THE CHOICE OF BLOOD DONOR
The physiology of blood groups having been examined, the principles
governing the choice of a blood donor can be more readily understood.
It is evident that this choice is determined largely by blood groups,
and in the present chapter therefore the clinical methods of testing
for the groups will be described.
Before, however, the bloods can be tested, a willing donor must
be found, and this is not always an easy matter. During the war,
even when transfusion was being practised on a large scale, there
was never any difficulty in finding volunteers among the men that
were more lightly wounded. In addition to the genuine and ready
response which many men would make at once to a call for help in a
matter of life and death, there was the glamour of novelty and the
feeling of satisfaction following an act of conscious heroism--for
such the sacrifice of blood was held to be, the days having long
been forgotten when as much blood was “let” in the treatment of
almost any ailment. In the Expeditionary Force, too, the unofficial
reward of a fortnight’s leave in England proved a potent inducement,
and the rejection of a volunteer on the ground of incompatibility
was regarded almost as an injustice or as a reflection upon the
physical condition of the candidate. In civilian life, however, such
inducements cannot be held out, and it will be found that many a
man “does not like the idea” of parting with a pint of blood, even
though the sacrifice may save another’s life. Often, however, a
near relative of the patient may happen to be willing and suitable,
or, failing this, in a hospital ward there will usually be some
young man who has been admitted for a slight operation, such as the
radical cure of a hernia, and will accede to a request for blood
if the procedure, its object, and its harmlessness to himself be
briefly explained. Notoriety is fortunately seldom a motive for
volunteering, and though paragraphs have occasionally appeared in the
daily press with headings such as “Police Inspector’s Sacrifice,”
this has probably not been done by the donor’s own wish. It is, after
all, natural that to the mind of a layman the giving to another of
so personal a possession as his blood should seem to be an act of
heroism, and it is also natural that occasionally a man should feel
some repugnance to taking part in a strange performance which he but
dimly understands. To the young, on the other hand, the procedure may
appeal by its faint flavour of adventure.
Occasionally during the last two years advertisements for blood
donors have appeared in newspapers, probably not in vain. If the
demand for blood donors becomes greater than it has been as yet, it
will certainly result in the creation of a class of “professional
blood donors,” who already exist in some numbers in the United States
of America, where blood transfusion is a more widely recognized form
of therapeutics than it is in this country. These professionals have
even formed a Trade Union, so that as high a fee as possible may be
obtained from those who need their blood. Apart from this, some of
the advantages of having these professionals available have already
been explained in the chapter on the dangers of blood transfusion.
It is evident that certain sources of danger can be eliminated in
advance, and in an emergency it is obviously better to have donors
of known groups available, so that no time is lost in testing the
prospective donors of whom several in succession may be found
unsuitable. Probably it will be easier for practitioners to arrange
for such professionals to be available at the shortest notice than
for necessary arrangements to be made in a hospital. Even in large
institutions it is usually difficult for any of the men employed in
them to be spared from their work for twenty-four hours, so that,
although suitable men of known groups are always within call, it may
be impossible to use them. This, however, is not the place to discuss
the organization that is necessary to make a blood transfusion a
really efficient form of emergency treatment in a hospital. It may
merely be observed that in every hospital it should be possible
to give a blood transfusion to a patient suffering from urgent
hæmorrhage within fifteen minutes of his arrival on the premises.
Whether the donor be a “professional” or an “amateur,” it may be
useful to mention a few points to be observed in choosing him. There
can be no doubt that the most satisfactory individuals for the
purpose are young men between the ages of eighteen and twenty-five.
The younger the donor, the less likely is he to be suffering from
certain of the diseases mentioned in the chapter on the dangers, the
less will be the immediate effect of the withdrawal of circulating
fluid, and the more quickly will he recuperate from the loss of blood.
It must not be supposed, however, that the withdrawal of even 1,000
cc. of blood will usually have an appreciable effect upon a healthy
man. It is impossible to predict from the donor’s appearance what
immediate effect the loss of blood will have upon him. It sometimes
happens that the most robust-looking individual becomes faint after
losing a few hundred cubic centimetres, whereas another, to all
appearances pallid and much less satisfactory, will not evince the
slightest discomfort from the loss of 750 cc. or even more. Normally
a man should be able, by his physiological mechanisms, to compensate
reflexly and at once for the removal of this amount of fluid from
his circulation. In any case, the worst effect that is seen in a
well-chosen donor is a transient faintness; it is usually wise to
keep him on his back for two or three hours after the operation, and
he should not, if it can be avoided, return to his work on the same
day. During the late war a medical officer of my own acquaintance
gave 750 cc. of blood for a severely wounded friend and continued
his arduous duties as Surgical Specialist in a Casualty Clearing
Station immediately afterwards. In this case, however, the donor was
solely responsible for his own welfare; usually this responsibility
rests upon another, and greater care must be exercised. The effect,
indeed, of a transfusion upon the donor seems to depend more upon
psychological than upon physiological factors. A nervous and
excitable donor is more likely to suffer than one who approaches the
operation without apprehension. This is another point in favour of
employing a professional donor, who soon becomes familiar with the
whole procedure and will lose all symptoms of fear.
