Blood volume monitoring a crucial step in reducing mortality
By Anne Diroll, RN, CNN
Article from Hema Metrics, manufacturer of the Crit Line device.
Ms. Diroll teaches and trains blood volume monitoring in her role as a clinical support specialist
for Hema Metrics, based in Salt Lake City, Utah. Hema Metrics manufactures the Crit Line, a
device that monitors blood volume during dialysis. “It’s easy to adjust the labs. What good is it if you have good numbers, but everyone’s dying or
in the hospital?”
This is a quote from former dialysis administrator Joseph Atkins in The Atlantic article, “God
Help You. You’re on Dialysis,” written by Robin Fields.
1
It was one of four articles prepared and
written by Fields investigating quality of care within the End-Stage Renal Disease Program.
According to the United States Renal Data System, rates of mortality due to congestive heart
failure are growing. This mortality rate rose 7% between 2000 and 2006, while mortality due to
atherosclerotic heart disease fell 51%, and mortality due to acute myocardial infarction fell
42%. Commentary from the USRDS 2008 annual data report states: “In light of multiple new
strategies for treating CHF in the general population, reasons for this growth are unclear.”
The 2009 ADR for children with end-stage renal disease is even worse. There has been no
progress in the five-year survival of pediatric patients over the last decade. Infectious and
cardiovascular complications are high, with the latter being the main cause of death in this
young population. High heart failure rates may reflect long-term burden of hypertension and
fluid overload.
In 2006, the adult population’s cardiovascular admissions increased 8% overall. These rates
were up 27% in the 20-44 year old age group, and up 53% in pediatric patients. Cardiovascular
admissions were also up 20% among Blacks with ESRD.
2
Lab tests don’t tell the story
Currently the lab tests, to which Mr. Atkins refers, include Kt/V, urea reduction ratio and
hemoglobin. Targets achieved for the former are 93%, and for the latter 83%. Yet in spite of
“adequate” dialysis, based on these labs, 50% patients continue to exhibit left ventricular
hypertrophy (LVH). One of the drivers of increased left ventricular mass is small increases in
extracellular volume. As noted by Glassock et al., persistence of vascular volume increase is due
to excess salt intake and inadequate ultrafiltration. The major factor in the failure of LVH to
regress is persistence of volume overload and hypertension, Glassock and colleagues wrote.
3
Inadequate anemia management seems to play a minor role – yet reimbursement has
monetized the use of erythropoiesis stimulating agents. Poor control of intravascular volume,
persisting hypertension, and aortic stiffness are the dominant causes of LVH. Updated markers needed
To identify LVH earlier, it seems that the markers for adequate dialysis need updating. Currently
lab emphasis is on solute removal and anemia management. Healthy kidneys also regulate
sodium and water. Nephrologists Sinha and Agarwal have suggested echo, blood volume
monitoring, and N-terminal-proBNP to better monitor kidney function.
4
Researchers involved
in the DRIP study, which involved desensitization of highly pre-sensitized dialysis patients
waiting for kidney transplantation using Rituximab, Intravenous Immunoglobulin-L (IVIG-L) and
rescue plasmapheresis (AMC-DRIP), also incorporated blood volume monitoring. Their data
provide support for the hypothesis that extracellular volume expansion, even in the absence of
clinical signs of volume overload, may mediate hypertension.
5
They have also validated the use
of relative plasma volume (RPV) monitoring as a marker of dry weight. They found that flat RPV
slopes suggest a volume overloaded state.
As they note, RPV monitoring is relatively easy, commercially available, and inexpensive.
6
Agarwal has subsequently demonstrated that flatter RPV slopes identifying hypervolemia are of
prognostic value. This is significant in that 217 hospitalizations per 1,000 patient years are
attributed to congestive heart failure.
7
Reddan et al.
8
concluded that IBVM was associated with higher nonvascular and vascular
access-related hospitalizations and mortality compared with conventional monitoring. BVM led
to higher non-volume related hospitalizations. Mortality over six months was greater in the
BVM group than the conventional monitoring group (8.7 and 3.3% respectively).
The stable UF profiles and volume surrogates suggest that BVM did not result in an aggressive
change in UF. Before intervention, 69% and 68% of patients in the BVM group, and
conventional monitoring group, had a 3% to 8% change in intravascular volume. After
intervention, 68% and 65% of patients in the BVM and conventional monitoring groups had a
3% to 8% change in intravascular volume. Stability of volume surrogates across treatment
groups supports that the availability of BVM did not systematically alter net ultrafiltration.
Predialysis systolic BPs were 151.8 (+/- 26.9) in the BVM group, and 152.7 (+/- 27.1) in the
conventional group. Predialysis diastolic BPs were 82.0 (+/- 16.2) in the BVM group, and 80.4
(+/- 15.2) in the conventional group.
8
However, as Agarwal stated, the uncertain adherence to the protocol makes it difficult to
conclude that RPV monitoring was the cause of the higher complication rates.
7
A monitoring
and intervention algorithm was developed. Algorithm use was encouraged but not mandated in
a trial that permitted the voluntary non-use of the information from the BVM device. BVM
monitoring was studied as a voluntary adjunct to care.
