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94 Cards in this Set
- Front
- Back
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Acute renal failure is characterized by what?
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Azotemia
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what is azotemia
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retention of nitrogenous waste products from metabolism of proteins and amino acids
urea creatinine uric acid |
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what is the most common cause of new onset renal failure in postop period?
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Sepsis
decreased RBF and Decreaed DFR and the neuronal response cascade |
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What is specific gravity in prerenal failure? in renal failure?
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>1.018
< 0.012 |
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in pt with acute oliguria, what are the 2 common possible causes
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Hypovolemia
(osmolality > 500 & sg >1.018) Acute tubular necrosis can distiguish the two by examining osmolarolity and specific gravity so a high urine osmolality mean it is not acute tubular necrosis (b/c urine in this case is dilute) |
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Type so Glomerulopathies in CRF
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damage to may areas of the neprhon:
Glomerulonephritis DM HTN Amyloidosis SLE Postinfectious glomerulonephritis Glomerulopathies ass. with systemic disease: |
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Types of Tubulointerstitial disease ass. with CRF
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Analgesic nephropahthy
reflux nephropathy with pyelopnephritis myeloma kidney sarcoid |
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type of Hereditary diseases ass. with CRF
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polycystic kidney diease
Alport syndrome Medullary cystic disease |
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Classification of chronic renal disease
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Stage 1: GFR > 90
Stage 2: GFR 60-85 Stage 3: GFR 30 - 59 stage 4: GFR 15-29 Stage 5: GFR < 15 (uremic syndrome and kidney failure) |
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What are the electrolyte disturbances ass. with chronic renal failure
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hyperkalemia
Hyperphosphatemia Hypocalcemia Hypermagnesemia Increased uric acid decreased albumin |
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what are the cardiovasculare manifestations?
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HTN
Fluid overload CHF LVH uremic pericarditis Tamponade |
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what are the hematologic manifestations of chronic renal failure
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Anemia
Impaired WBC and platelet function |
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What a re the pulmonary manifestations of chronic renal failure
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Increased minute ventialtion (compensation for metabolic acidsois)
Interstitial edema pulmonary edema & pleural effusions |
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what are the endocrine manifestations fo chronic renal failure
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Insulin resistance
secondary hyperparathyroidism |
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what are the neurologic manifestations of chronic renal failure
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peripheral neuropathy
autonomic neuropathy Sz (hypermagnesemia and hypocalcemia) lethargy |
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What are the GI manifestations of chronic renal failure
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anorexia
N & V Gastroparesis |
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osmotic diuretics
mechanism & site of action |
Increase osm tubular fluid
PCT |
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Loop diuretics
mechanism & site of action |
decreased K, CL reabsorption
Loop of henle |
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Thiazide diuretic
mechanism & site of action |
Decreased Na reabsorption
DCT |
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what is the worst conditon of CRF? (end stage)
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Uremic Syndrome:
anorexia, N/V, anemia. pruirtis, fatigue, fluid overload, coapulopathy |
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Potassium sparing diuretics
mechanism & site of action |
decreased Na reabsoprtion
collecting tubules |
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Carbonic anhydrase inhibitors
Mechanism & site of action |
interfer with Na reabsorption
PCT |
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what type of graft is preferred and why?
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native arteriovenous fistula
(cephalic to radial artery) |
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What are the main function of the kidney?
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1. Filters blood -- allowing toxins and wastes to go out
2. Regulates volume ans chemical make up of blood 3. maintains proper balance b/t water and salts and acidbase |
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How much blood does the kidney filter/day (what % of cardiac output)
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200 liters/day
20-25% of CO |
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How much uirne is made per day
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1-2 L/day
produces 180 Liters of filtrate (a lot of the filtrate is reabsorbed) |
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8 functions of the kidney
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1. Excretions of waste products
2. Regulation of water & electrolytes 3. Regulation of osmolarity 4. Regulation of acid-base 5. Regulation of BP (renin) 6. secretion, metabolism, & excretion of hormone erythropoietin, to stimulate RBC production 7. Gluconeogenesis 8. Activation of Vitamin D |
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What are some Prerenal condtions that can affect kidney function
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Hypotension
hypovolemia Anemia Stenosis of renal arteries |
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Where do the arteries and nerves enter and exit the kidneys
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Renal Hiatus
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What are some postrenal conditions that can affect kidney function
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Ureter stones/tumors
kinking of ureter BPH pregnancy |
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What are some intrarenal conditions that can affect kidney function
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Kidney stones/tumors
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What is the functional unit of the kidney?
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Nephron
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What are the 2 capillary beds in each nephron?
