What is Starling's Law of Capillary forces?
How does this explain why a nutritionally deficient child would have edema?
Starling's Law describes how fluids move across the capillary membrane. There are two major
opposing forces that act to balance each other, hydrostatic pressure (pushing water out of the
capillaries) and osmotic pressure (including oncontic pressure, which pushes fluid into the
capillaries).
Both electrolytes and proteins (oncontic pressure) in the blood affect osmotic pressure, high
electrolyte and protein concentrations in the blood would cause water to leave the cells and
interstitial space and enter the blood stream to dilute the high concentrations.
On, the other hand, low electrolyte and protein concentrations (as seen in a nutritionally
deficient child) would cause water to leave the capillaries and enter the cells and interstitial fluid
which can lead to edema.
How does the RAAS (Renin-Angiotensin-Aldosterone System) result in increased blood
volume and increased blood pressure?
A drop in blood pressure is sensed by the kidneys by low perfusion, which in turn begins to
secrete renin.
Renin then triggers the liver to produce angiotensinogen, which is converted to Angiotensin I in
,the lungs and then angiotensin II by the enzyme
Angiotensin-converting enzyme (ACE). Angiotensin II stimulates peripheral arterial
vasoconstriction which raises BP.
Angiotensin II is also stimulating the adrenal gland to release aldosterone, which acts to
increase sodium and water reabsorption increasing blood volume, while also increased
potassium secretion in urine.
How can hyperkalemia lead to cardiac arrest?
Normal levels of potassium are between 3.5 and 5.2 mEq/dL. Hyperkalemia refers to
potassium levels higher that 5.2 mEq/dL.
A major function of potassium is to conduct nerve impulses in muscles. Too low and muscle
weakness occurs and too much can cause muscle spasms.
This is especially dangerous in the heart muscle and an irregular heartbeat can cause a heart
attack
The body uses the Protein Buffering System, Phosphate Buffering System, and
Carbonic Acid-Bicarbonate System to regulate and maintain homeostatic pH, what is the
consequence of a pH imbalance
,Proteins contain many acidic and basic group that can be affected by pH changes. Any
increase or decrease in blood pH can alter the structure of the protein (denature), thereby
affecting its function as well
Describe the laboratory findings associated with metabolic acidosis, metabolic
alkalosis, respiratory acidosis and respiratory alkalosis. (ie relative pH and CO2 levels).
Normal ABGs (Arterial Blood Gases) Blood pH: 7.35-7.45 PCO2: 35-45 mm Hg PO2: 90-100
mm Hg HCO3-: 22-26 mEq/L SaO2: 95-100%
Respiratory acidosis and alkalosis are marked by changes in PCO2. Higher = acidosis and
lower = alkalosis
Metabolic acidosis and alkalosis are caused by something other than abnormal CO2 levels.
This could include toxicity, diabetes, renal failure or excessive GI losses.
Here are the rules to follow to determine if is respiratory or metabolic in nature. -If pH and
PCO2 are moving in opposite directions, then it is the pCO2 levels that are causing the
imbalance and it is respiratory in nature.
-If PCO2 is normal or is moving in the same direction as the pH, then the imbalance is
metabolic in nature.
, The anion gap is the difference between measured cations (Na+ and K+) and measured
anions (Cl- and HCO3-), this calculation can be useful in determining the cause of
metabolic acidosis.
Why would an increased anion gap be observed in diabetic ketoacidosis or lactic
acidosis?
The anion gap is the calculation of unmeasured anions in the blood.
Lactic acid and ketones both lead to the production of unmeasured anions, which remove
HCO3- (a measured anion) due to buffering of the excess H+ and therefore leads to an
increase in the AG.
Why is it important to maintain a homeostatic balance of glucose in the blood (ie
describe the pathogenesis of diabetes)?
Insulin is the hormone responsible for initiating the uptake of glucose by the cells. Cells use
glucose to produce energy (ATP).
In a normal individual, when blood glucose increases, the pancreas is signaled to produced in
insulin, which binds to insulin receptors on a cells surface and initiates the uptake of glucose.
Glucose is a very reactive molecule and if left in the blood, it can start to bind to other proteins
and lipids, which can lead to loss of function.
