Quick Hits - Kidney Flashcards by Bryan Groff

What 4 things does the kidney produce?

Renin

Erythropoietin (Secreted in response to hypoxia)

Calcitriol (converts inactive Vitamin D to active)

Prostaglandins - vasodilate renal arteries, Thromboxane A2 constricts the renal arteries

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What is the function of aldosterone?

Controls extracellular volume
(Na and water are reabsorbed together)

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What is antidiuretic hormone?

Produced in the hypothalamus and stored in the posterior pituitary

Water is reabsorbed but Na is not

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How is long, intermediate, and short term BP controlled?

Long - thirst and sodium/water excretion

Intermediate - Renin, aldosterone, angiotensin system

Short- Baroreceptor reflex

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Which two organs maintain pH balance?

Kidneys - titrating non volatile acids (Hydrogen)

Lungs- volatile acids (CO2)

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How can the kidneys regulate glucose homeostasis?

The kidneys can synthesize glucose from amino acids

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How much of the Cardiac output do the kidneys receive ?

25% or 1250 mL

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What are the parameters of autoregulation?

MAP 50-180
Sys - 80-180

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Which area of the kidney is more sensitive to hypotension?

Medulla because it only receives 10% of the renal blood flow why the cortex receives 90%

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Blood pathway through the kidneys?

Renal artery
Renal segmental artery
Interlobar artery
Arcuate Artery
Interlobar artery
Afferent arterioles
Glomeular bed
Efferent arterioles
Peritubular bed
Venules
Interlobar vein
Arcuate vein
Interlobar vein
Renal segmental vein

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How does the kidney respond if they perfusion is too low? Too high?

Too low -increases flow by reducing renal vascular resistance

Too high - decreases flow by increasing renal vascular resistance

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Is urine autoregulated?

NO, it’s lineraly related to MAP

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What are the most important mechanisms to renal autoregulation?

Myogenic Mechanism - Constriction or dilation of afferent arteriole

Tubuloglomerular feedback- juxtaglomerular negative feedback of chloride and sodium

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What renal structures receive sympathetic innervation? Which levels?

Afferent and efferent arterioles

T8 - L1

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How does ischemia, sepsis, and surgical stress affect the kidneys?

Vasoconstricts and retains sodium

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How does vasoconstrtion and sodium retention affect renal blood flow, GFR, Urine output, and sodium excretion?

Decreases all of them

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How does prostaglandins, ANP, and Kinins affect the kidneys?

Causes vasodilation and sodium excretion

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How does vasodilation and sodium excretion affect the RBF, GFR, Urine output, and sodium excretion?

Increases them

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Which three things increase renin release?

1, Decreased renal perfusion
2. Beta 1 stimulation (SNS activation)
3. Decreased Na and Cl delivery to the distal tubule (Tubuloglomerular feedback)

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Where is aldosterone synthesized?

Zona Glomerulosa of the adrenal gland

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How does ADH affect the aquaporin-2 channels?

It upregulates them

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Which two mechanisms control the release of ADH?

Increased osmolarity
Decreased blood volume

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How does ADH restore blood pressure?

Stimulates V1 receptor which causes vasoconstriction (IP3, DAG, CA)
Stimulates V2 receptor in the collecting ducts (Increased cAMP) which upregulates aquaporin 2 channels

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Which three pathways promote renal vasodilation?

Prostaglandins
Natriuretic peptides
Dopamine receptors

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How can NSAIDS affect the kidneys?

Harm them through inhibition of COX. (this prevents renal arteries from vasodilating)

What is the response from the kidneys with increased ANP?

Inhibit renin release Promote Na and water excretion

What is fenoldopam?

Selective DA1 receptor agonist that increases renal blood flow

What is a normal GFR? What substances are freely filtered?

125mL/min Water, electrolytes, and glucose are filtered Plasma protein are not

What is the most important determinant of GFR?

Glomerular hydrostatic pressure which determined by arterial BP, afferent arteriole resistance, and efferent arteriole resistance

nephron photo

photo

**What is reabsorption?

Substance is transferred from the tubule to the peritubular capillaries

**What is secretion?

Substance is transferred from the peritubular capillaries to the tubule

What is excretion?

Substance is removed from the body to urine

What is an example of maximum transport?

Glucose - only so much can be transported so the excess is eliminated through the urine

Where does the bulk of reabsorption of solutes and water occur?

Proximal convoluted tubule

What occurs in the descending loop of Henle?

Forms concentrated urine Permeable to water and solutes

What occurs in the ascending loop of Henle?

Not permeable to water Reabsorbs 20% of sodium

What occurs in the distal convoluted tubule?

Fine Tunes solute concentration

What occurs in the collecting duct?

regulation of final concentration of water

Where does aldosterone and ADH act on the nephron?

Collecting ducts Distal tubule

What is ADH's effect on water and solutes?

Retains water but not solutes

What is aldosterone's effect on water and solutes?

Retains both water and solutes Increases K and H secretion

Where does the parathyroid hormone promote Calcium reabsorption?

Distal tubule

Which part of the nephron is impermeable to water?

Ascending loop of Henle

Examples of carbonic anhydrase inhibitors? Where do they work? When are they used?

Acetazolamide Proximal tubule Binds to carbonic anhydrase which reduces the reabsorption of Bicarb, Na, and water Causes metabolic acidosis Causes urine to be alkaline Useful in high altitude, glaucoma, and sleep apnea

Examples of osmotic diuretics? Where do they work? When are they used?