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Glomerulus: highest pressure of any capillary bed in the body; supports filtration
Peritubules: low pressure; supports reabsorption |
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What is ultra filtrate
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everything in the blood minus protein and cells
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What are the 6 functional divisions of the nephron?
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Glomerulus
Proximal Tubule Loop of Henle Distal Tubule Collecting Tubule Juxtaglomerular apparatus |
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What is the function of the Proximal Convoluted Tubule (PCT)
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Reabsorbs Glucose, potassium, lactate, Na, bicarb from the fitrate into the blood
once glucose max. (375 mg/dl) is reached no more glucose can be reabsorbed and glucosuria results |
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What is the function of the Loop of Henle?
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Divided into descending and ascending limb (thick ascending limb is metabolically very active)
Reabsorption of NaCl, H2O, K, Ca, Mg |
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What part of the loop of Henle is vulnerable to hypoxia?
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Thick Ascending Limb (TAL): highly metabolically active
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What is the fucntion of the distal convoluted Tubule
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functions more in secretion than reabsorption (H, K, and Ca)
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Name a drug that inhibits prostaglandin synthesis
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NSAIDs
prostaglansins assist in the endogenous control of intrarenal blood flow and promote vasodiation NSAIDs can upset this and promote medulllary ischemia |
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What are the 2 internal layers of the kidney
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Cortex: outer
Medulla: has Medullary (renal) cone-shaped pyramids separated by columns (each medullary is considered a lobe) |
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What is the renal pelvis?
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flat, funnel shaped tube, that forms the termianl part of the collecting system
-lateral to the hilus |
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What % of renal nephrons are cortical and what % are juxtamedullary?
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85% are cortical; get 80% of renal blood flow
15% are juxtamedullary |
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Why is blood pressure high in the glomerulus?
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b/c it consists of afferent arterioles that have higher pressure than efferent arterioles.
this allows fluids and solutes to be forced out of the blood (supports filtration) |
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what is the low pressure capillary system in the kidney?
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Peritubular beds: porous capillaries that arise form the efferent arterioles
support reabsorption |
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Why is it important to maintain renal blood flow and blood pressure?
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because it is the driving force fo the glomerular filtration rate
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What are the 3 layers of the filtration membrane in the glomerular capsule
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Fenestratred Endothelium
Basement membrane (filters plasma proteins) Foot processes of podocytes |
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What are the 3 major processes involved in urine formation
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Glomerular filtration
tubular reabsorption secretion |
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Are plasma protiens filtered into the urine?
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no, they are used to maintain oncotic pressure of the blood
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Why is the glomerulus more efficeint than other capillary beds at filtration?
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1. its filtration membrane is more permeable
2. Glomerular blood pressure is higher 3. Its has a higher net filtration pressure |
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WHat is NFP
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Net filtration pressure = the pressure responsible for filtration formation
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What is GFR
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total amount of filtrate formed per minute by the kidneys
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What is the best measure of renal function?
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GFR
nl value = 125 ml/min |
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What types of things can pass thru the basement membrane in the glomerulus?
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small moledcules with + charge
water, Na, urea, isulin, glucose (the glycoprotiens of the membrane have negative charge, so don't allow anions to pass thru) - |
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What does the stress response during surgery do to the RBF and GFR?
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can cause decrease RBF and GFR causing afferent arterole vasoconstriction -- this can lead to Acute renal failure form ischemic damage
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What happens if the GFR is too high
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needed substances cannot be reabsorbed and are lost int he urine
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What happens if the GFR is too low
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everything is reabsorbed, including wastes that are normally excreted
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What are the 3 mechanisms that control GFR
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Renal autoregualtion /intrinsic systems
Neural controls (renal sympathetic nerves) Hormonal mechanisms (renin angio system) |
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what are the 2 renal autoregulation mechanisms for GFR
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1. Myogenic autoregulation: responds to changes in pressures in the renal blood vessels
2. Tubuloglomerular feedback mechanism: senses changes in juxtaglomerular apparatus (rel.renin) |
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List some conditions that alter the GFR
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chronic, uncontrolled HTN, IDDM
kidney stones hypotension renal artery stenosis ace inhibitors sympathetic stimulation |
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List factors contributing to riskd of acute renal failure after surgery
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properative renal function is the signle most reliable predictor of postop rneal dysfuction
2. age > 65 3. diabetes 4. Preop cardiac dyfuction 5. High risk surgery, such as renal artery surgery, AAA 6. Exposure to Nephrotoxins |
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List the exogenous nephrotoxins commonly found in the hospital setting
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Antibiotics: aminoglycosides
anesthtic agentsL mehoxyflurane, enflurane NSAIDS: Ketorolac chemotherapy/immunosupressants contrast media |
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what anesthetic drug has minimal effecs on RBF and GFR
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Fentanyl
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What are the hormonal extrinsic controls of RBF that take over when the body experiences stress?
