1 HRS SNM/VOICE CEU
 

A Tutorial by Stephen M. Karesh, PhD


Adapted for the Web by Steve M. Karesh, PhD & Marsha Lipps CNMT


RED CELL MASS/ PLASMA VOLUME STUDIES

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 µCi, for PV measurement

● Cr-51-RBC, 50-75 µCi, 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

Expected Value
Measured Value
% Deviations
Plasma Volume
3300
3250
-1.5
Red Cell Volume
2200
2250
+2.3
Total Blood Volume
5500
5500
0.0


PATIENT # 2: SEVERE DEHYDRATION

Expected Value
Measured Value
% Deviations
Plasma Volume
3300
2550
-22.7
Red Cell Volume
2200
2140
+2.7
Total Blood Volume
5500
4690
-14.7

PATIENT # 3: POLYCTHEMIA VERA

Expected Value
Measured Value
% Deviations
Plasma Volume
3300
3400
+3.0
Red Cell Volume
2200
2650
+20.5
Total Blood Volume
5500
6050
+10.0

PATIENT # 4: DEHYDRATED POLYCYTHEMIC

Expected Value
Measured Value
% Deviations
Plasma Volume
3300
2650
-19.7
Red Cell Volume
2200
2650
+20.5
Total Blood Volume
5500
5300
-3.6
 
 

 


 

 

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  February 16, 2010