Acid-Base Disorders: Normal Physiology and Compensation Flashcards
what is the modified Henderson-Hasselbach equation?
H+ = (K+ x pCO2)/HCO3-
where is most of your acid eliminated?
lungs
how much HCO3- is reabsorbed in a day w/ a GFR of 120 ml/min?
120 ml/min x 1440 min/day x l/1000 ml x 24 mmol/l = 4080 mmol HCO3- filtered/day
causes of NAG metabolic acidosis
- renal causes
- extrarenal causes
renal causes of NAG metabolic acidosis
- distal (type 1) RTA
- proximal (type 2) RTA
- hyporenin hypoaldosteronism (type 4) RTA
- medications (acetazolamide, topiramate, ifosfamide)
extrarenal causes of NAG metabolic acidosis
- diarrhea
- enterovesical fistula
- “dilutional”
- hyperalimentation
- Addison’s (hypoaldosteronism)
in proximal (type 2) RTA
dumping HCO3- in urine
in distal (type 1) RTA
impaired ammoniagenesis (low NH4+ excretion)
urine AG
urine (Na+ + K+) - (Cl-)
causes of proximal (type 2) RTA
- congenital (cystinosis)
- medications (acetazolamide, topiramate)
- acquired; usually Fanconi’s syndrome (glycosuria, aminoaciduria, phosphaturia) from ifosfamide, tenofovir, or MM
symptoms of proximal (type 2) RTA
- asymptomatic
- hyperventilation as compensation from metabolic acidosis
- growth restriction in children
tx for proximal (type 2) RTA
- 10-15 meq/kg/day NaHCO3- and/or K+citrate
- +/- PO4 and vitamin d for normal growth in children
causes of distal (type 1) RTA
- hereditary causes
- acquired causes
hereditary causes of distal (type 1) RTA
- AD
- AR w/ deafness
- AR w/o deafness
acquired causes of distal (type 1) RTA
- AI causes; Sjögren syndrome, or SLE
- hypergammaglobulinemia
- chronic liver disease; primary biliary cholangitis, chronic hepatitis
- ifosfamide
- amphotericin B
- topiramate (can cause both proximal and distal RTA)
signs/symptoms of distal (type 1) RTA
- severe hypokalemia
- muscle weakness
- nephrolithiasis (MC calcium PHOS stones)
- nephrocalcinosis (bone is buffer)
- alkaline urine
- hypoCITRATURIA
- CKD
- osteopenia
- growth restriction in children
how much K+citrate do you need to neutralize daily net acid load in adult?
1-3 meq/kg/day
how much K+citrate do you need to neutralize daily net acid load in children?
2-5 meq/kg/day
serum bicarb in proximal (type 2) RTA
14-20 mmol/l
serum bicarb in distal (type 1) RTA
< 10 mmol/l
serum bicarb in hyperkalemic (type 4) RTA
16-22 mmol/l
UpH in proximal (type 2) RTA
5 at steady state
K+ in proximal (type 2) RTA
LOW
tx in proximal (type 2) RTA
K+citrate 10-15 mmol/kg/day
UpH and UAG in distal (type 1) RTA
> 5.5 and positive UAG
K+ in distal (type 1) RTA
LOW
tx in distal (type 1) RTA
K+citrate 1-3 mmol/kg/d
UpH in hyperkalemic (type 4) RTA
5.5-6.5
K+ in hyperkalemic (type 4) RTA
HIGH
tx in hyperkalemic (type 4) RTA
- loop diuretic
- fludrocortisone
- NaHCO3
AD genetic abnormality in distal (type 1) RTA
NaCl exchanger
AR genetic abnormality in distal (type 1) RTA
B1 and a4 subunits of H+ATPase
AR genetic abnormality in proximal (type 2) RTA
NaHCO3 cotransporter
AR genetic abnormality in distal and proximal (type 3) RTA
carbonic anhydrase 2
genetic abnormalities in hyperkalemic (type 4) RTA
- pseudohypoaldosteronism type 1; mineralocorticoid receptor, Na+ channel
- pseudohypoaldosteronism type 2 (Gordon’s) WNK 1 and 4 kinases
