Plasma volume by Evans blue: Effects of eating and comparison
with other methods at altitude
Loeppky JA, Luther DK, Maes D, Riboni K, Hinghofer-Szalkay H, Charlton
GA, Icenogle MV
AVIATION SPACE AND ENVIRONMENTAL MEDICINE
73 (9): 902-906 SEP 2002
Abstract:
Hypothesis: Measurements of plasma volume (PV) and its changes (Delta%PV)
by Evans blue (EB) dye are presumed to be valid only in fasting subjects.
In addition, Delta%PVEB with acute altitude exposure has not been compared
with other methods employing the concentration or dilution of naturally occurring
blood (hematocrit (Hct), hemoglobin (Hb)) and plasma (density, proteins)
components, but should be similar if capillary permeability and the sampled
vein/whole body Hct ratio remain unchanged. Methods. PVEB was determined
in six subjects while fasting or eating on different days, with injection
and sampling in the same arm, 4-h extrapolation to time zero and correcting
readings with the 620-740 lambda method. For 93 experiments at altitude,
Delta%PVEB was obtained similarly from a 3-h extrapolation near the end of
a 12-h chamber exposure to 426 mm Hg (approximate to4880 m =16,000 ft) and
at the same time on the preceding control day. Results. Mean PVEB with and
without eating was not significantly different (SE of absolute difference
= +/-2.8%). The EB decay curves had significantly more scatter with eating
than fasting. The fasting vs. non-fasting values for the single 20-min post-injection
point also gave a close comparison (r = +0.97). At altitude the loss in PV
measured with EB was significantly greater (Delta%PVEB = -6.3%) than losses
estimated from Hct-Hb (-2.9%), plasma protein (-3.7%), and plasma density
(-3.9%). The expected larger PV loss in subjects tolerant to altitude sickness
compared with intolerant ones was most clearly shown by Delta%PVEB (8.8%).
Conclusions. Obtaining more samples can offset reproducibility lost by eating.
The Delta%PVEB were largest and nearest to values previously reported at altitude,
perhaps because the single baseline and altitude samples utilized by the
other methods are more sensitive to subtle, transient fluctuations in body
water and vasomotor tone associated with apprehension, vomiting, fluid intake,
and regional vasodilation and constriction.
Author Keywords:
altitude exposure, albumin space, Evans blue, fasting, hypoxic diuresis,
plasma volume
KeyWords Plus:
ACUTE MOUNTAIN-SICKNESS, EXERCISE, HYPOXIA
Addresses:
Loeppky JA, New Mexico Resonance, C-1,2301 Yale Blvd SE, Albuquerque, NM
87106 USA
New Mexico Resonance, Albuquerque, NM 87106 USA
Lovelace Resp Res Inst, Albuquerque, NM USA
Graz Univ, Sch Med, Dept Physiol, A-8010 Graz, Austria
Vet Affairs Med Ctr, Cardiol Sect, Albuquerque, NM USA