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Norepeinephrine is released by SNS
Epinephrine is released by the adrenal medulla Afferent arterioles constrict and filtration is inhibited SNS stimulate the renin angiotensin mechanism |
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How is the renin angiotensin mechanism triggered?
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1. when the juxtamedulllary cell release renin (in response to hypotensive episode)
2. SNS in response to stress |
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What happens to the basement membrane in DM
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it is thickened
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What are the 2 types of intrinsic controls of renal autoregulation of GFR
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1. Myogenic: responds to changes i n pressure in the renal blood vessels
2. Tubuloglomerular feedback mechanism: sense changes in the juxtaglomerular apparatus (decrease GFR -- decrease flow to loop of henle -- this will cause them to rel. renin) |
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What does Angiotensin II do?
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1. Causes MAP to rise
2. Stimulates the adrenal cortex to release aldosterone ( this increase fluid/electrolyte reabsorption-- increases systemic and glomerular hydrostatic pressure) |
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What 4 things trigger Renin release?
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1. Reduced stretch fo the granular JG cells (hypotension)
2. Stimulation of the JG cells by activated macula densa cells 3. Direct stimulation of the JG cells vie Beta adrenergic receptors by renal nerves 4. Angiotensin II |
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What is AVP
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Arginine Vasopressor
ADH (antidiuretic Hormone) |
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Where is AVP released?
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Released by posterior pituitary in response to
increased osmolality Decreased extracellular volume Positive pressure ventilation Surgical stimulation (pain) |
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What are the effects of AVP?
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Increased permeabolity of the collecting duct to water by insertion of Aquaporins:
reabsorption of water concentrated urine |
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what Hormone is released in response to Hypervolemia
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Atrial Natruiritic pepetide
rel in response to stretch of atria and large vessels |
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What does Atrial natriuretic peptide do?
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1. Blocks vasoconstitive effects of NE and Angio II
2. Results in prompt and sustained elevation in GFR (Promotes Na filtration and water loss) 3. Inhibits: -Renin secretion by the kidneys -Aldosterone Release |
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What 4 things can trigger the release of AVP (arginine vasopressin)
AKA Anti-diuretic Hormone |
1. Decreased Osmolality
2. Decreased ECF 3. Pos. pressure ventilation 4. surgical stimulation |
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what horomone is released in response to Positive pressure ventilation
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AVP (arginine vasopressin)
aka ADH |
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What is filtered in Glomerular Filtration?
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1. Waste products
2. hormone metabolites 3. Electrolytes 4. Amino acids (reabsorbed) |
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What are waste products?
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Urea
Uric acid - from nucleic acids Creatinine - form muscle creatine Bilirubin - from Hb |
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When BUN is > 50, what happens to GFR?
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it is decreased
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what can cause a high bilirubin level?
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GI bleeding
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What are some things that can cause increased BUN, but normal GFR?
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high dietary protein
GI bleeding Dehydration catabolic states (febrile) |
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Why do small changes in Creatinine level suggest renal disease in elderly patients?
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they produce less creatinin b/c their mus. mass is less
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what can cuase proteinuria?
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strenuous exercise or prolonged standing
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what causes albuminuria?
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damage to the glomerular wall (normally has negatively charged glycoproteins to repel negatively charged proteins)
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What 4 lab tests evaluated glomerular function
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BUN
serum creatinine creatinine clearance proteinuria |
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what 4 lab tests evaulate tubular function?
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utine specific gravity
urine osmolarity urine Na excretion glycosuria Enzymuria |
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what can cause a low BUN
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severe liver disease
low protein diet |
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how do anesthetic agents cause decrease in GFR and RBF
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Myocardial depression and venous pooling
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what 3 factors contribute to permanent kidney damage after surgery
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abnormal kidney function preoperatively
prolonged hypovolemia nephrotoxins |
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what part of the nephron is at greatest risks for nephrotoxic injury b/c it is metabolically most active?
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medullary thick ascending limb of loop of henle
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what does specific gravity measure
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compares the wight of urine to that of distilled water
-estimates urine concentrating ability |
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what are the 2 most common causes of acute oliguria?
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hypovolemia
acute tubular necrosis |
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why does a high urine osmolarity preclude the diagnosis of acute tubular necrosis in acute oliguria?
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b/c with ATN, the ability to concnetrate urine is impaired, so urien osmolarity is low (350 mOsm)
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what percent of nephrons are left when uremic syndrome occure in renal failure
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less than 10%
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