Pathophysiology Dr. Martin: Exam 1

what makes up total body water? (TBW)

intracellular fluid (2/3 TBW) & extracellular fluid (1/3 TBW)

what makes up the ECF?

interstitial fluid (80%) & plasma (20%)

what does equilibrium mean?

no net movement

what determines concentration?

solvent and solute ratio

what causes a shift in water?

the concentration gradient between the ICF & ECF

in ECF concentration if Na+ is most abundant, what is this considered?

normal

in ECF concentration what happens if glucose is most abundant?

diabetes mellitus

what are the characteristics of a isotonic solution?

- normal concentration

- (280-300)

- normal H20 and solute

what are the characteristics of a hypotonic solution?

- more dilute

- (<280)

- more H20 and less solute

- cells expand

what are the characteristics of a hypertonic solution?

- more concentration

- (>300)

- less H20 and more solute

- cells shrink

does ADH affect H20 retention?

yes

does aldosterone affect sodium levels?

yes

does sodium retention cause water retention?

yes

what drives the movement of H20 within the ECF?

2 pressures: hydrostatic & oncotic pressure

what defines hydrostatic pressure?

forcing water out of the blood (pushing out water)

what defines oncotic pressure?

trying to keep H20 in the blood (taking in water)

if blood volume is increased, is hydrostatic pressure increased or decreased?

increased

what plays the most significant role in oncotic pressure?

the plasma protein albumin

as albumin levels in the blood stream increase, what happens to oncotic pressure?

oncotic pressure increases

albumin decrease, _____ ______

oncotic decreases

what defines edema?

excess accumulation of fluid in the interstitial fluid compartment

what are the 4 factors that favor edema formation?

- anything that increases plasma hydrostatic pressure ( raise or increase in BV)

- anything that reduces plasma oncotic pressure (decrease in albumin levels)

- anything that increases capillary permeability (if the capillaries are able to leak easier, more water is able to get out---> 2 causes: inflammation and trauma)

- anything that causes lymphatic obstruction

what is the normal blood Na+ ?

135-145 mEg/L

can Na+ abnormalities affect ECF concentration?

yes

what defines hypernatremia?

- Na+ > 145 mEg/L

- they have a hypertonic ECF (cells shrink)

- decrease in H20 from H20 loss/lack of intake

- increase in Na+ from gain/increased consumption

- dehydrated

what does diabetes insipidus result in?

water loss

how do you treat hypernatremia?

- we give them an isotonic IV fluid so the patient reaches an isotonic range

- they cannot drink water & cannot receive intravenous water (red cells would burst)

what defines hyponatremia?

- Na+ < 135 mEg/L

- increase in H20 bc of increased water intake or increased ADH

- decrease in Na+ bc of diuretic use

(diuretics are used to increase urine output which results in losing both water & sodium, but more sodium loss occurs)

how is blood volume (BV) affected by water & sodium levels?

- increased BV: caused by the increase of water

- decreased BV: caused by the decrease of sodium from diuretic use (body is peeing out more urine & losing water & sodium)

why do we care if we have a hypotonic ECF?

- results in cell expansion

- If (Na+ = 115), the ECF is so dilute, water would shift into the cells very rapidly and water would have no where to go.

- brain swelling also becomes a worry

do you correct hyponatremia at a slow or fast pace?

- slowly, you don't want to correct hyponatremia faster than 8 mEg/L per 24 hours

what is the normal blood K+ ?

3.5-5.0 mEg/L

can K+ abnormalities affect neuromuscular excitability?

yes, especially (cardiac NM excitability)

does aldosterone lower blood potassium levels?

yes

does insulin lower blood potassium levels?

yes

what defines an acute episode?

rapid, very fast (more problematic)

what defines a chronic episode?

slow, longer period of time

what defines hyperkalemia?

- K+ > 5.0

- slows down impulse activity/conduction and can potentially stop the heart

- increase in neuromuscular excitability (in hyperkalemia, it moves resting membrane potential closer to the threshold increasing NM excitability)

what determines threshold?

Calcium levels (Ca+)

what determines resting membrane potential (RMP)?

Potassium levels (K+)

when is a patient considered to have severe hyperkalemia and how do you treat them?

- when it reaches 8.2

- treatment: give them Ca+ gluconate (protects the heart by making threshold more positive & moving it back)

- give insulin + glucose (insulin lowers potassium levels & glucose lowers blood sugar) both insulin & glucose are given together to prevent hyperglycemia

what are some causes of hyperkalemia?

- increase in K+ intake

- decrease in K+ excretion (loss)

- K+ retaining drugs: reduce the amount of aldosterone the body produces (ACE inhibitors, ARBS)

- renal insufficiency: kidney's aren't working properly

- adrenal insufficiency: adrenal glands aren't working properly (results in decrease of aldosterone)

where is hyperkalemia most seen?

- crush injuries & burns (K+ shifts to ECF)

what defines hypokalemia?

- K+ < 3.5

- decrease in muscular excitability

what are some causes of hypokalemia?

