Kidney Flashcards
There are three pathways that promote renal vasodilation:
Prostaglandins
Natriuretic Peptide
Dopamine Receptors
How do prostaglandins influence renal artery dilation?
The IEDs won’t kill your kidneys
What do natriuretic peptides do?
Released from the atria with distention
Inhibit renin release and promote sodium and water excretion
What dopamine receptors are present in the kidney?
D1
Increase cAMP, leading to vasodilation
What is fenoldopam?
It’s a D1 agonist that increases renal artery dilation without causing systemic dilation. Very useful in cardiac patients during aortic surgery
Trace the nephron from beginning to end
Afferent arteriole
Glomerulus
Proximal Tubule
Loop of Henle
Distal Tubule
Collecting Duct
Which nephron components are located in the cortex?
Which nephron features are contained in the medulla?
Everything that involves concentrating is in the medulla:
loop of henle
Collecting duct
What triggers erythropoietin release from the kidneys?
Hypoxia, from high altitude, heart failure, anemia etc)
Which prostaglandins vasoDILATE the renal artery?
PGI2 and PGE2
Which prostaglandins vasoCONSTRICT the renal artery?
Thromboxane A2
How does the kidney impact calcium levels?
In response to PTH stimulation, it produces calcitriol, which stimulates bone breakdown, decreases Ca renal excretion, and increases Ca reabsorption from GI tract
Which two organs can perform gluconeogenesis?
The kidneys can too! they rival the liver in producing glucose in fasting states!
The kidneys receive _____% of the cardiac output
20-25
What percentage of RBF is filtered in the glomerulus?
20%
What percent of filtrate is excreted as urine?
Only 1%!!
Renal blood flow decreases ____% each decade after ______
10% each decade after 50
Which region of the kidney is most sensitive to ischemia?
The medulla. It has a much lower PaO2 at baseline and much less blood flow
When do infants achieve normal RBF levels?
about 2 years
How quickly does RBF change in the newborn?
Doubles in the first two weeks!
What are the two most important methods of autoregulation in the kidney?
Myogenic
Tubuloglomerular Feedback
Describe the myogenic mechanism
When blood pressure in the afferent arteriole increases, it constricts to prevent the glomerulus from being overloaded
When pressure is low, it dilates
The juxtaglomerular apparatus is located in the:
distal tubule
Innervation of the kidneys occurs at what spinal level?
T8-L1
What is the generalized effect of SNS stimulation on the kidneys?
Decreased GFR
Increased Na/H2O retention
Decreased UO
What renal structures are innervated by the SNS?
Afferent and Efferent arterioles
What does the Juxtaglomerular device measure?
Na and Cl concentration
Angiotensin causes constriction of the _______
EFFERENT arteriole
How is urine output autoregulated?
IT ISN’T!
It has a linear relationship with MAP above 50mmHG
Where is aldosterone released from?
zona glomerulosa of The adrenal gland
There are three things that trigger renin release:
Afferent Autoregulation: Decreased renal perfusion pressure
Sympathetic Stimulation: Beta 1
Tubuloglomerular Feedback
What is the MOA of aldosterone?
Stimulates the Na/K ATPase pump in the distal tubule AND collecting duct
What effect does aldosterone have on serum osmolarity?
NONE! it effects sodium and water reabsorption equally
In addition to RAAS activation, Aldosterone is stimulated by:
Hyponatremia
Hyperkalemia
Conn’s disease is:
excess aldosterone
Exhibits all the “cons” of aldosterone
Addison’s disease is:
Inadequate cortisol and aldosterone
Need to “add” aldosterone
What is osmolality?
Osmoles per Kg
What is osmolarity?
Osmoles per Liter
L is NOT FOR LITER
Where is ADH produced?
Nuclei of the HYPOTHALAMUS
What is the calculation for Serum Os?
You can’t get a sugar daddy until you’re 18
Where is ADH stored and released?
The posterior pituitary
There are two things that control ADH release:
- Increased osmolarity
- Decreased blood volume
ADH stimulates _______ receptors
V1 and V2
What does V1 stimulation cause?
Vasoconstriction in the PERIPHERY
What does V2 stimulation cause?
Activates aquaporin channels in the collecting ducts, leading to water reabsorption
What is a normal serum os?
280-290
What is a normal GFR?
125 ml/min
Destruction of ______ leads to proteinuria
The basement membrane of the glomerulus
Where is MOST sodium reabsorbed?
