Metabolic Acidosis
1. anion gap increases 2. osmolar gap decreases
What happens to anion gap and osmolar gap when methanol is converted to formic acid overtime?
isopropyl (rubbing) alcohol
toxic alcohol that does NOT produce an anion gap but DOES cause an osmolar gap
pH < 7.35
definition of acedemia
AG = Na+ - (Cl- + HCO3-)
equation for anion gap
corrected AG = 2.5 (4 - alb) + AG
equation for corrected anion gap
1. alteration of O2 binding to hemoglobin 2. reduced cardiac contractility and output 3. vasodilation --> HTN 4. altered mental status 5. predisposition to arrhythmias
five major consequences of acidosis
respiratory acidosis (hypoventilation)
if measured pCO2 > 1.5(HCO3-) + 8 +/- 2
less than 10 - 15
normal range of osmolar gap
non anion-gapped metabolic acidosis
AKA hyperchloremic metabolic acidosis - loss of bicarbonate or lack of excretion of acid
oxalic acid
What does ethylene glycol convert to?
formic acid
What does methanol convert to?
pyruvic acid, acetic acid, lactic acid, propionaldehyde
What does propylene glycol convert to?
pCO2 = 1.5(HCO3-) + 8 +/- 2
Winter's formula equation
greater release
a decrese in pH causes a __________ release of oxygen from hemoglobin
1. Glycols - ethylene, propylene 2. 5-Oxyprolene (metabolite of acetaminophen intoxication) 3. L-lactic acidosis 4. D-lactic acidosis (short gut syndrome) 5. Methanol 6. Aspirin 7. Renal failure (uremia) 8. Ketosis - diabetic, alcoholic, starvation
anion-gapped metabolic acidosis - mnemonic "GOLDMARK"
1. Methanol 2. Uremia (renal failure w/ symptoms) 3. Diabetic ketoacidosis (DKA) 4. Paraldahyde (not used in US) 5. Iron, INH 6. Lactic acidosis 7. Ethylene glycol (in antifreeze, suicide attempts) 8. Salicylate toxicity (aspirin)
anion-gapped metabolic acidosis - mnemonic "MUDPILES"
calculated osmolality = 2Na+ + Glc/18 + BUN/2.8 + ethanol/4.8
calculated osmolality equation
osmolar gap
created by an unmeasured osmole in the bloodstream = measured osmolality - calculated osmolality - should be less than 10 - 15 - > 10 may be indicative of an alcohol intoxication
(patient's AG - 10) / (24 - patient's HCO3-)
delta delta equation
delta delta
equation in which change in bicarbonate should be equal to change in anion gap - 1/1 ratio - if result is > 1, metabolic alkalosis - if result is < 1, non-gapped acidosis
Winter's formula
equation that determines if appropriate respiratory compensation or if a respiratory process also present - if greater than range --> respiratory acidosis (hypoventilation) - if less than range --> respiratory alkalosis (hyperventilation)
1. serum HCO3- is low (< 22 - 26 depending on lab) 2. check ABG for pH to confirm acidosis present (< 7.35) 3. calculate anion gap 4. use Winter's formula to assess respiratory compensation 5. use delta/delta to look for additional disturbance
five major steps to interpreting acid base disorders
urine anion gap
helps to decipher b/w renal causes (RTA) and non-renal causes of non anion-gapped metabolic acidosis UAG = (urine Na+ + urine K+) - urine Cl- - positive value indicates renal cause - negative value non-renal cause
non-gapped acidosis
if delta delta < 1
metabolic alkalosis
if delta delta > 1
respiratory alkalosis (hyperventilation)
if measured pCO2 < 1.5(HCO3-) + 8 +/- 2
1. Hyperalimentation, Hyperchloremia 2. Acetazolamide, Addision's Ammonium chloride 3. Renal tubular acidosis - Types I, II, IV 4. Diarrhea 5. Ureterosigmoid fistula 6. Pancreatic fistula
non anion-gapped metabolic acidosis mnemonic "HARDUP"
metabolic acidosis
pathologic disturbance characterized by low arterial pH w/ dec plasma HCO3- conc
salicylates (aspirin)
substance that causes BOTH anion gapped metabolic acidosis AND respiratory alkalosis
acidosis
the process that caused acidemia - metabolic or respiratory
1. inc acid generation 2. dec acid excretion 3. loss of bicarbonate
three major causes of metabolic acidosis
1. blindness 2. anion gap 3. osmolar gap
three major results when methanol converts to formic acid
1. ethylene glycol 2. methanol 3. propylene glycol
three major toxic alcohols that produce an anion gap and an osmolar gap
1. anion-gapped 2. non anion-gapped
two types of metabolic acidosis
UAG = (urine Na+ + urine K+) - urine Cl-
urine anion gap equation
6 ~ 12
what is the normal range of anion gap?
