Equations to Calculate the Effects of Plasma Volume Change on Blood and Plasma Concentrations

Abstract Background and Aims It is well known that haemoglobin significantly increases after haemodialysis and it is associated with the rate of weight loss during dialysis. However, it has been shown that the increase in haemoglobin is not always proportional to the rate of body weight loss during haemodialysis (ultrafiltration). The purpose of the study was to investigate the correlation between haemoglobin changes, body weight loss and plasma volume changes during haemodialysis Method A prospective study was performed on 92 patients in mid-week treatments. Pre-dialysis and post-dialysis haemoglobin and weight were measured. 27 patients were excluded because clinical instability, no change or a decrease in Hb and low pre-dialysis haemoglobin (< 9 g/dL). The correlation was statistically significant between %ΔPV and ΔHb in both groups (R2=0.59), whereas the correlation between %ΔBW and ΔHb was lower (R2=0.19). So, analysis show that only 19% of the variability in haemoglobin is explained by %ΔBW, and that 59% of the variability in haemoglobin is explained by %ΔPV. Results The mean age was 61.16 ± 13.11 year. The men were 52 (56%). The mean pre-dialysis Hb was 11.31 ± 1.16 g/dL, the mean post-dialysis Hb level was 12.53 ± 1.47 g/dL. The mean absolute change of haemoglobin (ΔHb g/dL) and percent of change of haemoglobin (%ΔHb) were 1.22 ± 0.76 and 9.44 ± 5.31, respectively. Average percent of weight change (%ΔBW) was - 2.44 ± 1.01. Percent of plasma volume change was - 9.22 ± 5.46. The patients were divided in two groups according post-dialysis haemoglobin level: Group A with haemoglobin Hb < 13 g/dL (64 patients) and group B with Hb ≥13 g/dL (28 patients). The mean time average haemoglobin concentration (TAC Hb) in all patients was 11.68 ± 1.11 g/dL.(Predicted Hb TAC was calculated according Krisper′s formula) In both groups there was an increase in %ΔHb, but in the group with post dialysis Hb ≥ 13 g/dL, %ΔHb was greater than in group B with post dialysis Hb < 13 g/dL (13.08 ± 5.11 versus 7.87± 4.61, P = 0.000) despite the relatively small difference of %ΔBW between the two groups (- 2.85 ± 0.95 versus - 2.23 ± 1.02; P = 0.010). However, the difference in %ΔPV between the two groups was significant (- 12.90 ± 5.63 versus - 7.61 ± 4.57; P < 0.000). Conclusion The intradialytic changes in haemoglobin levels are predominantly determined by changes in plasma volume. Changes in body weight are of little predictive value in evaluation of variation of haemoglobin levels. TAC Hb determination should be performed in patients with large variations in plasma volume, because the plasma volume has very little effect on TAC Hb.

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Factors associated with vasopressin release in exercising swine

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1994.266.1.r118 ◽

1994 ◽

Vol 266 (1) ◽

pp. R118-R124 ◽

Cited By ~ 4

Author(s):

C. L. Stebbins ◽

J. D. Symons ◽

M. D. McKirnan ◽

F. F. Hwang

Keyword(s):

Plasma Volume ◽

Plasma Concentrations ◽

Plasma Osmolality ◽

Plasma Renin ◽

Treadmill Running ◽

Maximal Heart Rate ◽

Ang Ii ◽

Strong Correlations ◽

Vasopressin Release ◽

Lysine Vasopressin

This study examined the effect of dynamic exercise on vasopressin release in the miniswine and factors that may elicit this response (n = 15). Thus lysine vasopressin (LVP), the catecholamines epinephrine and norepinephrine (EPI and NE), plasma renin activity (PRA), and plasma volume, Na+, and osmolality were measured before and during treadmill running at work intensities of 60, 80, and 100% of each swine's maximal heart rate reserve (HRR). LVP increased in a progressive manner similar to that of humans, ranging from 5.9 +/- 0.4 pg/ml before exercise to 30.1 +/- 4.5 pg/ml during maximal exercise. EPI, NE, and PRA [an index of angiotensin II (ANG II) activity] demonstrated a pattern of response comparable to LVP. Although these hormones can influence the release of LVP, only PRA displayed a strong correlation with LVP (r = 0.84). When ANG II synthesis was blocked (captopril, 1-3 mg/kg, intra-atrial injection) during exercise (80% HRR), plasma LVP was reduced from 9.9 +/- 0.6 to 7.5 +/- 0.6 pg/ml (P < 0.05). In addition, moderate-to-strong correlations were found between plasma concentrations of LVP and plasma osmolality (r = 0.79) and body temperature (r = 0.78). Plasma LVP also correlated with decreases in plasma volume (r = 0.84). These data suggest that the miniswine model is a good one for studying vasopressin effects during exercise and that ANG II appears to be a particularly strong stimulus for the release of this hormone.

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