Mobilization of Fluid and Fluid Currents During Hemodialysis
Conditions: Patients Undergoing Hemodialysis
Sponsor: Joachim Zdolsek

 
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Mobilization of Fluid and Fluid Flows in 
Hemodialysis 
 
 
21st March 2024 
 
 

 
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STUDY PROTOCOL 
 
MVVH 
Title 
Mobilization of Fluid and Fluid Flows in Hemodialysis 
 
Short title: Fluid Flows in Hemodialysis 
 
 
Contact Information Principal investigator 
Joachim Zdolsek, MD 
Associate Professor  
Department of Anesthesiology and Intensive Care  
University Hospital  
581 85 Linköping 
 
Co investigator  
Erik Golsäter, MD 
Department of Anesthesiology and Intensive Care  
Vrinnevi Hospital Norrköping  
603 79 Norrköping 
 
Robert Svensson, MD 
Director 
Department of Anesthesiology and Intensive Care  
Vrinnevi Hospital Norrköping  
603 79 Norrköping 
 
Jonatan Bodare, MD 
Department of Medicine  
Vrinnevi Hospital Norrköping  
603 79 Norrköping  
 
Fredrik Sundelin, MD 
Department of Medicine  
Vrinnevi Hospital Norrköping  
603 79 Norrköping  
 
Robert G. Hahn  
Professor 
Karolinska Institute Danderyd Hospital (KIDS),  
Stockholm 
 
Trial site: 
Dialysis Department  
Vrinnevi Hospital  
Norrköping  
 
 
 

 
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Synopsis 
During dialysis, three goals are achieved: 1. Blood is cleansed of waste products. 2. Excess 
water is removed. 3. Electrolytes are regulated. These processes occur simultaneously but 
vary from patient to patient depending on their specific needs. Some patients have residual 
urine production but of poor quality. Others have no residual urine production at all and 
require removal of fluid from both blood and tissues. Episodes of hypotension may occur 
during dialysis. These are related to intravascular hypovolemia and inadequate fluid 
reinfusion, which is common with fluid removal exceeding 400 ml/hour. The rate of fluid 
removal is influenced by fluid recruitment from the tissues. This mainly occurs in two 
different ways: either through osmotic recruitment across the capillary membranes from the 
perivascular space or via lymphatic return. The proportions are not yet clear. When fluid 
recruitment from the perivascular space occurs, influx of albumin and immunoglobulins is 
unlikely. This differs from lymph, where albumin and immunoglobins are present. This 
difference in protein content can be used to calculate the different proportions of fluid 
recruited from the tissues. This is performed with mass balance calculations based on fluid 
removal, colloid osmotic pressure, hemoglobin, albumin, and immunoglobulin 
concentrations. 
 
The rate and proportions of fluid reinfusion into the bloodstream are not yet clarified. Hence 
the purpose of this study, is to explore these aspects. 
 
 
 

 
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Background 
 
 
In Sweden, approximately 3200 patients are treated annually with hemodialysis1. In some 
cases, the goal is solely blood purification, but for most patients, there is also a need to 
remove excess fluid accumulated since the last dialysis treatment. The amount of fluid 
removal is prescribed by the dialysis physician and depends primarily on how much 
secondary urine the patient produces but also on the patient's fluid intake between dialysis 
treatments.  
The most common complication of hemodialysis is hypotension during treatment, 
occurring in about 10% of treatment sessions according to previous studies. These 
hypotensive episodes lead to temporary hypoperfusion, and repeated episodes can result in 
permanent organ damage2.  
The main cause of these hypotensive episodes is the decrease in circulating 
volume associated with ultrafiltration, i.e., fluid removal3. The excess fluid accumulated by 
the patient between treatments mostly resides outside the bloodstream. Therefore, during fluid 
removal in hemodialysis, there is compensatory recruitment of fluid into circulation, which 
increases the circulating volume and prevents hypotension. How this recruitment occurs and 
from which fluid compartments fluid is recruited has not been mapped.  
To increase understanding of hemodialysis and optimize treatment while 
minimizing the risk of hypotension, it is of interest to understand how fluid recruitment 
occurs and from which fluid compartments the recruitment occurs.  
With the help of fluid kinetic calculations, it has in connection with albumin 
infusion been possible to measure whether fluid is recruited perivascularly or from the 
lymphatic system depending on the concentration of proteins such as IgG and IgM over time4.  
 
