Week 2 - Fluid and Electrolyte Imbalances Flashcards
How much body weight is made up of fluid (water)
~60%
- 2/3 intracellular fluid
- 1/3 extracellular fluid
Thirst regulation
osmoreceptors in the hypothalamus
What do osmoreceptors measure?
blood osmolarity
How do kidneys regulate fluid and electrolytes?
by varying the amounts excreted and reabsorbed
- directly and hormone related
Hormones that act on the kidneys to regulate fluids and electrolytes
- Antidiuretic hormone (ADH)
- Aldosterone
- Atrial Natriuretic Peptide
What does the Antidiuretic hormone (ADH) regulate?
regulates water level
What does Aldosterone regulate?
regulates Na+ and water level
What does Atrial Natriuretic Peptide regualte?
Regulates Na+ and water level
How does water move between compartments?
- filtration
- osmosis
What drives filtration?
hydrostatic pressure
What drives osmosis?
Osmotic pressure
What is filtration?
movement of water and solutes from blood (high pressure) to ISF (low pressure) area
What is osmosis?
movement of water from low solute concentration (ISF) to high concentration (blood)
What does movement of water depend on?
permeability of the compartment barrier to water
diffusion
movement of solutes (Na+, glucose) from high concentration to low concentration
Active transport
movement of solute using carrier and energy from low concentration (ISF) to high concentration (Cell)
what does the movement of electrolytes between compartments depends on?
how ‘permeable’ the membrane barrier is to the electrolyte AND the concentration gradient of the ion
Edema
excess fluid in the interstitial compartment
- isotonic, hypotonic, or hypertonic
Possible consequences of edema
- swelling within the tissues (localized or general)
- functional impairment
- pain
- impaired circulation
4 causes of edema
- high local blood pressure
- plasma protein loss
- blocked, or missing, lymphatic vessel
- increased capillary permeability
Edema - high local blood pressure
Increased hydrostatic pressure
- increased net fluid movement into interstitial space
Edema - plasma protein loss
(usually albumin - most abundant protein in the blood)
Decreased osmotic pressure in the blood
- Increased net fluid movement into interstitial space
What is the most abundant protein in the blood?
Albumin
Edema - blocked, or missing, lymphatic vessel
Fluid and protein not filtered into lymphatic drainage for return to circulation
- localized edema
Edema - increased capillary permeability
excess flow of fluid and proteins into interstitial fluid.
- protein movement also increases interstitial fluid osmotic pressure
Edema - high local BP - Pathological states
- congestive heart failure
- severe hypertension
- increased blood volume
Edema - plasma protein loss - pathological states
- kidney disease (excess protein excretion in urine
- malnutrition or malabsorption (impaired protein synthesis)
Edema - blocked, or missing, lymphatic vessel - pathological states
- tumor blocking lymphatic drainage
- lymph node removal
Edema - increased capillary permeability - pathological states
- infection
- inflammatory response
Dehydration
water loss > water intake
Dehydration common causes
- insufficient fluid intake
- sweating
- vomiting
- diarrhea
- excess excretion (urine)
Dehydration signs and symptoms
- thirst
- dry mouth/lips
- nausea
- fatigue
- lightheadedness
- irritability
- decreased BP, increased HR
- vasoconstriction
Dehydration net results
- isotonic dehydration
- hypotonic dehydration
- hypertonic dehydration
Isotonic dehydration
water + electrolyte loss
Hypotonic dehydration
more electrolytes lost than water
Hypertonic dehydration
More water lost than electrolytes
Na+
-critical ion for maintaining volume and osmolarity of the extracellular fluid
- essential in electrical conduction of nerves, muscle contraction, general cellular function
Hyponatremia
- losing more Na+ than water OR gaining more water than Na+
Hyponatremia effect
- fluid imbalances (water moves into cells)
- skeletal muscle cramps, weakness, fatigue
- nausea/vomiting, GI cramping, diarrhea
- headache, confusion, seizures, coma
Hypernatremia
gaining more Na+ than water OR losing more water than Na+
Hypernatremia effects
- fluid imbalances (water moves out of cell)
- increased thirst/decreased urine output, dry mucous membrane
- rapid HR
- Headache, agitation, seizures, coma
K+ role
Important role in maintaining cell resting membrane potential, essential function in excitable tissue: nerve conduction, muscle contraction
Hypokalemia
due to anything that causes excess K+ loss or inadequate intake, or more K+ entering cells
Hypokalemia effects
- cardiac dysrhythmia
- muscle weakness, fatigue, paralysis
- pins and needles
Hyperkalemia
due to anything that causes K+ build up in extracellular fluid, or more K+ to exit cells
Hyperkalemia effects
- cardiac dysrhythmia
- muscle cramps
- pins and needles (paresthesia)
Effect of K+ imbalance on AP formation
- Hyperkalemia = hyperexcitable cells
- Hypokalemia = less excitable cells
What are the 3 mechanisms for acid-base balance?
- buffer system in the blood
- respiratory system
- Kidneys
What is the main buffer system in the blood?
Bicarbonate-Carbonic acid buffer system
How does the respiratory regulate acid-base balance?
regulation of CO2 level in the blood
How do the kidneys regulate acid-base balance?
variable excretion/reabsorption of H+ and HCO3-
Respiratory acidosis?
due to increased CO2
Metabolic acidosis
due to decrease in HCO3- (excess acid present in the blood)
Respiratory alkalosis
due to decreased CO2
Metabolic alkalosis
due to increased HCO3- (excess acid loss from the blood)
What causes respiratory acidosis?
- acute: pneumonia, airway obstruction, chest injury, drug OD
- chronic: emphysema, pulmonary edema due to congestive HF
Respiratory acidosis compensation
- Metabolic: kidneys reabsorb HCO3- and excrete H+
- respiratory: increase rate and depth of breathing
Metabolic acidosis causes
- excess HCO3- loss from diarrhea
- increased buffering due to acid build up (lactic acid, ketoacidosis)
- hyperkalemia
- kidney disease/failure (decreased excretion of acids/decreased production of HCO3-)
Metabolic acidosis compensation
- Metabolic: kidneys reabsorb HCO3- and excrete H+
- Respiratory: hyperventilation to expel more CO2
Respiratory alkalosis cause
hyperventilation (anxiety, high fever, aspirin OD)
Respiratory alkalosis compensation
Metabolic: kidneys excrete HCO3- and reabsorb H+
Metabolic alkalosis causes
- excess HCl loss from the stomach (vomiting)
- Hypokalemia (H+/K+ swap in cells)
- excess ingestion of antacids
Metabolic alkalosis compensation
- Respiratory: hypoventilation to increase CO2 level in blood
- metabolic: kidneys excrete HCO3- and reabsorb H+
