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Cpr 3 other > (2.1) Acid/Base Disorders [DSA-Selby] > Flashcards

(2.1) Acid/Base Disorders [DSA-Selby] Flashcards

1
Q

Bicarbonate reaction

A

CO2 + H2O <=> H2CO3- via carbonic anhydrase

H2CO3- H+ + HCO3-

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2
Q

What is the Henderson Hasselbach equation? What is the relationship between pH and PCO2?

A

HCO3- and pH directly related

PCO2 and pH inversely related

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3
Q

How do the lungs regulate pH?

A

Control concentration of PCO2 by increasing or decreasing respiratory rate

Inc RR = more CO2 blown off

Dec RR= less CO2 blown off

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4
Q

How do the kidneys regulate pH?

A

Excreting acidic or alkaline urine

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5
Q

How is acid excreted by the kidneys?

A

Renal epithelial cells secrete large amounts of H+ into the tubular lumen => acid removed from ECF

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6
Q

What are the 4 acid-base disturbances and their relationship to the buffer system?

A

Metabolic Acidosis
– Low serum HCO3-
Metabolic Alkalosis
– High serum HCO3-
Respiratory Acidosis
– High PCO2

Respiratory Alkalosis
– Low PCO2

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7
Q

Normal anion gap metabolic acidosis (NAGMA) is also referred to as _____ acidosis

A

Hyperchloremic acidosis

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8
Q

How is base excreted by the kidneys?

A

Large amounts of HCO3- continuously filtered into the urine

If not reabsorbed, will be excreted => base removed from ECF

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9
Q

How are the acid-base disturbances compensated

A

Lung compensates for kidney disturbance

Kidney compensates for lung disturbance

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10
Q

Compensation formula for metabolic acidosis

A

Winter’s formula: PCO2 = 1.5[HCO3-] + 8 +/- 2

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11
Q

Compensation formula for metabolic alkalosis

A

Dr. Karius’s formula: (0.5 - 1.0) x [HCO3-} = PCO2

Dr. Selby: PCO2 increases by 0.7 mmHg for ever 1.0 mEq/L increase in HCO3- from normal (normal HCO3- is 24)

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12
Q

Compensation formula for:

Acute respiratory acidosis

Chronic respiratory acidosis

A

Dr. Karius:

Acute: [HCO3-] = PCO2/10 +/- 3

Chronic: 24 + (PCO2 - 40)/10 = [HCO3-]

Dr. Selby:

Acute: HCO3- increases by 1 mEq/L for every 10 mmHg increase in PCO2 from normal (normal is 40)

Chronic: HCO3- increases by 3.5 mEq/L for every 10 mmHg increase in PCO2 from normal (40)

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13
Q

Compensation formula for:

Acute respiratory alkalosis

Chronic respiratory alkalosis

A

Dr. Karius:

Acute: 24 - 2(40 - PCO2)/10 = [HCO3-]

Chronic: 24 - 5(40 - PCO2)/10 = [HCO3-]

Dr. Selby:

Acute: HCO3- will decrease by 2 mEq/L for every 10 mmHg decrease in PCO2 from normal (normal is 40)

Chronic: HCO3- will decrease by 5 mEq/L for every 10 mmHg decrease in PCO2 from normal

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14
Q

How many acid-base disturbances can someone have at one time?

A

3

(4 is impossible, cannot breathe fast and slow simultaneously)

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15
Q

What is the anion gap equation?

A

AG = Na+ - (HCO3- + Cl-)

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16
Q

What is a normal anion gap?

A

Normal AG = 12 +/- 2

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17
Q

Why does the anion gap remain normal in NAGMA?

A

H+ is buffered by HCO3-, which drops HCO3- =>

Cl- levels rise and offset HCO3- => normal AG

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18
Q

How does hypoalbuminemia affect anion gap? How is this corrected?

