In Vivo Non Imaging Procedures:

PLASMA VOLUME AND RED CELL MASS STUDY

INDICATIONS

• Rule out Polycythemia Vera (in conjunction with RBC Mass determination).
   
• Evaluation of fluid or blood loss in postoperative patients
   
• Evaluation of patient prior to major surgery to rule out hypovolemia

RADIOPHARMACEUTICALS

• I-125 HSA, 10 mCi, for PV measurement
   
• Cr-51-RBC, 50-75 mCi, for RCM measurement

PROCEDURE

• Two identical syringes are used, each containing 10 mCi of I-125 HSA.
   
• Syringe 1 is emptied into a 1000 ml volumetric flask (the STANDARD) and 1.0 ml aliquots removed in triplicate to ensure precision.
   
• Syringe 2 is injected into the patient. Activity in patient therefore equals activity in flask
   
• Blood samples are drawn at 10 and 20 min post injection to insure that equilibrium has been reached.
   
• Plasma samples are drawn from the 20 min specimen and counted along with 1 ml samples from the standard.
   
• Test is example of principle of isotope dilution

CALCULATIONS: PLASMA VOLUME STUDY

            Activity in STD  = activity in patient

 THEREFORE

   1000 ml x cpm STD = PV x cpm plasma

         ml                       ml

INTERPRETATION: PLASMA VOLUME STUDY

Actual volume should be within 15% of expected volume, based on body surface area of patient. If not within 15-20%, abnormal study.

PATIENT # 1: NORMAL STUDY

PATIENT # 2: SEVERE DEHYDRATION
 

PATIENT # 3: POLYCTHEMIA VERA

PATIENT # 4: DEHYDRATED POLYCYTHEMIC