Fluid and Electrolytes Flashcards
Electrolyte
An element or compound that, when dissolved or dissociated in water or solvent, separates into ions
Ions
Cations: positively charged (Na+, K+, Ca²+)
Anions: negatively charged (Clˉ, HCO3ˉ, SO4ˉ)
Osmolality
is a measure of the solute concentration per kg in a solution.
Solute
is a substance dissolved in a solvent
Solvent
is a substance that is capable of dissolving a solute (liquid or gas).
Tonicity
is the tension or effect that the osmotic pressure of a solution with impermeable solutes exerts on cell size due to water movement across the cell membrane.
Hypertonic
Solutes move out of the cell, having a higher osmotic pressure than a particular fluid.
Hypotonic
Solutes move into the cell, having a lower osmotic pressure than a particular fluid.
Capillary permeability
the movement of fluid
components (i.e. electrolytes, glucose, minerals)
between organs & between cells.
Movement depends on the ability of the cell membrane to allow the passage of fluid components with in the vascular system.
Occurs because of osmosis, diffusion, filtration, or active transport
Osmosis
Movement of water across a semipermeable membrane from an area of lesser to one of greater concentration
Water moves into the vascular compartment/intracellular space from extracellular space
Diffusion
Random movement of a solute through a semipermeable membrane from higher to lower concentration
Capillary Filtration
Movement of water through capillary pores due to mechanical forces
Active Transport
Movement of ions against their concentration gradient. Requires energy
Filtration & Hydrostatic pressure
Venous side should have lower hydrostatic pressure
Chronic hypertension can cause edema in interstitial space
Colloid osmotic pressure contains protein (less in people with renal disease, with edema)
Hydrostatic Pressure
Fluid pushing force inside the capillary
Inside capillaries hydrostatic pressure and capillary filtration pressure are equal
Colloidal Osmotic Pressure
Pulling force created by particles (i.e. plasma proteins) that do not pass through capillary pores
Capillary colloidal pressure is greater than interstitial colloidal pressure
Lymph Drainage
Return of fluids and osmotically active plasma proteins from interstitium into the lymphatic system to return to circulation
Factors Causing Edema
Increased capillary filtration pressure
Decreased capillary colloidal osmotic pressure
Increased capillary permeability
Obstruction of lymph flow: mastectomy/impaired lymphatic drainage
What does an increased _____ pressure cause? How does edema form?
Anasarca: edema throughout the body. Can be caused by capillary osmotic pressure?
> Blood volume = higher capillary filtration pressure
Regulation of Body Fluids
Fluid intake: Thirst-control center: the hypothalamus
Intake is about 2200 to 2700 ml/day (2-3 L)
Hormone Regulation: Antidiuretic hormone (ADH) Renin-angiotensin-aldosterone mechanism
Atrial natriuretic peptide: release fluid to prevent edema
Fluid Output: Fluid is lost through kidneys, skin, lungs (humidity, increasing respiratory rate), and GI tract
Insensible loss: increasing respiratory rate
maintain homeostasis
Cations
Sodium (Na+)
Potassium (K+)
Calcium (Ca2+)
Magnesium (Mg2+)
Anions
Chloride (Cl-)
Bicarbonate (HCO3–)
Phosphate (PO43-)
Sodium (Na+)
135-145 mEq/L
- the most abundant cation in ECF
- functions: maintain water balance, nerve
impulse transmission, regulate acid-base
balance, and participate in cellular
chemical reactions.
- regulated by dietary intake & aldosterone
secretion
Antidiuretic Hormone (ADH)
AKA: vasopressin (stimulates arterial vasoconstriction)
Levels controlled by ECF volume and osmolality
High osmolality = High ADH, Hypernatremia
Some conditions favor abnormal increases in ADH (tumors). Swollen, hyponatremic
ETOH (alcohol) inhibits ADH
Hyponatremia
< 135 mEq/L
Causes: sodium loss (GI, renal, & skin losses: sweating);
pshychogenic
polydipsia (drinking water increase); water intoxication; SIADH (Excess ADH)
S/S of Hyponatremia
lethargy, edema, headache, disorientation, seizures, coma.
Pure Na loss: hypovolemia
Dilutional: Hypervolemia
Hypernatremia
> 145mEq/L
Causes: Excess salt intake, aldosterone secretions, Diabetes Insipidus, increased sensible & insensible water loss, water deprivation (hypertonic/hypernatremic)
S/S of Hypernatremia
thirst, dry & flushed skin, dry & sticky m.m., postural hypotension, fever, CNS: agitation, decreased reflexes, convulsions, restlessness, & irritability.
