Fluid, Electrolyte, And Acid-Base Imbalances Flashcards
What makes up the Extracellular Fluid (ECF) Compartment
- Interstiitial fluid (tissue fluid)
- Blood Plasma
- Lymph
- Specialized fluids: CSF, synovial fluid, aqueous humor, serous fluid
Where does H2O in the body come from?
- Ingestion of fluids and food
- Product of cell respiration
How is water lost in the body?
- Urine
- Perspiration/sweat
- Exhaled air (water vapor)
- Feces
What is the thirst mechanism in the hypothalamus?
- Osmoreceptors sense fluid volumes and concentrations
- Promotes intake of fluid as needed
How does ADH regulate water intake and output
- Promotes reabsorption of H2O from kidney tubules into blood -> LESS FLUID LOST via urine
How does Aldosterone regulate water intake and output?
- Increases reabsorption of Na from kidney tubules -> H2O follows the Na via osmosis
- Conserves more fluid when there is a deficit
How does ANP regulate water intake and output?
- Promotes loss of Na ions and H2O in urine (excrete more urine)
What are electrolytes?
-Chemicals that dissolve in H2O, dissociating into ions
-> most are inorganic (minerals)
-> Cations: (+) ions
-> Anions: (-) ions
- Create osmotic pressure, regulates movement of H2O between compartments
-> areas of higher electrolyte concentration have higher osmotic pressure
How does Aldosterone regulate electrolytes?
Increases reabsorption of Na and the excretion of K by the kidneys
-> Increases blood Na levels
-> Decreases blood K levels
How does ANP regulate Electrolytes ?
Increases excretion of Na by the kidneys
decreases blood Na levels
How does Parathyroid hormone regulate electrolytes?
- Increases reabsorption of Ca from bones and increases absorption in small intestines
- Decreases reabsorption of phosphate at convoluted tubules
- Increases blood calcium levels, decreases blood phosphate levels
How does Calcitonin regulate electrolytes?
- Promotes removal of Ca and phosphate from blood to form bone matrix
- Decreases blood calcium and phosphate levels
What is the most abundant cation and anion in the intracellular fluid?
- Most abundant cation: K
- Most abundant anion is HPO4
- Protein anions are also abundant
What is the most abundant cation and anion in the plasma of the Extracellular fluid
Plasma
- Most abundant cation: Na
- Most abundant anion: Cl
- Protein anions are significant
Interstitial (tissue) fluid
- same as plasma except fewer protein anions
What are Sodium’s (Na) functions
- Most abundant cation in ECF
- Regulates osmotic pressure in ECF
- Essential for electrical activity of neurons and muscle cells
What are Potassium’s (K) functions
- Most abundant cation in ICF
- Regulates osmotic pressure in ICF
- Essential for electrical activity of neurons and muscle cells
What are Calcium’s (Ca) functions
- Most is found in bones and teeth
- Maintains normal excitability of neurons and muscle cells
- Essential for blood clotting
What are Magnesium’s (Mg) functions
- Most is found in bones
- More abundant in ICF than in ECF
- Essential for ATP production, as well as neural and muscle activity
What are Chloride’s (Cl) functions
- Most abundant anion in ECF
- Diffuses easily in and out of cells; helps regulate osmotic pressure
- Part of HCl in gastric juice
What is Bicarbonate’s (HCO3) functions
- Part of bicarbonate buffer system
What is Phosphate’s (HPO4) functions
- Most is found in bones and teeth
- Primarily an ICF anion
- Part of DNA,RNA, ATP, phospholipids
- Part of phosphate buffer system
What is Sulfate’s (SO4) functions
- Part of some amino acids and proteins
How do fluids circulate throughout the body?
- Movement depends on relative hydrostatic and osmotic pressures within compartments *
Filtration
-> High pressure to low pressure
-> Hydrostatic pressure is “push” force to move fluid OUT of an area
Osmosis
-> Low solute concentration to higher solute concentration
-> Osmotic pressure is “pull” force to draw fluid INTO an area
What are the potential causes of excess fluid?
- Kidney disease
- Liver disease
- Hypoalbuminemia
-> Decreased production in liver
-> Kidney disorder causing excess protein excretion
-> Malabsorption syndromes
-> Low dietary intake of protein - Electrolyte imbalance
What are the sign/symtomes of excess fluid
signs and symptoms may vary depending upon the cause of the fluid imbalance
- localized edema/swelling (feet, hands, ascites)
- weight gain
- lethargy; possible seizures
- pale or red skin color
- slow, bounding pulse
- high BP
- pulmonary congestion, cough
- decreased hematocrit
- increased urine output; low specific gravity
What are potential causes of fluid deficit
- Dehydration
-> vomiting and diarrhea
-> excessive sweating (affects Na and H2O levels)
-> Insufficient water/fluid intake
-> diabetic ketoacidosis
- loss of fluid, electrolytes, and glucose in urine
-> severe hemorrhage
-> 3rd spacing following trauma
What are sign/symptoms of fluid deficit
*Signs and symptoms may vary depending upon the cause of the fluid imbalance
- Sunken eyes
- Fatigue, weakness, possible confusion
- Pale skin, decreased skin turgor
- Dry mucous membranes
- Weight loss
- Rapid, weak, thready pulse
- Low BP and orthostatic hypotension
- Increased hematocrit
- Decreased urine output, high specific gravity
What is Hyponatremia and what are the possible causes?
