Acid Base Disorders Flashcards
What does pH represent
concentration of free hydrogen ions in circulation
What is normal human pH
7.4
What is an acid
a molecule that releases hydrogen ions in solution
What is a base
any substance that can accept a hydrogen ion
How are acids eliminated from the body?
- pulmonary excretion of Co2
- metabolic utilization
- renal excretion of non volatile acids
How does the body become acidic
excess CO2 drives the circulation rxn to the right–> increase in H+ ions
How does the body become alkalotic
excess HCO3- drives circulation rxn to the left–> decrease in H+ ions
What is the equilibrium reaction
CO2+H2O=H2CO3=HCO3-+H+
When do you gain hydrogen ions
- increased CO2
- production of phosphoric and sulfuric acid
- loss of bicarb from GI (diarrhea)
- loss of bicarb in urine
What causes a loss of hydrogen ions
- emesis
- urine
What are common causes of metabolic acidosis
- excess production of lactic acid
- formation of ketone bodies
- loss of bicarb
What causes respiratory acidosis
hypoventilation or respiratory disease can result in retention of CO2
What causes respiratory alkalosis
hyperventilation–>blowing off CO2
What is the anion gap
difference between the plasma concentration of the major measure cation (Na) adn the sume of measured anions (Cl and HCO3)
What things can produce excess lactic acid
- severe exercise
- seizure
- shock/hypoxia
What things can form ketone bodies in the body
- uncontrolled DM
- fasting states
What does the anion gap represent
the concentration of unmeasured anions like phosphates, sulfates, organic acids and proteins
What is the normla AG
8-16 mEq/L
What is the AG equation
AG= Na- {Cl+HCO3]
What does a normal anion gap tell you in metabolic acidosis
excessive bicarbonate loss
What causes of metabolic acidosis would show a normal anion gap
- diarrhea
- small bowel, pancreatic or biliary fistula drainage
- ileostomy drainage
- renal tubular acidosis
What does an elevated anion gap in metabolic acidosis tell you
excess metabolic acid production
What causes of metabolic acidosis would show an elevated anion gap
- lactic acidosis
- DKA
- alcoholic ketoacidosis
- starvation ketoacidosis
- poisoning of toxic alcohols
- kidney dysfuntion
What is the most common cause of metabolic acidosis in a hospitalized patient
lactic acidosis
What is the cause of type A lactic acidosis
hypoxia–> decreased tissue perfusion–> LA production
What types of things cause type A lactic acidosis
- cardiogenic, septic, hemorrhagic shock
- carbon monoxide poisoning
- cyanide poisoning
Is type A or type B lactic acidosis more common
type A
What causes type B lactic acidosis
impaired cellular metabolism or tissue ischemia without systemic hypoperfusion
What things can cause type B lactic acidosis
- DKA
- alcoholism
- infection
- malignancy
- metformin
- bowel necrosis
Mnemonic for AG metabolic acidosis
“MUDPILES”
Methanol Uremia DKA Propylene glycol Isoniazid Lactic acidosis Ethylene glycol and ethanol Salicylates and starvation
How do you treat metabolic acidosis
- treat underlying cause
- IV or oral bicarb if severe
What can cause metabolic alkalosis
- ingestion or administration of alkali
- stomach loss of H+
- renal loss of H+
- diuretic use (contraction alkalosis)
What are the two theories behind contraction alkalosis
1- loss of large volume of bicarb free fluid
What is milk alkali syndrome
when a person consumes excessive amounts of milk along with alkaline antacids
Why does milk alkali syndrome occur
hypercalcemia reduces the glomerular filtration rate which increases bicarb reabsorption
How do you know if an acid base disorder is cause by a respiratory problem
primary defect in a change in pCO2
How do you know if an acid base disorder is due to a metabolic problem
primary defect is change in HCO3
How do the kidneys respond to acidosis
- bicarb binds H+
- additional H+ are excreted bound to other buffers (hydrogen phosphate)
- new bicarb is formed during tubular glutamine metabolism
How do the kidneys respond to alkalosis
- H+ binds bicarb
- bicarb is excreted in the urine
- tubular glutamine metabolism is decreased to lower bicarb productio
H+, HCO3-, CO2 change in…
respiratory acidosis
respiratory alkalosis
metabolic acidosis
metabolic alkalosis
Resp acidosis-
everything increase
Resp alk-
everything decreased
Met acidosis-
increased H+
decreased HCO3/CO2
Met alkolosis-
decreased H
increased HCO3/CO2Appropriate HCO3 and PCO2 compensation for…
metabolic acidosis metabolic alkalosis acute resp acidosis chronic resp acidosis acute resp alkalosis chronic resp alkalosis
FYI
metabolic acidosis-
HCO3 dec by 1
PCO2 dec by 1.2
metabolic alkalosis-
HCO3 dec by 1
PCO2 dec by 0.4-0.7
A. resp acidosis-
pCO2 inc by 10
HCO3 inc by 1-2
C. resp acidosis
pCO2 inc by 10
HCO3 inc by 3.5
A. resp alkalosis
pCO2 dec by 10
HCO3 dec by 1-2
C. resp alkalosis
pCO2 dec by 10
HCO3 dec by 5
What are the steps for determining ABGs
1: acidosis or alkalosis
2: is compensation appropiate?
3: check anion gap
