Inter-dialytic variations in blood volume and total body water in uraemic patients treated by dialysis.
BACKGROUND
An optimal balance of sodium and water is one of the most important goals of haemodialysis (HD) therapy. However, while inter-dialytic variations in blood volume (BV) have been well described, very little is known about the dynamics of fluid accumulation and distribution in body compartments during the inter-dialysis period.


METHODS
We studied inter-dialysis variations in BV, measured as percent variation of plasma haemoglobin (Hb) concentrations (% triangle up BV) and percent variation of total body water (% triangle up TBW), in 24 uraemic patients treated by standard bicarbonate dialysis. These parameters were determined at the end of the last weekly dialysis (T0), after 24 h (T1), 48 h (T2), and at the beginning of the following dialysis session (T3). At each time point we measured Hb, haematocrit (Hct), serum albumin (sAlb), plasma sodium (Na), plasma potassium (K), blood urea nitrogen (BUN), plasma osmolality (Osm), body weight (BW), systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). All patients were clinically stable and had no evidence of acute blood loss in the 3 weeks before the study.


RESULTS
During the inter-dialysis period, there were increases in BUN, K and Osm, but Na did not change. SBP and DBP also did not change. HR tended to decrease, and showed a significant reduction between T0 and T3. TBW increased in a linear fashion whereas BV increased exponentially, showing a slow rise during the first 24 h followed by a greater increase in the following time intervals. This was confirmed by concomitant but opposite percent variations in Hct and sAlb concentrations.


CONCLUSIONS
Despite the limitations of the current methodology, our data show that the increase in TBW is redistributed during the long inter-dialysis period and this may prevent the effects of a too premature expansion of the intra-vascular compartment. This is especially evident during the first 24 h after HD, during which % triangle up BV is lowest, indicating a preferential distribution of the fluid load towards the extra-vascular space. During the following time intervals, the extra-vascular compartment refills in conjunction with an exponential expansion of BV that reaches its maximum in the last 24 h before HD.
Movilli
Ezio
E
Division of Nephrology, School of Medicine, Spedali Civili and University of Brescia, Piazzale Ospedale Civile 1, 25123 Brescia, Italy. eziomov@libero.it
Cancarini
Giovanni C
GC
Cassamali
Silvia
S
Camerini
Corrado
C
Brunori
Giulio
G
Maffei
Camilla
C
Maiorca
Rosario
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D001810:Blood Volume / Q000502:physiology*; D001834:Body Water / Q000502:physiology*; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000503:physiopathology* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D006435:Renal Dialysis; D014511:Uremia / Q000503:physiopathology* / Q000628:therapy; D014882:Water-Electrolyte Balance