Low sodium imbalance
Possible causes
- Excessive sweating, diarrhea, or vomiting
- Renal failure
- Excessive water intake
- Hormone imbalances
What is Hypernatremia and what are the possible causes
Excessive sodium levels
Possible causes
- Excessive sodium ingestion w/o increased water intake
- Loss of thirst mechanism
- Hormone imbalance (insufficient ADH)
- Severe watery diarrhea
What is Hypokalemia and what are the possible causes
Low Potassium levels
Possible causes
- Excessive losses caused by diarrhea or vomiting
- Diuresis associated with some medications
- Endocrine dysfunction
- Decreased dietary intake
-> may occur with alcoholism, eating disorders
- Kidney disease
What is hyperkalemia and what are the possible causes
Excessive Potassium levels
Possible causes
- Renal failure
- Endocrine dysfunction (aldosterone deficit)
- “Potassium-sparing” diuretics
- Extensive tissue damage (burns or crush injuries)
-> leakage of intracellular potassium into ECF
What is hypocalcemia and what are the possible causes
low calcium levels
Possible causes
- Hypoparathyroidism
- Malabsorption syndromes ->decreased intestinal absorption of calcium or vitamin D
- Renal failure
What is hypercalcemia and what are the possible causes
Excessive calcium levels
Possible causes
- Hyperparathyroidism
- Demineralization caused by immobility
-> Decrease stress on bone leads to increased osteoclast activity
- Increased calcium and vitamin D intake
- Malignant bone tumors -> uncontrolled release of calcium ions from bones
Normal pH range of blood and intracellular fluid
Normal pH range of blood: 7.35-7.45
Normal pH range of intracellular fluid: 6.8-7.0
What are the 3 mechanisms to control pH
- Buffer systems
- Fastest mechanism - Respiratory system
- Alter CO2 (carbonic acid) levels to change pH - Kidneys
- Modify excretion rate of acids
- Modify production and absorption of bicarbonate ions
- Most significant control mechanism
- Slowest mechanism
What do Buffer Systems do?
- Prevent drastic changes in pH
- Weak acid and base pairs react with strong acids or bases to prevent large shifts in pH
- Fastest response, but lowest capacity
-> react w/in fraction of second
-> limited number of molecules in body fluids - Major systems
-> Bicarbonate buffer system
-> Phosphate buffer system
-> Protein buffer system
What is the Bicarbonate Buffer System
Important in blood and tissue fluid
Components
- Carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3)
- H2CO3 reacts with strong bases, producing weaker base that doesn’t affect pH as much
- NaHCO3 reacts with strong acids, producing weaker acid that doesn’t affect pH as much
Normally, more sodium bicarbonate is needed than H2CO3
- Ration of NaHCO3 to H2CO3 ~ 20:1
What is the Phosphate Buffer System?
Components
- Sodium dihydrogen phosphate (NaH2PO4) and sodium monohydrogen phosphate (Na2HPO4)
Important in regulation of blood pH by kidneys
- Cells of kidney tubules can remove excess H+ ions by forming NaH2PO4 which is excreted in urine
- Retained Na ions returned to blood in peritubular capillaries, along with bicarbonate ions
-> Bicarbonate ions are synthesized by renal cells from CO2 and H2O
What is the Protein Buffer System?
Most important intracellular buffer system
Ex: Hemoglobin buffers the H+ formed during CO2 transport
- Amino acids have carboxyl group (COOH) and an amine (or amino) group (NH2)
-> COOH group can act as acid (can “donate” hydrogen)
-> NH2 group can act as a base (can “pick up” excess hydrogen)
What is the Role of the Kidneys in Acid-Base Balance
Greatest role in maintaining pH of blood and tissue fluid
-Kidney response when body fluids are too acidic
-> Secrete more H+ ions into renal filtrate
-> Return more bicarbonate to blood
-> Increase blood pH back to normal
- Kidney response when body fluids are too alkaline:
-> Return H+ ions to blood
-> Excrete more bicarbonate in urine
-> Decreased blood pH back to normal
How does Respiration affect Acid Base Balance
- Regulates amount of CO2 in body fluids
- Chemoreceptors in medulla detect pH and CO2 levels
-> RR and depth increase when pH lowers
- More carbonic acid exhaled and pH increases
-> RR decreases and breaths become shallower when pH is high
- Body retains more carbonic acid to decrease pH
What is acidosis (respiratory or metabolic)
- Excess H+ ions
- Decreases in serum pH
What is Alkalosis (respiratory or metabolic)?
- Deficit of H+ ions
- Increase in serum pH
What is Metabolic acidosis and what are the potential causes and compensation mechanisms
decreased serum HCO3 ions
Potential causes
- Kidney disease
- Diarrhea or vomiting
- Diabetic ketoacidosis
Compensation Mechanisms
- Increased respiratory rate
- Deeper respirations
What is Metabolic alkalosis and what are the potential causes and compensation mechanisms?
Increased serum HCO3 ions
Potential Causes
- Over ingestion of bicarbonate meds
- Gastric suctioning
Compensation Mechanisms
- Decreased respiratory rate
- Shallow respirations
What is Respiratory acidosis and what are the potential causes and compensation mechanisms
Increased CO2
Potential Causes
- Decreased respiratory efficiency: lung infections, COPD, etc
- Paralysis of respiratory muscles
- Decreased RR from drug overdose
Compensation Mechanisms
- Kidneys excrete more H+ and reabsorb more Na and HCO3 ions into blood
What is respiratory alkalosis and what are the potential causes and compensation mechanisms
Decreased CO2
Potential Causes
- Hyperventilation
- Increased respiratory rate at high altitudes
Compensation Mechanisms
- Kidneys retain more H+ ions and excrete more Na and HCO3 ions into urine