 
Purpose and Objectives 
 
The aim is to study: 
   • 
 How much fluid is drawn from the interstitial space during dialysis, depending on 
whether fluid removal is needed or not. 
 
   • 
The size and rate of fluid reinfusion during ongoing dialysis. 
 
   • 
 The composition of the recruited fluid from the interstitium, i.e., the proportion 
consisting of lymph/lymphatic return and the proportion recruited across capillary 
membranes/venulae from the pericapillary space. 
 
 

 
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Hypotheses 
The null hypothesis is that we do not find any detectable difference in fluid flows or source of 
fluid recruitment between patients undergoing extensive dialysis and those patients who do 
not have significant fluid removal during dialysis. 
The alternative hypothesis is that we find a clinically relevant difference in fluid flows from 
the tissues and the pathway of fluid recruitment to the bloodstream. 
 
Outcome Measures 
Primary outcome variables are: 
Recruitment of fluid from the interstitium calculated from fluid removal and hemoglobin 
changes.5,6. 
Proportion of recruited fluid via lymph or via capillary/venular walls based on fluid 
recruitment and changes in plasma albumin and immunoglobulins G and M. 
 
Secondary outcome variables are: 
Weight, blood pressure and changes in bioimpedance variables. 
 
Study Design 
Open-label, prospective clinical observational study, where patients are divided into two 
groups. One group patients with sufficient urine production and dialysis performed solely to 
"purify" the blood, and another group without or with minimal urine production, who, in 
addition to blood purification, are in need of a significant fluid removal. 
 
Number of Patients  
The study population consists of 15 patients with minimal fluid removal during dialysis and 
15 patients in need of fluid removal exceeding 2000 ml. 
According to earlier experience, 15 patients in each group should be sufficient to clearly 
observe a pattern in fluid recruitment from the tissues (lymph or pericapillary fluid). For 80% 
power at 25% difference in fluid recruitment balance between the groups and a standard 
deviation of 20%, at least 11 patients should be recruited to each group to achieve a 
significance level below 0.05 with a T-test or Wilcoxon (if the material is not normally 
distributed). 
 
Recruitment and Consent  
Patients receiving hemodialysis regularly at the dialysis department at Vrinnevi Hospital in 
Norrköping are screened if they are expected to meet the inclusion criteria for the study. 
Those who meet the inclusion criteria and have no exclusion criteria to participate are asked 
for participation and consent. Consent is obtained by one of the investigators 
verbally and in writing, during a hemodialysis session prior to the actual study procedure. 
 
Inclusion Criteria: 
Patients receiving hemodialysis (<500 ml or >2000 ml ultrafiltration): 
Signed informed consent that the patient accepts participation in the study after oral and 
written information.  
 
 
Exclusion Criteria: 
Patients who may be affected by blood sampling, i.e., have low hemoglobin concentration, 
independent of dilution before dialysis (Hemoglobine 85 g/L). 

 
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Patients who drink large amounts of water during regular dialysis (> 2 glasses, approximately 
0.4 L). 
The study is discontinued in case of a severe reaction (even if not related to the study), such as 
the need to interrupt dialysis. The patient or participant may also choose to discontinue 
participation in the study at any time. 
 
 
 
Intervention and Procedures 
Patients in need of dialysis and who regularly undergo dialysis at the dialysis unit at Vrinnevi 
Hospital in Norrköping are asked to participate in the study. Patients who are eligible are 
those who have fluid removal of either <500 ml or >2000 ml. These patients are approached 
during a routine dialysis visit to the dialysis unit. If the response is positive, a trial session is 
planned for a later date. 
 
