Acid-base disorders Flashcards
In the most general terms what causes metabolic acidosis?
Endogenous acid production or loss of bicarbonate.
What is the normal bicarbonate range?
22 - 26mEq/L
What is often seen on physical exam in patients with metabolic acidosis?
Compensatory tachypnea
What is one of the first laboratory signs of acidosis?
- low bicarbonate
- normal homeostasis acidosis is buffered by kidneys via H+ excretion and bicarbonate reabsorption and regeneration
- when this system is overwhelmed (uses up all bicarbonate) acidosis occurs
What other lab/ ABG value directly correlates with bicarbonate?
Base deficit
What blood gas abnormalities are seen in metabolic acidosis?
pH < 7.35
PCO2 < 35
HCO3 < 22/normal
BDE </= -3
What blood gas abnormalities are seen in metabolic alkalosis?
pH > 7.45
PCO2 > 40-45
HCO3 > 26
BDE >/= 3
What blood gas abnormalities are seen in respiratory acidosis?
pH < 7.35
PCO2 > 45
HCO3 > 26
BDE -
What blood gas abnormalities are seen in respiratory alkalosis?
pH > 7.45
PCO2 < 35
HCO3 < 22
BDE -
What are causes of anion gap acidosis?
Methanol
Uremia
DKA
Paraldehyde
Infection
Lactate
Ethanol
Salicylates
Is the ABG or the BMP/CMP a more accurate assessment of plasma bicarbonate?
BMP/CMP
-bicarbonate on the blood gas is a calculated value where it is actually measured in chemistry values
What is the base deficit/excess?
Calculated value of the amount of strong acid or base required to bring 1L blood in vitro at temp 38C and PCO2 40mmHg to pH 7.4
-approximates the severity of acidosis
-only useful in metabolic derangements
What is the anion gap?
The difference in concentration between routinely measured cations (Na+ and K+) and anions (Cl- and HCO3-)
What is the normal anion gap range?
8-12mEq/L
How is lactate produced?
In anaerobic glycolysis through the reduction of pyruvate by lactate dehydrogenase
How is lactate cleared?
Mostly hepatic some renal and other organs
What lactate isomers is tested on routine labs?
L- lactate
Where is D- lactate thought to be produced?
GI tract through metabolism via gut bacteria breakdown of carbohydrates
When should you consider D-lactate acidosis?
In anion gap acidosis in setting of intestinal disease and confusion especially if it happens after a carb load
Between lactate and base deficit which is a better predictor of mortality?
Lactate
-Elevated lactate correlates w/ higher mortality and longer length of stay
-BDE showed no correlation w/ mortality
What are some non-focal ischemia causes of lactic acidosis?
-lung injury/ARDS
-asthma d/t elevated oxygen demand and liver ischemia
-seizures
-pheochromocytoma
-burns
-neuroleptic malignant syndrome
-cardiopulmonary bypass d/t inadequate perfusion causing a shock like state
-use of epinephrine d/t potentiation of tissue malperfusion
-liver mets
-metformin (and other biguanides)
-malnutrition (d/t thiamine and biotin deficiency which are required for pyruvate metabolism, if it isn’t broken down it accumulates and leads to lactate)
What is type A lactic acidosis?
Due to hypoperfusion or hypoxemia
What is type B lactic acidosis?
Lactic acidosis in the absence of hypoperfusion and hypoxemia
From an acid/base status what occurs when GFR < 25mL/min?
Impaired renal acidification, reduced bicarbonate reabsorption, impaired renal homeostatis all leading to metabolic acidosis