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Nephrology > Acid Base > Flashcards

Acid Base Flashcards

1
Q

What is the henderson hasselbach equation for Carbonic Acid

A

pH = 6.1 + log[HCO3/0.03(PaCO2)]

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2
Q

How does the body react to metabolic acidosis

A 
1. instantaneous:
ECF: bicarb
ICF: bicarb and phosphates
2. Short term: tachypnea to blow off CO2
3. Long latency: renal compensation
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3
Q

How does renal compensation for Metabolic acidosis work?

A

PCT, TAL, DCT: Na-H exchange = excrete H+, carbonic anhydrase activity
CD:
alpha-intercalated cells = H+ pump
H-K exchange pumps

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4
Q

What do alpha-intercalated cells excrete and absorb?

A

excrete: H+
absorb: Bicarb
through the activity of Carbonic Anhydrase

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5
Q

How and where is H+ renally excreted (as what molecule)

A

Ammonia in mainly the PCT as a response to acidosis

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6
Q

Where is ammonia reabosored in the kidney and what happens to it?

A

ammonia is reabsorbed in the TAL then:

  1. excreted in the thin descending limb
  2. absorbed in CD and H+ is excreted by alpha intercalated cells
  3. reabsorbed and processed by liver
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7
Q

What is the renal response to alkalosis (and where)

A

reduction in PCT H+ excretion
Increased CD excretion of HCO3- (by PENDRIN in B-intercalated cells)
Pendrin = Cl-HCO-3 exchanger
Cl is reabsorbed, HCO3 is excreted

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8
Q

How do you calculate the Anion Gap? what is the normal Anion Gap?

A

Anion gap = [Na+] - [HCO3- + Cl-]

normal AG = 8-12 meq/L

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9
Q

What are the two types of Metabolic acidosis.

A

Anion gap and Non-anion gap

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10
Q

What is the pH, Bicarb, pCO2 criteria for a Non-anion gap acidosis

A

pH<7.38, Bicarb <22mm/L, Normal pCO2 = 40mmHg

occurs due to excess or reduced availability of K+ or Cl-

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11
Q

How do you interpret an Anion Gap? in presence of metabolic acidosis (if >12, if normal

A

If >12 = then there is an anion gap (extrinsic acid present = unmeasured anions)
if normal = increased H+ or loss of bicarb+

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12
Q

What is happening physiologically during a non-anion gap metabolic acidosis? and how is this compensated for?

A

increased of Cl- in the ECF is causing a compensatory loss of HCO3- = metabolic acidosis
kidneys will try to excrete H+ in the form of NH4+

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13
Q

How do you distinguish a renal and nonrenal cause of metabolic acidosis?

A

Normal kidney = will excrete NH4+
renal disease = impaired NH4+ excretion
ESTIMATED BY URINE OSMOLALITY GAP:
Renal cause>40 osmole gap>non-renal cause

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14
Q

What two things cause a non-Anion gap metabolic acidosis

A
  1. loss of bicarb (diarrhea, GI problems)

2. Renal Disease (Cant Excrete H+) from meds (lithium, topiramte, acetazolamide)

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15
Q

How do you estimate if there is respiratory compensation for a metabolic acidosis?

A

PaCO2 = 1.5 [HCO3] + 8 ± 3 (winter’s formula)

if pCO2 is above or below estimation - primary resp acidosis or alkalosis is present

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16
Q

What is the pH and HCO3- criteria for a metabolic alkalosis?

A

pH >7.42, [HCO3-] > 26mmol/L

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17
Q

What are the causes of metabolic alkalosis?

A
  1. ECF volume contraction (body keep Na in xchange for H and K)
  2. excess glucocorticoids/mineralocorticoids (increase bicarb resorption)
  3. Loss of H+ (vomiting, nasogastric suction)
  4. Depletion of ECF chloride ions
  5. Hypercapnia - chronic lung disease (CO2 retainer)
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18
Q

What is the first thing to figure out when correcting metabolic alkalosis

A

if the cause if from:
1. renal wasting
or
2. retention of chloride

19
Q

How do you differentiate from renal wasting and retention of chloride in metabolic alkalosis?

A

Spot urine-chloride
Cl- urine <25mmol = Chloride responsive
Cl- urine >40mmol = chloride unresponsive

20
Q

What is the correction for chloride responsive alkalosis?

