Renal Dry Lab 1 - Liang Flashcards

1
Q

How is urine flow rate quantified?

A

Urine flow rate UF

UF = Urine volume / Collection interval

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2
Q

How is renal clearance of a solute calculated?

How about renal excretion?

A

Cx = (Ux/Px)*UF

Ex = (Ux)*UF

This is intuitive; the urinary concentration or ratio of urinary to plasma concentrations, times the flow rate.

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3
Q

How is osmolar clearance calculated?

How is renal free water clearance? What is the significance of this?

A

Cosm = (Uosm/Posm)*UF (this is renal clearance for all solutes)

CH2O = UF - C<span>osm</span> (This reveals the relative tonicity of urine. If hypertonic, this is negative; if isotonic, it is zero; and if hypotonic, it is positive.

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4
Q

Calculate the urine flow rate, osmolar and free water clearance, and sodium excretion in this patient. Try to not use a calculator!

Volume collected: 150mL

Time: 300min

Vosm: 900mOsm, Posm: 300mOsm

[Na+]U: 100mEq/L

A

UF: 0.5 mL/min

Cosm: 1.5 mL/min

CH2O: -1.0 mL/min

<span>Exc</span>Na+: 50µEq/min

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5
Q

What are some fairly typical ranges for urine flow, osmolar and free water clearances in a hydrated, but not volume-loaded person at rest?

A

Urine flow: ~0.5 - 1mL/min (recall: 125mL filtered, 124mL reabsorbed)

Cosm: ~1.5 - 2.0 mL/min

CH2O: ~-0.5 - -1.5 mL/min (urine is “typically” hypertonic)

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6
Q

What are the effects of water consumption on renal parameters?

A

Increased urinary flow rate, of which osmolarity is low. Time-normalized electrolyte excretion is normal.

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7
Q

What are the effects of beer consumption on renal parameters?

A

Incrase in urinary flow rate, moreso than with water because of alcohol’s anti-ADH effect. Maybe some increased electrolyte excretion, depends on the composition of beer.

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8
Q

If urinary osmolarity is less than plasma osmolarity, what can be said of the free water clearance?

A

It must be positive.

CH2O = UF * (Uosm/Posm)*UF

or

CH2O = UF * (1 - Uosm/Posm)

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9
Q

Compare the relative efficacies of acetazolamide and furosemide as diuretics.

A

Furosemide is massively more powerful as a diuretic than acetazolamide, and also causes more electrolyte wasting.

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10
Q

What is the main source of feedback for kidney control & regulation?

A

The juxtaglomerular apparatus.

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11
Q

How will the body fluid compartments change in composition with administration of a hypertonic solution?

A

ICF loses volume due to flux of water to the ECF. Both compartments increase osmolarity.

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12
Q

What is the effect of renal sympathetic nerve stimulation?

A

Increase of both renin and sodium reabsorption.

These effects are both pro-retention; think of these processes as countering loss of volume due to injury/exsanguination.

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13
Q

What is the effect on the urine of bicarbonate consumption?

Why does potassium excretion increase?

A

Urine becomes alkalotic.

Intercalated cells secrete potassium in order to retain hydrogen ion, to counter plasma alkalosis.

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14
Q

Compare and contrast the effects of bicarbonate and acetazolamide treatment.

A

Both increase sodium and potassium excretion. The bicarbonate solution may have higher free water clearance, as acetazolamide’s osmolar clearance seems higher (depends on solution concentration).

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