Acid Base Disorders Flashcards
If serum Cl is low with respect to Na, what does that suggest?
metabolic alkalosis
chronic respiratory acidosis
If serum Cl is high with respect to Na, what does that suggest?
normal gap metabolic acidosis
chronic respiratory alkalosis
When will an increase in the anion gap occur?
increase in unmeasured anions
decrease in unmeasured cations
What is the most common cause of an increased anion gap?
metabolic acidosis from addition of non-Cl acid
What is the pathophysiology of an increased anion gap to due addition of a non-Cl acid?
HX combines with sodium bicarb and generates more NaX and H2CO3 - converted to CO2 and water and blown out
sodium bicarb has been replaced by NaX
What is the pathophysiology of a normal gap acidosis?
if you add more NaCl - sodium bicarb replaced by NaCl - removal of sodium bicarb causes water diuresis which leads to higher Cl concentration
In general, what will cause a normal gap acidosis?
addition of HCl
removal of sodium bicarb
Why is it important to always calculate the anion gap?
it may be the only indication of a metabolic acidosis
What are the five causes of a normal anion gap metabolic acidosis?
dilution with NaCl (saline) admin of Cl containing acid chronic ketoacidosis GI loss of bicarb: diarrhea, fistulae (most common) renal tubular acidosis (by exclusion)
How does dilution with NaCl cause a normal anion gap acidosis?
dilutes bicarb and CO2 but lungs return CO2 to normal quickly
What are the three types of renal tubular acidosis?
Type 1 - hypokalemic distal RTA - CD can’t acidify urine
Type 2 - proximal RTA - can’t reclaim bicarb
Type 4 - Hyperkalemic distal RTA - CCD can’t secrete H and K
How can the urinary acid excretion distinguish between extra renal and renal acidosis?
patients with extra renal have increased rates of renal acid excretion (>30-60)
renal have decreased rates of acid excretion
How does urinary ammonium help distinguish different types of normal gap acidosis?
elevated in metabolic acidosis of extrarenal origin
normal to decreased in RTA
How can urinary ammonium be estimated?
calculate urinary anion gap (UAG)
positive value indicates low rates of ammonium excretion and RTA
What are the causes of anion gap acidosis?
lactic acidosis
ketoacidosis (more acute than normal gap)
renal failure - more advanced CKD = uremic acidosis
overdoses