How does this explain why a nutritionally deficient child would have edema?
Starling's Law describes how fluids move across the capillary membrane. There are two major
opposing forces that act to balance each other, hydrostatic pressure (pushing water out of the
capillaries) and osmotic pressure (including oncontic pressure, which pushes fluid into the
capillaries).
Both electrolytes and proteins (oncontic pressure) in the blood affect osmotic pressure, high
electrolyte and protein concentrations in the blood would cause water to leave the cells and
interstitial space and enter the blood stream to dilute the high concentrations.
On, the other hand, low electrolyte and protein concentrations (as seen in a nutritionally
deficient child) would cause water to leave the capillaries and enter the cells and interstitial fluid
which can lead to edema.
How does the RAAS (Renin-Angiotensin-Aldosterone System) result in increased blood
volume and increased blood pressure?
A drop in blood pressure is sensed by the kidneys by low perfusion, which in turn begins to
secrete renin.
Renin then triggers the liver to produce angiotensinogen, which is converted to Angiotensin I in
,the lungs and then angiotensin II by the enzyme
Angiotensin-converting enzyme (ACE). Angiotensin II stimulates peripheral arterial
vasoconstriction which raises BP.
Angiotensin II is also stimulating the adrenal gland to release aldosterone, which acts to
increase sodium and water reabsorption increasing blood volume, while also increased
potassium secretion in urine.
How can hyperkalemia lead to cardiac arrest?
Normal levels of potassium are between 3.5 and 5.2 mEq/dL. Hyperkalemia refers to
potassium levels higher that 5.2 mEq/dL.
A major function of potassium is to conduct nerve impulses in muscles. Too low and muscle
weakness occurs and too much can cause muscle spasms.
This is especially dangerous in the heart muscle and an irregular heartbeat can cause a heart
attack
The body uses the Protein Buffering System, Phosphate Buffering System, and
Carbonic Acid-Bicarbonate System to regulate and maintain homeostatic pH, what is the
consequence of a pH imbalance
,Proteins contain many acidic and basic group that can be affected by pH changes. Any
increase or decrease in blood pH can alter the structure of the protein (denature), thereby
affecting its function as well
Describe the laboratory findings associated with metabolic acidosis, metabolic
alkalosis, respiratory acidosis and respiratory alkalosis. (ie relative pH and CO2 levels).
Normal ABGs (Arterial Blood Gases) Blood pH: 7.35-7.45 PCO2: 35-45 mm Hg PO2: 90-100
mm Hg HCO3-: 22-26 mEq/L SaO2: 95-100%
Respiratory acidosis and alkalosis are marked by changes in PCO2. Higher = acidosis and
lower = alkalosis
Metabolic acidosis and alkalosis are caused by something other than abnormal CO2 levels.
This could include toxicity, diabetes, renal failure or excessive GI losses.
Here are the rules to follow to determine if is respiratory or metabolic in nature. -If pH and
PCO2 are moving in opposite directions, then it is the pCO2 levels that are causing the
imbalance and it is respiratory in nature.
-If PCO2 is normal or is moving in the same direction as the pH, then the imbalance is
metabolic in nature.
, The anion gap is the difference between measured cations (Na+ and K+) and measured
anions (Cl- and HCO3-), this calculation can be useful in determining the cause of
metabolic acidosis.
Why would an increased anion gap be observed in diabetic ketoacidosis or lactic
acidosis?
The anion gap is the calculation of unmeasured anions in the blood.
Lactic acid and ketones both lead to the production of unmeasured anions, which remove
HCO3- (a measured anion) due to buffering of the excess H+ and therefore leads to an
increase in the AG.
Why is it important to maintain a homeostatic balance of glucose in the blood (ie
describe the pathogenesis of diabetes)?
Insulin is the hormone responsible for initiating the uptake of glucose by the cells. Cells use
glucose to produce energy (ATP).
In a normal individual, when blood glucose increases, the pancreas is signaled to produced in
insulin, which binds to insulin receptors on a cells surface and initiates the uptake of glucose.
Glucose is a very reactive molecule and if left in the blood, it can start to bind to other proteins
and lipids, which can lead to loss of function.
