Acid-Base - Wall Flashcards
What are volatile acids and how are they excreted?
Carbonic acid
Lungs
What are nonvolatile acids and how are they secreted?
Non-carbonic acids (ie phosphoric, sulfuric acid)
Excreted by kidney
What is the equation for the bicarbonate buffer system?
CO2 + H20 <-> H2CO2 <-> H + HCO3
What is the equation for the hydrogen ion concentration?
H = 24 * CO2 / HCO3
CO2 = 40
HCO3 = 24
Must convert pH to nEq/L (pH 7.4 = 40 nEq/L)
What is the corresponding [H] for the given pHs: 7.1, 7.4, 7.7?
- 1 - 80
- 4 - 40
- 7 - 20
What is the defintion of a metabolic disorder?
Process that directly alters bicarbonate concentration
What is the definition of a respiratory disorder?
Process that directly alters CO2
What is the major extracellular buffer?
Bicarbonate
What are the major buffers in ECFV, urine, and ICF?
ECFV - bicarbonate
Urine - Phosphate and ammonia
ICF - Protein
What are the secondary mechanisms or metabolic and respiratory disorders and how quickly do they act?
Respiratory system compenates for metabolic disorders (rapid, minutes)
Bicarbonate concentration compensates for respiratory disorters (1-2 days)
What are the changes in pH, HCO3, and pCO2 in metabolic acidosis?
pH - decreases
HCO3 - decreases (PRIMARY)
pCO2 - decreases (COMPENSATORY)
What are the changes in pH, HCO3, and pCO2 in metabolic alkalosis?
pH - increases
HCO3 - increases (PRIMARY)
pCO2 - increases (COMPENSATORY)
What are the changes in pH, HCO3, and pCO2 in respiratory acidosis?
pH - decreases
HCO3 - increases (COMPENSATORY)
pCO2 - increases (PRIMARY)
What are the changes in pH, HCO3, and pCO2 in respiratory alkalosis?
pH - increases
HCO3 - decreases (COMPENSATORY)
pCO2 - decreases (PRIMARY)
What causes metabolic acidosis?
Decreased renal acid excretion (RTA I, RTA 4)
Direct bicarbonate losses (GI or urine)
Increased acid generation (Lacticacidosis, ketoacidosis aspirin, animal protein)
What causes respiratory acidosis?
Hypercapnia (too much carbon dioxide)
Decrease breathing (ie obstructive pulmonary disease)
What is the compensatory mechanism in response to respiratory acidosis?
Buffering raises plasma bicarbonate
Kidney increses acid excretion (NH4) in 2-3 days
What causes respiratory alkalosis?
Reduced carbon dioxide
Panic attacks, pregnancy
What is the compensatory response to respiratory alkalosis?
Kidney reduces ammonium secretion and eliminates bicarbonate into the urine
What changes equally and inversely with plasma HCO3 in respiratory disorders?
Plasma Cl
What causes metabolic alkalosis?
Vomiting
Diuretic therapy
Primary hyperaldosteronism
How can you differentiate chloride responsive vs resistant metabolic alkalosis?
Responsive - U Cl < 20 mEq / L
Resistant - U Cl > 20 mEq / L
What causes the plasma anion gap?
Strong acids dissociate into H+ and A-.
H+ binds HCO3-
Typically A- is excreted in urine and Cl- is responsible for anion gap
Increased anion gap if A- is not excreted
What does a high anion gap imply?
Metabolic acidosis
What do positive and negative urine anion gaps indicate in metabolic acidosis with normal plasma anion gap?
Positive - Renal tubular acidosis
Negative - Diarrhea
What is titratable acid?
The amount of acid excreted with phosphate
What is urine ion gap?
Na + K - Cl
Normally positive ~10 mEq/L
What is altered in all acid base disorders (except increased plasma anion gap metabolic acidosis)?
Plasma Cl
