Approach to Acid-base disorders Flashcards
what is arterial pH
7.35-7.45
increase in HCO3- does what to pH
increase in PCO2 does what to pH
increase pH
decrease pH
increase in RR does what to pH
decrease in RR does what to pH
increase in RR = increase CO2 blown off and increase pH
decrease in RR = decrease in CO2 blown off and decrease in pH
what are the two types of Metabolic acidosis
High anion gap metabolic acidosis (HAGMA)
Normal anion gap metabolic acidosis (NAGMA)
what are the two types of Metabolic Alkalosis
Saline responsive (hypovolemia) -aka contraction alkalosis( or chloride deficiency alkalosis)
Saline non responsive (euvolemia of hypervolemia)
Compensations: metabolic acidosis? Metabolic alkalosis? respiratory acidosis? respiratory alkalosis?
Compensations:
metabolic acidosis = respiratory alkalosis (decreased pCO2 via increased RR)
Metabolic alkalosis = respiratory acidosis (increase PCO2 via decrease RR)
respiratory acidosis = metabolic alkalosis (increase HCO3 via reabsorption and production of HCO3)
respiratory alkalosis = metabolic acidosis
(secretion and decreased production of HCO3)
Compensation formula: Metabolic acidosis
Winters formula = PCO2 = 1.5[HCO3] + 8 +/- 2
compensation formula: Metabolic alkalosis
PCO2 will increase by .7 mmHg for each 1.0 mEq/L increase from 24 HCO3-
Compensation respiratory acidosis acute and chronic
Acute: HCO3- will increase by 1 mEq/L for every 100 mmHg increae in PCO2 from normal (40)
Chronic: HCO3- will increase by 3.5 mEq/L for every 10 mmHg increase in PCO2 from normal (40)
compensation respiratory alkalosis acute and chronic
Acute: HCO3- will decrease by 2 mEq/L for every 10 mmHg decrease in PCO2 from normal (40)
Chronic: HCO3- will decrease by 5 mEq/L for every 10 mmHg decrease in PCO2 from normal (40)
how many Acid base disturbances can be present at once in a patient?
up to 3
Normal values: pH HCO3- PCO2 Anion gap Osmolality gap
pH: 7.35- 7.44
HCO3-: 24 mEq/L
PCO2 = 40 mmHg
Anion Gap = 12
Osmolality gap = 10 mosm/kg
How to calculate the anion gap? what is normal? what is it used for?
Anion gap = Na+ - (HCO3 + Cl)
- normal AG = 12 +/- 2
help distinguish if the metabolic acidosis is HAGMA or NAGMA
How to calculate the serum Osmolaity? what is considered normal?
what is the osmolar gap? how is it calculated and what is it used for? and what does that tell us?
Calculated serum Osmolality = 2(Na) + (glucose/18) + (BUN/2.8)
-normal serum osmolality = 275- 290 mosm/kg
Osmolar Gap = Measured serum osmolality - calculated serum osmolality
- normal osmolar gap is < 10 mosm/kg
- if osmolar gap is > 10 mosm/kg suggestive of additional solutes to blood
Clinically useful for screening alcohol ingestions, particularly in HAGMA cases
- screening for ketoacidosis
- lactic acidosis
what does a AG of > 20 highly suggestive for?
alcohol ingestion
what is the Delta-Delta Gap used for?
Used in patients with HAGMA to determine if there is a coexistent NAGMA or metabolic alkalosis present
how to calculate the Delta-Delta gap and delta HCO3
Essentially for every increase in AG there should be equal decrease in serum HCO3
Delta gap = calculated AG - normal AG (12)
Delta HCO3 = normal HCO3 (24) - Delta gap
what does it mean if the measured HCO3 value is close to the delta HCO3, greater than or less than?
if the measured HCO3 was close to Delta HCO3 = no additional acid base disorder present
if the measured HCO3 was greater that the Delata HCO3 then there is a metabolic alkalosis present in addition to the HAGMA
if the measured HCO3 was less than 16 then a non-gap metabolic acidosis (NAGMA) is present with the HAGMA
what is the HAGMA DDx
GOLD MARK
- Glycols (ethylene and propylene)
- Oxoproline (Pyroglutamic acid) (acetaminophen toxicity
- L-lactic acidosis
- D-Lactic acidosis (seen in short bowel syndromes)
- Methanol
- Aspirin
- Renal Failure
- Ketoacidosis (alcoholic, diabetic, starvation)
what is the treatment and diagnosis of Pyroglutamic acidosis
Diagnosis: urinary organic acid screen
Treatment: Discontinue acetaminophen
- IVF
- N-acetylcysteine
Differential diagnosis of increased Osmolar Gap
ME DIE
Methanol
Ethanol’
Diethylene glycol (diuretic Mannitol) Isopropyl alcohol (rubbing alcohol not associated with MA) Ethylene glycol
Propylene glycol
ketoacidosis and lactic acidosis (smaller increase in osmolar gap)
DDx for Normal anion gap metabolic acidosis (NAGMA)
DURHAAM
- Diarrhea!!!
- Ureteral diversion (ileal conduit) or fistula
- Renal tubular acidosis!!!
- Hyperalimentation (enteral nutrition or total parenteral nutrition, TPN)
- Acetazolamide (carbonic anhydrase inhibitor)
- Addisons disease (adrenal insufficiency)
- Miscellaneous (toluene toxicity - glue sniffing, pancreatic fistula, medications)
what does Renal Tubular Acidosis Mean?
- RTA is a condition in which net acid excretion by the kidneys is impaired
- results in a NAGMA
- cannot be diagnosed in the setting of AKI
impaired H+ secretion
impaired HCO3- reabsorption
what are the three types of RTA
RTA type 1 (distal RTA)
-results from decreased net H+ ion secretion in distal tubules and collecting duct
RTA type 2 (proximal RTA)
-results from decreased HCO3 reabsorption in the proximal tubule
RTA type 4 (Hyperkalemic RTA)
- results from decreased aldosterone secretion or aldosterone resistance
- leads to decreased net H+ and K+ secretion in collecting duct