Metabolic Acidosis Flashcards
what is metabolic acidosis?
pH of blood < 7.35 due to an increase in H+, lactate, and organic acids OR a loss of HCO3-
what are 4 broad categories of metabolic acidosis?
- Increased H+ production
- Acid ingestion
- Bicarb losses via GI/renal
- Decreased H+ excretion
how do you calculate the serum anion gap?
AG = [Na] - ( Cl- + HCO3-)
what is the equation for urine anion gap?
urine Na + urine K - urine Cl
what unmeasured anions are typically major contributors to metabolic acidosis?
lactate and acetoacetate
what does HAGMA stand for?
High Anion Gap Metabolic Acidosis (HAGMA)
there is a gain of extra acidic anions
what does NAGMA stand for?
Normal Anion Gap Metabolic Acidosis (NAGMA)
there is a loss of bicarb or a failure of kidneys to excrete acid
what does HARDASS stand for re: NAGMA?
H - Hypercholeremia/Hyperalimentation
A - Addison’s Disease
R - Renal tubular acidosis
D - Diarrhea
A - Acetazolamide
S - Spironolactone
S - Saline infusion
Hypercholeremia and hyperalimentation cause NAGMA by increasing ___ which decreases ___ making the pH _____
increasing Cl-
decreasing HCO3-
decreases pH
Addison’s disease (adrenal insufficiency) causes NAGMA by not producing ________ (hormone) which impacts _____ (ion) resulting in _____ not being excreted
aldosterone
impacts Na+ ➔ more Na+ is being excreted than supposed to (salt wasting)
H+ not being moved into the tubule fluid and being excreted
Renal tubular acidosis causes NAGMA by the kidneys _____________ the acid
not being able to remove acid from the blood into urine for excretion
how does diarrhea cause NAGMA?
increased GI losses of bicarb = more acid in the blood = acidosis
How do carbonic anhydrase inhibitors cause NAGMA? what is one type/the name of one?
Causes an accumulation of carbonic acid ➔ acidifies the blood
A - Acetazolamide
How does spironolactone cause NAGMA?
spironolactone = aldosterone blocker → leaves Na+ in urine (not reabsorbed) → H+ cannot be excreted in urine
saline can cause NAGMA because _______
external infusion of more Cl- which leads to a decrease in HCO3-
and just more fluids = dilutional acidosis as there is no additional administration of HCO3-
how do you distinguish if a NAGMA is from a GI (diarrhea) or renal loss (renal tubular acidosis) of bicarb?
use the urine anion gap
if gap is positive/normal = renal tubular acidosis ➔ doesn’t change because the kidneys are not able to compensate for the bicarb loss
if gap is negative/low = diarrhea ➔ bc the kidneys are still able to try to compensate for the loss of bicarb, so its increasing ammonium excretion
what does GOLDMARK stand for re: HAGMA?
G - Glycols
O - Oxoproline - chronic acetaminophen use
L - L-lactate
D - D-lactate → very rare, usually have hx of short bowel syndrome
M - Methanol - organic alcohol
A - Aspirin/ASA
R - Renal Failure (Uremia)
K - Ketoacidosis
how do glycols cause HAGMA?
they are metabolized into acid, which acidifies the blood ➔ lowers the pH
real-life examples of glycols (ethylene glycol and propylene glycol) are?
antifreeze, brake fluid, paints
what medication is associated with Oxoproline (pyroglutamic acid)?
acetaminophen
how does oxoproline cause HAGMA?
it’s also known as pyroglutamic acid, and is an organic acid that can accumulate and acidify the blood
how does L-lactate and D-lactate cause HAGMA?
D-lactacte, can be broken down into other organic acids by bacteria in the colon ➔ more seen in pts with short gut syndrome
L-lactate is a byproduct of normal metabolic ➔ lactic acid
both cases accumulation = additional organic acids = pH lowers
what is methanol? how does it cause HAGMA?
organic alcohol
converted into formic acid ➔ accumulate acid ➔ pH lowers
how does ASA cause HAGMA?
stops the electron transport chain in mitochondria ➔ build-up of lactic acid ➔ pH lowers
how does renal failure/uremia cause HAGMA?
injury to kidney ➔ not able to excrete acid anions ➔ accumulation ➔ pH lowers
why does renal tubular acidosis cause NAGMA and renal failure/uremia cause HAGMA?
renal tubular acidosis ➔ only problem with tubules, so only a defect with ability to acidify the urine and excrete acid ➔ there is balance because some level of hyperchloremia as well (negative Cl and positive H)
renal failure/uremia ➔ problem with both glomeruli and tubules ➔ so low excretion of acid and also low reabsorption of HCO3 ➔ HAGMA, larger anion gap bc additional acids not getting excreted
how do ketones cause metabolic acidosis?
ketones are broken down into excess hydrogen ions ➔ binds up bicarb ➔ decreased bicarb ➔ decreased pH
what states can cause ketoacidosis for metabolic acidosis?
diabetic, alcoholic, and starvation
alcohol causes ketoacidosis because it inhibits the body’s ability to _____ forcing the body to make ketones
produce glucose
starvation causes ketoacidosis because ____ in the body so it’s forced to make ketones
no glucose
what s/s might you see for acidosis?
- hyperventilation to remove CO2 ➔ respiratory compensation to increase the pH (Kussmaul)
- altered mental status ➔ confusion
- tachycardia
- electrolyte imbalances
- N/V, abdo pain
what is the major risk of having hyperkalemia with metabolic acidosis?
cardiac arrhythmias
how would you treat a metabolic acidosis?
- correct the underlying cause ➔ consider antidotes for toxicities, dialysis, abx, insulin/glucose, thiamine (alcohol/starvation) and bicarbonate solutions
- fluid resuscitation
- correct electrolyte abnormalities
what are some ways you can correct hyperkalemia?
- IV insulin and IV glucose
- inhaled albuterol (Ventolin)
- Dialysis ➔ AEIOU
bicarb or resins are not recommended for routine use if other options haven’t been explored yet
what is the AEIOU for dialysis?
A - acidosis
E - electrolyte imbalances
I - intoxications
O - overload fluid
U - uremia
what are the main AEs we’re concerned about when there is acute metabolic acidosis (2)?
heart: decreased cardiac output and arterial dilation w/ hypotension and poor oxygen delivery ➔ arrhythmias
immune: impaired immune response
what are the main AEs are we concerned about for chronic metabolic acidosis? (2)
muscle degradation
abnormal bone metabolism
