Unit 2.2 - Fluid and Electrolytes

Filtration

Movement of fluid through a cell or blood vessel membrane because of water pressure.

A “pushing” pressure.

Diffusion

Movement of particles across a permeable membrane from high to low particle concentration.

Shape, size, and charge determines if particle is allowed to move across membrane.

Osmosis

Movement of water through a semi-permeable membrane from low to high solute concentration.

A “pulling” pressure.

If particles are not allowed to move, water will move instead.

Osmolality

Concentration of molecules/ions in a liquid solution.

Regulation of Fluid Balance

Aldosterone - body responding to low Na in extracellular fluid compartment; signals kidney to retain Na and H2O; increases blood osmolarity and volume.

Antidiueretic Hormone - body responding to increased Na in bloodstream; signals kidney to retain water (decrease urination).

Natriuretic Peptides - body responding to increased blood volume and pressure; signals kidney to excrete Na, H2O, and Cl (increase urination); decreases blood osmolarity and volume.

Renin-Angiotensin-Aldosterone System (RAAS)

1. Low blood pressure/volume/Na/O2

2. Kidney secretes Renin

3. Increased retention of Na and H2O to increase blood pressure

Fluid Imbalance Causes

Dehydration: diarrhea, vomiting, diaphoresis, NPO/impaired swallowing, hemorrhage, burns, fever, diuretic use.

Overload: excessive fluid replacement, heart or kidney failure.

Dehydration

Mild dehydration common in healthy adults, caffeine or alcohol can increase fluid loss.

Leads to low blood pressure.

Dehydration Assessment

History: weight, changes in ring or shoe tightness, medications, kidney disease.

Signs and Symptoms: low BP, high heart rate, poor turgor, BP lowering from lying to sitting to standing (orthostatic hypotension).

Fluid Overload Assessment

Heart contracts more forcefully, swelling in legs, hands, or lungs, increase excretion of Na and H2O.

Sodium Intake

Hypernatremia ‘Big and Bloated’:

Cues - thirst, increased body temperature, confusion, HTN, tachycardia.

Causes - kidney failure, fever, dehydration.

Action - give drugs that promote Na loss (diuretics), adequate water intake, reduce Na intake from diet.

Hyponatremia ‘Depressed and Deflated’:

Cues - weak pulse, confusion, hypotension, tachycardia.

Causes - kidney failure, diaphoresis, heart failure, hyperglycemia, fluid volume overload.

Action - reduce drugs that promote Na loss (diuretics), increase Na intake from diet, reduce fluid intake.

Calcium Intake

Hypercalcemia ‘Swollen and Slow’:

Cues - hypotension, bradycardia, weakness, constipation, lethargy.

Causes - hypoparathyroidism, excessive vitamin D and calcium intake, bone cancer, CKD.

Action - stop taking calcium, or vitamin D, give drugs that inhibit calcium resorption from bone.

Hypocalcemia:

Cues - numbness/tingling of fingers, toes, and mouth, bone fractures, hypotension, Trousseau and Chvostek signs.

Causes - hypoparathyroidism, decreased vitamin D intake, lactose intolerance, kidney disease.

Action - calcium and vitamin D supplementation, easy calcium rich foods.

Potassium Intake

Hyperkalemia ‘Action and Contraction’

Cues - hypotension, bradycardia, weakness or twitching, tachycardia, numbness, dysrhythmia.

Causes - diabetic ketoacidosis, metabolic acidosis, kidney failure.

Action - administer IV glucose and insulin, give K-binding meds and K-excreting diuretics, monitor heart.

Hypocalcemia ‘Low and Slow’

Cues - fatigue, anorexia,, skeletal muscle weakness, polyuria, hypotension, dysrhythmia.

Causes - diuretics, vomiting, diarrhea, diaphoresis.

Action - K supplements, increase dietary intake, monitor respiratory rate and oxygen saturation.

Magnesium Intake

Hypermagnesemia ‘Calm and Quiet’

Cues - flushing, hypotension, weakness, drowsiness, lethargy.

Causes - kidney disease.

Action - give loop diuretics, give calcium if severe.

Hypomagnesemia ‘Buck Wild’

Cues - dysrhythmia, tachycardia, hypertension, tremors, numbness and tingling.

Causes - diuretics, malnutrition, alcohol use disorder, diarrhea.

Action - stop loop diuretics.