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PY Van, MD ? SD Cho, MD ? SJ Underwood, MS GJ Hamilton, BS ? LB Ham, MD ? MA Schreiber, MD - PowerPoint PPT Presentation


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Blood Volume Analysis Can Distinguish True Anemia from Hemodilution in Critically Ill Trauma Patients. PY Van, MD ∙ SD Cho, MD ∙ SJ Underwood, MS GJ Hamilton, BS ∙ LB Ham, MD ∙ MA Schreiber, MD. Background. Hemorrhage leading cause of preventable death in trauma victims

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slide1

Blood Volume Analysis Can Distinguish True Anemia from Hemodilution in Critically Ill Trauma Patients

PY Van, MD ∙ SD Cho, MD ∙ SJ Underwood, MS

GJ Hamilton, BS ∙ LB Ham, MD ∙ MA Schreiber, MD

background
Background
  • Hemorrhage leading cause of preventable death in trauma victims
  • Decreased peripheral hematocrit (pHct) used as marker for blood loss
  • pHct may not represent true red blood cell volume (RBCV)
background2
Background
  • Surrogate measures to deduce volume status
    • Vital signs and physical exam
    • Laboratory tests
    • Invasive monitoring
  • Experienced clinicians frequently wrong
    • 51% concordance with blood volume analysis

Androne, AS et al. Am J Cardiol 2004

blood volume analysis
Blood Volume Analysis
  • Indicator dilution principle
    • Known quantity of tracer injected into unknown volume (intravascular space)
    • After equilibration of tracer, plasma sampled
      • Concentration of tracer in sample is measured
      • Unknown volume is inversely proportional to concentration of tracer in the sample volume
      • Larger the unknown volume, more dilute the tracer
indicator dilution principle
Indicator Dilution Principle

C2

C1

=

V2

V1

Concentration of tracer injected

Unknown volume (plasma volume)

Conc. tracer in sample withdrawn

Volume of sample withdrawn

blood volume analysis1
Blood Volume Analysis
  • Single injection radiolabeled131I-albumin.
  • Serial blood samples drawn over 40 minutes
  • Analysis yields actual and ideal TBV, RBCV, PV
blood volume analysis2
Blood Volume Analysis

RBCV

=

pHct

+

PV

RBCV

TBV = RBCV + PV

blood volume analysis3
Blood Volume Analysis
  • Normalized hematocrit (nHct)
    • pHct is adjusted for volume derangement:

Measured TBV

nHct =

pHct x

Ideal TBV

hypothesis
Hypothesis

Use of pHct alone in critically ill trauma patients will result in over-diagnosis of anemia

methods
Methods
  • Trauma ICU pts recruited 24hrs post admission
  • Baseline blood sample
  • Injection of 1mL 25 µCi of 131I-albumin
  • 12 minute equilibration period
    • Then 5 serial blood draws, 6 minutes apart
  • Samples processed on BVA-100 Blood Volume Analyzer (Daxor Corporation, NY, NY)
methods1
Methods

Measured volumes compared to ideal -- percent deviation from ideal calculated

methods2
Methods
  • Pts stratified into 3 groups based on deviation from ideal total blood volume
    • Hypovolemic: > 8% deficit relative to ideal
    • Normovolemic: < 8% variation relative to ideal
    • Hypervolemic: > 8% excess relative to ideal
characteristics
Characteristics

All values are mean ± standard deviation

volume status and fluids
Volume Status and Fluids

All values are medians (interquartile range)

All p = NS, Mann-Whitney U test

No significant difference in volume of fluids given or net fluid balance between each volume status

results1
Results
  • No linear correlation between net fluid balance and changes in TBV, RBCV, and PV between each analysis
  • Moderate linear correlation between pHct and RBCV (R2 = 0.3)
results2
Results
  • No differences in ISS when compared across the volume status groups
  • No correlation between ISS and rate of albumin transudation
phct versus nhct
pHct versus nHct

Paired t-test

* p < 0.05

Chi-squared

† p < 0.05

conclusions
Conclusions
  • Assessing volume status is challenging
  • No differences in amount of fluids administered to volume status groups
  • pHct compared to nHct
    • Overestimates anemia in hypervolemic pts
    • Underestimates anemia in hypovolemic pts
limitations
Limitations
  • Preliminary study -- small number of patients
  • BVA not a dynamic test – snapshot in time
  • Assume RBCV constant during testing
    • Not reasonable if bleeding > 100mL/hr
  • Availability of tracer and personnel
future directions
Future Directions
  • Further characterize effects of fluid and blood product administration on volume status
  • Blood volume analysis upon ICU admission
    • Establish baseline
    • Initiate therapies based on blood volumes
    • Avoid unnecessary CT scans and transfusion when BVA shows low pHct due to hemodilution