Lecture 3 Flashcards
Fluid Intake Methods (3)
Metabolism - 10%
Food - 30%
Beverages - 60%
Fluid Excretion Methods (4)
Feces - 4%
Sweat - 8%
Insensible Loss (Skin/Lungs) - 28%
Urine - 60%
Triggers of Thirst (3)
- Osmolarity
- Volumetric
- Angiotensin
Osmolarity
Increased osmolarity from increased salt intake or decreased water volume triggers thirst response to try and fix the osmolarity of the blood.
Volumetric
Decreased blood volume. Limited vascular restriction assistance. Need to increase intake and volume to offset the imbalance.
Receptors to Detect Volumetric Imbalance
- Low Pressure - baroreceptors in great veins, pulmonary vessels, and right atrium
- High Pressure - baroreceptors in carotid sinus & aorta
Angiotensin II Effects (5)
- Thirst
- More Water/Na+ absorption
- Releases aldosterone
- Vasoconstriction
- ADH Secretion
ADH Mechanism
Released by hypothalamus. Causes blood vessels to constrict and makes the collecting duct highly permeable to water to allow for lots of its reabsorption (doesn’t affect salt). Increases blood pressure and volume
Aldosterone Mechanism
Acts on Na+/K+ pumps and increases their numbers in the kidneys. Pulls more sodium out of cell and increases amount of sodium in blood stream that causes water to follow it.
Other ways to Intake Fluids (3)
- IV
- Gastric Tubes
- Subcutaneously
Body Fluid Compartments (3)
- Vascular - blood vessels
- Interstitial - in between vessels and cells
- Intracellular - inside cells
Fluid Forces (3)
- Hydrostatic pressure - pushes fluid from inside the vessel out, decreases in pressure the farther away from the heart you get
- Osmotic pressure - pushes fluid from outside the vessel in, constant throughout the body
(net out closer to the heart, net in farther away) - Osmosis - driven by osmolarity, water moves towards hypertonic solutions
Types of Fluid Imbalances (2)
- Extracellular fluid
2. Body fluid concentrations
Extracellular Imbalances (aka Saline Imbalances)
Impacts vascular and interstitial fluid volumes. Caused by too little or too much fluid. Concentration is right, just not the right volume.
How do extracellular imbalances occur? (too little volume) (5)
- Loss of salt water from the body (vomiting, diarrhea)
- Excess renal excretion of salt & water (excess use of diuretics or aldosterone deficiency)
- Hemorrhaging
- Excessive sweating (diaphoresis)
- Burns
Thiazide Mechanism
Block Na+/Cl- transporter in distal tubule, preventing Na+ absorption, decreasing blood volume due to Na+ and H2O excretion
Potassium-Sparing Diuretic Types
- Sodium Channel Inhibitors
2. Mineral Corticoid receptor antagonist
Sodium Channel Inhibitors Mechanism
Block sodium channels in collecting duct, decreases Na+ reabsorption and subsequent excretion of potassium. Water follows the Na+
Mineral Corticoid Receptor Antagonist Mechanism
Competes with aldosterone receptor, decreases sodium reabsorption of sodium channels
Loop Diuretics Mechanism
Block Na+/K+/2Cl- transport in thick, ascending loop of Henle preventing Na+ absorption. Leads to PROFOUND Na+ & H2O loss
Volume Deficient Clinical Manifestations (6)
- Sudden weight loss (2+ lbs in 24 hours)
- Flat neck veins (lying down, no JVD)
- Decreased Skin Turgor
- Sunken eyeballs
- Deeper longitudinal furrows in tongue
- Sunken fontanels in infants
Causes of Excess Volume (4)
Excessive intake or retention of salt water
- Excessive IV infusion
- Excessive aldosterone
- Corticosteroid therapy
- Cushing Disease
Excess Volume Clinical Manifestations (5)
- Sudden weight gain
- Circulatory overload - bounding pulse, hypertension, JVD when upright
- Edema - swelling
- Bulging fontanel in infants
- Dyspnea and orthopnea
Hyponatremia
“Hypotonic Syndrome,” gain more water than salt, causes cells to swell with fluid and risk bursting.
