CH 17. Fluid and electrolytes

Less volume

Less pressure

More volume

More pressure

Transcellular

• Can’t access

• Urine, swear, digestive secretions, CSF

Electrolytes

Substance whose molecules dissociate into ions when placed in water

What are some examples of cations?

• Na

• K

• Mg

• Ca

What are some examples of anions?

• Cl

• PO₄³

• HCO3

What do electrolytes help do?

• Regulate and maintain pH in the body

• Essential for activity of body system

To function normally, body cells must have fluid and electrolytes in?

The right COMPARTMENT and right AMOUNT

What separates the compartments?

Semipermeable membranes

Body fluids

Transport nutrients to the cell and then carry waste products from the cells

Water accounts for % of an adult's total weight?

60

Diffusion

A solute moves through a solvent across a permeable membrane from high to low concentration requiring NO energy source

Facilitated diffusion

Bigger particles/solute (like glucose) moves through a solvent across a permeable membrane from high to low concentration requiring NO energy source, BUT does require help from a protein carrier

Osmosis

Movement of only water across a membrane from a low to higher concentration requiring NO energy source

Active transport

Movement of everything across a membrane from a low to higher concentration requiring ATP since it is going against the gradient

Osmotic pressure

• Force created by solutes that pulls water toward them across a semipermeable membrane

• More solutes there are, greater the pull

• “Salt Sucks”

The higher concentration of solutes

The greater the osmotic pressure or pulling power

Trick for OsmoLALITY

Sounds like reALITY

• Prefer to live in reality

Osmolality

Number of solute particles per kilogram

• mOsm/kg

• More precise / preferred

Osmolarity

Solutes per liter of solution

• mOsm/L

Hypotonic solution

Solutes are less concentrated than in cells

• Hypoosmolar

• Water moves into cell, causes swelling / potential bursting

• Hippo

Isotonic solution

Same as cell interior

• No major fluid shift

Hypertonic solution

Solutes are more concentrated than in cells

• Hyperosmolar

• Water moves out of cell, causes shrinkage / potential cell death

Hypotonic %

0.45%

Isotonic % (baseline, what we want)

0.9%

Hypertonic %

3%, 5%

What are all the systems that help fluids get regulated?

• Renal

  • GI

• Hypothalamic-Pituitary

• Adrenal Cortical

• Cardiac

Renal Regulation

• Kidneys filter & secrete

• Intake & Output

  • Intake: Oral & IV

  • Output: excretion & insensible losses

  • GI Tract regulation: Diarrhea & Vomiting

What can we use as an indicator of overall fluid volume loss or gain?

• Daily weights

• Strict I&O’s

Renal tubules are sites of action of

ADH and aldosterone

Hypothalamus =

Sensor + Thirst Center

Hypothalamic- Pituitary regulation

1. Hypothalamus detects deficit of fluids

2. Signals the Posterior Pituitary to release ADH

3. ADH then increases water reabsorption

Adrenal cortical regulation

Activates RAAS (Renin-Angiotensin-Aldosterone System) which triggers the release of Aldosterone to “hold on” to sodium and water while excreting potassium.

When would the adrenal cortical regulation trigger RAAS to release Aldosterone?

• Low BP / Low Blood Volume [think dehydration]

• Low Sodium levels

• High Potassium levels

Cardiac regulation

• ANP [Atrial natriuretic peptide] & BNP [B-type natriuretic peptide]

• Made by myocardial cells

• Released in response to increased pressure within heart chambers to stimulate the ELIMINIATION of water & sodium in urine

