Non Imaging In Vivo Plasma Volume Plasma Volume

Non Imaging In Vivo Plasma Volume

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

Plasma Volume • The technique for measuring plasma volume is similar to that for RBC Volume. • I 125 RISA or HAS – I 125 labeled to albumin – I 125 has an energy of 32 ke. V • Thus plasma volume is performed prior to RBC volume, Cr 51 has an energy of 320 ke. V

Technique for Plasma Volume • Recommended to administer Lugol’s solution 4 - 5 days, everyday prior to administration of I 125 – Prevents thyroid uptake of Iodine • Inject 10 -20 u. Ci 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. • 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 CF = cpm/ml from 5 ml volume x 2000 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. • TBV = PL Volume 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.

Formula Calculations • Plasma Volume (m. L)= Net Standard Count x 4000 Net Plasma Count • WB Volume (m. L)= Net Standard Count x 4000 Net Whole Blood Count • RC Volume (m. L) = Whole Blood Volume - Plasma Volume • Radioactive Hematocrit = Red Cell 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. Take two separate blood samples form the patient and extrapolate the data. – – – 10 minutes = 20. 5 k 20 minutes = 16. 5 k Extrapolate to 0 time = 26 k

Normal Findings • Males and females 30 - 45 ml/kg

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

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