Before dialysis begins, the patient is weighed. Then, the regular dialysis procedure starts, with 
the dialysis machine being connected. At the same time, Bioimpedance is also connected to 
the patient, and values for lean body mass (LBM), fat mass (FM), ECV, and ICV are 
recorded. Pulse and blood pressure are also recorded. Once the dialysis machine is connected 
with an intravenous access, the first blood samples, i.e., "zero samples," are taken. Dialysis 
then commences. 
 
The selected dialysate is recorded, as well as the continuous fluid removal and blood pressure. 
Blood samples are taken every 30 minutes for 150 minutes (Hb, hematocrit, albumin, 
Immunoglobulins G and M, and colloid osmotic pressure (COP)), bioimpedance values are 
recorded, and pulse and blood pressure are registered. This continues until the end of dialysis. 
At the end of dialysis, the final samples and measurements are taken. The patient is weighed 
once again. 
 
Fluid intake if it occurs is also recorded. When the patient leaves the dialysis unit, the study 
concludes. 
 
In case of pressure drops, these are treated in the usual manner, i.e., the patient is placed in the 
Trendelenburg position or supplemented with Albumin 20%. Measures are recorded. 
 
In total, blood sampling amounts to approximately 50 ml, at most 75 ml, equivalent to 3 to 5 
tablespoons.  
 
 
 
 
 

 
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Measurements 
Weight is taken before and after dialysis. 
Bioimpedance is connected and values for body composition, i.e., lean body mass (LBM), fat 
mass (FM), ECV, and ICV are recorded before and after dialysis, as well as during blood 
sampling. 
Hb, albumin, Ig G + M, and COP are measured and analysed before, at 1, 30, 60, 90, 120, and 
possibly at 150 minutes after the initiation of hemodialysis, as well as at the end of dialysis. 
These samples are taken from the access (cannula) used during dialysis. Therefore, no 
additional punctures are needed. 
Fluid removal and any spontaneous diuresis are recorded. Patients with spontaneous diuresis 
are asked to urinate before and after dialysis. 
Oral fluids consumed during dialysis are recorded. 
 
Risk- Benefit assessment 
Disadvantage for patients is a loss of approximately 50 to 75 ml of blood, which corresponds 
to half a decilitre of blood (3 to 5 tablespoons) (about 1% of the total blood volume). In 
connection with the study, there is enhanced monitoring, and the closer pressure and pulse 
controls can detect an impending drop in blood pressure slightly earlier. 
The advantage of the study is more long-term. The study contributes to mapping how the 
recruitment of fluid/oedema from the interstitium occurs. Consequently, one should be able to 
more easily predict potential drops in blood pressure by taking take preventive measures such 
as adjusting composition of dialysate and rate at which the hemodialysis is performed. 
 
Treatment and administration of other medications 
Hemodialysis is performed according to standard procedures. No restrictions on the 
administration of medications or treatments will be made, except for a selection of patients 
who do not drink more than 2 glasses, approximately 0.4 litres of water, during regular 
dialysis sessions. 
The study does not affect the patient's ongoing care or management. 
 
Studied data/Registration of effects 
Changes in Hemoglobine, albumin, and COP during hemodialysis 
Changes in plasma volume are calculated partly using changes in Hemoglobin and partly 
using Mass Balance calculations. 
Once all samples are analyzed, any remaining blood/plasma is destroyed. 
 
 
 
 
 

 
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Mass balance 
Plasma volume. Initial blood volume calculated with the Nadler formula 7.  
BV0, based on height h, (meters), weight w (kg) and gender.  
 