  • INHIBITS ADH & RAAS

  • Patient excretes more urine

ANP is released from the

Atria

BNP is released from the

Ventricles

Hypovolemia

• Decreased circulating blood volume

• Loss of water & electrolytes in equal proportions

Dehydration

Loss of water alone

Hypervolemia

• Increased circulating blood volume

• Too much water & electrolytes

Overhydration

Too much water alone

Hypovolemia S/S

• VS: ↑ HR, ↓BP, ↓CVP, ↑ RR, ↓ O2 sat, ↑ or ↓ temperature

• CV: Thready pulse, ↓ cap refill, flattened neck veins

• Neuro: Dizziness, syncope, confusion, weakness, fatigue, seizures

• GI: Thirst, dry mucosa, nausea, vomiting, anorexia, acute weight loss

• GU: Oliguria

• Skin: Cool & clammy, diaphoresis, poor skin turgor & tenting

• Other: sunken eyeballs

Hypervolemia S/S

• VS: ↑HR, ↑ BP, ↑ CVP, ↑ RR

• CV: Bounding pulse, distended neck veins

• Respiratory: Crackles, cough, dyspnea

• Neuro: Weakness, visual changes, paresthesia, altered LOC, seizures (if sudden hyponatremia water excess)

• GI: Ascites, ↑motility, liver enlargement, weight gain

• GU: ↑ urine output, dilute urine

• Skin: Peripheral edema, cool with pallor

When would we use IV therapy?

• Unable to take substances orally

• Replace water, electrolytes, and nutrients more rapidly

• Provides immediate access to vascular system

Crystalloids

• Aqueous solution of mineral salts and other small, water-soluble molecules

• Contain no proteins or colloids

• Low cost

• Short half-life

• Fewer side effects

• Hypotonic, isotonic, hypertonic

Colloids

• Stay in vascular space & increase oncotic pressure

• Large insoluble molecules

• Do not diffuse through membranes easily

• All colloids affect blood coagulation, by interfering with coagulation factor VII

• Human plasma products (albumin, fresh frozen plasma, blood)

• Semisynthetics (dextran and starches, [hespan])

Isotonic solutions

• Ideal to replace ECF volume deficit due to acute loss, such as diarrhea, blood loss

• Same osmolality as body fluids

  • 0.9% Sodium Chloride [Normal Saline, NS, Saline]

  • Lactated Ringer’s Solution

0.9% Sodium Chloride [Normal Saline, NS, Saline]

• Used when both fluid and sodium are lost

• Only solution used with blood

Lactated Ringer’s Solution

• Contains sodium, potassium, chloride, calcium & lactate

• Expands ECF – ideal for surgery, trauma, burns & GI losses

  • Remember, if your ECF volume is too low, your body faces risks like low BP, organ injury, etc.

  • Caution with liver disease since it contains lactate

    • If your liver can’t metabolize lactate and convert to bicarbonate = metabolic issues (lactic acidosis)

Hypotonic solutions

0.45%NS, D5W

0.45%NS, D5W

• More dilute solutions & have a lower osmolality than body fluids

• Cause movement of water into cells by osmosis – Dilutes ECF because more solvent than solute

• Replace deficits of total body water

• Hydrate cells but can deplete circulatory system

• Usual choice for maintenance fluids but should be administered slowly to prevent cellular edema

  • Monitor for changes in mentation because of cellular edema

When would you not give hypotonic solutions?

• Patient’s at risk for increased ICP

• Extensive burn or trauma – they are already hypovolemic – will worsen

Hypotonic D5W- 5% Dextrose

• Behaves differently in the bag vs. in the body!

• 5 grams of dextrose per 100mL

• Technically isotonic in the bag, but hypotonic in the body

  • Since the dextrose is rapidly metabolized!

