Renal Phys- Muster Flashcards
What are the 3 primary signaling pathways that stimulate renin release?
- sympathetic imput (increased NE)
- Decreased stretch in the afferent arteriole
- Decreased chloride (Na+) delivery to the Macula Densa
What are the primary actions of angiotensin II?
- Stimulates ALDOSTERONE
- Systemic Vasoconstrictor
- Stimulates Proximal Tubule Reabsorption of Na+
- Increases sympathetic activity
Where is aldosterone secreted from?
Cortex glomerulosa of adrenal gland
What does aldosterone do once it leaves the cortex glomerulosa of the adrenal gland?
Lipophillic
Crosses membrane, and binds steroid response element
Increases transcription of:
- Na/K ATPase on basolateral side
- ENac channel on luminal side (Na gets reabsorbed)
- ROMK channel (K+ leaves cell)
What is Liddle Syndrome?
Gain of function mutation
Increases ENaC channels
Increased Na+ reabsorption in collecting tubules
Autosomal dominant
Results in hypertension, hypokalemia, metabolic alkalosis, decreased aldosterone
What is Gitelman Syndrome?
Reabsorptive defect of NaCl in DCT
Autosomal recessive
Leads to hypokalemia, hypomagnesemia, metabolic alkalosis, hypocalciuria
Bartter Syndrome
Reabsorptive defect in thick ascending loop of Henle
Autosomal recessive
Affects NKCC cotransporter
Results in hypokalemia and metabolic alkalosis with hypercalciuria
What symptoms would you expect with a low serum concentration of Na+
Nausea Malaise Stupor Coma Seizures
What usually causes hyponatremia with low urinary osmolarity
Almost always due to excessive water intake (primary polydipsia) - typically a psych disorder
What is normal serum sodium concentration?
135-145 meq/L
What equation can you use to estimate the plasma/serum osmolarity? What should it be at?
Serum osmolarity = 2[Na] + BUN/2.8+ Glucose/18
Should be 285-300
Where does ADH bind? Then what happens?
V2 receptor in collecting tubules
- activates a protein kinase
- causes Aquaporin 2 to move from cytoplasm to luminal membrane
- forms water channels
ADH is released in response to?
Serum hyperosmolarity
Hypovolemia
What should you do if patient has hyponatremia and the urinary osmolarity is > 100? (Concentrated urine)
Looks at urinary Na+ concentration and volume status (on physical exam)
How do you treat hyponatremia if patient is also volume depleted?
Give normal saline to replenish volume and turn off ADH
How do you treat hyponatremia when neutral volume or volume expanded?
Restrict fluid intake!! or treat states of poor perfusion
May also give ADH antagonist
MOA of Tolvaptan and Conivaptan?
ADH antagonists –> target ADH receptors
Indicated in volume expanded hyponatremia
At what rate should you correct hyponatremia out of the “danger range”?
0.5 meq/L/hour
What is the “danger range” of hyponatremia?
115-120
What treatment should you use if hyponatremia and serum sodium is 115-120?
3% NaCl solution
If siezures - 100 cc over 10 mins IV
If just other neuro symptoms- 30-50 cc/hr for several hours
In what circumstances would you see hypernatremia?
due to excessive water losses and inadequate intake
What is the difference between Central diabetes insipidus and nephrogenic diabetes insipidus?
central = hypothalamus/pituitary axis not releasing ADH so kidney can’t reabsorb free water
nephrogenic = collecting tubules don’t respond to ADH so kidney can’t reabsorb free water
*can be partial or complete!
What medication can induce nephrogenic diabetes insipidus?
LITHIUM!
What fluids would you give for hypernatremia?
Free water orally
D5W IV
1/4 NaCl for hypernatremia due to volume depletion (Na+ is also depleted)
NS if patient is hypotensive with fluid losses
What is normal serum K+ concentration?
4-5 meq/L
What are the two primary functions of potassium?
Cell metabolism (protein and glycogen synthesis)
The RATIO of intracellular/extracellular is primary determinate of resting membrane potentials
How much K+ is stored intracellularly?
98%
How does Insulin affect the activity of the Na/K+ ATPase?
Increases its activity!
Promotes skeletal and muscle uptake
When we eat, we stimulate insulin, which alleviates a sharp rise in concomitant K+ serum levels
How does catecholemines affect the Na/K ATPase?
B2 receptors stimulate the Na-K ATPase inducing cellular uptake
Immediate treatment for hyperkalemic patient
INSULIN! (and glucose)
Give Ca+ to stabalize cardiac membrane (lasts 45 minutes)
Which part of the nephron is the primary site for K+ excretion?
Principle cell in the collecting duct!
Which two channels facilitate the excretion of K? Are they always in the membrane?
ROMK - stored intracellularly and inserted
BK - always in membrane, but only open at HIGH [K+]
What symptoms would you see in hypo/hyper kalemia?
-symptoms relate to inability to generate action potentials in muscles
Cramps
Muscle weakness/ paralysis (starts in the legs)
EKG changes
Cardiac arrhythmias
List the primary solutes of the different body compartments
Intracellular = K+, PO4, and anions
Intravascular (plasma) = Na+
Interstitial = Na+
What percent of your body is water? How much is intracellular? interstitial? Plasma?
60% (50% in females)
2/3 of that is intracellular
Of the remain 1/3
3/4 of that is interstitial
1/4 of that is plasma
What compartments does normal saline distribute to?
Interstitial & Plasma!
Extracellular volume will increase
No effect on intracellular volume or osmolality –> cannot enter cells!*