- #1 cause is the loss of K+, NOT reduced intake

- K+ losses (in urine or from GI tract)

- urinary K+ loss (diuretics cause us to pee off K+)

- GI loss (vomiting/diarrhea)

can Ca+ abnormalities affect neuromuscular excitability?

yes

what is the normal Ca+ blood concentration?

8.5-10.5 mg/dL

what defines hypercalcemia?

- Ca+ > 10.5 mg/dL

- decreases NM excitability

- threshold moves away from RMP

what are some causes of hypercalcemia?

- hyperparathyroidism (increase in parathyroid hormone PTH which raises blood Ca+

- cancer (specifically lytic bone lesions) breaks down bone & calcium releasing it into the blood stream & results in a increase of Ca+

- PTH related proteins

what defines hypocalcemia?

- Ca+ < 8.5 mg/dL

- increase in NM excitability

- threshold moves closer to RMP

what are some causes of hypocalemia?

- hypoparathyroidism (decrease in parathyroid hormone PTH which lowers blood Ca+)

- vitamin D deficiency

what is the normal arterial blood pH?

7.35-7.45

how do we maintain acid-base balance?

- metabolic regulation & respiratory regulation

- buffer systems: result in a change in pH

- kidneys: hold on or get rid of pH

how do we determine acid-base status?

draw blood (arterial blood gas) ABG

what is the normal ABG range?

pH= 7.40

CO2= 35-45

HCO3= 22-26

normal CO2 range in an ABG?

35-45

normal HCO3 range in an ABG?

22-26

what determines respiratory regulation in ABG & is it an acid or a base?

CO2 (acid)

what determines metabolic regulation in ABG & is it an acid or a base?

HCO3 (base)

what defines an acidosis?

pH < 7.35

- high in acid, low in base

what defines an alkalosis?

pH > 7.45

- low in acid, high in base

interpret the following ABG:

pH= 7.30

CO2= 35

HCO3= 16

- pH is lower than normal (ACIDOSIS)

- CO2 level is normal

- HCO3 level is low (indicates a metabolic issue)

Patient has a metabolic acidosis

what defines a metabolic acidosis?

- can be categorized as having a normal anion gap or a elevated anion gap

what causes a normal anion gap?

caused by the loss of HCO3

what causes an elevated anion gap?

caused by the accumulation of organic acid

what defines an anion gap?

negatively and positively charges equal eachother

what is the normal anion gap range?

3-12 mEg/L

how do you calculate anion gap?

AG = Na - (Cl + HCO3)

what are some causes of a high anion gap metabolic acidosis?

main 3:

- uremia (renal failure)

- diabetic keto acidosis (DKA)

- lactic acidosis (tissue hypoxia)

how do you determine if there is an appropriate respiratory compensation for a metabolic acidosis?

Winter's Formula

CO2 = (1.5 x HCO3) + 8 + & - 2

determine the following ABG & determine if compensation is present:

pH= 7.3

CO2= 35

HCO3= 16

- pH is low (acidosis)

- CO2 levels are high

- HCO3 is low (metabolic issue)

- Patient has a Metabolic Acidosis

- According to Winter's formula, the patient does not have an appropriate respiratory compensation.

what defines hypocapneia?

if CO2 is less than 35

what defines hypercapneia?

if CO2 is greater than 45

determine the following ABG:

pH= 7.51

CO2= 40

HCO3= 36

- pH is high (alkalosis)

- CO2 is normal

- HCO3 is high (metabolic issue)

Patient has a metabolic alkalosis

determine the following ABG:

pH= 7.49

CO2= 26

HCO3= 24

- pH is high (alkalosis)

- CO2 is low (respiratory issue)

- HCO3 is normal

Patient has a respiratory alkalosis

determine the following ABG:

pH= 7.32

CO2= 55

HCO3= 24

- pH is low (acidosis)

- CO2 is high (respiratory issue: hyperventilation)

- HCO3 is normal

Patient has a respiratory acidosis

determine the following ABG:

pH= 6.94

CO2= 75

HCO3= 5

- pH is low (acidosis)

- CO2 is high (respiratory issue)

- HCO3 is low (metabolic issue)

Patient has a combination metabolic & respiratory acidosis

(could also have DKA, respiratory failure, or renal failure)

determine the following ABG:

pH= 7.53

CO2= 47

HCO3= 35

- pH is high (alkalosis)

- CO2 is high, but CO2 does not cause an alkalosis

- HCO3 is high (metabolic issue)

According to Winter's formula, the patient also has appropriate respiratory compensation.

Patient has a metabolic alkalosis w/ respiratory compensation

A patient is volume overloaded secondary to excess water intake.

- What would be the ECF concentration?

- Blood Na+?

- Would they benefit from IV isotonic fluid? Explain why or why not.

- ECF concentration: hypotonic (more water, less solute)

- Blood Na+: hyponatremia

- no, because the patient is volume overloaded & giving them more fluid will overload the patient even more. The simple solution would be restricting water.