can be hypovolemic, isovolemic, or hypervolemic

• primary organ that struggles with this is the brain → it increases ECF osmolality, causing water to move out of cells; brain cells are particularly sensitive to this water loss

manifestations

• weakness, lethargy, muscle twitching, hyperreflexia, confusion, coma, seizures

evaluations

• serum Na+>145mEq/L, urine specific gravity >1.030, increases hemotocrit and plasma protein levels

treatment

• isovolemic and hypovolemic → increase oral H2O or IV D5W

• loop diuretics → to promote sodium excretion

signs and symptoms of dehydration

• Increases serum Na+ concentration

• Thirst

• Headhache

• Sudden weight loss

• Oliguria (low urine)

• Hard stools

• Decreased skin turgot

• Dry skin/mucous membranes

• Decreased sweating and tears

• Elevated body temperature

• Soft eyeballs

• Sunken fontanels (infants) → the skull in the baby is not fully developed so lots of fluid the ehad can become bigger than normal and also skin in

• Prolonged capillary refill time

• Tachycardia

• Weak pulses

• Postural hypotension

• Low blood pressure

• Hypovolemic shock

• lethargy/weakness

• confusion/coma

hyponatremia

pathophysiology

• decreased sodium, water excess, cellular dysfunction

• can be hypovolemic, isovolemic, dilutional, or hypervolemic

• means there is less sodium compared to the amount of water

manifestations

• water shifts into cells, potentially causing cellular swelling especially in the brain; depends on types, nausea, vomiting, edema, irritability, lethargy, headache, confusion, apprehension, seizures, coma

evaluation

• serum Na+ level <135mEq/L, elevated hematocrit and plasma, urine specific gravity <1/010

• low concentration of urine because there is so much water

treatment

• depends on the contributing disorder, restrict water intake, give sodium because there is not enough sodium

• severe hyponatremia give hypertonic (is 3%) normal saline

potassium (K+)

• is the major intracellular cation

• primary organ for this is the heart and muscles because potassium has to do with the depolarization and repolarization

• aldosterone, insulin, and epinephrine facilitate K+ into the cells

• insulin deficiency, aldosterone deficiency, acidosis, and strenuous exercise facilitate K+ out of the cells

• the sodium potassium pump maintains concentration

• potassium is essential for the transmission and conduction of nerve impulses, normal, cardiac rhythms, and skeletal and smooth muscle contraction

• normal adult: 3.5-5.0 mEq/L

hypokalemia

pathophysiology

• less than normal potassium in the blood

• decreased intake, increased renal loss (loosing potassium through the kidneys) shift from extracellular fluid to intracellular fluid

manifestations

• mild losses are usually asymptomatic (no symptoms)

• symptoms include skeletal muscle weakness, fatigue, muscle cramps, decreased gastrointestinal motility, constipation, and cardiac dysrhythmias

• LOW AND SLOW

• severe <2.5Eq/L: skeletal muscle weakness, smooth muscle atony, cardiac dysrhythmias, glucose intolerance, and impaired urinary concentrating ability

evaluation

• serum K+ level <3.5mEq/L

treatment

• depends on the contributing disorder, replace K+ oral or IV → be very careful with giving potassium

ECG changes

hypokalemia

• impaired repolarization → resting state

  • notice the longer PR interval, depressed ST segment, flattened T-wave, prominent U-wave

  • ventricular arrhythmias, bradycardia

hyperkalemia

• impaired depolarization → contraction

  • notice the low or absent P wave, longer PR interval, widened QRS complex, peaked/narrow T wave

  • bradycardia, ventricular fibrillation, cardiac arrest

hyperkalemia

pathophysiology

• elevated level of potassium

• excessive intake, decreased renal loss (not losing potassium), shift from intracellular fluid to extracellular fluid

manifestations

• mild: increased irritability, restlessness, intestinal cramping and diarrhea

• sever: decreases the resting membrane potential = muscle weakness, loss of muscle tone and paralysis

• major immediate danger is potentially fatal cardiac dysrhthmia

• wider and taller

evaluation

• serum K+>5.5 mEq/L

treatment

• depends on the contributing disorder, corrected excessive K+

• calcium gluconate insulin and/or glucose, buffered solutions, dialysis

three hormones that regulate calcium and phosphate

1. PTH increases plasma calcium levels via kidney reabsorption

2. vitamin D increases calcium absorption from the GI tract

3. calcitonin decreases plasma calcium levels

normal adult total Ca+

2.1-2.5 mmol/L

normal range for adult ionized calcium

1.5 mmol/L - 1.25 mmol/L

normal range for adult albumin

35-55 g/L

• remember: changes in this can affect total calcium, while ionized calcium more directly reflects physiologically active calcium

normal range for adult phosphate

1.0 - 1.5 mmol/L

normal range for adult magnesium

0.6 - 1.05 mmol/L

hypocalcemia

pathophysiology

• inadequate intake or absorption, decreases PTH and vitamin D, alkalosis, blood transfusions, excessive amounts of dietary phosphorus, severe hypomagnesemia, hypoalbuminemia

manifestations

• increased neuromuscular excitability (partial depolarization), tingling, intestinal cramping, muscle spasms, chvostek and troussea signs, convulsions, tetany, ECG changes is a prolonged QT interval

