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The technical princ iples of the BVM
BVM continuously determines the blood volumechanges during
dialysis, by measuring the time
(figure 3) taken forultrasound pulses totravel through a
pre-cisely defined cuvette(figure 5) located inthe arterial blood
line,
which is then convertedinto sound speed.
Since the amount ofblood cells and proteins
in the intravascular space does not change
duringultrafiltration, the reduction of blood water leadsto an
increase in blood density.
As there is a positive correlation betweenthe speed of sound and
blood density, anincrease in blood density leads to faster
soundspeeds, which are a measure for blood waterconcentration.
This data is used to determine the Relative BloodVolume (RBV),
initially set at 100 % and theabsolute Haematocrit and Haemoglobin
values.
Based on the patients actual RBV value, theclinically validated
control algorithm of the BVMcontinuously adjusts the
ultrafiltration rate in
order to prevent the RBV being reduced to anindividual critical
level (figure 6, red zone)where hypovolaemia related side effects
aremost likely to occur.
During dialysis the actual RBV is also influencedby processes
other than ultrafiltration e.g. food
and fluid intake, changes in posture or indialysis fluid
osmolarity, which have to be takeninto consideration.
Fig. 3 Determination of the transit time of
ultrasound pulses through blood.
Fig. 6 Course of RBV monit ored by BVM duringa blood volume
controlled dialysis.
Fig. 4 The 4008 H haemodialysis machineincluding the BVM m
odule.
Fig. 5 Scheme of sensor head.
Chang es in postureand food intake
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Techn ical chang es reserved
Fresenius Medical Care
Else-Krner-Strae 1
D 61352 B ad H omburg
G ermany
D 61346 B ad H omburgP hone: +49 (0) 6172-609-0
Fax: +49 (0) 6172-609-8340
E-M ail: dialysis-marketing@ fmc-ag.com
Internet: http://www.fmc-ag.com
Use of the Blood Volum e M onitor BVM
Relative Blood Volume (RBV) 1.7 % (absolute)
Haematocrit (Hct) 2.9 Hct %*
Haemoglobin (Hb) 0.8 g/dl
Temperature 0.1 C (33.5 40C)
* if plasma protein concentration range is 60-85 g/l
The operation of BVM is very convenient, thanks to an: easy
insertion of the BVM cuvette during the lining of
the extracorporeal blood circuit
automatic calibration of the BVM during priming
rapid entry of the Critical RBV value and
initiation of the BVM control by pressing theUF Control key.
The routine use of blood volume management with the BVMhas
proven to be a powerful tool in the attempt to reduce
hypotensive episodes.Another important factor for the prevention
of Hypotension,is the intradialytic stabilisation of the body
temperature, asdemonstrated in recent studies.
A precise, individual and non-invasive control of patient'sbody
temperature during dialysis is possible today bymeans of the Blood
Temperature Monitor BTM, anotheroptional module of Fresenius
Medical Cares concept ofPhysiological Dialysis.
In a unique combination Fresenius Medical Care offers
theautomatic control of blood volume and body temperature,two of
the major physiological parameters, in order to reduceSymptomatic
Hypotension and to improve the interdialyticphysical wellness of
dialysis patients.
1. Bhler J :Blutvolumen- und Bluttemperatursteuerung whrend der
Hmodialyse.Spektrum der Nephrologie (2001) 4:3-11
2. Daugirdas J T:Dialysis hypotension:A haemodynamic
analysis.Kidney Int (1991) 39:223-246
3. Klingel R: Bedeutung der Dialysat- und Bluttemperatur fr die
hmodynamischeStabilitt whrend der Hmodialyse. J Nephrol Team (1997)
3:102-105
4. Krmer M:Die Ultraschallmethode zur kontinuierlichen
Blutvolumenmessung.Dial J (1997) 16 (59): 152-160
5. Maggiore Q (on behalf of the study group):The Effects of
Control of ThermalBalance on Vascular Stability in Hemodialysis
Patients:Results of the EuropeanRandomized Clinical Trial.Am J
Kidney Dis (2002) 40 (2):280-290
6.Rosales LM, Schneditz D, Morris AT, Rahmati S, Levin
NW:Isothermic hemodialysisand ultrafiltration.Am J Kidney Dis
(2000) 36 (2):353-361
7. Steuer R, Conis JM:The incidence of hypovolemic morbidity in
hemodialysis.D&T (1996) 25, 5:272-281
Technical Data / Accuracy Literature
Fig. 7 The combination of BTM and BVM can reducehypotensive side
effects.
Patient
