creatinine-picrate complex, an orange yellow colored complex, which absorbs at 510 nm; the rate of formation is proportional to the creatinine in the sample BUN-Enzymatic--- urease hydrolyzes urea in the sample and the ammonium ion produced in the reaction is quantified; the most common method couples the ureas rx w/ glutamate dehydrogenase (GLDH) and the rate of disappearance of nicotinamide adenine dinucleotide (reduced NADH) at 340 nm is measured Uric Acid – Enzymatic--- use uricase, the enzyme that catalyzes the oxidation of uric acid to allantoin; measure the differential absorption of uric acid and allantoin at 293 nm; the difference in absorbance before and after incubation w/ uricase is proportional to the uric acid concentration Ammonia – Enzymatic --- use glutamate dehydrogenase; the decrease in absorbance at 340 nm as NADPH is consumed in the rx is proportional to the ammonia concentration in the specimen; NADPH is the preferred enzyme b/c it’s used specifically by glutamate dehydrogenase; Adenosine diphosphate (ADP) is added to the rx mixture to increase the rate of the rx and to stabilize GLDH 5. Calculate the Creatinine Clearance given a set of laboratory data. CrCl=Ucr x Vml/Pcr x Tmin Ucr = urine creatinine in mg/dl Vml = total volume in ml Pcr = plasma creatinine in mg/dl Tmin = time of collection in minutes CrCl is in mL/minute Can be corrected for body surface area CrCl = (Ucr x Vml/ Pcr x Tmin) x (1.73/BSA) 6. Explain the difference between the creatinine clearance and the corrected creatinine clearance. If the patient’s body surface area varies greatly from the average (i.e obese or pediatric patients ) this correction for body mass must be included in the formula
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