Acid-Base Disorders - Exam 2 Flashcards
what does pH represent?
the concentration of free hydrogen ions (protons) in circulation
normal pH?
7.4
pH needs to be maintained at what and for what?
maintained at 7.35-7.45 for optimal functioning of body cells
pH >7.4 means?
alkalosis (basic)
pH <7.4 means?
acidosis (acidic)
what is an acid?
a molecule that releases H+ ions (protons) in solution
what is a base?
any substance that can accept a hydrogen ion -> removes free protons from solution
how do you eliminate acids in the body?
pulmonary excretion of CO2 (when breathe out, breathe out CO2)
metabolic utilization of organic acids
renal excretion of nonvolatile acids (combine H+ ions w/ buffers)
how does the kidney excrete acids?
by combining H+ ions with buffers
what are buffers?
chemicals that bind to H+ ions to excrete them from kidney
if have excess CO2, what occurs in the equilibrium rxn?
Excess CO2 drives the reaction to the right -> increase in H+ -> acidic
if have excess bicarb (base), what occurs in the equilibrium rxn?
Excess bicarb drives the reaction to the left -> decrease in H+ -> alkalotic
how do you gain hydrogen ions?
increased CO2
production of phosphoric and sulfuric acids (metabolism of proteins and other organic molecules)
loss of bicarb from GI losses (ex: diarrhea)
loss of bicarb in urine
how do you loss hydrogen ions?
loss of hydrogen ions from emesis (b/c stomach is acidic environment and vomit a lot, lose H+ ions and become alkaloid)
loss of hydrogen ions in urine
how can changes in CO2 levels occur?
hypoventilation or rest diseases (ex: obstructive) or hyperventilation
how does hypoventilation or obstructive respiratory diseases cause changes in CO2 levels and what change?
they result in retention of CO2 -> respiratory acidosis
causes of respiratory acidosis?
obstructive lung diseases (ex: COPD), septic, any condition where can’t blow off CO2
how does hyperventilation cause changes in CO2 levels and what change?
in hyperventilation you are blowing off CO2, resulting in respiratory alkalosis
what causes respiratory alkalosis?
states of anxiety - panic attacks
blow off excessive CO2
common causes of metabolic acidosis?
excess production of lactic acid (>4mEq/L): severe exercise or seizure or shock/hypoxia
formation of ketone bodies (uncontrolled DM or fasting states)
loss of bicarb (diarrhea)
what is the anion gap?
difference between the plasma concentration of the major measure cation (Na+) and the sum of the measured anions (Cl- and HCO3-)
anion gap equation?
AG = Na - [Cl + HCO3]
what does the difference in the anion gap represent?
the concentration of unmeasured anions as phosphates, sulfates, organic acids, and proteins
normal AG?
8-16mEq/L
what does an elevated anion gap mean?
that someone has excessive elements in their blood that shouldn’t be there
what causes you to lose a base and have a normal anion gap metabolic acidosis?
excessive bicarb loss (intestinal losses)
renal losses (renal tubular acidosis)
what causes you to gain an acid and have an elevated anion gap metabolic acidosis
excess metabolic acid production (lactic acidosis, DKA, alcoholic ketoacidosis, starvation, poisoning with toxic alcohols like ethylene glycol)
impaired elimination of metabolic acids; kidney dysfunction
what is the most common cause of metabolic acidosis in hospitalized patients?
lactic acidosis
what are the 2 types of lactic acidosis?
Type A lactic acidosis (hypoxic) - M/C
Type B lactic acidosis
what is the most common type of lactic acidosis?
Type A (hypoxic)
what is Type A (hypoxic) lactic acidosis? Examples?
Decreased tissue perfusion í increase LA production
-Ex: Cardiogenic, septic, hemorrhagic shock; Carbon monoxide or cyanide poisoning
what is Type B lactic acidosis? Examples?
Impaired cellular metabolism or tissue ischemia without systemic hypoperfusion
Ex: DKA, alcoholism, infections, malignancy, metformin, bowel necrosis (important reason to check LA)
mnemonic for AG metabolic acidosis
- M - methanol
- U - uremia (indication for urgent hemodialysis) í uremia is from severe kidney dysfunction
- D - DKA
- P - Propylene glycol
- I - Isoniazid
- L - Lactic acidosis
- E - Ethylene glycol and ethanol (alcoholic ketoacidosis)
- S - Salicylates (aspirin) and starvation
metabolic acidosis treatment?
treat underlying cause
-consider admin of IV or oral sodium bicarb if severe
causes of metabolic alkalosis?
ingestion or administration of alkali (CaCO3 or bicarb - ex: Tums)
stomach loss of H+ (vomiting)
Renal loss of H+ (excess mineralocorticoids -> primary hyperaldosteronsim, cushings)
diuretic use
milk alkali syndrome
2 theories of contraction alkalosis d/t diuretics?
Theory #1
- Loss of large volumes -> Quantity of bicarbonate remains constant -> concentration increased
- When diuresis a pt, losing a lot of fluid which is bicarb free, so have increased concentration of bicarb b/c now have less fluid
Theory #2
-Renal compensation for volume loss -> increased renin -> increased angio II -> increased aldosterone -> decreased potassium -> intracellular shift of protons
diuretic use can cause what?
contraction alkalosis and impaired chloride reabsorption
what is impaired chloride reabsorption?
Diuretics block Cl reabsorption and further enhances NaHCO3 reabsorption (instead of NaCl)
what is milk alkali syndrome?
- Persons who consume excessive amounts of milk (Ca2+) along with alkaline antacids (ex: tums)
- Hypercalcemia reduces glomerular filtration rate which increases bicarb reabsorption
- Alka-seltzer contains sodium bicarb
treatment for metabolic acidosis?
- Treat underlying cause
- Remove or reduce offending agent
if have respiratory problem, primary defect is change in what?
pCO2
if have metabolic problem, primary defect is change in what?
HCO3
