Red Cell Volume

Pictorial Guide To The RCV Procedure

Blood Volume Determination

The fundamentals of the dilution principle are

based on the following equation and hold true for all dilution type equations that are applied in vitro:

V = Q

C

V = Volume Q = Dose of the activity injected

C = Sample of the activity extracted

Applications of formula

V = Q/CV = Q/CHence, by adding a known quantity of activity to an unknown volume of liquid and extracted a sample fromthe unknown liquid you can determine its volume. This formula is the basis for all volume determinations in nuclear medicine.

Equipment used Cr-51 Tag

Identify materials for the tagging of the RBCs

ACD vial Shielding for ACD vial Ascorbic Acid Cr-51 Shielding Cups for Standard Prep Tubes for collecting RBCs

Preparing the syringe

Wet a 20 cc syringe with 1 ml of ACD Solution.

Using a 19 gauge needle take the syringe and draw 15 ml of whole blood from the patient.

Preparing the blood for the tag

After drawing 15 ml of whole blood from the patient slowly add it to the ACD vial

Starting the tag

Add 100 uCi of Cr-51 to the ACD vial

Mixing the contents

Mix the contents in the ACD vial after adding contents

Mix every 5 to 10 minutes after that for a total of 30 minutes

Ampule of ascorbic acid

Concentration of ascorbic acid is 1000 mg/2ml

Calculate a 50 mg dose

Reducing the Cr-51

After 30 minutes add 30 - 50 mg of ascorbic acid

Mix contents again This reduces the Cr-51

and locks it into the RBCs

End Product - Labeled RBCs

After waiting 5 minutes 10 ml is withdrawn from the ACD vial

Labeled RBCs are then injected into the patient

Dose circulates for 10 to 20 minutes before withdrawing WB2

Preparation of Standards

While the labeled RBCs are circulating in the patient make your standard.

99 ml of water is measured twice and added to two separate containers.

The Standards 1 ml of WB is added to 99

ml of H2O

After collecting a 4 ml blood sample it is spun down and 1 ml of Plasma is drawn off and added to 99 ml of H2O

2 - 4 ml samples from each container is drawn up to a test tube and labeled WB1 and Pl1

Patient’s Whole Blood Using a 19 gauge needle

with a 20 ml syringe approximately 20 ml of whole blood is drawn from patient

4 - 4ml purple top tubes are used to collect 4 equal samples of whole blood.

Three of these tubes are spin down to collect 4 ml of plasma for Pl2

What about the other tubes?

1 - 4 ml tube of patients whole blood is collected for WB2

1 - 4 ml blood sample is collected from ACD vial to determine Hct1 from ACD vial

1 - 4 ml blood sample is collected from pts to determine Hct2

Time to count

Count bkg for 20 minutes

Count all tubes for 20 minutes

Take them to the formula

Now just plug in the counts

WB1 - Pl1(1 - Hct1)

WB2 - Pl2(1 - Hct2)x Hct2 x 1000 = RCV in ml

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