Renal Flashcards
What percentage of sodium filtered by the glomerulus is typically excreted in the urine?
~5%
What part of the kidney does furosemide act on?
The ascending loop of Henle
How does ADH work in the kidney?
Increases aquaporin-2 water channels in the collecting ducts
Of the following areas, which is most responsible for concentrating urine: proximal tubule, ascending loop of Henle, distal convoluted tubule, collecting duct
Collecting duct; by the time the filtrate gets to the collecting ducts, the medullary interstitium is very concentrated and the filtrate is hypotonic, allowing for lots of water to move into the interstitium and out of the “urine”
How does aldosterone work?
Increases the density of K+ channels and Na/K ATPase enzymes in the cortical collecting duct
What is Conn’s Syndrome?
Hyperaldosteronism: hypokalemia
What are the effects of angiotensin II?
Causes mesangial cells in the juxtaglomerular apparatus to contract (decreases glomerular blood flow -> increased renin) + increases aldosterone release from adrenal cortex
What is the process by which angiotensin II is made?
Renin secreted from juxtaglomerular apparatus of the kidney -> converts angiotensinogen to angiotensin I -> angiotensin I is covered to angiotensin II by ACE in the lungs
How does dopamine and fenoldapam affect the kidneys?
Dilates both afferent and efferent arterioles and increases GFR
FeNa 2%?
BUN/Creatinine > 20?
Pre-renal etiology of renal problems
What is a common electrolyte problem seen with rhabdomyolysis?
Hyperkalemia (also hyperphosphatemia)
What is the mechanism of action of spirinolactone?
Direct aldosterone receptor antagonist
What is the mechanism of action of acetazolamide?
Carbonic anhydrase inhibitor -> decreased bicarbonate uptake
What is the mechanism of action of loop diuretics?
Inhibits Na-K-2Cl transporter in the thick ascending limb of the loop of Henle
What is the mechanism of action of thiazide diuretics?
Inhibits Na-Cl transporter in the distal convoluted tubules
What would muddle brown casts be pathopneumonic for?
Acute tubular necrosis
Definition of oliguria in the ICU?
< 0.5cc/kg/hr
What electrolyte abnormalities do you see with loop diuretics? Thiazide diuretics?
Loop: hypokalemia, HYPOcalcemia, hypomagnesemia
Thiazide: hypokalemia, hypomagnesemia, HYPERcalcemia
Which medication can result in digoxin toxicity if co-administered with digoxin: lisinopril, spironolactone, triamterene, fenoldopam, furosemide?
Furosemide: digoxin competes with K+ on the Na/K ATPase, so if you are hypokalemia (with Lasix), then digoxin further out-competes and leads to toxicity
What is the formula for plasma osmolality and what is the normal value?
Plasma osmolality = (2* Na) + (Gluc/18) + (BUN/2.8)
Normal: 290 mOsm/kg H2O
What is the correction for hyperglycemia and sodium levels?
For every increase in glucose of 100 mg/dL above 200 mg/dL, add 1.6
What is the classic ECG finding for hypokalemia?
U waves (can also see prolonged PR intervals, flattened T wave, and ST depression)
How can you treat hypercalcemia?
Fluids + loop diuretic (hypocalcemia)
What two electrolyte abnormalities would prolong NMB?
HypoPO4 and hyperMg
What are examples of non-gap metabolic acidosis?
Renal tubular acidosis (increased plasma Cl-) GI losses (i.e. diarrhea) Excess NS administration
What is the most common nerve injury?
Ulnar neuropathy
What vertebral levels does the obturator nerve derive from?
L2-L4
What nerve plexus innervates the general visceral afferent fibers of the bladder?
Hypogastric plexus (from T10)
What do you see with TURP syndrome when surgeons are using glycine irrigating solution?
Hyponatremia + hyperammonemia (glycine is metabolized to ammonia) + hyperglycemia + transient blindness
To do a cystoscopy under epidural anesthesia, at what level of loss of cold discrimination is needed to cover surgical pain?
T6 (fibers as high as T8 need to be completed blocked for loss of sensation to bladder, ureters, and renal pelvis so 2 levels above that)
Most common cause of perioperative renal dysfunction?
Hypovolemia and anemia
What causes the release of renin?
Decreased afferent blow flow or sympathetic stimulation