65% of sodium and water is reabsorbed in the proximal tubule
Where are acids, bases, and hydrogen ions secreted?
The proximal tubule
What occurs in the descending loop of henle?
HIGHLY PERMEABLE TO WATER
but not ions, and passes through counter-current, resulting in concentration of the filtrate
20% of water is reabsorbed here
What occurs in the ascending loop of henle?
IMPERMEABLE TO WATER
20% of sodium is reabsorbed here and pumped into the tubular interstitium, creating the countercurrent!
Is the distal tubule permeable to water?
It is impermeable EXCEPT in the presence of aldosterone or ADH
What three substances impact the collecting duct?
Aldosterone
ADH
Atrial Natriuretic peptides
What impact does aldosterone have on K and H secretion?
It INCREASES secretion of K and H
Where does calcium reabsorption occur?
Distal tubule
What is the MOA of carbonic anhydrase inhibitors?
Noncompetitively inhibit carbonic anhydrase in the PROXIMAL TUBULE
This leads to excretion of bicarb and mild metabolic acidosis
What are the clinical uses for acetazolamide?
Open angle glaucoma (reduces aqueous humor production)
Altitude sickness (acidosis increases RR)
OSA (Increases RR)
What are the complications of acetazolamide?
HYPOkalemia
Metabolic acidosis
which patients should not receive mannitol?
Patients who can’t tolerate brief fluid overload
Patients whose BBB is NOT intact (glucose can cross and cause seizures)
What is the MOA of loop diuretics?
Inhibits the Na-K-2CL pump transporter in the ASCENDING loop of henle
What is the MOA of thiazide diuretics?
Inhibit Na-Cl cotransporter in the DISTAL TUBULE
What is a unique feature of thiazide diuretics?
They cause hyperglycemia and increases calcium reabsorption
Name four thiazide diuretics
HCTZ
Chlorthalidone
Metolazone
Indapamide
Name three potassium sparing diuretics
“SALT”
Spironolactone
Amiloride
Triamterene
Where do potassium sparing diuretics exert their effects?
The COLLECTING DUCT
List five side effects of potassium sparing diuretics
Hyperkalemia
Metabolic acidosis
Gynecomastia
Libido changes
Nephrolithiasis
List three drug classes that increase the risk of hyperkalemia in a patient taking a potassium sparing diuretic
Beta blockers
NSAIDS
ACE-Is
Which blood tests assess GFR?
BUN and CR
Which blood tests assess tubular function?
Fractional excretion of sodium
Urine Os
Creatinine undergoes renal _____ but not ______
filtration but not reabsorption
What is a normal BUN:Cr ratio?
10:1
A BUN:Cr ration greater than ________ indicates prerenal azotemia
> 20%
What is urea?
Primary metabolite of protein breakdown in the liver
Why is Cr a better indicator of GFR than BUN?
BUN undergoes filtration AND reabsorption
Who is at the highest risk for a perioperative AKI?
CHF
Sepsis
Renal Dx (duh)
Advanced age
The risk of prerenal azotemia is reduced by:
Keeping the MAP > 65
providing adequate hydration
How does CKD impact coagulation?
Inhibits platelet function. This means bleeding time will be elevated, but PT/PTT/INR will be normal
What is a side effect of exogenous Epo administration?
HTN
You should assume that all patients with CKD also have _____
Coronary Artery Disease
This is usually what kills them
What cardiac abnormality is associated with uremia?
Pericarditis
What pH abnormalities occur with CKD?
Anion gap acidosis from all the uremic acid built up
How does uremia impact the neurological system?
It impairs nerve conduction, leading to sensory AND motor neuropathy
Why are CKD patients at an increased risk for infection?
Impaired WBC function and the need for a low protein diet
What are the best NMBAs for patients with CKD?
Cis and Atracurium
Will patients with CKD need more or less propofol?
Maybe more, because they have hyperdynamic circulation and an impaired BBB
What can be done to avoid an AKI from contrast?
IV fluid bolus
Bicarb
Low-osmolar contrast
Which class of antibiotics is the worst for the kidneys?
Aminoglycosides (gentamycin etc)
What is the classic TURP syndrome triad?
HTN
Bradycardia
Decreased LOC
Correcting serum Na too quickly increases the risk of
central pontine demyelination
What are absolute contraindication to ESWL?
Pregnancy and anticoagulation