The same considerations may be applied to the use of women as blood
donors. In them the spirit of self-sacrifice is commonly more highly
developed than it is in men, and some of the most eager donors will
be found among them. The disability of nervousness will, however,
occur more often in women, and another consideration of importance
is that the veins of a woman are usually much less easily accessible
than those of a man. Not only is the abundant subcutaneous fat an
impediment in women, but usually the superficial veins are all of
small size. The method of choice for performing a blood transfusion
will be presently described, and it will then be seen that the
operation is easier and that much less damage is inflicted on the
donor if a large superficial vein can be tapped. In women this will
very often be difficult or even impossible. In general, therefore, it
may be stated that the use of women as blood donors is to be avoided.
The fallacies concerning the indiscriminate transfusion of an infant
with its mother’s blood and of any patient with the blood of a near
relation have already been explained.
TESTING FOR BLOOD GROUPS
Reference to the table of blood reactions given on p. 71 will show
that in order to discover the blood group of any individual it is
only necessary to test his corpuscles against the serum of Groups II
and III. These reactions may be recapitulated as follows:
(i) If he be Group I, his corpuscles will be agglutinated by the
serum of Groups II and III.
(ii) If he be Group II, his corpuscles will be agglutinated by the
serum of Group III only.
(iii) If he be Group III, his corpuscles will be agglutinated by
the serum of Group II only.
(iv) If he be Group IV, his corpuscles will be agglutinated by
neither serum.
Only the serum, therefore, collected from people known to belong
to Groups II and III need be kept in stock. This can generally
be obtained from the Lister Institute, and if kept sterile will
retain its agglutinating properties for some months, but under no
circumstances should serum more than six months old be used, since
the consequences of a failure to agglutinate may be very serious.
Nevertheless, the agglutinins contained in serum are very resistant
to physical and chemical changes in their environment. Dried serum
has been successfully used for testing purposes, and Culpepper has
shown that the reactions are not interfered with by cold or by
heat until actual coagulation of the serum takes place. Bacterial
contamination does not affect the reactions, so that the serum is
still active even when putrid. Various methods have been used for
preserving the serum. Its properties are not affected by the addition
of dilute cresol (1 : 250) or of chloroform.
In the absence of any stock sera, the agglutinating test may be
applied directly. A few cubic centimetres of blood are taken from
the patient, and the serum as soon as it has separated is tested
against the corpuscles of the prospective donor. If agglutination
occurs, this donor is at once excluded. If no agglutination occurs,
he is either of the same group as the patient or belongs to a
compatible group. Supposing that a donor actually of the same group
as the patient is wanted, then the reverse test must be performed
in addition, that is to say, the corpuscles of the patient must be
tested against the serum of the donor. If both tests are negative,
then donor and patient are proved to be of the same group. The method
of direct test cannot be applied in an emergency owing to the loss of
time involved; it is better, therefore, that anyone who intends to
be ready to perform a blood transfusion should always have serum of
Groups II and III immediately available.
The collection of stock sera is not a matter of any difficulty. With
strict aseptic precautions 20 cc. of blood are withdrawn in a syringe
from persons known to belong to Groups II and III; the bloods are put
into a sterile test-tube and allowed to clot. As soon as the serum
has separated it is drawn up into sterile glass bulbs of suitable
capacity, which are sealed off at each end. The most convenient
form of storage for actual use is a capillary glass tube sealed at
each end. Each tube may be made to hold a single drop, which is the
amount used for a test. There is then no wastage of serum, and no
chance of contaminating the remaining stock. When the blood has been
withdrawn and has clotted, the complete settling of the corpuscles
can be hastened by the use of the centrifuge. If the serum be left
in contact with the corpuscles for more than twelve hours, some
auto-hæmolysis may take place, so that the serum will become tinged
with hæmoglobin. It is exceedingly important that the two stock sera
should not become confused, and this may easily happen unless each
tube has some distinguishing mark.
The methods of testing for blood groups have been simplified by
successive observers since the existence of the groups was first
demonstrated in 1907. Moss used an elaborate technique such as was
essential for putting a new discovery upon a secure scientific basis.
In order to obtain a suspension of corpuscles, blood was drawn into a
syringe containing a solution of sodium citrate to prevent clotting.
The corpuscles were collected by means of the centrifuge, and were
thoroughly washed twice in normal saline solution so that they
were finally collected free from serum and from citrate. Serum was
collected in the manner already described. A series of small tubes
was then filled with equal quantities of serum and the suspension of
corpuscles, and was incubated for two hours at 37·5° C. At the end of
this time observations were made and again after the tubes had stood
for twelve hours in an ice chest. Varying degrees of agglutination
and hæmolysis were then accurately recorded, and far-reaching results
were obtained.
