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CLS 701 > Day 2 - Kidneys, ABG > Flashcards

Day 2 - Kidneys, ABG Flashcards

1
Q

What does the BUN stand for? The BUN test assesses the function of…

A

Blood urea nitrogen

How well liver and kidneys are functioning

  • liver breaks down proteins and makes ammonia
  • ammonia combines with other elements to form urea
  • travel through blood to kidneys
  • kidneys filter urea out of blood into urine
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2
Q

What are the 2 equations for the osmole gap?

A

Osmolality - [1.86(Na+) + glucose/18 + BUN/2.8 + 9]

Osmolality - [2(Na+) + glucose/20 +BUN/3]

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3
Q

What are the 2 equations for the anion gap?

A

[Na+] – ([Cl-] + [HCO3-])

[Na+] + [K+] – ([Cl-] + [HCO3-])

-K can be excluded

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4
Q

What are the 3 functions of the kidneys

A

Filtration

Reabsorption

Secretion

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5
Q

Blood arrives in the kidneys through the ___ arteriole and exit via the ___ arteriole

A

Afferent

Efferent

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6
Q

Approximately ___ of blood flows through kidneys every minute. Approximately ___ of water containing low MW substances pass through the glomerulus to be filtered…

A

1.2 liters

120 ml/min

  • 10% of 1.2 liters
  • most water is reabsorbed
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7
Q

Substances below this molecular weight can pass through the kidneys. What percentage of fluid and electrolyte get reabsorbed in the PCT?

A

70,000

80%
-most Na reabsorbed, most K not reabsorbed

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8
Q

During Na reabsorption, ___ is exchanged for Na

A

H+

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9
Q

Afferent arterioles are larger/smaller than efferent arterioles. Why?

A

Larger

Creates hydrostatic pressure to drive GFR

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10
Q

Where is carbonic anhydrase located and what is its function?

A

Renal tubules

Uses water and CO2 to make H+ and bicarbonate
-acid-base balance

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11
Q

What is the specific gravity of the glomerular filtrate?

A
  1. 01, same as plasma

- glucose and protein reabsorbed at beginning of tubules, resulting in plasma filtrate without glucose and protein

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12
Q

The kidneys excrete these 3 major products of protein catabolism

A

Creatinine - skeletal muscle dehydration product. Constant rate proportional to muscle mass

Urea (BUN) - ammonia that is converted to urea for excretion

Uric acid - from purine breakdown

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13
Q

Of the 3 major excretion products of protein catabolism, which one can be reabsorbed and which one is excreted?

A

Urea and uric acid can be reabsorbed

Creatinine excreted

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14
Q

Of the 3 major excretion products of protein catabolism, which one is commonly used to assess how well the kidneys are functioning? Why (2)?

A

Creatinine (creatinine clearance test)

Excreted into circulation at a constant rate
All creatinine excreted in urine (none reabsorbed)
-also <70,000 MW, stable, measureable within time interval

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15
Q

When kidneys are damaged, levels of BUN and creatinine in the blood are…

A

Elevated

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16
Q

What is uremia?

A

Elevated blood BUN (azotemia) with renal failure

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17
Q

What does a clearance test (ie creatinine clearance test) measure?

A

Rate at which kidneys remove a substance within a timed interval

  • endogenous vs exogenous substance
  • creatinine is endogenous substance (made in body)
  • exogenous = injected
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18
Q

Clearance test - what is the gold standard for an endogenous substance? Exogenous?

A

Creatinine

Inulin
-IV or orally introduced

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19
Q

Creatinine clearance test - how long should urine be collected for?

A

24 hours

-greatest source of error is during collection

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20
Q

What is the creatinine clearance formula?

A

CrCl (mL/min) = [UrineCr x UrineVolume] / [PlasmaCr x time]

-time = 24 hours = 1440 mins
~80 ml/min is the creatinine “blind range”

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21
Q

What is the formula for the corrected creatinine clearance?

A

CrCl x (1.73 / A) = corrected CrCl (mL/min)

-takes into account height and weight

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22
Q

What are the 2 widely used creatinine clearance assays? Which one is more widely used?

A

Jaffe method - more widely used
-cheap, easy

Enzymatic

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23
Q

Jaffe method vs enzymatic method - Which one is more accurate. Why?

A

Enzymatic

Less interferences
-Jaffe method has a lot of interferences

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24
Q

Is the creatinine clearance calculation an underestimate or overestimate of the GFR? Why?

A

Overestimate

Extra creatinine is secreted by the distal convoluted tubule, causing overcalculation of GFR

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25
Q

Chronic kidney disease is a GFR less than…

A

60 ml/min

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26
Q

The MDRD GFR Study equation takes into account (3)… What is the equation?

