Approach To Acid-Base Disorders Flashcards
(28 cards)
What is normal arterial pH?
7.35- 7.45
What is the normal intracellular pH?
7.0- 7.3
How do the lungs compensate metabolic acidosis?
They increase respiratory rate
How do the lungs compensate metabolic alkalosis?
They decrease respiratory rate
How do the kidneys compensate for respiratory acidosis?
They increase reclamation and generation of new HCO3-
How do the kidneys compensate for respiratory alkalosis?
They decrease reclamation and generation of new HCO3-
How do you calculate anion gap?
Na - (HCO3 + Cl)
Why is it necessary to know the anion gap?
It can help differentiate etiologies of metabolic acidosis, diagnose paraproteinemias, or diagnose lithium/bromide/iodide intoxications
What can cause normal anion-gap metabolic acidosis?
Hyperchloremic metabolic acidosis
Renal tubular acidosis
Diarrhea
How does hypoalbuminuria affect anion gap?
It falsely lowers it
What is the osmolar gap useful for?
Screening for alcohol ingestions (particularly in HAGMA cases) - if AG >20 = alcohol ingestion
Screening for ketoacidosis
Screening for lactic acidosis
What is the delta-delta gap?
Used in patients with HAGMA to determine if there is a coexistent NAGMA or metabolic alkalosis present
Ex) AG = 20; 8 above normal value of 12
HCO3- should be 16 (8 below normal value of 24)
What is the normal value for anion gap?
12
What is the normal value for osmolality gap?
10 mmol/L
What is the DDx for HAGMA?
G- Glycols (ethylene and propylene)
O- Oxoproline (pyroglutamic acid - from acetaminophen toxicity)
L - Lactic acidosis
D - Lactic acidosis (colonic metabolization of glucose, starch, or other carbs by bacteria; seen in short bowel syndromes)
M- Methanol
A- Aspirin
R - Renal failure
K- Ketoacidosis (Alcoholic, Diabetic, Starvation)
What is the DDx for people with an increased serum osmolar gap?
M - methanol E- ethanol D- diethylene glycol (diuretic [mannitol]) I - isopropyl alcohol E - ethylene glycol
Is acidosis associated with hyper or hypokalemia? What about alkalosis?
Acidosis = hyperkalemia
Alkalosis = hypokalemia
What is the DDx for NAGMA?
D- diarrhea
U- ureteral diversion (ileal conduit) or fistula
R- renal tubular acidosis
H - hyperalimentation (i.e. enteral nutrition)
A- Acetazolamide (carbonic anhydrase inhibitor)
A- Addison’s disease
M - miscellaneous (toulene toxicity - glue sniffing, pancreatic fistula, medications)
Where is most of HCO3 reabsorbed?
Proximal tubule
What is the pathophys of Proximal RTA (Type 2)?
There is decreased capacity in the PT to reabsorb HCO3, so the filtered HCO3 load exceeds PT reabsorptive capacity and thereby increases distal HCO3- delivery which overwhelms the reabsorption mechanisms downstream in the TAL and DT, leading to HCO3 loss in the urine and thereby a low serum HCO3
How do you diagnose Proximal RTA (Type 2)?
Urine pH canbe high or low depending on serum HCO3 level
Urine anion gap can be positive or negative
What can cause proximal (type 2) renal tubular acidosis?
Drugs and toxins (outdated tetracycline, gentamicin, streptomicin, lead, cadmium, mercury)
Tubulointerstitial disease (post-transplantation rejection, balkan nephropathy, medullary cystic disease)
Other (bone fibroma, osteopetrosis, paroxysmal nocturnal hemoglobinuria)
What is a urine anion gap used for?
To differentiate renal from non-renal causes of NAGMA
What is the pathophys in Distal RTA (type 1)?
These patients cannot acidify their urine which is due to decreased net H+ secretion in the distal nephron
This is due to abnormally permeable distal tubule and collecting duct allowing secreted H+ ions to flow back into tubular cell
