Alliyah EvangelistaPathophysiology, Chp. 2 - Fluid, Electrolyte and Acid – Base Imbalances
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Approximately how much of an adult’s body weight is water?
60%
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The extracellular compartment contains:
- intravascular fluid (IF)
- interstitial fluid (ISF)
- cerebrospinal fluid (CSF)
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To maintain a constant level of body fluid, how much water should enter the body?
The same amount that's leaving.
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How is fluid lost?
- urination
- defecation (in the feces)
- insensible loss (perspiration)
- exhaled air
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How does the body maintain the balance of water?
- Thirst: cells sense the internal environment and promotes the intake of water.
- Antidiuretic hormone: controls the amount of fluid leaving the body from urination and promotes the reabsorption of water into the blood.
- Aldosterone: conserves fluid when there's a fluid deficiency and controls the balance of water and sodium in the kidneys.
- Natriuretic peptide hormones: stimulates the elimination of water and sodium in the urine to prevent salt induced hypertension.
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How does fluid move through the body?
Through filtration and osmosis.
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When the hydrostatic pressure exceeds that of the plasma osmotic pressure in the capillary, where does the fluid go?
Towards the tissue into the interstitial compartment as it is pushed out by the hydrostatic pressure.
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When the plasma osmotic pressure exceeds that of hydrostatic pressure in the capillary, what happens?
Fluid is pulled into the capillary as the hydrostatic pressure decreases.
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What is edema?
An excessive amount of fluid in the interstitial compartment which causes it to swell and enlarge.
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Name 4 of the causative factors of edema?
1. Increased capillary hydrostatic pressure: because the hydrostatic pressure increases and exceeds the osmotic pressure, the fluid is pushed to the interstitial compartment and out of the capillaries. When there's an excess of this fluid the tissue swells.
2. Loss of plasma proteins: results in a decrease in plasma osmotic pressure (loss of albumin, therefore loss of plasma), which allows the hydrostatic pressure to exceed the osmotic pressure and pushes fluid out.
3. Obstruction of lymphatic circulation: when the excess fluid and proteins isn't being returned to the general circulation as a result of an obstruction (tumors, damaged lymph nodes).
4. Increased capillary permeability: with increased permeability, more fluids leaks out of the capillary and into the interstitial compartment.
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What is pitting edema?
Edema but when pressure is applied to the area, the excess fluid moves, which creates a depression.
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What is dehydration?
Insufficient body fluid resulting from inadequate intake or excessive loss of fluids (or a combination of the two).
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Define these terms:
- Isotonic dehydration - Hypotonic dehydration - Hypertonic dehydration
- Isotonic dehydration: equal loss of electrolytes and fluid- Hypotonic dehydration: more electrolytes lost than fluid- Hypertonic dehydration: more fluid lost than electrolytes
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Name some causative factors of dehydration.
- vomiting and diarrhea
- excessive sweating
- insufficient water intake
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What are some of effects of dehydration?
- low bp
- fatigue
- decreased mental function
- confusion
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What is the primary cation in ECF?
Sodium (Na)
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Na levels are ___ in the ECF and ___ in the cell.
Na levels are high in the ECF and low in the cell.
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What are electrolytes?
Minerals in the body that contain an electrical charge. Ex. Na and Ka
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Hyponatremia is a deficit in sodium. What causes it and the effects?
Causes:
- excessive sweating
- diarrhea
- excessive water intake
Effects:
- fatigue
- muscle cramps
- weakness/seizures
- impairment of nerve conduction
- brain cells may swell causing confusion, headache, weakness or seizures
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Hypernatremia is an excess in sodium in the body. What causes it and the effects?
Causes:
- watery diarrhea
- prolonged rapid respiration
- excess loss of water from the body
Effects:
- increased thirst
- decreased urine output
- weakness
- dry rough mucous membrane (somewhat in a state of dehydration)
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Potassium is a major ___ cation.
intracellular
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Deficiencies and excessive amounts of potassium can lead to ___.
cardiac arrest because it has a significant affect on cardiac contractions.