A

Hypoalbuminemia falsely lowers AG

For every 1 g/dL drop in albumin, calculated AG decreases by 2.5 mEq/L and may mask an elevated AG

Correct by adding back the deficit to get the correct AG

Albumin-Corrected Anion Gap = Anion Gap + 2.5 x ([Normal Albumin] - [Observed Albumin])

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19
Q

What is the serum osmolality equation? What is the normal?

A

Calculatedulated serum osmolality = 2(Na) + (Glucose/18) + (BUN/2.8)

Normal = 275 - 290 mosm/L

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20
Q

What is the osmolar gap? What is the normal?

A

Osmolar gap = Measured serum osmolality - calculated serum osmolality

Normal osmolar gap < 10 mosm/L

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21
Q

If osmolar gap >10 mosm/L, what is that suggestive of?

A

Additional solutes in blood

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22
Q

What level of anion gap is highly suspicious for alcohol ingestion?

A

AG >20

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23
Q

What is osmolar gap most clinically useful for?

A

Screening for alcohol ingestion, particularly in HAGMA

(can also screen ketoacidosis and lactic acidosis)

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24
Q

What is the Delta-Delta gap used for?

A

Used in pts with HAGMA to determine if there is coexistent NAGMA or metabolic alkalosis

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25
How do you calculate the Delta-Delta Gap?
Every increase in AG, there should be an equal decrease in serum HCO3- Delta gap = calculated AG - normal AG (12) Delta HCO3- = normal HCO3- (24) - Delta gap
26
What is the range for normal pH?
7.35-7.44
27
Normal HCO3-?
24 mEq/L
28
Normal PCO2?
40 mmHg
29
Preferred Ddx for HAGMA?
GOLD MARK (previously MUDPILES) **G**lycols (ethylene and propylene) **O**xoproline (Pyroglutamic acid), tylenol toxicity **L**-Lactic acidosis **D**-Lactic Acidosis - only seen with colonic metabolization **M**ethanol **A**spirin **R**enal failure **K**etoacidosis (alcoholic, diabetic, starvation)
30
45 yo female presents to the ED. Upon examination, she appears malnourished and weak. Pt states that she takes acetaminophen daily for headaches. What kind of acid-base disturbance might you see?
Pyroglutamic (5-oxoproline) acidosis (Seen more in women who are malnourished or critically ill)
31
What mechanism is responsible for pyroglutamic acidosis?
Acetaminophen depletes glutathione =\> Increased formation of pyroglutamic acid and accumulation
32
What diagnostic test would you order for pyroglutamic (5-oxoproline) acidosis?
Urinary organic acid screen
33
What is the treatment for pyroglutamic (5-oxoproline) acidosis?
**Discontinue acetaminophen** IVF N-acetylcysteine
34
Ddx for increased osmolar gap?
ME DIE (same...) **M**ethanol **E**thanol **D**iethylene glycol - Mannitol diuretic **I**sopropyl alcohol (rubbing alcohol) **E**thylene glycol (also propylene glycol, ketoacidosis, and lactic acidosis)
35
If a patient has metabolic acidosis, association of which alcohol can be ruled out?
Isopropyl alcohol (NOT associated with metabolic acidosis)
36
What is the relationship between acidosis and serum potassium?
Acidosis is associated with hy**_per_**kalemia (H+ enter cells, K+ exit)
37
What is the relationship between alkalosis and serum potassium?
Alkalosis is associated with hy**_po_**kalemia (H+ exits the cells, K+ enter)
38
Ddx for normal anion gap metabolic acidosis (NAGMA)?
**DUR**HAM **Diarrhea** **Ureteral diversion (ileal conduit) or fistula** **Renal tubular acidosis (RTA)** Hyperalimentation (Enteral nutrition) Acetazolamide (carbonic anhydrase inhibitor) Addison's disease (adrenal insufficiency) Miscellaneous (toulene toxicity - glue sniffing)
39
Type 2 RTA has decreased capacity in the ____ to reabsorb \_\_\_\_
