Jan10 M2-Acid Base Pathophysiology Flashcards
most common acid base disturbance + compensation
metabolic acidosis. compensate by hyperventilating
3 mechanisms that lead to metabolic acidosis
- increased acid production or accumulation
- loss of bicarb
- impaired renal acid excretion
3 mechanisms of met acidosis by increased acid production
- lactic acidosis
- ketoacidosis (often uncontrolled DM)
- Ingestions (aspirin, methanol, ethylene glycol = antifreeze)
2 mechanisms of met acidosis by loss of bicarb
- GI loss (diarrhea, pancreatic, etc.)
2. RTA (renal tubular acidosis) type 2 (proximal)
3 mechanisms of met acidosis by decreased acid excretion by the kidneys
- Renal failure (decreased NH4+ excretion)
- Type 1 RTA (distal)
- Type 4 RTA (hyperaldo)
anion gap formula and used when
Na - (Cl + HCO3) = AG
Used in METABOLIC ACIDOSIS
normal AG value + what AG indicates in MA
- indicates that there are unmeasured anions associated with an acid (ex. lactic acid: H+ + lactate)
why is bicarb low in AGMA
because the H+ that came with the extra anion is consuming the bicarb. you’re left with low bicarb and more anions
conditions where there is no AG and why is there no AG
RTA (type 1 distal, 2 proximal, 4 hypoaldo) or GI losses: pure bicarb loss
normal blood albumin
40g/L
how to correct anion gap value when hypoalbuminemia and why
-2.5 for every -10g/L because albumin is an anion
AGMA possible causes
Methanol Uremia (renal failure) Diabetic ketoacid.. Propylene glycol Isoniazid, iron Lactic acidosis Ethylene glycol Salicylates (aspirin)
how to quickly tell if an AGMA is due to methanol or ethylene glycol
calculate the osmolal gap: measured osms - calculated osms (2xNa + glucose + urea)
normal osmolal gap + formula
measured osms - (Nax2 + glucose + urea). normal is 12
caution using osmolal gap
ethanol causes osmolal gap but isn’t a cause for acidosis
does ethanol cause acidosis
no
NAGMA differential
loss of bicarb (GI) or renal failure and can’t excrete NH4+ or RTA (type 1,2 or 4)
RTAs that are acid excretion impairment vs RTAs that are loss of bicarb
loss of bicarb: RTA 2 proximal
acid excretion impairment: RTA 1 distal and RTA4 hypoaldo
lactic acidosis: normal prod daily and from what
15 mmol/kg daily. plasma conc is 0.5-1.6 mmol/L. glucose anaerobic metabolism
lactic acidosis indicates what
low tissue O2 delivery
DKA (diabetic ketoacidosis) happens how
lack of glucose in the cells so burn fatty acids and products are acids
in DKA, what is something that accentuates the acidosis
high glucose in the blood creates osmotic diuresis so left volume contracted
rule for IV bicarb as treatment for MA (when to give) + other thing that must be done to treat
when low pH and bicarb below 10 + fix primary disturbance (ex. give insulin if ketoacidosis)
urine pH in RTA
above 5.5. not good bc if blood acid, urine should be too
type 1 RTA pathophgy
-H ATPase or H-K ATPase failure or poisoning
-deficient NH4+ prod
(distal, alpha int cells)
why can have hypokalemia and hyperCa in RTA type 1
K not reabsorbed properly
Ca resorption from bone bc acid is buffered by the bone
Type 2 RTA pathophgy 3-4 causes
defective or poisoned PCT or Fanconi syndrome or acetazolamide (CAi) and bicarb not reabsorbed
Type 4 RTA 2 types
hypoaldo (aldo deficiency) or aldo resistance
3 main symptoms of hypoaldo
low BP, hyperK, slightly low bicarb
urine pH in RTA type 4
below 5.5
treatment for RTAs
RTA type 1 and 2: give bicarb (sodium citrate and will get converted 1:1 to bicarb)
RTA type 4: give aldo p.o. (fluorinef)