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What is normal pH range of serum?
7.35-7.45
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The body tends to be more acidic, why is that?
Because of cell metabolism which produces CO2, and CO2 is acidic.
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What are the three mechanisms that control serum pH?
1. Buffer pairs
2. The respiratory system, which alters the CO2 levels in the body by changing the respiratory rate
3. The kidneys which modify the excretion of acids
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What is the difference between the lungs and kidneys when it comes to changing pH levels?
The lungs can only change the amount of CO2 (a type of acid), whereas the kidneys are slow but can get rid of all types of acids.
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What are the 4 types of imbalances?
1. Respiratory acidosis - ^CO2 levels from respiratory levels.
2. Metabolic acidosis - a decrease in bicarbonate ions (base) from metabolic problems.
3. Respiratory alkalosis - ^respirations that cause a decrease in CO2.
4. Metabolic alkalosis - loss of H ions through the kidneys or GI tract.
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A large volume of water is present in the digestive secretions entering the stomach and small intestine. Why might diarrhea cause a fluid deficit more rapidly than coughing or sneezing with a cold?
Because you excrete large amounts of water with the diarrhea.
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Which body compartment contains the most water?
Intracellular fluid.
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Describe hoe excessive fluid is lost from the body during strenuous exercise on a very hot day. Explain how the can respond to this fluid loss to maintain homeostasis.
The body loses excess water through insensible loss (hyperhidrosis) and exhaled air (excessive breathing). Homeostasis is maintained by promoting the intake of water through thirst.
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When it comes to balancing water and electrolytes in the body, what do natriuretic peptide hormones do?
It stimulates the elimination of water and sodium in the urine to prevent salt induced hypertension.
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Which way does fluid move in the arteriolar and venous ends of a capillary and explain how that relates to their purposes.
At the arteriolar end, the blood's hydrostatic pressure (push) exceeds the interstitial hydrostatic pressure and the plasma osmotic pressure, so the blood is pushed out of the capillary and into the ISF. This makes sense because the purpose of arteries is to carry oxygenated blood and nutrients towards tissues and cells. At the venous end the blood hydrostatic pressure is decreased, and osmotic pressure (pull) is higher, so fluid is pulled back into the capillary. Remember veins carry deoxygenated blood back to the heart and lungs, meaning it has to pull the "used" blood back to bring it to be oxygenated.
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In osmosis, water moves from an area of ___ concentration to a ___ solute concentration.
low, high
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A hypotonic solution means what?
The solution has a low solute concentration.
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Edema is more serious in dependent areas of the body where the force of gravity is greatest such as the feet and ankles. True or false?
True; because it can interfere with venous return which can then affect cell function.
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One of the causes of edema is obstruction of the lymphatic circulation. Describe how it may cause edema and relate it to the lymphatic system's purpose.
It usually causes localized edema because of excessive fluid and protein not being returned to the general circulation. One of the main purposes of the lymphatic system is to return ISF leaking from blood vessels back into the capillaries and into circulation, but if it's blocked then the excess ISF can't be brought back. Meaning that there will be an excess of it in the interstitial compartment.
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What is sodium essential for?
In the conduction of nerve impulses and muscle contraction.
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What are the common causes and effects of hypocalcemia?
Causes:
- hypoparathyroidism (parathyroid not sending enough enough calcium to the blood)
- malabsorption syndrome
Effects:
- twitching
- spasms
- tetany
- abdominal cramps
- weak heart contractions
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What are the common causes and effects of hypercalcemia?
Causes:
- uncontrolled release of calcium from bones due to neoplasms
- increased milk and dairy intake
- hyperparathyroidism
Effects:
- muscle weakness
- loss of muscle tone
- lethargy and stupor
- anorexia
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When serum pH is more acidic, what ions are more present?
Hydrogen ions (they make serum pH more acidic the more there are).
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When the body is in acidosis, how might it compensate?
The body might include deep rapid breathing (inhaling ^O2 to decrease CO2) and secretions of acidic (low pH) urine.
