F-cell shift and protein loss strongly affect validity of PV reductions indicated by Hb/Hct and plasma proteins

Abstract

Numerous studies have focused on alterations in plasma volume (PV) on interventions like quiet standing, exercise, or heat stress. However, no method seems capable of truly estimating the PV alteration. Therefore, an attempt was made to validate commonly used indexes of PV changes. Quiet standing was used to cause graded PV reductions estimated from hemoglobin and hematocrit (Hb/Hct) and from serum concentrations of total protein, albumin, and "large proteins" (LP; total protein minus albumin). Results indicated the following. 1) Hb/Hct, with the merit that the marker (erythrocyte) stays within the circulation, reflect accurately a small-to-moderate PV loss (</=10% of control PV). At large PV decrease (>/=15-20% of control), however, F-cell shift can cause Hb/Hct to underestimate the response by up to 25-30%. 2) Albumin and total protein underrate PV loss due to protein escape (mainly albumin) from the circulation. 3) LP also underestimate the PV decline due to protein escape but can often predict large PV reductions clearly better than Hb/Hct. 4) Prolonged standing can lead to pronounced 25% PV decline.

Effect of sauna-based heat acclimation on plasma volume and heart rate variability

“…First, changes in PV were estimated via changes in Hct and Hb concentrations. This method assumes the erythrocytes remain within the circulation and accurately reflects small to moderate changes (<10%) in PV although underestimates large changes in PV by 25−30% (Lundvall and Lindgren 1998). Nevertheless, we demonstrated a coefficient of variation of 5.5% in PV measurement prior to sauna exposure and are confident that our statistical analysis provides a clear and practical indication of the sauna induced changes.…”

Relative Blood Volume Changes Underestimate Total Blood Volume Changes during Hemodialysis

“…This assumption is not true because Ht in the microcirculation is lower than in the macrocirculation (7,8). The lack of uniform mixing of erythrocytes throughout the circulation would probably not induce a great error in ⌬RBV measurements as long as the difference in Ht between the different vascular beds would remain constant during HD-in other words, if the F cell ratio would not change (19,23). This study, however, clearly demonstrates that the F cell ratio increases markedly during HD.…”

“…This time interval was chosen to allow adequate distribution of the radioiodinated isotopes (15,16). For avoidance of the widely known influence of postural changes on blood volume (18) and F cell ratio (19,20), patients were placed in a supine position 20 min before blood sampling for erythrocyte labeling with 51 Cr and remained in this position until the study protocol was completed (from 100 min before the start of HD until the stop of HD). After completion of the erythrocyte labeling with 51 Cr, the patients' own blood supplemented with 125 I-albumin was administered.…”

Exercise-induced plasma volume expansion and post-exercise parasympathetic reactivation

“…In the present study, plasma volume changes were estimated via changes in hematocrit and hemoglobin concentrations. This method, which assumes that the marker (erythrocyte) stays within the circulation, has been shown to accurately reflect a small-to-moderate change in plasma volume (accurate to within *10% over a range of controlled plasma volume changes) (Lundvall and Lindgren 1998). Nevertheless, comparisons we make with other studies in the following sections should be considered in light of the fact that small differences exist between changes in plasma and blood volume, and that the technique we have used cannot provide insight into blood distribution.…”