In a subsequent study, Rodriguez et al., used the same intervention algorithm. The difference
being that intervention was mandated, not voluntary. Voluntary non-use of the information
was not permitted. Thus, 10 of the 13 patients who had DW reduced by >1kg, had a decrease in
BP. There was a mean reduction of 17 mmHg for SBP, and a 13 mmHg for DBP (157/81 prestudy vs. 140/68 post-study). In the Reddan study, BPs remained unchanged. In the Rodriguez
study, hospitalizations for fluid overload were reduced from 15 admissions in the 12 months prior to prescriptive use of BVM to 1 admission in the 18 months following the regular
prescriptive use of BVM.
9
Summary
Weir articulates it best in his editorial commentary in Hypertension: “Ultimately, the main goal
of treatment of blood pressure is to prevent cardiac events. Perhaps the most important
strategy in the dialysis patient is to achieve an appropriate dry weight, minimize volume
overload, and use blood pressure–lowering medications only in the setting of ‘hypertension’
when dry weight is truly probed and demonstrated. It is possible that if more patients achieved
dry weight, then less antihypertensive medication would be required, as is observed in patients
on longer-session nocturnal hemodialysis. I suspect that long-term volume/pressure overload
of the left ventricle, because of inadequate achievement of dry weight, may be one of the most
important cardiovascular concerns in the hemodialysis patient.”
10
I do believe euvolemia is possible. In the Grass Valley study (Rodriguez et al), we evaluated
post-dialytic vascular compartment refill. After deciding that refill could be evaluated after 10
minutes of ultrafiltration in minimum (200mL/hour), we used the following steps.
Step 1. Note hematocrit
Step 2. Place UF in minimum
Step 3. Wait 10 minutes
Step 4. Note hematocrit
If hematocrit declines by 0.5 or more in 10 minutes, patient has refill, and is “not dry.” If
hematocrit declines by 0.4 or less in 10 minutes, patient is "vascularly dry." If additional fluid is
available, and willing to shift from the extracellular compartment to the intravascular
compartment, it will decrease the hematocrit by hemodilution, hence the "not dry" patient has
a decline in hematocrit in the absence of ultrafiltration.
Blood Postdialytic Sx of hypovolemia/ Dry weight
Volume vascular postdialysis fatigue change
Reduction refill
Yes No No No
Yes No Yes Revise up
Yes Yes No Revise down
Yes Yes Yes Revise down
No No No Revise down
Mathematically, blood volume is a function of both ultrafiltration and plasma refilling. As Boyle
& Sobotka noted, the hypothesis of titrating decongestion therapy to reduce interstitial edema
without embarrassing intravascular volume is applicable to all forms of decongestion therapy.
Using hemoconcentration as a surrogate for PRR is amenable to therapies in which there is
continuous access to blood such as ultrafiltration. References
1. Fields R. God help you. You’re on dialysis. The Atlantic 2010, 306:5: 82-92
2. Annual Data Reports, 2008 and 2009. U.S. Renal Data System, Atlas of Chronic Kidney Disease
and End-Stage Renal Disease in the United States, National Institutes of Health, National
Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Md.
3.Glassock RJ, Pecoits-Filho R, Barbareto S. Increased left ventricular mass in chronic kidney
disease and end-stage renal disease: What are the implications? Dialysis &Transplantation 2010
39:1:16-19
4. Sinha AD, Agarwal R. The pitfalls of the clinical examination in assessing volume status.
Seminars in Dialysis 2009 DOI: 10.1111/j/1525-139X/2009/0087641.x
5. Agarwal R, Alborzi P, Satyan S, Light RP. Dry-weight reduction in hypertensive
hemodialysis patients (DRIP): A randomized, controlled trial. Hypertension. 2009:53:500-507
6. Sinha AD, Light RP, Agarwal R. Relative plasma volume monitoring during hemodialysis
aids in the assessment of dry weight. Hypertension. 2010;55:305-311
7. Agarwal R. Hypervolemia is associated with increased mortality among hemodialysis
patients. Hypertension, published online Jul 12, 2010;
http://hyper.ahajournals.org8. Reddan DN et al. Intradialytic blood volume monitoring in ambulatory hemodialysis patients:
A randomized trial. J Am Soc Nephrol 2005:16:2162-2169
9. Rodriguez HJ, Domenici R, Diroll A, Goykhman I. Assessment of dry weight by monitoring
changes in blood volume during hemodialysis using Crit Line. Kidney Int. 2005; 68:854-861
10. Weir M. Relative plasma volume monitoring and blood pressure control: An overlooked
opportunity to achieve dry weight in the hemodialysis patient. Hypertension 2010;55:226-227
11. Boyle A, Sobotka P. Redefining the Therapeutic Objective in Decompensated Heart Failure:
Hemoconcentration as a Surrogate for Plasma Refill Rate Journal of Cardiac Failure Vol. 12 No.
4 200
http://hemametrics.com/PressRelease/Outcomes%20(2)_02_11rev-1_(AD).pdf
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