Acid-Base Disorders DSA and CIS Flashcards

1
Q

What is normal arterial pH?

Intracellular?

A

arterial: 7.35 - 7.45
intracellular: 7.0 - 7.3

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2
Q

Bicarbonate buffer sys equation

A
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3
Q

Henderson-Hasselbach equation

A
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4
Q

How do the lungs affect bicarbonate buffering?

A

control concetnration of PCO2

incr respiration = incr CO2 blown off = incr pH

(the more PCO2, the lower the pH

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5
Q

What are the 4 kinds of acid-base disturbances?

A

metabolic acidosis = low serum bicarb

metabolic alkalosis = high serum bicarb

respiratory acidosis = high PCO2

respiratory alkalosis = low PCO2

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6
Q

What is normal anion gap metabolic acidosis also called?

A

hyperchloremic acidosis

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7
Q

What are the two types of metabolic alkalosis?

A

saline-responsive (hypovolemia) aka contraction alkalosis or chloride deficiency alkalosis

saline-non-responsive (euvolemia)

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8
Q

What is winter’s fomula and what is it used for?

A

PCO2 = 1.5[HCO3] + 8 +/- 2

used to calculate compensation in metabolic acidosis?

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9
Q

How do you calculate the compensation for metabolic alkalosis?

A

PCO2 will incr by 0.7 mmHg for each 1.0 mEq/L incr in HCO2 from normal

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10
Q

How do you calculate compensation for respiratory acidosis (acute and chronic)?

A

acute: HCO3 will incr by 1 mEq/L for every 10 mmHg incr in PCO2 from normal (40)
chronic: HCO3 will incr by 3.5 mEq/L for every 10 mmHg incr PCO2 from normal

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11
Q

How do you calculate the compensation for respiratory alkalosis (both acute and chronic)?

A

acute: HCO3 will decrease by 2 meq/L for every 10 mmHg decrease in PCO2 from normal (40)
chronic: HCO3 will decrease by 5 mEq/L for every 10 mmHg decrease in PCO2 from normal

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12
Q

How many acid-base disturbances can be present at once?

A

3 total

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13
Q

What are common cations in the body?

A

Na+, K+, Ca+, Mg+

protein, but not many

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14
Q

What are common anions in the body?

A

Cl-, HCO3-

Proteins (esp albumin)

HpO4-

SO4-

organic ions

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15
Q

What is an anion gap?

A

fabricated concept in clinical medicine

in the body cations and anions equal each other

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16
Q

What are the most prominent anions and cations?

A

Na+

Cl-

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17
Q

How do you calculate an anion gap?

A

Na+ - (HCO3 + Cl-)

normal = 12 +/- 2

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18
Q

Why does renal tubular acidosis or diarrhea result in NAGMA?

A

we do not know

thought that loss of HCO3 in these conditions along w/ its cation Na+ produces a volume contraction –> NaCl retention w/in the kidney

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19
Q

How does hypoalbuminemia affect the anion gap?

A

will falsely lower AG and thus must be corrected

for every 1 g/dL drop in albumin –> AG drops by 2.5 mEq/L

(the AG will actually be higher and they can have HAGMA that isn’t apparent at first)

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20
Q

What is normal serum albumin?

A

~3.5 g/dL

21
Q

What is the equation for calculated serum osmolality and what is the normal range?

A

2(Na) + (glucose/18) + (BUN/2.8)

normal = 275 - 290 mosm/L

22
Q

How do you calculate an osmolar gap and what is the normal range?

A

osmalar gap = measured serum osmolality - calculated serum osmolality

normal < 10 mosm/L

im osmolar gap > 10 mosm/L, suggestive of additional solutes to blood

23
Q

What is calculating the osmolar gap useful for?

A

screening for alcohol ingestions, particularly in HAGMA cases

AG > 20, should be highly suspicious for alcohol ingestion

screening for ketoacidosis and lactic acidosis

24
Q

What is the delta-delta gap and what is it useful for?

A

used in pts w/ HAGMA to determine if there is a coexistent NAGMA or metabolic alkalosis present

delta gap = calculated AG - normal AG (12)

delta HCO3 (expected) = normal HCO3 - delta gap

(if measured HCO3 is less than delta HCO3 –> NAGMA is also present)

25
Q

What are the normal blood values for pH, bicarb, CO2, anion gap, and osmolality gap?

A

pH: 7.35 - 7.44

HCO3 = 24 mEq/L

PCO2 = 40 mmHg

Anion Gap = 12

osmolality gap = 10 mmol/L

26
Q

What is the acronym to remember Ddxs for high anion gap metabolic acidosis?

A

GOLD MARK

Glycols (ethylene and propylene)

Oxoproline (Pyroglutamic acid; acetaminphen toxicity)

L-Lactic acidosis

D-Lactic acidosis (bacteria in colon metabolizing carbs; seen in short bowel syndromes)

Methanol

Aspirin

Renal Failure

Ketoacidosis

27
Q

What is pyroglutamic acidosis?

A

seen when acetaminophen depletes glutathione –> get buildup of pyroglutamic acid

Dx: urinary organic acid screen

Tx: discontinue acetaminophen, IVF, N-acetylcysteine

28
Q

What are the Ddxs of increased osmolar gap?