evaluation

• total calcium levels <8.5mc/dL and ionized levels <5.5mg/dL, serum phosphate may be elevated, albumin and magnesium may be low

treatment

• calcium gluconate, calcium replacement, decrease phosphate intake

hypercalcemia

pathophysiology

• hyperparathyroidism (if hypothyroid gland is enlarged it creates a lot of hyperparathyroidism hormone which role is to absorb calcium), bone metastasis (destroying cells of the bone), excess vitamin D (role of vitamin is to absorb calcium), immobilization, acidosis, sarcoidosis

manifestations

• decreased neuromuscular excitability, fatigue, weakness, lethargy, anorexia, nausea, consitpation, impaired renal function, dysrhythmias, fractures

evaluations

• calcium levels >10.5 mg/dL

treatment

• oral phosphate, IV normal saline, biphosphonates, calcitonin, denosumab

hypophosphatemia

pathophysiology

• similar symptoms to hypercalcemia (very slow and low)

• intestinal malabsorption and renal excretion, vitamin D deficiency, antacid use, alcohol abuse, malabsorption syndromes, weakness, organs not working properly

manifestations

• diminished released of oxygen, osteomalacia, muscle weakness, bleeding, disorders (platelets impairment), leukocyte alterations, rickets

evaluation

• serum phosphate level <2.0mg/dL

treatment

• treat underlying condition scuba respiratory alkalosis and hyperparathyroidism

hyperphosphatemia

pathophysiology

• acute or chronic oliguric renal disease, chemotherapy, long-term use of phosphate enemas, hypoparathyroidism

manifestations

• same as hypocalcemia with possible calcification of soft tissue

evaluation

• serum level >4.7mc/dL

treatment

• treat underlying condition, aluminum hydroxide, and dialysis

magnesium (Mg2+)

• major intercellular cation, second to potassium

• 40% to 60% is stored in muscle and bone, 30% in the cells

• extracellular magnesium is needed for normal neuromuscular excitability and nerve conduction

• magnesium improved myocardial cell function; reduces cardiac dysrhythmias; improves lipid and glucose metabolism

• magnesium also inhibits platelet function, including platelet aggregation and adhesion

hypomagnesemia

pathophysiology

• malnutrition, malabsorption, alcoholism, urinary loss

manifestations

• behavioural changes, irritability, increased reflexes, muscle cramps, ataxia, tetany, seizures, hypertension

evaluation

• serum level <1.5 mEq/L

treatment

• treat underlying condition, magnesium sulfate IM or IV

hypermagnesemia

pathophysiology

• oliguric renal failure, excessive intake of magnesium, adrenal insufficiency

manifestations

• lethargy, drowsiness, loss of deep tendon reflexes, nausea, vomiting, muscle weakness, hypotension, bradycardia, respiratory depression, heart block, cardiac arrest

evaluation

• serum level >3.0mEq/L

treatment

• treat underlying condition, avoid magnesium, dialysis

pharmacotherapy of fluid and electrolyte imbalances

classification → drug

• potassium supplements → potassium chloride

• intravenous solutions → isotonic, hypotonic, hypertonic

potassium chloride

indications for use

• treating or preventing hypokalemia, mild forms of alkalosis

mechanisms of action

• well absorbed, widely distributed, excreted via kidneys

desired effects

• increased serum potassium, decreased dysrhythmias, maintenance of acid-base balance

adverse effects

• GI: abdo pain, N/V, diarrhea, bleeding/ulceration

• local: pain and irritation at IV site, phlebitis

• hyperkalemia

nursing implications

• careful monitoring for dysrhthmias

• contraindicated with severe renal impairment and K+ sparing diuretics

• instruct to take with meals

• check serum K+ levels before administering

• have client report any symptoms of hypokalemia

isotonic - intravenous solution

• expand intravascular volume and replace extracellular fluid losses

• fluid replacement for ECF volume deficit (expands only ECF)

• no net loss or gain from the ICF

hypotonic - intravenous solution

• intracellular dehydration provides more water than electrolytes, diluting ECF

• osmosis produces movements of water from ECF to ICF

• after osmotic equilibrium reached, ICF and ECF have same osmolality; both compartments expanded

hypertonic - intravenous solution

• treatment of hypovolemia and hyponatremia raises osmolality of ECF and expands it

• higher osmotic pressure causes water to shift out of cells and into ECF

fluid replacement solution

indications for use

• dehydration

mechanisms of action

• crystalloids can diffuse quickly across membranes, leaving plasma and entering ICF

• colloids drawing fluid from ICF and increase plasma osmolality and osmotic pressure

desired effects

• treat the volume deficit with the missing fluid

adverse effects

• hemorrhage, hypersensitivity to medication, SOB, cough, chest congestion, heart palpitations

nursing implication

• obtain incomplete health and drug history, physical exam, lab results

• contraindicated in clients with renal failure, hypervolemic conditions, severe heart failure

• monitor closely for first 30 min for hypersensitive reactions

• freq monitor I+O, VS, and neurological status

• have client report any flushing, SOB, cough, chest congestions, or heart palpations

• have client report any signs of bleeding, bruising blood in urine or stool