Hypertonic solutions

• D5W in NS (D5NS) or D5W in 0.45% NS (D5 ½ NS)

  • D5 ½ NS more common

• D5W in LR (D5LR)

• D10W or D20W or D50W

• 3% or 5% NS (most common)

D5W in NS (D5NS) or D5W in 0.45% NS (D5 ½ NS)

D5W in LR (D5LR)

D10W or D20W or D50W

3% or 5% NS

• Higher osmolality compared with plasma

• Draws water out of cells into ECF

• Electrolyte replacement & shift fluid from cells to vascular space

• Requires frequent monitoring of BP, lung sounds, serum sodium levels

  • Since it can cause fluid overload

Colloid solutions

• Dextran

• Hetastarch (Hespan)

Dextran

• Volume expander

  • Monitor for circulatory overload / increased bleeding

• No electrolytes included

• Increases plasma volume by 1 to 2 times

• Increases urine output

  • Treatment for severe hypovolemic shock, burn-related shock, hemorrhage, surgery, trauma

  • First 500ml – give at 20-40 ml/hr if hypovolemic; reduce rate if additional volume is required

    • Slow administration

Trick to remember dextran

• Dextran = Detour

• it is not a permanent solution and is only temporary

Hetastarch (hespan)

• Synthetic colloid volume expander

  • Lasts 24-36 hours

• Treatment & prevention of dangerously low BP / hypovolemia

For both dextran and hetastarch (hespan) always monitor for

Fatal anaphylactic reactions

Albumin

• “Protein puller”

  • Pulls proteins back into blood to expand volume

• Equivalent to plasma

• Available is 5% and 25% solutions

• Used to treat hypoproteinemia in burns and hypoalbuminemia in shock and ARDs

• Used to support blood pressure in dialysis and acute liver failure

Mannitol

• Osmotic Diuretic

  • Makes water move to extracellular & vascular spaces

• Comes in 5%, 15%, 20%, 25% solutions

• No dilution required

  • All crystals must be dissolved to infuse

• Treatment of ARF, cerebral edema (decreases ICP), generalized edema

• Monitor electrolytes – may induce dehydration with hyperkalemia, hypokalemia, or hyponatremia

• 20% & 25% solutions are vesicants

• NCLEX – Requires caution with impaired cardiac or renal systems (contraindicated with anuria, severe pulmonary & cardiac congestion, & intracranial bleeding)

Vesicants

Medications or solutions that can cause tissue damage (necrosis or blistering) if they leak out of the vein during intravenous (IV) administration.

Trick for mannitol

• Mannitol = “Magnet” for water

• Brain, eyes, kidneys

Na⁺

• 135-145 mEq/dL

• Major ECF cation

• Movement: Diffusion through active transport that is controlled by the sodium-potassium pump

• Forms: Sodium chloride & sodium bicarbonate

• Regulation: Controlled by kidneys through the action of aldosterone

• Functions:

  • Maintains fluid balance

  • Generating and transmitting nerve impulses, muscle contraction

  • Acid-base balance

  • Blood pressure

• Imbalances are typically associated with parallel changes in osmolality

Causes of hypernatremia

• Water loss

• Hyperventilation

• Heat stroke

• Insufficient ADH - Diabetes insipidus

• Loss of thirst mechanism

• Inadequate water intake

Causes of hyponatremia

• Drinking water for fluid replacement

• Inadequate sodium intake Loss of sodium-containing fluids

• Psychogenic polydipsia

• D₅W

• Hormonal imbalances - insufficient aldosterone, adrenal insufficiency, SIADH

S/S of hypernatremia

• Fluid shift out of the cells due to increased osmotic pressure of interstitial or extracellular fluid

• Thirst; tongue and mucosa dry and sticky

• Weakness, lethargy, agitation

• Edema

• Elevated BP, tachycardic

• Decreased urine output

S/S of hyponatremia

• Impairs nerve conduction

  • Muscle cramps, abdominal discomfort or cramps with nausea & vomiting, anorexia

  • Fatigue, lethargy, muscle weakness;

• Late - shallow, ineffective respiratory movement R/T skeletal muscle

• Decreased osmotic pressure in extracellular compartment causing fluid shift into cells resulting in hypovolemia & decreased BP