Men:  𝐵𝑉0  =  0.3669  ℎ3 +  0.03219  𝑤 +  0.6041 
Female: 𝐵𝑉0 =  0.3561  ℎ3 +  0.03308  𝑤 +  0.1833 
 
How mass balance calculations will be performed is described in a work on 5% albumin 
solution. 5,6. Total mass hemoglobin at study start is calculated from BV0 and hemoglobin at 
start of hemodialysis, Hb0; 7 
𝑀𝐻𝑏0  = 𝐵𝑉0  𝑥 𝐻𝑏0 
Blood volume (BV) at a later occasion, t, is calculated in a similar manor; 
𝐵𝑉𝑡= 𝑀𝐻𝑏𝑡
𝐻𝑏𝑡
 
Plasma volume (PV) is calculated; 
𝐵𝑉𝑡 (1 −𝐻𝑐𝑡𝑡) = 𝑃𝑉𝑡 
 
The percentage increase/decrease in plasma volume will then be (∆PV%); 
𝑃𝑉𝑡−𝑃𝑉0
𝑃𝑉0
×  100 = ∆𝑃𝑉% 
 
Recruited fluid (RE) from the tissue is based on the change in plasma volume and total 
diuresis/fluid removal. However, this volume must be corrected for diuresis and ingested fluid. 
𝑅𝐸 𝑒𝑥𝑡𝑟𝑎𝑣𝑎𝑠𝑐𝑢𝑙𝑎𝑟= 𝑈𝑙𝑡𝑟𝑎𝑓𝑖𝑙𝑡𝑟𝑎𝑡𝑒+ 𝐷𝑖𝑢𝑟𝑒𝑠𝑖𝑠−𝐼𝑛𝑔𝑒𝑠𝑡𝑒𝑑+ (𝑃𝑉𝑡−𝑃𝑉0) 
 
 
Statistics and Data Processing 
 
The study aims to follow a fluid kinetic process. In previous studies, we routinely used 10 
healthy subjects to study similar processes. This has been sufficient to describe clear trends 
and differences in how the body responds to fluid infusions. However, in this study, we 
increase the number of participants to fifteen in each group to even more clearly establish the 
processes. 
 
As there are only two groups to be compared, a t-test will primarily be used for the primary 
variable, i.e., the effect on plasma volume. For secondary variables, chi-square tests will be 
used. In the case of non-normally distributed data, Wilcoxon's test will be used instead. 
 
 
 
 
 
 
 
 

 
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Safety Regulation 
The study will be conducted according to the protocol and applicable regulations, LVFS 
2011:19, ICH GCP, and the latest version of the Helsinki Declaration. Patients will be 
monitored in the usual manner in the dialysis department. 
 
Quality Assurance 
 
- 
relevant health status data from medical records or health declaration 
- 
signed consent 
- 
The study is conducted in accordance with the protocol 
 
Study Director Joachim Zdolsek participated in a GCP course at Linköping University 
Hospital on April 25 - 26, 2007, and subsequently conducted several studies approved by the 
Medical Products Agency. 
 
 
Ethics 
Patients are approached for participation in a calm stage when they are receptive to 
information. If there is potential interest from the patient to participate, the study investigator 
informs the patient about the study. The responsible physician obtains the patient's written 
consent, and a copy of the signed consent form is provided to the patient. 
 
The care for the individual patient is minimally affected. Patients will not be impacted in any 
other way except for undergoing additional tests. However, it may be necessary to retrieve 
information from the medical record, which could potentially be seen as an intrusion into 
personal privacy. 
 
Participation in the study is noted in the medical record. 
 
The longer-term benefit of the study would be that through a better understanding of fluid 
dynamics, hemodialysis for dialysis-dependent patients could be tailored in a physiologically 
better way. 
 
 
Source Data/Original Data and Archiving 
Laboratory analyses (e.g., B-Hb, P-albumin...) conducted by the laboratory medicine 
department will be requested in printed form, so that they can be sorted into binders and used 
as reliable primary data when needed. Analyses conducted by the study group themselves 
(e.g., colloid osmotic pressure) will be immediately entered into the patient's Case Report 
Form (CRF) at the time of analysis. All study-related data (CRF and laboratory results) will 
be recorded in "CRF binders," with all collected information divided by individual patients. 
All CRF binders will be kept locked and only accessible to the trial team. 
 
