Acute Kidney Injury (AKI) (Teitelbaum) Flashcards
Cockroft and Gault formula. For what is it used and what is the formula?
Another way to estimate GFR is to estimate the creatinine clearance using the Cockcroft and Gault formula:
Creatinine clearance = [(A) x (140 - age) x weight]/ (72 x SCr)
Where: the creatinine clearance is in ml/min A=l.0 if male, 0.85 if female Age is in years Weight is in kg Serum creatinine is in mg/dL
What is required for a 24 hr createnine clearance test? What equation is used to calculate it?
Patient urine for 24 hour period, blood draw to determine plasma levels of creatinine.
ClCr = (UCr) V/ PCr where
ClCR = Creatinine clearance in mL/min UCR = Urine creatinine in mg/dL V = urine flow rate -->24hr urine volume /1440 (minutes in a day) in mL/min Pcr = plasma creatinine in mg/dL
**note that this is the same equation used to calculate GFR for a generic substance, here we just make it specific for creatinine
x
x
SNGFR is proportional to _____.
PGC
Vasodilation of the afferent arteriole is largely maintained by:
PGE1 and PGI2
Vasoconstriction of the efferent arteriole is largely maintained by:
ATII
Decreased afferent resistance will __ the GFR. What causes this?
Increase. Nitric oxide, prostaglandins E2 and I2, high protein diet/amino acids
Increased efferent resistance will ___ the GFR. What causes this?
Increase the GFR. Angiotensin-II.
Decreased efferent resistance will ___ the GFR. What causes this?
Decrease. ACE inhibitors and ARBs.
Increased afferent resistance will ___ the GFR. What causes this?
Decrease. NSAIDs, adenosine, norepinephrine, endothelin, thromboxane
Na (plasma)
Na- 140 ± 3 mEq/L (Tells you about the relative amount of water in the ECF compared with Na. It tells you nothing about total body Na; best considered as an indirect but readily available assessment of plasma osmolality that is accurate under most (but not all) circumstances).
K (plasma)
K- 4.5 ± 0.6 mEq/L (Tells you about plasma K; relatively poor indicator of total body K).
Cl (plasma)
Cl- 104 ± 3 mEq/L (Generally considered a passive anion; used in the anion gap calculation as described below).
CO2 (plasma)
Total CO2 (tCO2)- 27 ± 2 mEq/L (Total CO2 content of blood; about 3 mEq/L higher than the arterial HCO3- because of dissolved CO2. Used for calculation of anion gap).
Glucose (plasma)
Glucose (Fasting)- 90 ± 30 mg/dL
Creatinine (plasma)
Creatinine- 1.0 ± 0.3 mg/dL (Used to estimate renal function; reciprocal (1/cr)
directly proportional to CrCl and, indirectly, to GFR).
BUN (plasma)
BUN- 12 ± 4 mg/dL
Phosphorus (plasma)
Phosphorus- 4.0 ± 1.0 mg/dL
Ca (plasma)
Calcium- 9.5 ± 1.0 mg/dL
Cholesterol (plasma)
Cholesterol- 140-200 mg/dL
Osmolality (plasma)
Around 285 ± 3 mosm/kg H2O (Direct measurement of plasma osmolality;
difficult to obtain in a short time from a clinical lab).
Azotemia:
Buildup of nitrogenous wastes in the blood; i.e. Blood Urea Nitrogen (BUN) and serum creatinine are increased.
Oliguria
Urine volume is
Anuria
Urine volume is
What is the FENa? What is the clinical significance of this number?
FENa is the ratio of clearance of Na to Creatinine. It can help distinguish prerenal azotemia from other causes of AKI. FENa 2% indicates other cause. (radiocontrast and rhabdomyolysis are cause FENa
Postrenal obstruction would likely show what on a FENa? Why?
FENa>2%. Obstruction generally decreases tubular sodium resorption, so the levels in urine will rise. Also, an impairment of H2O resorption lowers urine creatinine concentrations.
UA pattern for prerenal azotemia
Relatively high specific gravity, no heme pigment, normal sediment (i.e. any casts are waxy or finely granular).
UA pattern for Glomerulonephritis
Variable tonicity, + heme pigment, sediment exam reveals RBC and RBC casts.
UA pattern for AIN
Isotonic urine, +/- heme pigment, white blood cell casts,
eosinophils (with allergic interstitial nephritis)
UA pattern for Vascular
Variable isotonicity, +/- hematuria
UA pattern for ATN
Typically isotonic, variable heme pigment (+ if from hemolysis or rhabdomyolysis). Sediment exam will show pigmented coarsely granular casts and renal tubular epithelial cells (RTEs).
UA pattern for Obstruction
Tonicity usually isotonic or hypotonic, usually heme is negative unless superimposed infection. Micro may be totally benign or show evidence of superimposed infection (e.g. RBCs & WBCs).
What is the most common cause of a sudden drop in GFR in hospitalized patients?
Pre-renal azotemia
What does it mean to have a low Effective Arterial Blood Volume (EABV)?
This applies in cases of pre-renal azotemia that occur in hyper (versus hypo) volemic states. Examples are Congestive heart failure and cirrhosis, where volume overload is a problem, but kidneys are still unperfused due to low CO.
Please name as many causes of pre-renal azotemia as you can.
Due to decreased volume - GI losses, Hemorrhage, 3rd space losses, renal losses
Due to low CO - CHF, MI, valvular disease, tamponade
Due to systemic arterial vasodilation - cirrhosis, sepsis, medication, autonomic neuropathy
Please name as many causes of post-renal azotemia as you can.
Obstruction of ureters:
–Extraureteral (e.g. carcinoma of the cervix,
endometriosis, retroperitoneal fibrosis, ureteral ligation) o Intraureteral (e.g. stones, blood clots, sloughed papilla).
–Bladder outlet obstruction (e.g. bladder carcinoma, urinary infection, neuropathy).
–Urethral obstruction (e.g. posterior urethral valves, prostatic hypertrophy or carcinoma).
Please state the four categories of intrinsic glomerular disease and give some specific examples.
Vascular diseases: e.g. cholesterol emboli, renal vein thrombosis
Glomerular diseases: e.g. acute glomerulonephritis, hemolytic uremic
syndrome
Interstitial diseases: Acute interstitial nephritis (e.g. allergic interstitial nephritis (AIN)), infection, myeloma kidney.
Tubular diseases: Ischemic or nephrotoxic acute tubular necrosis (ATN).
True/False: Hyaline casts are found in healthy individuals and are not associated with pathology. (What forms these casts)
True. Tamm-Horsfall proteins secreted by the tubular cells form these proteins.
