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.
CHAPTER VII
THE METHODS OF BLOOD TRANSFUSION
Some reference has already been made in the first chapter to the rapid development in recent years of the technique of performing a blood transfusion. The earlier operators, owing to the difficulties introduced by the coagulation of blood outside the body, were constrained to make use of some method of direct transfusion, the blood flowing directly from an artery of the donor into the patient’s veins. This has now been largely replaced by one of the methods of indirect transfusion, the blood being withdrawn from the donor into a vessel in which clotting is delayed or prevented, and then injected or allowed to run into the patient’s circulation.
Direct Transfusion.—The obvious method of performing a direct transfusion is by making an end-to-end anastomosis between an artery of the donor and a vein of the recipient. The most readily accessible artery is the radial at the wrist, and this is indeed almost the only artery that is available. The most accessible vein is the median basilic or the median cephalic at the elbow. The operation of end-to-end anastomosis, using an artery of so small a calibre as the radial artery at the wrist is usually found to be, is one of great technical difficulty; this effectually prevented transfusion from being used at all frequently. A modification has been used by Sauerbruch and others, in which the end of the radial artery is drawn into the lumen of the vein through a slit in its wall. A suture is passed through the radial artery close to its cut end, and the needle is then passed through the slit in the vein and out again through the wall of the vein an inch or so higher up. Traction on the suture then pulls the artery into the vein. The artery has meanwhile been temporarily occluded by a clip, which is removed when the artery is inside the vein, so that the blood can then flow from one to the other. This is easier to do than the anastomosis, but, in addition to the other objections to direct transfusion to be mentioned presently, the difficulty occurs of occlusion of the artery by the physiological process of inversion of its coats at the cut end. This is likely to happen before much blood has passed, so that apparent success at first is often not maintained. Sauerbruch claimed that the amount of blood that had passed could be estimated by measuring the time taken for 1 cc. of blood to flow from the artery before it was introduced into the vein; but there is no proof that the rate of flow remains constant.
If direct transfusion be desired, there can be no doubt that Crile’s method, introduced some fifteen years ago, is the best to employ. After much patient work Crile perfected a method of anastomosis which ensures that no occlusion of the vessels can take place at the site of junction. This depends on the use of a short silver tube, through which the end of the artery is threaded. The artery is then pulled back again outside the tube in the form of a cuff and fixed in position. The end of the artery has thus been made rigid, and over this the vein is pulled in its turn and fixed by a ligature. A watertight junction is thus made, and blood can flow through it without interruption—unless clotting takes place in the vessels as the result of handling and injury to their walls. This method has been extensively used in America, and it was the first to render the operation of transfusion a comparatively popular one.
Various other devices for achieving the same result have been elaborated by other workers, and attention may be drawn to those of Elsberg and Bernheim, both of which are described in the book by the latter on “Blood Transfusion.” During the war a simpler method was introduced by Colonel Andrew Fullerton, who, working at a Base Hospital in France, found that he could get good results by employing a thin rubber tube with a small silver cannula at either end. The apparatus was first coated on the inside with a thin layer of paraffin wax, in order to discourage clotting within the tube, and the cannulæ were introduced into the donor’s artery and the recipient’s vein respectively. The blood could then flow freely from one to the other. The fact that blood was being transmitted was taken to be proved by the visible pulsation of the thin rubber connecting-tube synchronously with the arterial pulsations. The disappearance of this was assumed to be evidence that clotting had occurred. This method was described by Colonel Fullerton to the surgeons working at the Casualty Clearing Stations, where blood transfusion was likely to be of most service, but it was never used extensively. The coating of the inside of the tube with paraffin is in itself an operation of some difficulty. Under conditions in which any loss of time could not be permitted, success by this method was not attained with sufficient certainty, and it was shortly afterwards replaced by the more satisfactory methods described below. The most recent work on direct transfusion has been done by J. M. Graham at Edinburgh, who has however reached the conclusion that the technique is always more difficult than that of indirect transfusion.
It can easily be seen, therefore, that all the known methods of direct blood transfusion present great technical difficulty, which renders the method unsuitable for general use. There are, in addition, certain other objections to it of an obvious nature. It is, in the first place, impossible to measure the amount of blood which has passed from the donor to the recipient. Sometimes an indication may be obtained from the evident improvement in the condition of the patient, accompanied by the signs of loss of blood in the donor. More often clotting takes place, unknown to the operator, at some point, with the result that blood ceases to pass a considerable time before the end of the operation, and the patient has consequently received very much less blood than is supposed. It has been claimed by Libman and Ottenberg that the amount of blood transferred may be estimated by weighing the donor before and after the operation. This presupposes that a very accurate weighing machine is easily available, which usually is not the case.