Measurement of Blood Volume Loss During Burn Surgery

Burn surgery is associated with significant changes (reductions) in hematocrit. However, it
is unclear whether these reductions are the result of hemodilution from non-red cell
containing intraoperative transfusions or from loss of red blood cells. The investigators
will be using the Daxor Blood Volume Analyzer (BVA-100), an FDA approved instrument that can
measure total blood volume, plasma volume, and RBC volume using the indicator dilution
technique. With this technique, a tracer substance (I-131 albumin) is mixed with an unknown
volume. An identical amount of the tracer is mixed into a solution with a known volume. By
comparing the concentration of the indicator between the known and unknown volumes, the
investigators can determine the volume of the unknown volume (or in this case, the blood
volume).

The investigators will be measuring the change in blood volume, plasma volume, and RBC volume
from the pre-operative to the post-operative state after completion of burn surgery. We
hypothesize that these reductions in hematocrit are primarily the result of hemodilution
rather than blood loss and that there will be a statistically significant change in measured
plasma volume from the pre-operative to the post-operative measurements.

Average plasma volume for male and female patients is 2950ml SD=590 ml. To detect a 10%
increase in plasma volume from hemodilution with a power 0.80 and alpha error 0.05, a one
tailed normal distribution t-test determines a sample size fifty. To account for a 10% data
loss (technical difficulty, patient withdraw) a sample size of fifty-five would be required.

Fifty-five consecutive adult patients (18 years or older) having burn surgery will be
enrolled. Patients with recognized coagulopathy will be excluded. The outcome variables
included blood volume (BV, ml), plasma volume (PV, ml) and red blood cell volume (RBCV, ml).
All three outcome variables will be measured at two time points; pre-surgery and
post-surgery. The pre-surgery measurement will be collected precisely after induction of
general anesthesia but prior to surgery start. The post-surgery measurement will be taken
immediately after the operation and after all intraoperative red blood cell transfusions are
complete. For those patients receiving blood transfusions in the operating room prior to all
data collection points, the transfused RBC volume will be recorded and subtracted from the
RBCV measured after the transfusion. Transfused RBCV will take into account Hct of 60% for
pRBCs. Additional baseline information, including age (year), sex (male, female), weight
(kg), and surgery type, will be collected. For the tracer dilution method, the following
blood samples will be collected: a baseline (no radiation sample), a first sample 12 minutes
after injection (after complete mixing in the blood volume) and additional samples every 6
minutes for at least three successive timed sample points. These multiple timed sample points
produce a logarithmic curve of radiation over time, as only a small fraction of albumin
leaves the blood volume into the interstitial space. The investigators will compare the
pre-operative and post-operative blood volume, RBC volume, and plasma volume measurements to
determine if the decrease in hematocrit associated with burn surgery is truly due to
hemodilution or loss of RBC volume.

Inclusion Criteria:

- Sustained thermal burn of a depth that is deep partial thickness to full thickness and
requires operative management

- Burn excision must occur within one week of thermal injury

- Burn size between 10-50% of total body surface area

- Must survive initial resuscitation

- Must consent for blood product transfusion

- Male or non-pregnant female

Exclusion Criteria:

- Cause of burn other than thermal injury (ie electrical or chemical injury)

- Women who are nursing, pregnant, or think they may be pregnant

- Patients with recognized coagulopathy