Red Cell Volume

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Red Cell Volume

• Pictorial Guide To The RCV Procedure

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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

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

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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.

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Preparing the blood for the tag

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

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Starting the tag

• Add 100 uCi of Cr-51 to the ACD vial

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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

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Ampule of ascorbic acid

• Concentration of ascorbic acid is 1000 mg/2ml
• Calculate a 50 mg dose

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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

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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• After waiting 5 minutes 10 ml is withdrawn from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

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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.

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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

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Patients 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

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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

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Time to count

• Count bkg for 20 minutes
• Count all tubes for 20 minutes
• Take them to the formula

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Now just plug in the counts
WB1 - Pl1(1 - Hct1)
x Hct2 x 1000
RCV in ml
WB2 - Pl2(1 - Hct2)
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