Concentration Urine

You may use any written references you deem necessary (e.g. lab manual, textbooks) but you MAY NOT consult with other students (past or present), other TAs, professors, neighbors, relatives, pets, extraterrestrials, friends (real or imaginary), beings from another plane of existence, etc.

Please show all work, including appropriate units, and box your answer to receive full credit.

1. Your weight is _______ lbs, which is equal to _______ kg. The lab manual (pg 67) specifies how much you should drink based on your weight. Calculate the four volumes. You only need to show details of the calculations for one of the experimental solutions.

a. Volume of distilled water you should drink: _____________

b. Volume of isotonic saline you should drink: _____________

c. Volume of bicarbonate you should drink: _____________

d. Volume of fluid you should drink if you are the control: _____________

2. The last time you urinated was at 10:40 AM. It is now 1:15 PM. You completely void your bladder, filling a one-liter bottle. What is your flow rate in mL/min?

3. Assume your flow rate is 2.75 mL/min. Estimate the creatinine concentration of your urine. Use the estimates of GFR and plasma creatinine concentration given in the lab manual (pg 70). Express your answer in mg/L.

4. In order to accurately measure creatinine concentration using a spectrophotometer, you must dilute your estimated creatinine concentration to 30 mg/L. Using the value of estimated creatinine concentration from question 3, calculate the required dilution factor in order to wind up with a urine creatinine concentration of 30 mg/L. Round your answer UP to the next whole number.

5. Assuming you start with 1 mL sample of urine, how much distilled water should you add in order to obtain a dilution factor of 12?

6. Suppose your optical density reading from the spectrophotometer is 1.1. Assume the standard curve to estimate the creatinine concentration of your DILUTED urine sample results in the following equation:

y = 0.1411x – 0.0236

where: y is the spectrophotometer reading

x is the creatinine concentration

a. Calculate the creatinine concentration of your DILUTED urine sample.

b. Using the dilution factor calculated in question 4, find the creatinine concentration of your UNDILUTED urine.

7. Using the undiluted urine creatinine concentration you calculated from question 6 and the flow rate from question 2, calculate your creatinine clearance.

8. Is the creatinine clearance rate you calculated in question 7 closed to the expected normal value for a healthy adult? If not, what should it be approximately (include units)?

9. Suppose your sodium meter reading is 80 mV. Using the standard curve (see last page), calculate your sodium clearance using the flow rate from question 2.

10. At what times should you prepare your diluted urine samples for creatinine analysis?

1

SPEC. A

y = 0.1411x – 0.0236

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

024681012

Concentration, (mg/dL)

Spec Reading

Na+ Meter #1

y = 25.927Ln(x) – 56.3

-100

-50

0

50

100

150

1101001000

Concentration, (mEq/L)

Voltage, (mV)