Mannitol, Glycerin, Isosorbide Undergoes filtration but not reabsorption in the proximal tubule. Increases Plasma osmolarity Mannitol is a free range scavenger Can cause cerebral edema if the BBB is disrupted

Examples of loop diuretics? Where do they work? When are they used?

Lasix, Bumex, Ethacrynic acid Ascending loop of Henle They disrupt the Na-K-Cl transport which forces solutes to stay in the tubule Can cause ototoxicity, low electrolytes, muscle weakness, reduced lithium clearance

Examples of thiazide diuretics? Where do they work? When are they used?

Hydrochlorothiazide, Chlorthalidone Inhibits Na-Cl in the distal tubule ***causes hyperglycemia

Examples of potassium sparing? Where do they work? When are they used?

Spironolactone (aldosterone antagonists), amiloride Collecting ducts Side effects, Hyperkalemia, metabolic acidosis, gynecomastia, libido changes, nephrolithiasis

Which three drug classes increase the risk of hyperkalemia in a patient who is taking a K sparing diuretic ?

NSAIDs, Beta blockers, Ace inhibitors

What are the best tests of tubular function?

Urine osmolality Fractional excretion of sodium

What are the best tests of GFR?

BUN and creatinine clearance

A BUN < 8 indicates?

-Overhydration -Decreased Urea production (malnutrition or liver disease)

A BUN of 20-40 indicates?

-Dehydration -Increased protein input -Decreased GFR

A BUN > 50 indicates?

Decreased GFR

Why is serum creatinine a useful indicator of GFR?

Creatinine undergoes renal filtration but not reabsorption

A 100% increase in creatinine indicates?

a 50% reduction in GFR

Normal BUN: Creatinine ratio?

10:1

A BUN:Cr ration of >20:1 indicates?

Prerenal azotemia

What is the fractional excretion of sodium?

Relates to sodium clearance to creatinine clearance

If the fractional excretion of sodium is less than 1%, what does this indicate?

More sodium is conserved to the amount creatinine is cleared Suggestive of pre renal azotemia

If the fractional excretion of sodium is greater than 3%, what does this indicate?

More sodium is excreted relative to the amount of creatinine cleared Suggestive of impaired tubular function

What amount of protein in the urine indicates glomerular injury?

>750mg/day

Urinary sodium less than 20 indicates?

Prerenal oliguria

Urinary sodium greater than 20 indicates?

Acute tubular necrosis

Urine osmolality > 500 indicates?

Pre renal oliguria

Urine osmolality < 400 indicates?

Acute tubular necrosis

Most common cause of perioperative kidney injury?

Ischemia - reperfusion injury

Normal BUN, Creatinine, and Creatinine clearance? What does this indicate?

Best to assess GFR BUN 10-20 Creatinine 1-1.5 Creatinine Clearance 110-150

What is creatinine ?

Breakdown of muscle

What is the most useful indicator of GFR?

Creatinine Clearance

Kidney function

Absolute contraindications to lithotripsy?

Pregnancy Risk of bleeding

What is a risk of percutaneous nephrolithotripsy

Pneumothorax

Most common anesthetic for a TURP? What level?

Neuraxial T10

CKD stages? What lab value?

What are the most common causes of CKD?

1. Diabetes 2. HTN

What is the most common event during dialysis ?

Hypotension

Ways to prevent kidney injury related to contrast?

-Lowest volume of contrast -Iso or low osmolar contrast - Hydrate with 0.9% -Use sodium bicarb - N acetylcysteine is a free radical scavenger

How can sevo harm the kidneys?

Compound A Free fluoride ions

Nephrotoxic antibiotics?

'mycin and amphotericin B

Which paralytic should be avoided with low kidney function?

Pancuronium

Which kidney injury is associated with hypoalbuminemia?

Nephrotic syndrome because they lose the protein in the urine

Which irrigation fluid presents the greatest risk for microshock during a TURP?

LR or .9 because they are highly ionized and good conductors

Which diuretic is the most likely to increase preload?

Mannitol, glycine, isosorbide

Which hormone controls plasma osmolarity ?

ADH

Which hormone controls ECF?

Aldosterone

Which 6 mechanisms regulate the renal blood flow

1. Myogenic 2. Tubuloglomerular feedback 3. Renin-angiotensin-aldosterone 4. Prostaglandins 5. ANP 6. SNS

What are the 3 determinants of glomerular hydrostatic pressure?

Arterial blood pressure Afferent arteriole resistance Efferent arteriole resistance

What is the most accurate predictor of bleeding risk?

Bleeding time

List the S&S of uremic syndrome?

Anemia Fatigue N/V Anorexia Coagulopathy

Why does anemia occur in patients with chronic renal failure?

Decreased production of erythropoietin

What is the most common cause of death in chronic renal failure patients?

CAD

What leads to gap metabolic acidosis in chronic renal failure patients?

Decreased excretion of non-volatile acids (hydrogen)

At what potassium level is dialysis recommended?

Which opioids are best in renal failure?

Any of the Fent's

Which paralytics are best in renal failure?

Benzylisoquinolines 1. Cisatracurium

What are the three signs of TURP syndrome?

HTN Bradycardia Mental status change

What sodium level will seizures occur?

<110

Rough estimate of blood loss per minute during TURP?

2-5 ml of blood per resection time

With a neuraxial block, how does a bladder perforation present?

Abdominal and shoulder pain

What is increased with a patient who has renal osteodystrophy?

Phosphate and parathyroid hormone 2 P's

Does the dose of anticholinesterase inhibitors need to be changed with renal injury?