Acid Base Disorders Flashcards

1
Q

If serum Cl is low with respect to Na, what does that suggest?

A

metabolic alkalosis

chronic respiratory acidosis

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2
Q

If serum Cl is high with respect to Na, what does that suggest?

A

normal gap metabolic acidosis

chronic respiratory alkalosis

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3
Q

When will an increase in the anion gap occur?

A

increase in unmeasured anions

decrease in unmeasured cations

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4
Q

What is the most common cause of an increased anion gap?

A

metabolic acidosis from addition of non-Cl acid

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5
Q

What is the pathophysiology of an increased anion gap to due addition of a non-Cl acid?

A

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sodium bicarb has been replaced by NaX

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6
Q

What is the pathophysiology of a normal gap acidosis?

A

if you add more NaCl - sodium bicarb replaced by NaCl - removal of sodium bicarb causes water diuresis which leads to higher Cl concentration

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7
Q

In general, what will cause a normal gap acidosis?

A

addition of HCl

removal of sodium bicarb

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8
Q

Why is it important to always calculate the anion gap?

A

it may be the only indication of a metabolic acidosis

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9
Q

What are the five causes of a normal anion gap metabolic acidosis?

A
dilution with NaCl (saline)
admin of Cl containing acid
chronic ketoacidosis
GI loss of bicarb: diarrhea, fistulae (most common)
renal tubular acidosis (by exclusion)
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10
Q

How does dilution with NaCl cause a normal anion gap acidosis?

A

dilutes bicarb and CO2 but lungs return CO2 to normal quickly

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11
Q

What are the three types of renal tubular acidosis?

A

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

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12
Q

How can the urinary acid excretion distinguish between extra renal and renal acidosis?

A

patients with extra renal have increased rates of renal acid excretion (>30-60)
renal have decreased rates of acid excretion

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13
Q

How does urinary ammonium help distinguish different types of normal gap acidosis?

A

elevated in metabolic acidosis of extrarenal origin

normal to decreased in RTA

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14
Q

How can urinary ammonium be estimated?

A

calculate urinary anion gap (UAG)

positive value indicates low rates of ammonium excretion and RTA

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15
Q

What are the causes of anion gap acidosis?

A

lactic acidosis
ketoacidosis (more acute than normal gap)
renal failure - more advanced CKD = uremic acidosis
overdoses

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16
Q

What can cause lactic acidosis?

A
circulatory collapse
anemia
hypoxemia
metabolic blockade
seizures
17
Q

What can cause ketoacidosis?

A

diabetic
starvation
alcoholic

18
Q

What can cause anion gap acidosis from overdoses and what clinical manifestations would be present?

A

methanol - formic acid causes visual impairment and hemodynmic instability
ethylene glycol - calcium oxalate crystals in urine
salicylates - tinnitus and respiratory alkalosis
first two also increase osmolar gap

19
Q

What is the approach to a patient with increased anion gap metabolic acidosis?

A

aggressive
measurement of BUN and creatinine tells if due to renal failure
certain clinical findings can indicate overdose
measurement of blood lactate or ketoacids in plasma and urine

20
Q

How can you tell if measured bicarb is equal to predicted bicarb?

A

bicarb should decrease the SAME amount of excess anion gap

21
Q

What two things does the generation of metabolic alkalosis require?

A

generation of new bicarb
increased ability of kidney to reclaim filtered bicarb
generation can be renal or extrarenal

22
Q

How is metabolic alkalosis maintained?

A

decreased EABV
K depletion: decreased GFR lowers filtered bicarb, stimulates proximal tube H secretion, increased ammonia synthesis, inhibits aldo release
increased aldo + distal delivery of Na and volume

23
Q

What are the main mechanisms of renal generation of metabolic alkalosis?

A

increased distal Na delivery
mineralocorticoid excess
K deficiency

24
Q

What is post-hypercapneic alkalosis?

A

chronic respiratory acidosis causes compensatory metabolic alkalosis
pCO2 suddenly corrected

25
Q

What can generate metabolic alkalosis and what can maintain it?

A

exogenous admin of base, GI acid loss and renal acid loss

only kidney can maintain

26
Q

What is the approach to the patient with metabolic alkalosis?

A

if maintenance due to contracted EABV - will respond to expansion with saline
urinary Cl 20 suggests maintenance by other mechanisms

27
Q

How can you tell the difference between Barter’s and Gitelman’s clinically?

A

Barters has high urinary Ca

Gitelmans has low urinary Ca

28
Q

What are the three causes of primary respiratory acidosis?

A

RARE
severe lung disease
CNS depression
Neuromuscular disease

29
Q

What are common causes of primary respiratory alkalosis?

A
anxiety
liver disease
sepsis
salicylate ingestion 
high progesterone levels (pregnancy)