Later workers had the advantage of using stock sera belonging to
known groups, so that the number of observations to be made was very
greatly reduced. Brem introduced in 1916 a method of testing in
which he mixed the serum and suspension of washed corpuscles in very
small quantities on a coverslip, which was inverted over an ordinary
cell slide rimmed with petroleum jelly. The results could then be
observed macroscopically or under the microscope, and the presence or
absence of agglutination could be determined within fifteen minutes.
The detection of hæmolysis by the hanging drop method requires that
the cells should be incubated and observed at intervals for several
hours, but it is not always easy to see the disintegrated corpuscles
unless the process has taken place extensively. The diagram on p. 105
gives in a tabulated form some idea of the appearances presented by
the corpuscles of the different groups when mixed with the stock sera
and observed in a hanging drop under a microscope. Agglutination must
be distinguished from the formation of rouleaux, which may be seen in
any of the mixtures.
For scientific purposes these very careful tests are necessary,
but it seems to be clear that for clinical purposes a much rougher
and quicker test is adequate. In the clinical determination of
blood groups it is superfluous to carry the test to the point of
watching for hæmolysis, for it is upon the presence of agglutinins
in the serum and the corresponding iso-agglutinins in the corpuscles
that the determination of the groups depends. Further, no error is
introduced by neglecting the hæmolysis, since it has been shown
that hæmolysis is invariably preceded by agglutination. It is the
occurrence of agglutination therefore that is of prime clinical
importance. If that is excluded, hæmolysis is necessarily excluded
also, and the prolonging of the test is seen to be only of academic
interest. In the methods described above the corpuscles were always
tested in the form of a washed suspension. This precaution was taken
on the supposition that the presence of any of the serum belonging to
the corpuscles might interfere with the reaction. If, however, the
amount of this serum be small relatively to the amount of the test
serum, then no such interference takes place.
[Illustration: Fig. 7.--TABULATION OF SERUM REACTIONS AS SEEN IN
HANGING DROPS.]
The ordinary clinical method of testing may therefore be greatly
simplified, and the one commonly used at the present time is as
follows: A single drop of each of the stock sera is placed on two
glass slides, or, better, side by side upon a white glazed tile or
plate, the numbers of the groups, II and III, being written above the
respective drops. The lobe of the ear of the person to be tested is
then washed with ether and pricked with a sterile surgical needle. A
small quantity of the blood which exudes is taken up on the end of
a blunt metal or glass rod, and is intimately mixed with the drop
of serum under the number II. The end of the rod is then carefully
wiped clean, and a similar small quantity of blood is mixed with
the drop of serum marked III. The amount of blood to be used should
not be so great as to make the drop of too deep a colour, which
may interfere with observation of the reaction, but it should be
enough to impart to it a very definite red tint. The slide or tile
is then gently rocked, so that some slight movement is imparted to
the drops, which are at the same time closely watched in a good
light. The agglutinating reaction is readily seen with the naked
eye, especially against the white background provided by the tile.
If the serum be properly active, the agglutination of the corpuscles
begins to be apparent as a definite granular appearance resembling
brick dust within a minute of mixing. With a little practice this
appearance is easily recognized, but it must be distinguished from
the appearance produced by a mechanical gravitation of the corpuscles
towards the centre of the drop. If agglutination is taking place, the
granulation appears simultaneously throughout the drop, and not only
in the centre. With an active serum the process may proceed rapidly,
so that in less than five minutes the corpuscles have been aggregated
into a few irregular masses; often it stops short of this, but the
drop presents, nevertheless, a coarsely granular appearance which is
quite unmistakable. If no granulation can be seen at the end of five
minutes, it can be assumed that the test is negative for the serum of
that group, and the group of the corpuscles may be deduced upon the
principles already explained.
The test carried out in this way is admittedly not susceptible of
the same finesse as if it were done with the assistance of the
hanging drop, the incubator, and the microscope; nevertheless, my own
experience in a large number of cases has shown that, clinically,
this test may be relied upon, and the same view has been expressed
by other writers on the subject. Very seldom is there any doubt as
to the presence or absence of agglutination. When doubt exists, it
is easy to repeat the test and obtain a confirmation of the result.
It may perhaps be urged that this test is quite insufficient for
eliminating the slighter degrees of incompatibility which have
produced serious results when the transfusion has been repeated
several times. But in the cases reported, the blood that was used
had not shown any agglutination even when most carefully observed
under the microscope. It seems, therefore, that the results were
probably due to another factor, as already suggested (see p. 57),
which the more elaborate test failed to eliminate. The efficiency of
the rapid test is therefore not invalidated. It is, nevertheless,
in the present state of knowledge, a wise precaution to perform
the direct test between patient and donor in addition to the group
test when circumstances permit. It is essential when the patient is
suffering from any form of blood disease. It is unnecessary when
the transfusion is to be performed as a life-saving operation in
hæmorrhage or shock.