A

MEDIE

Methanol

Ehtanol

Diethylene glucol (mannitol)

Isopropyl Acohol (not assoc w/ metabolic acidosis)

Ethylene glycol

(also propylene glycol, ketoacidosis, and lactic acidosis (smaller increase in osmolar gap))

29
Q

How are acidosis/alkalosis and serum potassium related?

A

acidosis assoc w/ hyperkalemia –> caused by shift of H+ out of cells for K+ so that cellular electroneutrality is maintained

(in acidosis, H+ enters cells and K+ exits)

alkalosis associated w/ hypokalemia

(in alkalosis, H+ ions exit cells and K+ enters)

30
Q

What are the DDxs for normal anion gap metabolic acidosis?

A

DURHAAM

Diarrhea

Ureteral diversion or fistula

Renal tubular acidosis

Hyperalimentation (enteral nutrition or total parenteral nutrition)

Acetazolamide

Addision’s Dz

Miscellaneus (toluene toxicity - glu sniffing, pancreatic fistula, meds)

31
Q

What is type 2 RTA?

A

proximal tubular

normally 80-90% of filtered HCO3 is reabsorbed in PT

in Proximal RTA, decr capacity to reabsorb bicarb –> bicarb loss in urine and low serum bicarb

eventually serum bicarb decreases to the point that kidney’s reabsorptive capacity not overwhelmed –> bicarb stabilizes, but at lower level

32
Q

What do alpha intercalated cells in the DT and colelcting duct do?

Principle cells?

A

Alpha: H+/ATPase and H+/K+ - ATPase

principle: ENaCs create net - lumin –> favors H+ secretion

33
Q

What is the most common cause of type 2 TRA in children?

A

cystinosis

34
Q

What is fanconi syndrome most often due to?

A

most adults w/ it have a secondary cause like multiple myeloma

however, some pts have an isolated reanl defect resulting in fanconi syn

35
Q

What are the clinical manifestations of Proximal RTA (type 2) and how do you diagnose it?

A

NAGMA with or w/out proximal tubular dysfunction

hypokalemia (mild compared to distal RTA)

Dx: urine pH can be high or low; if < 5.5, normal H+ secretion in distal nephron

urine anion gap can be positive or negative

36
Q

What is urine anion gap?

A

used to differentiate renal from non-renal causes of NaGMA

marker of NH4Cl excretion = appropriate urinary acidification

UAG = (urine Na + Urine K+) - Urine chloride

if negative –> appropriate distal nephron urinary acidification

if positive –> distal nephron fcked up

37
Q

What is type 1 renal tubular acidosis?

A

distal RTA

unable to acidify urine

decreased net H+ secretion in DCT

abnormally permeable distal tubule and CD allows H+ back into tubular cells

*amphotericin*

38
Q

What are two significant causes of distal RTA?

A

sjogren’s syndrome

glue sniffing - toluene

39
Q

What are the clinical manifestations of distal RTA and how do you diagnose it?

A

assoc w/ nephrolithiasis or nephrocalcinosis

Dx: unable to acidify urine pH < 5.5

hypokalemia, usually severe

UAG is positive

40
Q

What is type 4 RTA?

A

hyperkalemic RTA

distal nephron dysfunction from impaired excretion of H+ and K+ –> NAGMA and hyperkalemia

41
Q

What are the most common causes of hyperkalemic RTA (type 4)

A

deficiency of circulating aldosterone (DM, drugs)

aldosterone resistance in collecting ducts (interstitial renal dz, drugs)

either case leads to impaired Na reabsorption in principle cells –> decr luminal negativity –> impaired acidification bc lower driving force for H+ secretion

results in hyperkalemia

42
Q

What are clinical manifestations of type 4 RTA and how do you dx it?

A

usually asymptomatic, NAGMA, hyperkalemia; most pts in 50s-70s w/ hx of DM or CKD

Dx: variable urine Ph, usually > 5.5; UAG is +

43
Q

What are the 5 top causes of metabolic alkalosis?

A

hypokalemia (shift of H+ and K+)

vomiting or nasogastric tube suctioning (GI loss of HCl)

diuretics (thiazide and loop)

volume depletion

mineralocorticoid excess (appropriate and inappropriate)

44
Q

What do beta-intercalated cells in the CD do?

A

mirror image of alpha-intercalated cell

generate bicarb and secrete bicarb into lumen in exchange for Cl-

(in contraction alkalosis, must replete Cl- to help w/ HCO3- secretion)

45
Q

What causes repiratory alkalosis and acidosis?

A

alkalosis: anything that increases respiratory rate or tidal volume
acidosis: anthing that lowers RR or tidal volume, incr dead space, or worsens airway obstruction

46
Q

What should be your sequence of evaluation in a possible acidosis or alkalosis case?

A

acidotic or alkalotic?

metabolic or respiratory?

anion gap?

osmolar gap?

appropriate compensation?

UAG normal?

47
Q

How can a pulmonary embolus present (acidosis or alkalosis)?

A

can present as respiratory acidosis or alkalosis

if inadequate ventilator settings –> will not have high enough RR to blow of CO2 –> resp acidosis

48
Q

What does serum K+ look like in each type of RTA?

A

type 1 and 2: HypOkalemia

(type 1: dysfunction in H+ ATPase –> secrete K+ instead)

Type 4: HypERkalemia

49
Q

What type of RTA can be caused by heparin?

A

type 4