Hyponatremia Causes (6)
- Water Intoxication
- Excessive ADH
- Psychogenic Polydipsia- compulsive drinking of water from psychogenic drugs like ecstasy
- Forced Water consumption - hazing
- Excessive beer intoxication - needs to be a LOT, VERY QUICKLY to overcome the ADH inhibition that occurs when drinking alcohol
- Near drowning in fresh water
Hyponatremia Clinical Manifestations (7)
- Neurological - brain swelling
- Nausea
- Vomiting
- Headache
- Confusion
- Seizures
- Coma
Hypernatremia
“Hypertonic Syndrome,” water deficit. Can occur from gaining more salt than water or losing more water than salt.
Hypernatremia Causes (5)
- Limited access to water
- Hypertonic IV solution
- Near drowning in salt water
- Diabetes insipidus - low ADH
- Prolonged diarrhea and/or vomiting without intaking water
Hypernatremia Clinical Manifestations
Similar to hyponatremia manifestations except causes brain cells to shrivel and shrink instead of swell.
Hypokalemia
Decrease in interstitial potassium levels
Hypokalemia Causes
Many etiologies but diuretics can be a potential cause
Hypokalemia’s Effect on Cells
- Makes intracellular charges mores negative
- Hyperpolarized muscle cells (cardiac, skeletal, heart)
- Requires stronger signals to depolarize
Hypokalemia Clinical Manifestations (5)
- Skeletal & muscle weakness
- Flaccid paralysis
- Respiratory paralysis
- Cardiac dysfunction
- Gastrointestinal problems
Liquorice Poisoning
Blocks an enzyme that converts cortisol to cortisone. Stimulates aldosterone receptors and leads to sodium retention (hypertension) and potassium excretion (hypokalemia)
Hyperkalemia
Increase in interstitial potassium levels
Hyperkalemia Causes
Many etiologies including potassium injections, blood transfusions that are potassium rich, or diseases like cancer releasing excess potassium
Hyperkalemia’s Effect on Cells
Membranes become depolarized and more positive than negative.
Hyperkalemia Clinical Manifestations
Similar to Hypokalemia
Hypocalcemia
Free calcium ions at below normal serum levels
Forms of Calcium in Plasma (3)
- Ions bound to proteins (albumin)
- Ions bound to small organic ions (citrate)
- Free ions
Hypocalcemia Etiologies (5 commom)
- Steatorrhea due to low bile
- Vitamin D deficiency
- Massive transfusion
- Hypoparathyroid
- Excess phosphate
Calcium Pathophysiology
Key for neuromuscular junction response and muscle contractions. The amount of calcium directly correlates with the amount of sodium needed to fire an action potential (less calcium : less sodium needed, more calcium : more sodium needed)
Hypocalcemia Clinical Manifestations (6)
- Increased neuromuscular excitability
- Muscle twitching & cramping
- Tetany
- Positive Trousseau
- Positive Chvostek - muscles twitching/convulsing when touching muscle on cheek
- Cardiac problems
Hypercalcemia
Free calcium ions at higher than normal serum levels
Hypercalcemia Causes (3)
- Etiologies causing excessive intake and absorption
- Shift in storage (hyperparathyroidism, bone cancers)
- Decreased excretion
Hypercalcemia Clinical Manifestations (4)
- *Need more sodium to fire an action potential due to increased levels of calcium**
1. Decreased muscular excitability
2. Gastrointestinal abnormalities
3. Muscle weakness
4. Cardiac problems
Magnesium’s Effect on Muscle Contraction
Magnesium depresses acetylcholine release and effects the amount of neuromuscular excitability
Hypomagnesemia
Too much acetylcholine released and causes increased neuromuscular excitability.
Hypermagnesemia
Too little acetylcholine released and causes decreased neuromuscular excitability.
