r
340
RB. WENNESLAND ET AL.
a
Table Hl. Average Hematocrit and Cell
Volume (Vrbc) of Blood Samples Collected
10, 20 and 30 Minutes after Injection of
Teyged Celis in 27 Healthy Men.
Time of
:
.
Hematocrit
Sempling
%, cella
10
20
30
44.54
44.41
44.56
Vebc
i
2.06
2.06
205
IV sahaa os
Errors in collection and timing of blood
samples. 1. The indwelling needle. This has
the further advantage of obviating hemocon-
a ee
centration resulting from repeated veni-
puncture and tourniquet applications, The
phenomenon of “spontaneous hemodilution
following venipuncture”, which has been de-
scribed repeatedly (Gibson & Evans 1937;
Hanna & Marshall 1955) and has been observed by us under different circumstances
(Brown, Hopper, Sampson & Mudrick
1958), is nut found with this procedure. In
27 experiments, samples were taken 10, 20
and 30 minutes after delivering the cells. No
downward trend of the hematocrit readings
was observed (Table I).
Two suspicions arise about the indwelling
needle and the infusion apparatus; a) that
We la.
blow drawn for sampling might be contaminated by accumulation of Cr! in the needle
and vein near the site of injection and b)
that the samples taken shortly after discontinuation of the infusion might be coutaminated with saline. The following exprri-
sample was taken from a distant vein, with
care to avoid the effects of tourniquet Stasig
(bloud taken no less than 30 seconds after
releasing tourniquet; first 2 ml discarded).
Table ILI shows that the Vrbc determineg
from blood takenfrom separate sites was th.
same although the hematocrits of blood from
the freshly punctured veins averaged 1 scaje
division higher. To test whether the differ.
ence resulted from contamination with saline
from the infusion apparatus, we compareg
the hematocrits of two successive 6 my
samples taken from the same needle after
discontinuation of the infusion. In 15 experi.
mens, the first sample was not significantly
more dilute than the second (Table IV),
Thus, it appears that the indwelling needle
can be employed without fear uf contamina.
tion of the samples by either saline or Crt,
It has long been known that. significant
hemuconcentration can occur when blood js
taken during the application of tourniquets
(Peters, Eiseuman & Dulper 1925). When
no particular care was taken to prevent
stasis, ¢. y., when blanks were drawn tou de-
Table HII. Results of Measurements on
Blood Samples Collected from als Indwhelirag
Needle and from a Newly Placed Needte
a Distant Veig in 32 Experiments.
————
|
‘
Speciinen Collected from:
{
[in weiling [Newly Placed]
Neédle
i
~—e ae
| Mean]
ments were therefure done.
In 19 tests, one sample (was. takep [from Hematocrit
°%cells
45.30
the mdwelling needle in th ff
(inVibe, litera
2.08}
fusion discontinued for 30 col
nd the Vel, liters
2.52
first 2 mal oy rded). A’ second °
7
~
“
,
Needle
Differ.
°"*
——
ermine residual radioactivity from earher
O41
2.42
0.37
1.10/97
0.00)"
o.10
the 3 samples in a single experiment in this
series, however, was significantly higher than
jon was aS much as 7.8 scale divisions (aver-
samples were taken at 25, 30 and 35 minutes
measurement is based on the radioactivity
periments). As long as at least 10 minutes
are allowed for mixing and the subject has no
circulatory disorder, errors due lo premature
gastically elevated. In one case, the eleva-
in a succeeding 103 experiments in’ which
gn 87 cases, 2.5). This artifact does not
gilect the determination of Vrhe since the
(S.D. of a single reading = 52 mi in the
first 27, and 36 ml in the succeeding 103 ex-
gad dhe hematocrit of the same sainple. The
derived values, Vpl and Vwb, however, can
pe seriously affected (Table fH).
2, Time and number of samples. In direct
dterminations of Vpl based ou a single
ample, 10 minutes is usually cousidered an
glequate mixing time (Noble & Giregersen,
1946). However, three recent studies mivoly-’
ing the use of rapid multiple sampling: have
shown that fluctuations in thé concentration
of tagged cells or radioactive iodinated albumin may continue for fouper than JO mautes, and even as long as 25 minutes, after
injection of tags, -even in healthy subjects
(Pritchard, Moir & MacIntyre 1955; Funk-
sampling not be larger than I—2 per cent
(Noble & Gregersen £946). We prefer to
wait 25 minutes or longer for the reasons
outlined above and because there is no pro-
btem with toss of tag when using Cr!
Three samples were taken at S-minute
intervals in 103 experiments on healthy men
(Weinesland et af, 1959). Analysis of the
differences between idividual results showed,
for Vibx,
standard deviation of a single value
= Joni,
standard error of mean of 3 values
hauser 1957; Tuckmao, Fianerty & Huch-
plz }959). In 27 caperiments in which
‘amples’ were taken 10, 20 and 30 minutes
alter injection of the tagged cells, mean Virbe
was the same at each sampling time (Table
If}. The variation in ruhoactivity between
== 2b mb
These volumes are small in) comparison
with the standard deviations of the mean
predicted cell volumes for men and women,
10 and 134 ml, respectively (Wennesland
vi al
\ Table IV. Hematocrits of Tiea Suecesstve
6ml Samples of Hluod Laken from Endivethng Necdle after Ditcontinaing the Saline
Infusion mo 15 fo vpersients.
a
S.D.| Mean] 5 D. [Means
330]
O31
Jol
riments, the hematocrit was sometimes
a
TTT
3.40 [46.40
030} 2081
CRO aE ite OR DETERMINATION OF- RED CELL VOLUALE
‘Hematocra, "i cells
First sample
Mean
Renge
5D.
422
38.0-44.0
43
Second
saraple
423
380-41
a4
Dilfercnce
4008
-03- 108
0.27
1999, Drown et af). The SD. of a
staple value, $0 mb, represents tess than half
of the mean difference between results of
repeated measurements on
individual sub-
jects, BO CRable VO). Thus, the result
obtained from a single sample ts accurate
cuouh for inost clinical work; we take 2
sunples, primarily as a safeguard agatnst
loss or breakage, anc averaye the results.
Mixing may be delayed ta an important
depree am a number of pathological conditions, and premature sampling gives spur-