Le. Kass et al., PROSPECTIVE CROSSOVER STUDY OF THE EFFECT OF PHLEBOTOMY AND INTRAVENOUS CRYSTALLOID ON HEMATOCRIT, Academic emergency medicine, 4(3), 1997, pp. 198-201
Objective: To compare the changes in hematocrit (Hct) between phleboto
mized and nonphlebotomized individuals given IV crystalloid. Methods:
A prospective, crossover volunteer study was performed comparing Hct c
hanges immediately and 30 minutes after IV crystalloid bolus in 20 hea
lthy adults with and without prebolus phlebotomy. In the control porti
on, volunteers were given a 15-mL/kg bolus of normal saline over 30 mi
nutes with Hct determination before (H1), immediately after (H2), and
30 minutes after (H3) crystalloid infusion. At least 7 days later, the
same subjects were phlebotomized 1 unit of blood and then administere
d a 15-mL/kg IV bolus of normal saline 30 minutes later. Hcts were obt
ained before (H4) and 30 minutes after (H5) phlebotomy (immediately pr
ior to crystalloid infusion). Hcts were also obtained immediately afte
r (H6) and 30 minutes after (H7) crystalloid infusion. A post-hoc test
performance analysis was then performed to determine the Hct drop thr
esholds that would yield the maximal sensitivity and specificity for 5
00 mL of blood loss (via phlebotomy) in this population. Results: The
Hct (%) drops in the nonphlebotomized individuals receiving IV fluids
averaged 4.5 +/- 1.3 immediately and 3.2 +/- 1.3 30 minutes after infu
sion. These drops were different (p < 0.05) from the Hct drop in indiv
iduals receiving IV fluids after phlebotomy, which averaged 6.6 +/- 1.
5 and 5.7 +/- 1.1, respectively Post-hoc analysis revealed that Hct dr
ops of 5.4 immediately, or 4.3 at 30 minutes after infusion, had a sen
sitivity of >90% and a specificity of 75% for identification of patien
ts in the phlebotomy group. Conclusions: The practice of measuring ser
ial Hcts may be helpful to identify trauma patients with occult blood
loss. A prospective clinical trial is needed to validate these Hct dro
p thresholds (immediate and 30 minutes postinfusion) in crystalloid-re
suscitated trauma patients.