Decreased capacity in the PT to reabsorb HCO3- (results in low serum HCO3-, will eventually stabilize at the lower level)
40
Where is the majority of HCO3- reabsorbed in the kidney?
Proximal tubule (80-90%)
41
8 year old patient presents with type 2 RTA, what is their most likely diagnosis?
Cystinosis (Most common cause of Type 2 RTA in children)
42
An adult presenting with type 2 RTA likely has what etiology? With what secondary cause?
Fanconi syndrome with secondary Multiple Myeloma
43
A patient with proximal RTA may present with what clinical manifestations?
(Type 2 RTA) NAGMA w/ or w/o PT dysfunction Hypokalemia (milder than Type 1)
44
How do you diagnose a proximal (Type 2) RTA?
Urine pH high or low depending on serum HCO3- Can have urine pH \<5.5 when in new steady state (normal H+ secretion in distal nephron) Urine anion gap positive or negative
45
What is the urine anion gap (UAG) clinically used for?
Clinically used to differentiate renal from non-renal causes of NAGMA
46
What is the difference between a positive and a negative urine anion gap?
Negative = **appropriate** distal nephron urinary acidification Positive = **inappropriate** distal nephron acidification
47
What is urine anion gap a marker of?
NH4Cl (ammonium chloride) excretion =\> appropriate urinary acidification (will increase in the setting of metabolic acidosis)
48
What are the two main causes of distal (Type 1) RTA?
Unable to acidify urine due to: 1) Decreased H+ ion secretion due to channel defects 2) Gradient defect: abnormally permeable distal tubule and collecting duct allows H+ ions to flow back into tubular cell (lack of H+ ion secretion prevents urinary acidification and excretion of ammonium)
49
A patient taking amphotericin may be at risk for what type of RTA?
Distal (Type 1) RTA | (May cause gradient defect)
50
What clinical manifestations may be seen with distal (Type 1) RTA?
Nephrolithiasis Nephrocalcinosis
51
Which RTA presents with systemic disease?
Distal (Type 1 RTA) (usually presents with Sjogren's disease)
52
Which RTA can be caused by glue sniffing?
Type 1 (Distal) RTA due to toulene
53
What diagnostic criteria may present for Type 1 (distal) RTA?
NAGMA Unable to acidify urine pH \<5.5 Hypokalemia (severe) UAG positive
54
Type 4 RTA is also known as _____ RTA
Hyperkalemic Characterized by distal nephron dysfunction from impaired H+ and K+ excretion =\> NAGMA and hyperkalemia
55
What are the two main theories of hyperkalemic RTA?
Deficiency of circulating aldosterone (DM, NSAIDS, Bblockers, ACEi/ARB, high dose heparin) Aldosterone resistance in collecting ducts (interstitial renal disease, K+ sparing drugs)
56
60 yo male w/ hx of DM presents for a wellness check. Upon lab study, pt has NAGMA and hyperkalemia but does not appear symptomatic. What type of RTA is this pt likely to have?
Type 4 (hyperkalemic) (most pts in 50s-70s w/ hx of DM or CKD)
57
What diagnostic presentations might a patient with Type 4 RTA have?
Variable urine pH \>5.5 Positive UAG
58
In general, what factors may lead to a metabolic alkalosis?
Factors that stimulate Na+ reabsorption Increase H+ secretion and stimulate HCO3- reabsorption
59
Ddx for metabolic alkalosis?
Hypokalemia Vomiting/nasogastric tube suctioning Diuretics (loop and thiazide) Volume depletion (Contraction alkalosis) Mineralocorticoid excess (appropriate or inappropriate)
60
Contraction alkalosis would occur in what setting?
Volume depletion in the setting of Cl- depletion =\> RAAS activation and aldosterone secretion
61
What is the relationship between an alpha-intercalated cell and a beta-intercalated cell?
Beta-intercalated cell is a mirror image of alpha-intercalated HCO3- exits into tubular lumen In contraction alkalosis, must replete Cl- to help HCO3- secretion

Cpr 3 other (13 decks)

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