If you were walking across the Sahara Desert with an empty canteen, the amount of ADH secreted would most likely:
increase. (High plasma osmolality, hypernatremia, hypertonic)
Because your body would probably be dehydrated, it would try to retain as much fluid as possible. To retain fluid, ADH secretion increases.
If you placed two containers next to each other, separated only by a semipermeable membrane, and the solution in one container was hypotonic relative to the other, fluid in the hypotonic container would:
move out of the hypotonic container into the other.
Fluid would move out of the hypotonic container
into the other container to equalize the
concentration of fluid within the two containers.
Potassium (K)
3.5 – 5 mEq/L
- principle cation in ICF compartment
- functions: transmission & conduction of
nerve impulses, normal cardiac
conduction, skeletal/smooth muscle
contraction, and regulates metabolic
activities.
- Regulated by dietary intake & renal
excretion.
Kidney failure: can’t excrete Potassium
Aldosterone: releases K into urine (moves out)
Insulin: K moves into cell
The ion for DIASTOLE
Potassium’s role in the Acid-Base Balance
Acidosis- potassium shift occurs from the ICF to the ECF as hydrogen ions move into cells, aldosterone deficiency leads to hyperkalemia.
Alkalosis- potassium shift from ECF to ICF in exchange for hydrogen ions, thus lowering potassium in the ECF.
Hypokalemia (K)
< 3.5 mEq/L
Causes: Use of K+ wasting diuretics (most), polyuria, GI losses (vomiting, diarrhea, NG/colostomy outputs), alkalosis, Tx of DKA with insulin.
S/S: Skeletal muscle weakness U wave/ ECG changes (PR Interval increase) Constipation, ileus Toxic effects of digoxin Irregular, weak pulse Orthostatic hypotension Numbness (paresthesias)
Hyperkalemia (K)
> 5 mEq/L
Causes: Renal failure, fluid volume deficit, massive cellular damage (burns & trauma), acidosis (esp DKA), rapid infusion of stored blood, use of K+-sparing diuretics, salt substitutes.
S & S: ECG changes (tall, tented T wave), paresthesias, muscle weakness, abdominal cramping, diarrhea.
Calcium
8.5 – 10.5 mg/dL
- 50% bound to bound to albumin, 40%
free ionized, 10% in bone and teeth.
- functions: bone & teeth formation, blood
clotting, hormone secretion, cardiac conduction, nerve impulse transmission, & muscle contraction.
- PTH & Vitamin D responsible for maintaining
“Parathyroid pulls… Calcitonin keeps”
Hypocalcemia
8.5 mg/dL
Causes: Rapid administration of blood containing citrate, hypoalbuminemia, hypoparathyroidism, vitamin D deficiency, alkalosis, pancreatitis, Chronic Renal Failure (Vitamin D not activated), chronic alcoholism
S/S of Hypocalcemia
S & S: numbness & tingling of fingers and circumoral (around mouth) region, hyperactive reflexes, +Trousseau’s (nerve excitability/tetany of fingers during BP) & +Chvostek’s sign (Stroking cheek), muscle cramps, fractures (if chronic). ECG: prolonged ST & QT
Hypercalcemia
10.5 mg/dL
Causes: Hyperparathyroidism, Cancer, Paget’s disease, osteoporosis, prolonged bed rest, thiazide diuretics
S/S: Anorexia, abdominal pain & constipation, muscle weakness, hypoactive reflexes, lethargy, flank pain (if kidney stones), ECG: shortened QT & ST segment
Magnesium
1.5 – 2.5 mEq/L
the second most abundant cation in ICF
regulated by dietary intake, renal mechanisms, and actions of PTH.
Functions: enzyme reactions during carbohydrate metabolism, helps produce ATP, role in protein synthesis, and affects cardiac and skeletal muscle excitability.
Hypomagnesemia
1.5 mEq/L
Causes: inadequate intake, inadequate absorption, excessive loss from GI tract or urinary system. Alcoholics.
Similar to hypocalemia… The 3 Ts (tremors, twitching, tetany) & hyperactive Deep Tendon Reflexes. Chvostek’s & Trousseau’s sign.
CNS irritation: lethargy, confusion, seizures. Dysrythmias, N/V
STARVED
Hypermagnesemia
2.5 mEq/L
Causes: Renal failure, excessive intake.
S/S: hypoactive DTRs, weakness, drowsiness, decreased rate/depth of respirations, bradycardia, hypotension, flushing.
RENAL
