Acid Base Balance Flashcards
How should we approach a blood gas interpretation?
- Categorize pH
- Identify metabolic process
- Identify respiratory process
- Identify primary and/or compensatory process (if present)
What will two primary processes look like on a blood gas?
Both respiratory and metabolic changes are contributing to the pH change
What are the endogenous and exogenous anions involved with titrational metabolic acidosis
Endogenous Anions
- Uremic acids = Renal azotemia
- Lactic acid = Lactic acidosis
- Ketoacids = Ketoacidosis (diabetes, pregnancy)
Exogenous Anions
- Ethylene glycol toxicity (glycolic, glyoxylic, oxalic acids)
- Salicylate/ Aspirin toxicity
What does the anion gap reflect?
The gap reflects unmeasured ions that are present
Very basic, what are ways to increase or decrease the anion gap?
Increase
- increase unmeasured anions (albumin)
- decrease unmeasured cations
Decrease
- decrease unmeasured anions
- increase unmeasured cations
What is the general interpretation of an increased anion gap?
Titrational metabolic acidosis
What is the usual association on the chemistry panel with titrational metabolic acidosis?
Decreased tCO2
What is the most common cause of a decreased anion gap?
Hypoalbuminemia
What should you consider with a negative anion gap?
Bromide
this is because bromide is measured as Cl
What is the primary Acid-Base profile?
TCO2
Anion gap
Chloride
What is the secondary Acid-Base profile?
Potassium
Urine pH
What are 4 major reasons you would associate with increased tCO2 (metabolic alkalosis)?
- GI loss of HCl (vomit), abomasal sequestration
- Hypoalbuminemia
- Renal (paradoxical aciduria)
- Respiratory acidosis
What will you see with a metabolic alkalosis due to GI situation?
Increased TCO2 with decrease in Cl (seperate from Na)
In what clinical conditions should make you think about paradoxical aciduria?
- GI obstruction/vomiting
- Displaced abomasum
- Electrolyte depletion (Na, K, Cl)
What are the two biggest contributing factors (in the blood) to paradoxical aciduria?
Hypochloremia
Hypokalemia
What are the two driving forces of paradoxical aciduria?
Need for sodium re-absorption (dehydration, hypoNa)
Alkalosis
What is renal tubular acidosis (RTA)?
Acidemia with alkaluria
“inadequate acidification of urine”
What are the two major types of RTA? Explain the cause.
Proximal RTA - Can’t re-absorb HCO3
Distal RTA - Can’t secrete H
What urine pH changes will you see with the progression of proximal RTA?
Early: alkaline urine
Later: acid urine (deplete blood HCO3)
What will you see on the primary acid base profile with hypoproteinemic alkalosis?
TCO2 alone or with chloride may be in upper reference range (unusual pattern b/c Cl always runs from TCO2)… In this case both are available to compensate
What are 3 causes for secretional metabolic acidosis?
- GI/pancreatic secretions (obstruction, diarrhea)
- Saliva loss (mainly ruminants in choke)
- Urinary loss (proximal RTA)
Chloride increased relative to sodium suggests a decreased __________ and is interpreted as evidence for _______________
tCO2
Metabolic acidosis
Chloride decreased relative to sodium suggests an increase in __________ and is interpreted as evidence for _______________
tCO2
Metabolic alkalosis
How will we characterize a titrational metabolic acidosis based on the primary acid base profile?
Decrease TCO2
Increased AG
Normal Cl relative to Na (+/- 3)
How will we characterize a secretional metabolic acidosis based on the primary acid base profile?
Decrease TCO2
Normal AG
Increase Cl relative to Na
What changes will you see on the secondary acid base profile for acidosis?
Hyperkalemia to HN
- Hydrogen goes into cells, potassium comes out
What changes will you see on the secondary acid base profile for alkalosis?
Hypokalemia to LN
- Hydrogen comes out of cells, potassium goes in
Primary profile is use to ___________
define the disorder
Secondary profile is used to ______________
confirm corrective measures are appropriate
What are two critical findings related to potassium and the secondary renal profile?
- Hypokalemia + metabolic acidosis
2. Hypokalemia + unregulated DM patient
What are some factors that can contribute to change in urine pH?
- Postprandial alkaline tide
- Post renal factors:
- urease + bacteria (Staph, Proteus, Mycoplasma)
- sample handling