• Swelling in brain - confusion, headache, weakness, seizures; late – coma

Tx for hypernatremia

• Restrict sodium

• Dilute with sodium-free fluids to make sodium go down

• Daily weights

• I & O

• Recheck labs

Tx for hyponatremia

• Fluid restriction

• Needs sodium

• Hypertonic saline if having neuro problems

  • 3% or 5% NS

Severe hyponatremia

• Sodium [Na] <120 mEq/L

• Severe symptoms such as seizures, coma

• Give small amount of IV hypertonic saline solution (3% NaCl)

• Regardless of the cause or severity…

  • At risk for osmotic demyelination injury if hyponatremia is corrected too quickly

  • Monitor for lithium toxicity because hyponatremia slows lithium excretion

  • Monitor frequent VS, strict I & O, serial sodium levels

K ⁺

• 3.5-5.0 mEq/dL

• Major ICF cation

• Regulated by the kidneys

• Necessary for

  • Resting membrane potential of nerve and muscle cells

  • Regulates intracellular osmolality

  • Promotes cellular growth

  • Maintenance of cardiac rhythms

  • Acid-base balance

Tricks to remember for potassium

• King inside= Major ICF cation

• “About 3-5 bananas in each bunch… want them half ripe so 3.5-5”

• Potassium pumps

Causes for hyperkalemia

• Renal failure

• Deficit of aldosterone

• Potassium-sparing diuretics – spironolactone

• Massive cell destruction

• Metabolic acidosis

• Catabolic states (severe infections)

Causes for hypokalemia

• Abnormal losses from kidneys or GI tract

• Excessive aldosterone or glucocorticoids (Cushing’s syndrome)

• Decreased dietary intake - alcoholism, eating disorders, starvation

• Treatment of diabetic ketoacidosis with insulin

S/S for hyperkalemia

Cardiac dysrhythmias & conduction

• Bradycardia

• Prolonged PR interval, flat or absent P waves

• Widened QRS complex

• Depressed ST segment

• Tall & peaked T waves

• Conduction blocks, ventricular fibrillation

S/S for hypokalemia

Cardiac dysrhythmias - prolonged repolarization and eventual arrest

• Slightly prolonged PR interval, peaked P wave

• ST depression

• Shallow T wave

• Prominent U waves

• Lethal ventricular - PVCs, ventricular tachycardia

Tx for hyperkalemia

• Sodium polystyrene sulfonate

• Dialysis

Tx for hypokalemia

• PO or IV potassium chloride “K-riders”

  • Causes GI upset - give with food

  • Assess output before & during administration

• Increase dietary potassium

Trick to remember K-containing food

The thanksgiving song “Greens, beens, potatoes, tomatoes…”

Steps to treat hyperkalemia

1. Stabilize

   • Stabilize cardiac cell membrane by administering calcium chloride or calcium gluconate IV

     • Does not drop K levels but stabilizes heart

2. Force

   • Force K+ from ECF to ICF by IV regular insulin with dextrose and a ß-adrenergic agonist or sodium bicarbonate

3. Monitor

   • Use continuous ECG monitoring

Potassium administration (everything very very important)

• NEVER give IV Push, IM injection, or SQ injection!

• Always dilute IV KCl (10mEq in 100 mL)

• Never give by gravity – need an infusion pump

• Should not exceed 10 mEq/hr unless in critical care with cardiac monitoring

• Irritant

  • Monitor IV site frequently & stop immediately for signs of phlebitis or infiltration

Ca²⁺

• 9.0-10.5 mg/dL

• ECF cation

• Formation of teeth and bone

• Blood clotting

• Transmission of nerve impulses

• Muscle contraction

  • Myocardial contractions

• Ingested in food, stored in bone, and excreted from the body in the urine and feces

• Controlled by parathyroid hormone (PTH) and calcitonin, but it is also influenced by vitamin D and phosphate ion levels.

• Calcium and phosphate ions in the extracellular fluid have a reciprocal relationship.

