Comparison of two different methods for the evaluation of volume flows during preparative plasmapheresis S. T. Kießig1, A. Möller1, P. Hellstern2, K.-P. Krause1 1 Haema AG, Leipzig, Germany 2 Institute of Hemostaseology and Transfusion Medicine, City Hospital Ludwigshafen, Germany
Background
Preparative plasmapheresis is a widely used method for the preparation of plasma either for therapeutic use or for fractionation. Worldwide several guidelines regulate the number of donations per year, the maximal volume per donation with respect for the donor safety. The most probable seems to be a theoretic hypovolemic reaction. Therefore is a need to observe the volume flows between the different compartments during plasmapheresis. There are two methods available: 1. Plasma proteins were diluted during and after plasmapheresis by the inflowing interstitial volume. If the dilution factors are available, the volume diluting the plasma proteins can be detected. 2. Volumes in different compartment are detectable by impedance spectrometry. A comparison between these methods should increase the evidence of the conclusions.
Aim
A broader knowledge base is required to adapt guidelines to the general requirement for an evidence based medicine. Therefore two different methods were established to evaluate the exchange of volumes between body compartments. In plasmapheresis a volume up to 850 mL can be drawn. During this procedure an extra corporal volume up to 1100 mL can be reached. This loss of volume is balanced by an influx from the interstitial compartment. This exchange of volumes between different body compartments was observed either by impedance spectroscopy or by the detection of dilution of distinct plasma proteins.
Methods
The donation volumes were adjusted according to German guidelines. Citrate was added (1:16) to the whole blood collected; 300 mL of NaCl was given as volume substitute. In a first study, the different compartments were evaluated in 41 donors before (21 donors) and after plasmapheresis (n=20) using impedance spectroscopy (BCM, Fresenius Medical Care AG, Bad Homburg, Germany). BCM measurement procedure followed plasmapheresis either at the same day before and 0 – 20 min after or before and two days after plasmapheresis. Total body water (TBW), intracellular water (ICW) and extracellular water (ECW) and overhydration (OH) were evaluated before and after plasmapheresis using bioimpedance spectroscopy. Impedance is the frequency-dependent opposition of a conductor to the flow of an administered alternating current. The BCM system combines this bioimpedance spectroscopy technology with a physiologic tissue model. The measurement is non invasive, simple and fast (Figure 1). This volume model uses the electrical conductance in a cell suspension enabling TBW and ECW as well as ICW . Figure 1: System of Body Composition Monitor (The bioimpedance of tissues is strongly dependent on frequency. At low frequencies the impedance of the cell membranes and tissue interfaces is too large for conduction of current within the cells to occur. As a result the current is conducted only through the extracellular fluid.)[i, ii]
In a second study, the serum content of IgM, IgG, IgG subclasses, Albumin (Alb) and total protein (TP) were measured. All proteins were determined before and immediately after apheresis. IgM is present only in the plasma and is expected to be diluted by the influxing interstitial volume. IgG, Alb and TP are present in both compartments. PV during plasmapheresis is influenced not only by the amount of plasma drawn. Donors additionally receive isotonic NaCl and parts of the citrate anticoagulant solution[iii]. 49 donors selected for this study were frequent donors donating (750 mL or 850 mL) on AUTO-C. Individual blood volumes were calculated by the Nadler formula (Nadler et al., 1962) [iv]. Serum concentrations of IgM, IgG, IgG subclasses, Alb and TP were determined immediately before and after plasmapheresis using standard procedures (N AS IgG1, IgG2, IgM and IgG, N IgG3 and IgG4, Siemens Healthcare Diagnostics Inc.) (TP, Cobas®, Roche/Hitachi). Dilution factors were calculated from these values and compared by the Passing & Bablok method. The F-test was used to compare the variances.