A

Age
Gender
African-American

GFR (mg/dL) = 175 x PCr^(-1.154) x age^(-0.203) x [0.742 if female] x [1.210 if black]

-equation less reliable above 60 ml/min

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27
Q

Creatinine clearance calculation takes into account creatinine found in… GFR calculation takes into account creatinine found in…

A

Both plasma and urine creatinine

Just serum creatininediff

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28
Q

A new protein being proposed to use instead of creatinine is… What’s the advantage of using this protein over creatinine (2)?

A

Cystatin C

Larger than creatinine, so not removed by traditional dialysis
-assess if kidneys are functioning again
-made by all nucleated cells, not just muscles (creatinine)
-metabolized by nephrons, not secreted
No ethnicity involved in GFR calc, less adjustment for females

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29
Q

If we measure the specific gravity (concentration) of urine throughout the day, we can detect renal failure by this condition… What does it mean?

A

Isothenuria

Kidneys lack ability to concentrate or dilute urine so that blood filtrate remains unchanged and respond to the body’s hydration status
-specific gravity of urine is neither greater (more concentrated) nor less than (more dilute) that of protein-free plasma

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30
Q

Renal blood flow test (PAH; para-aminohippurate) is an example or endogenous or exogenous for tubular secretions?

A

Exogenous

-old method

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31
Q

Urine protein electrophoresis looks for this protein if the patient is suspected of having multiple myeloma…

A

Bence Jones protein

32
Q

Should protein ever show up in the urine? Why or why not?

A

No

Large proteins cannot pass glomerulus, small proteins that slip through get metabolized by nephrons
-proteins in the urine indicate a problem

33
Q

An acid is a substance that can give up ___. A base is a substance that can give up ___.

A

H+

OH-

34
Q

What does the K value mean?

A

Ability of an acid or base to dissociate in water

  • determines the strength of the acid or base
  • strong acids/bases completely dissociate in water
35
Q

What does the pK value mean?

A

Negative log of K

  • strong acid = pK < 3.0
  • strong base = pK > 9.0
36
Q

What is a buffer? Name the main buffer in the blood

A

Combination of a weak acid or weak base and its salt, resisting pH changes

Bicarbonate (HCO3-)

37
Q

What are the 3 blood “gases”?

A

pH

Carbon dioxide

Oxygen

38
Q

What is pH a measure of? How does low and high pH relate to the number of hydrogen ions?

A 
Hydrogen ions (H+) in solution
-logarithmic scale (pH 5 is 10x more acidic than pH 6)

Lower pH = higher hydrogen ion concentration
Higher pH = lower hydrogen ion concentration

39
Q

Most blood gases are collected from arteries or veins?

A

Arteries (ABG)

40
Q

What do the following blood gas terms stand for: t, a, v, c, B, P

A 
t = total
a = arterial
v = venous
c = capillary
B = blood
P = plasma
41
Q

Why is dried heparin the preferred anticoagulant over liquid heparin?

A

Liquid heparin may dilute sample

-also acidic

42
Q

Why is a glass or plastic syringe preferred over a vacuum tube?

A

Vacuum tubes don’t fill correctly all the way up. Vacuum leftover above blood level can cause loss of blood gas
-underestimate values

43
Q

How does the pCO2 in blood compare with pCO2 in air? What does this mean if there’s an air bubble in the ABG syringe? What happens to the pH?

A

pCO2 blood > pCO2 air

Exposure to air bubble causes both total CO2 and pCO2 to decrease in blood

Less CO2 = increase in pH

44
Q

How does the pO2 in blood compare with pO2 in air? What does this mean if there’s an air bubble in the ABG syringe?

A

pO2 blood < pO2 air

pO2 in blood will increase

45
Q

ABG samples are usually taken from the ___ artery. Good collateral flow through the ulnar artery can be performed using the ___ test

A

Radial

Allen test

46
Q

3 classes of patients likely to require blood gas analysis

A

Critical care: trauma, surgery, intensive care

COPD

Newborns

47
Q

pH balance/buffering is maintain by these two organs in the body. Which one is fast and which is slow?

A

Lungs = rapid, minutes

Kidneys = slow, days

48
Q

“Respiratory” and “metabolic” are terms used to refer to which organs?

A

Respiratory = lungs

Metabolic = kidneys

49
Q

Breathing (esp hyperventilation) can quickly remove these two things from the body

A

CO2

Hydrogen ion

50
Q

Carbon dioxide is transported in the body as…

A

Bicarbonate (HCO3-)

-carbonic acid (H2CO3) is intermediate molecule between CO2 and HCO3-

51
Q

What is the normal ratio of bicarbonate to carbonic acid in a healthy person?

A

20:1 (bicarbonate:carbonic acid)

52
Q

Total CO2 in the blood is composed of (4)

A

CO2 in solution

CO2 bound to proteins

CO2 as bicarbonate (HCO3-)

CO2 as carbonic acid (H2CO3)

53
Q

What does pCO2 measure?