Causes of hypercalcemia

• Uncontrolled release of calcium ions from the bones

• Hyperparathyroidism causes ⅔ of the cases

• Cancer - hematologic, breast, or lung

• Thiazide diuretics

• Immobilization

• Increased intake of calcium due either to excessive vitamin D or excess dietary calcium

Causes of hypocalcemia

• Decrease in the production of parathyroid hormone

• Radical neck surgery

• Malabsorption syndrome

• Deficient serum albumin

• Alkalosis

• Renal failure

S/S of hypercalcemia

Depress neuromuscular activity, leading to

• Muscle weakness, loss of muscle tone, lethargy, and stupor

• Apathy, personality changes, anorexia, and nausea

• Anorexia, nausea, constipation

Interferes with the function of ADH in the kidneys

• Less absorption of water

• Polyuria, thirst

Cardiac

• Contractions increase in strength

• Dysrhythmias may develop

• Increased BP

Effects on bone vary with the cause of hypercalcemia.

• If excess PTH is the cause, bone density will be decreased

• If intake of calcium is high, PTH levels will be low, and more calcium will be stored in the bone, maintaining bone strength.

May contribute

Shortened version to remember hypercalcemia s/s

• Stones

  • Kidney stones

• Bones

  • Bone pain, fractures

• Groans

  • Abd. pain, constipation, N/V

• Thrones

  • Polyuria, dehydration, sitting on throne (toilet)

• Psychiatric moans

  • Confusion, lethargy, depression

S/S of hypocalcemia

Increase in the permeability and excitability of nerve membranes

• Spontaneous stimulation of skeletal muscle > muscle twitching, carpopedal spasm, and hyperactive reflexes

• Laryngospasm

• Paresthesia

• Abdominal cramps

• Mental confusion, irritability

Heart contractions become weak, delayed conduction, arrhythmias develop, & BP drops

Tests for hypocalcemia

• Chvostek’s sign

• Trousseau’s sign

Chvostek’s sign

• “Cheek”

• Contraction of facial muscles in response to a light tap over the facial nerve in front of the ear

Trousseau’s sign

• “Tourniquet (BP cuff)”

• Carpal spasm induced by inflating a BP cuff above the systolic pressure for a few minutes

Tx for hypercalcemia

• Restricting dietary calcium

• Promoting urinary calcium excretion with loop diuretics

• Hydrating the patient with isotonic saline infusions

• Move!

• Safety precautions

• Medications that decrease serum Ca:

  • Bisphosphonates

  • Calcitonin

Tx for hypocalcemia

• Oral or IV calcium supplementation

• Vitamin D

• Phosphate binders to excrete phosphate & ↑ Ca

  • Sevelamer hydrochloride

  • Calcium acetate

Calcium imbalance meds.

IV 10% calcium gluconate

• Administer medications that increase calcium absorption

  • Aluminum hydroxide reduces phosphorus levels, causing the countereffect of increasing calcium levels

  • Vitamin D aids in the absorption of calcium from the intestinal tract

IV 10% calcium gluconate

Warm injection solution to body temperature, administer slowly, monitor for ECG changes, observe for infiltration

• Stabilizes heart

Hypocalcemia safety

• Provide a quiet environment to reduce environmental stimuli

• Initiate seizure precautions

• Move the client carefully, and monitor for signs of pathologic fracture

Calcium-containing food

• Dairy products

• Tofu

• Green leafy vegetables

• Salmon & sardines

• Almonds

• Sunflower seeds

• Dried beans

• Molasses

PO₄^3-

• 3.0-4.5 mg/dL

• Primary anion in ICF

• Essential to function of cell membrane regulation, muscle, RBC, nervous system

• Involved in acid-base buffering system, ATP production, cellular uptake of glucose, and metabolism of carbohydrates, proteins, and fats

• Found mostly in bones & teeth

• Reciprocal relationship with calcium

• Imbalances are typically, asymptomatic – problems are associated with hypo & hypercalcemia

Causes of hyperphosphatemia

• Acute kidney injury or chronic kidney disease

• Tissue damage or cancer chemotherapy