Results
On average 798 mL plasma including 133 mL of sodium citrate was collected from donors having a blood volume of 5.32 L including a plasma fraction of 2.95 L. 158 mL of sodium citrate were used, of which estimated 80 mL streamed in the donor. Considering the additionally infused 300 mL of NaCl during plasmapheresis a total loss of 473 mL was calculated after terminating plasmapheresis without any volume replacement included. This corresponds to about 1% of TBW. Thus, volume exchange from interstitium into plasma is suspected to be a very fast process and the calculated total volume loss could be further reduced to about 334 mL (Figure 2). Figure 2: Calculation of total loss of volume by BCM-method
-798 mL DV + 300 mL NaCl + 84 mL CVDonor + 80 mL InstV = -334 mL By the BCM method a total loss of intravasal fluids of 130 mL was found. The exchange between the compartments was already immediately detectable demonstrating highly accessible extracellular water. By the BCM method a loss of 334 mL was found. The calculated DF’s are presented in Table 1. IgM and Alb on average were diluted by factor 1.15, IgG by 1.18, TP by 1.17. This corresponds to a dilution of 15% to 18% of plasma volume. IgM dilution factor was similar to those proteins present both in plasma and interstitial fluid. Although the dilution factors did not differ among different proteins they were not correlated with each other (Table 2). The lowest correlation was found between IgM and IgG (r=0.61). This could be a hint for a selective transport mechanism. IgG3 showed the highest dilution factor. Inter-individual variation presented by variation coefficients was similar to TP and Alb and lower than IgM. IgM showed the highest variation (VK=15.9%; Table 3, Figure 2). Table 3: Dilution Factors IgG_DF
IgG1_DF
IgG2_DF
IgG3_DF
IgG4DF
IgM_DF
TP_DF
Alb_DF
Min
0.80
0.77
0.75
0.79
0.80
0.74
0.81
0.82
Max
1.35
1.34
1.30
1.35
1.46
1.50
1.31
1.32
MW
1.18
1.18
1.17
1.19
1.18
1.16
1.17
1.15
Med
1.20
1.21
1.20
1.21
1.19
1.19
1.20
1.18
SD
0.13
0.12
0.13
0.13
0.13
0.16
0.12
0.12
VK
10.7
10.5
11.1
10.7
10.8
13.5
10.0
10.3
Range
0.56
0.57
0.55
0.56
0.66
0.76
0.51
0.50
Using the IgM-dilution factor (1.16) and an average plasma volume of 2.9 L the influx was calculated with 464 mL. The infused NaCl (300 mL) plus the estimated citrate volume of 84 mL results in a total volume loss of 80 mL replaced by interstitial volume. The volume loss calculated with the dilution factor method was calculated with 414 mL (Figure 3). Figure 3: Calculation of total loss of volume calculated by dilution factor method
-798 mL DV + 300 mL NaCl + 84 mL CVDonor = -414 mL Both methods showed a high individual variability and were in the same range. Differences between both methods can be explained with little time gaps and the fast exchange of volumes already during plasmapheresis.
Conclusions
It can be concluded that both methods are able to detect the exchange of volumes between different compartments in the same range. Between 11% and 16% of the plasma volume was fast replaced by interstitial volume. The total body water was reduced by 130 mL, especially in the extracellular compartment (230 mL). The intracellular water was not influenced. Also the dilution factor method showed that 80 mL interstitial volume flows into the intravascular compartment. With both methods comparable losses of volumes were found: 334 mL using the BCM-method 414 mL using the dilution factor method respectively. Due to time differences for the measurement of either the Compartments by impedance spectroscopy or dilution factor method and the fast exchange of volumes between the compartments, the differences between both methods can be explained. The exchange of volumes was found by both methods as a very fast process. This confirms the known safety of the plasmapheresis procedures. Validation of bio-impedance spectroscopy: Effects of degree of obesity and ways of calculating volumes from measured resistance values, P L Cox-Reijven and P B Soeters: Intern J Obesity 2000; 24:271-280 ii Moissl, U et al., Body fluid volume determination via body composition spectroscopy in health and disease. Physiol. Meas 2006; 27: 921-933 iii Beeck et al., The influence of citrate concentration on the quality of plasma obtained by automated plasmapheresis: a prospective study, Transfusion 1999; 39:1266-1270 iv Nadler SB, Hidalgo JU, Bloch T. Prediction of blood volume in normal human adults. Surgery 1962, 51: 224-232 The lab tests were sponsored by Fenwal Europe s.p.r.l., Mont-St.-Guibert, Belgium i
Contact: S. T. Kießig, Blood Donation Center Dortmund, Ostenhellweg 50-52, 44135 Dortmund, Germany, Phone +49 231 28225320,
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45. Jahreskongress der Deutschen Gesellschaft für Transfusionsmedizin und Immunhämatologie (DGTI) 11.-14. September 2012, messecongress graz
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