A

Total dissolved CO2

54
Q

Acute bicarbonate compensation calculation… Give two scenarios when acute kidney compensation will happen…

A

Change HCO3 (mM) = 0.2 x change pCO2 (mmHg)

Hyperventilation
Suffocation

55
Q

Long term kidney compensation calculation… Give two scenarios when long term kidney compensation will happen…

A

Change HCO3 (mM) = 0.35 x change pCO2 (mmHg)

Long-term COPD
Living at high altitudes

56
Q

If imbalance is metabolic, compensation is by… If imbalance is respiratory, compensation is by…

A

Ventilation

Kidneys

  • kidneys slower (2-4 days) but better long term
  • lungs faster (minutes) but better acute
57
Q

Respiratory status (lungs) can be determined by this compound… Metabolic status (kidney) can be determined by this compound…

A

pCO2

HCO3-

58
Q

Respiratory acidosis: levels of blood pCO2, HCO3, pH

A

Increase

Increase

Decrease

  • release of carbon dioxide from blood into lungs decreased
  • lungs can’t expel CO2
  • COPD, pulmonary edema, bradycardia, drugs
  • asthma, respiratory distress syndrome in newborn
  • smoking long-term
59
Q

Respiratory alkalosis: levels of blood pCO2, HCO3, pH

A

Decrease

Decrease

Increase

  • hyperventilation
  • excessive crying
  • pregnancy
  • CNS respiratory center damage
  • fever
  • pulmonary embolism
  • living at high altitude
60
Q

Metabolic acidosis: levels of blood pCO2, HCO3, pH

A

Decrease

Decrease

Decrease

  • keto diet (ketosis)
  • kidney disorder
  • excessive diarrhea - loss of bicarbonate
61
Q

Metabolic alkalosis: levels of blood pCO2, HCO3, pH

A

Increase

Increase

Increase

  • eat a lot of bicarbonate, alkali antacids
  • severe loss of chloride (vomiting - lose gastric HCl)
  • corticosteroids, Cushing’s disease
62
Q

How do lungs compensate for metabolic acidosis?

A

Hyperventilation

  • releases CO2
  • kidney retains bicarbonate
63
Q

How do kidneys compensate for respiratory acidosis (2)?

A

Increased H+ excretion

Increase bicarbonate reabsorption and production

64
Q

How do lungs compensate for metabolic alkalosis?

A 
Slow breathing (hypoventilation)
-retains CO2
65
Q

How do kidneys compensate for respiratory alkalosis (2)?

A

Reabsorb H+ to blood

Increase bicarbonate excretion/reabsorb less bicarbonate

66
Q

Proper ABG sample collection requires sample stored at this temp… Tested within…

A

Ice

15 mins

67
Q

Which two other forms of hemoglobin can interfere with oxygen binding?

A

Carboxyhemoglobin (COHb)

Methemoglobin (MetHb)

68
Q

What are the units for the following: GFR, anion gap, creatinine clearance, serum osmolality

A

mL/min

mM or mEq/L

mL/min

mOsm/kg

69
Q

What is the Henderson-Hasselbalch equation to calculate pH? To calculate bicarbonate?

A

pH = 6.1 +log (HCO3-/ (0.03 x PCO2))

HCO3 = 0.03 * pCO2 * 10^(pH - 6.1)

70
Q

What do the following terms mean for oxygen gas in the blood: P or p, S or s, c, d

A

P or p = partial pressure (pO2)

S or s = saturation fraction (sO2)

c = concentration (cO2)

d = dissolved (cdO2)

71
Q

Factors that contribute to the oxygen dissociation curve (5)

A

Temperature

pH

pCO2 and 2,3-DPG levels

Interfering substances (ie carbon monoxide)

Presence of dysfunctional hemoglobin types

72
Q

If PO2 and oxygen saturation are high, this indicates a ___ shift of the oxygen dissociation curve. If PO2 and oxygen saturation are low, this indicates a ___ shift of the oxygen dissociation curve

A

Left

Right

73
Q

Increased 2,3-DPG or CO2 shifts the oxygen dissociation curve to the… Does hemoglobin affinity for oxygen increase or decrease?

A

Right

Decrease
-enhances release of oxygen

74
Q

As 2,3-DPG or CO2 increase, pH…

A

Decreases

  • increased CO2 = decreased pH
  • right shift
75
Q

How many oxygen molecules can one hemoglobin molecule carry?

A

4

76
Q

Methemoglobin - which form is iron in? Can this form bind oxygen?

A

Ferric (Fe 3+), cannot bind oxygen

77
Q

What is P50?

A

Partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen

CLS 701 (10 decks)

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