As the data are entered into Excel spreadsheets (i.e., computerized), they will be de-identified. 
However, a source data verification list will be established. This list will only be accessible to 
the investigators. The Patient ID list, which is only accessible to the trial team, and other 
study-related documents will be archived and stored for at least 15 years after the end of the 
study. 
 
 
 

 
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Insurance 
Region Östergötlands insurances apply. 
 
 
 
Publications/Timeframe 
Joachim Zdolsek is primarily responsible for data collection and report writing. All 
investigators will have access to trial data and are expected to contribute to data analysis and 
report writing. Approximately one and a half years after study begin, we expect that all 
patients will have completed the study. Results, evaluation, and initial drafting are expected to 
take an additional 6 months to a year after the practical experiments have concluded. 
Subsequently, the time required for final reporting in the form of a published article is 
estimated to be at least another one and a half years. In total, the estimated time from the start 
of the study to its completion is expected to be approximately 3 to 4 years. The objective is to 
present the study results at an international congress and publish them in an international 
journal. 
 
 
Other collaborators 
Responsible for the practical part of the study in Norrköping are Erik Golsäter, Jonatan 
Bodare, Robert Svensson, and Fredrik Sundelin. Support functions and patient care will be 
handled by regular staff (nurses and nurse assistants). They will be thoroughly informed about 
the study. Joachim Zdolsek will write the project description and the ethics application. He 
will also assist with evaluation and writing, along with Professor Robert Hahn. 
 
Information and responsibility 
Joachim Zdolsek is responsible for study planning and design. 
Erik Golsäter and Jonatan Bodare are responsible for the practical management at the Dialysis 
Department in Norrköping. 
Relevant personnel in Norrköping will be informed by Erik Golsäter and Jonatan Bodare. 
 

 
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References: 
 
1) Njurförbundet, Annual report 2021. 
 
2) Davenport A. Why is intradialytic hypotension the commonest complication of outpatient 
dialysis treatments? Kidney Int Rep. 2023;((3):405-418 
 
3)  Donauer J., Kölblin D., Bek M., Krause A., Böhler J. Ultrafiltration profiling and 
measurement of relative blood volume as strategies to reduce hemodialysis-related side effects. 
Am J Kidney Dis. 2000;36:115–123. 
 
4) Zdolsek JH., Zdolsek M., Hahn RG. Recruitment of efferent lymph during infusion of 20% 
albumin. Microvascular Research 2023;148:104539 
 
5) Zdolsek M, Hahn RG, Zdolsek JH. Recruitment of extravascular fluid by hyperoncotic 
albumin. 
Acta Anaesthesiol Scand. 2018 Oct;62(9):1255-1260. doi: 10.1111/aas.13150. Epub 2018 May 
29 
 
6) Zdolsek M, Hahn RH, Sjöberg F, Zdolsek JH. Plasma volume expansion and capillary 
leakage of 20% albumin in burned patients and volunteers. 
Crit Care. 2020 May 5;24(1):191. doi: 10.1186/s13054-020-02855-0 
 
7) Nadler SB, Hidalgo JH, Bloch T. Prediction of blood volume in normal human adults. 
Surgery 1962 Feb;51(2):224-32. 
 
 
 
 

 
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Signed agreement 
 
I agree to the terms of this study protocol. The study will be performed according to the 
protocol and according to the principles of LVFS 2011:19, ICH GCP and the latest version of 
the Helsinki agreement. 
Jag accepterar villkoren I detta studieprotokoll. Studien kommer att genomföras enligt 
protokollet och gällande regelverket, LVFS 2011:19, ICH GCP och senaste versionen av 
Helsingforsdeklarationen. 
 
 
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Date 
                        
Principal investigator/sponsor