Non Imaging In Vivo Plasma Volume

Usually performed in conjunction with RBC Volume. Usually performed in conjunction with RBC Volume. It also aids in the diagnosis of polycythemia It also aids in the diagnosis of polycythemia Occasionally it is performed for fluid balance Occasionally it is performed for fluid balance

Plasma Volume The technique for measuring plasma volume is similar to that for RBC Volume. The technique for measuring plasma volume is similar to that for RBC Volume. I125 RISA or HAS I125 RISA or HAS –I125 labeled to albumin –I125 has an energy of 32keV Thus plasma volume is performed prior to RBC volume, Cr 51 has an energy of 320 keV Thus plasma volume is performed prior to RBC volume, Cr 51 has an energy of 320 keV

Technique for Plasma Volume Recommended to administer Lugol’s solution 4- 5 days, everyday prior to administration of I125 Recommended to administer Lugol’s solution 4- 5 days, everyday prior to administration of I125 –Prevents thyroid uptake of Iodine Inject uCi in a 1.5 ml volume into the contralateral arm that samples will be drawn. Inject uCi in a 1.5 ml volume into the contralateral arm that samples will be drawn. –Count syringe in well counter to get CPM –Post injection count empty syringe Withdraw three 15 ml blood samples at 15, 25, and 35 minutes post injection. Withdraw three 15 ml blood samples at 15, 25, and 35 minutes post injection. Centrifuge samples and divide into 5 ml aloquats. Centrifuge samples and divide into 5 ml aloquats.

Formula for Calculating PV PL Volume = (Full syringe - empty syringe) x CF Patient counts per sample drawn Patient counts per sample drawn CF = cpm/ml from 5 ml volume x 2000 cpm from syringe above well cpm from syringe above well CF is predetermined and maintained using specific procedure that may vary according to department or manufacturer.

Total Blood Volume Total Blood Volume can be calculated after the plasma volume has been determined. Total Blood Volume can be calculated after the plasma volume has been determined. TBV = PL Volume TBV = PL Volume 1 - (Hct x 0.97 x 0.91) 1 - (Hct x 0.97 x 0.91) –1 - (Hct x 0.97 x 0.91) is equal to the corrected PLcrit The correction factor is needed due to the F-cell ratio. This is the relationship between venous hematocrit and the whole blood hematocrit. The hematocrit of smaller vessels differs from that of larger vessels. The correction factor is needed due to the F-cell ratio. This is the relationship between venous hematocrit and the whole blood hematocrit. The hematocrit of smaller vessels differs from that of larger vessels.

Formula Calculations Plasma Volume (mL)= Net Standard Count x 4000 Plasma Volume (mL)= Net Standard Count x 4000 Net Plasma Count WB Volume (mL)= Net Standard Count x 4000 WB Volume (mL)= Net Standard Count x 4000 Net Whole Blood Count RC Volume (mL) = Whole Blood Volume - Plasma Volume RC Volume (mL) = Whole Blood Volume - Plasma Volume Radioactive Hematocrit = Red Cell Volume Radioactive Hematocrit = Red Cell Volume Whole Blood Volume Whole Blood Volume

Recalculating Plasma Counts Approximately 10% of the injected plasma dose will leak out of the vascular pool per hour. Therefore a correction must be applied. Approximately 10% of the injected plasma dose will leak out of the vascular pool per hour. Therefore a correction must be applied. Take two separate blood samples form the patient and extrapolate the data. Take two separate blood samples form the patient and extrapolate the data. –10 minutes = 20.5k –20 minutes = 16.5k –Extrapolate to 0 time = 26k

Normal Findings Males and females ml/kg Males and females ml/kg

Condition Evaluations Increased PV Increased PV –Primary aldosteronism Due to reduced blood flow to kidneys Due to reduced blood flow to kidneys –Cushing’s Disease Due to edema Due to edema –Splenomegally Can’t destroy damaged cells Can’t destroy damaged cells –Starvation –Waldenstrom’s macroglobulinemia Malignant disorder, one symptom is bleeding disorders Malignant disorder, one symptom is bleeding disorders Decreased PV Decreased PV –Addison’s Disease Possible dehydration –Bacteremia Bacteria take up part of plasma volume –Burns Loss of fluid from burned area –Dehydration –Polycythemia –Shock, hemorrhage, and trauma –Sodium deficiency Responsible for regulating water balance

Errors in PV Not getting the nuclide in the vein Not getting the nuclide in the vein Wrong hematocrit Wrong hematocrit Return to the Table of Content Table of ContentTable of Content