A

fluids NaCl + KCl

21
Q

What is the cause and correction for chloride unresponsive alkalosis

A 
chloride wasting (hyperaldosteronism, bartter, gitelman)
correct Mg, Ca, find source of increased aldosterone
22
Q

How do you tell if there is respiratory compensation for metabolic alkalosis?

A

PCO2=0.7 X [HCO3] + 20 ±5

if pCO2 is above or below then there is primary respiratory alkalosis or acidosis present

23
Q

How do you tell if there is metabolic compensation for respiratory acidosis?

A 
acute compensation (2-5 days): +1 mmol [HCO3-] for each 10mmHg above 40mmHg
chronic compensation L +5mmol [HCO3-] for each 10mmHg above 40mmHg
24
Q

How do you tell if there is metabolic compensation for respiratory alkalosis

A 
Acute = ↓ 2mmol/L for PCO2 decrease per 10mm Hg below 40
Chronic = ↓ 5mmol/L for PCO2 decrease per 10mm Hg below 40
25
Q

What does the physical exam for acidosis look like?

A 
Kussmaul breathing
Accessory muscle use for breathing
Acetone breath (fruity)
Cyanosis
Clubbing
26
Q

What are the causes of an ANION GAP METABOLIC ACIDOSIS? (hint: GOLD MARRK)

A 
G-glycols (ethylene, propylene) - alcoholics
O-oxoproline (chronic acetominophen)
L-Lactate - MOST COMMON CAUSE
D-D-Lactate - anaerobic metabolism
M-Methanol
A-Aspirin
R-Renal failure
R-rhabdomyolysis
K-ketoacidosis
27
Q

What kind of acidosis/alkalosis can aspirin cause?

A

Metabolic Acidosis + Respiratory Alkalosis

28
Q

What kind of unmeasured anions can a urine dipstick detect. What kind cant be detected?

A

Can be detected - Acetoacetic acid

Cant be detected - B-hydroxybutyrate

29
Q

What are two causes of lactate accumulation?

A
  1. Anaerobic metabolism - ischemia

2. Hyperdynamic state (increased catecholamines) + oversupply of ATP (lots of energy, so lactate isnt broken down)

30
Q

What are the two categories of Lactic Acidosis. give examples of both

A

Hypoxic - global hypoxia, COPD

Non-Hypoxic - Renal dysfxn, thiamine deficiency, sepsis, drugs (antiretroviral, metformin, propofol)

31
Q

What are some Sx of lymphoma

A

Lactic acidosis, stupor

32
Q

How do you diagnosie lactic acidosis

A

Blood lactate level

33
Q

What is the treatment for lactic acidosis

A
  1. Volume Restoration - Crystalloids (0.9% NaCl)
    When BP stabilized - switch to plasma lite, or ringers lactate (lessens renal tubule acidosis)
  2. restore BP - inotrope
  3. restore circulation - dobutamine, nitro
34
Q

When is the only time to supplement with HCO3-

A

extreme lactic acidosis (severe cardiac decline)

35
Q

What is the unmeasured anion in Alcoholic liver disease

A

metabolic anion gap acidosis: B-hydroxybutyrate

36
Q

What is Diabetic Ketoacidosis (DKA)

A

glucose cant get into cells, builds up in blood, spills in urine
osmotic diuresis occurs - drags other ions and bicarb out into lumen
increased proteolysis
LACTIC ACIDOSIS, VOLUME CONTRACTION, fats are broken down into ketones (fruity breath)

37
Q

What causes DKA

A

no insulin

38
Q

What two ions are overproduced in DKA

A

acetoacetate + B-hydroxybutyrate

39
Q

What is the diagnostic criteria for DKA?

A

increased Anion gap metabolic acidosis
Hyperglycemia
Plasma ketones present

40
Q

What two ions are lost early in DKA

A

sodium and bicarb

41
Q

What is the main systemic effect of DKA

A

Ischemia of internal organs

42
Q

What are clinical signs of DKA

A

hypotensive, tachypnea (Kussmaul), tachycardia, lethargic (comatose), poor skin turgor, polyuria, polydipsia

43
Q

How do you adjust serum sodium calculation in relation to glucose elevation

A

add 2mEq/L Na per 100mg/dl of glucose above 100

44
Q

What is the treatment of DKA

A
  1. restoration of volume
  2. restoration of insulin deficiency(corrects ketoacidosis)
  3. slow correctsion (avoid cerebral edema)
  4. treat other factors (infections)

Nephrology (13 decks)

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