Hæmorrhage and Shock
Blood transfusion is pre-eminently the best form of treatment that is known for the condition of acute anæmia following hæmorrhage to whatever cause it may be due. Its good effects were seen by a number of operators in many hundreds of exsanguinated patients during the latter part of the war, and its value was then established upon a secure foundation. It was unusual during the war to meet with patients who were in danger of their lives from loss of blood alone without the additional factor of traumatic shock, but such cases did occur, and they are also to be met with in civil practice, as, for instance, in attempted suicide by throat cutting, in gastric ulcer with severe hæmatemesis, and in secondary hæmorrhage after operation. The more typical condition following war wounds, hæmorrhage with shock, will be faithfully reproduced in the victims of train or street accidents, in patients who have undergone certain severe operations, and in women suffering from post-partum hæmorrhage or a ruptured ectopic gestation.
The signs and symptoms of acute anæmia will be familiar to most readers. It is characterized by a peculiar greyness of the skin, by extreme pallor of the mucous membranes, by a cold perspiration, by a thready and rapid pulse which may exceed 140 beats to the minute, and by extreme restlessness. The “amaurosis” of the text-books is seldom met with, but in the last stages the patient becomes semi-unconscious, the restlessness tends to disappear, the muscles relax, and the respiration takes on a peculiar sighing character, which is described as “air hunger,” and probably indicates exhaustion of the respiratory centre. Meanwhile, if instruments are at hand, additional signs may be recognized. The most important of these is a fall in blood pressure. It has been stated that a systolic pressure below 70 mm. of mercury is scarcely compatible with life, but this is not in accordance with experience. It was common during the war to meet with blood pressures below 45 mm., so low in fact that they could not be measured with the ordinary apparatus that was available, but many patients whose lives had reached even so low an ebb as this were quickly restored by the administration of blood, provided that the exsanguinated state had not lasted for too long a time. If the medullary centres are damaged beyond recovery by inadequate oxygenation lasting for several hours, then no treatment is of any avail. But provided that it be given before this length of time has elapsed, a blood transfusion may succeed in saving life at any stage of the condition. Its efficacy is indeed only limited by the actual cessation of the patient’s heart beats. I have successfully treated a patient who before transfusion could only be described as moribund. He was almost unconscious, absolutely blanched, and his radial pulse imperceptible; his jaw was relaxed and his breathing had become a series of fish-like gasps, such as are only associated with imminent dissolution. His heart would certainly have ceased beating within a few minutes, yet his condition improved so rapidly after transfusion that an hour later it was possible, with the help of a second transfusion, to amputate his leg above the knee. This patient ultimately recovered, having been as near death as it is possible to be and yet remain alive.
The results of a blood transfusion upon a patient suffering from acute anæmia are, indeed, amongst the most dramatic effects to be obtained in the whole range of surgery. Within a few minutes of its commencement the whole aspect of the patient alters. His respiration becomes deep and regular, his restlessness disappears, colour returns to his face, his pulse rate falls, and he begins to take an intelligent interest in his surroundings. These changes taking place within a period of fifteen minutes may well strike an onlooker as little short of miraculous. Shortly afterwards the patient may fall into a natural sleep, a sure sign that the normal circulation has been restored to the exhausted central nervous system.
In considering how much blood should ordinarily be given in the treatment of acute anæmia, experience is a safer guide than any theoretical considerations. Nevertheless, it is worth while to inquire briefly into the experimental and theoretical basis upon which the treatment of acute anæmia rests. It is difficult to estimate accurately the total quantity of blood in the body of an adult, but it has been variously stated by physiologists to be from a twentieth to a tenth part of the body weight, or, in liquid measure, from 3 to 6 litres (approximately 5 to 10 pints). This has been estimated in several ways, the results of which show some discrepancy. A figure approaching the higher one was obtained long ago by the direct method of washing out the blood from the bodies of executed criminals. Recently it has been claimed by Haldane that these determinations were inaccurate; by means of his carbon monoxide method, with the details of which we are not concerned here, he has estimated that the blood volume is but one-twentieth of the body weight, or in very stout persons is even as low as one-thirtieth. Still more recently Haldane’s estimation has been challenged in its turn by observers who have injected a dye into the circulation and have then determined its degree of concentration in the blood by means of colorimetric comparisons. It is evident that if the dilution which occurs when a known quantity of dye is injected can be accurately estimated, then the total volume of circulating fluid can be calculated. This method could not be used until a non-toxic, non-diffusable dye had been discovered, but it was found in 1915 that “vital red” fulfilled these requirements (143). The results obtained in this way show that those originally given by the direct method were substantially correct. The blood volume was found to vary from 1/13 to 1/10·5 of the body weight; on the average it amounted to 5,350 cc., or 85 cc. per kilogram of body weight. These observations have been in their turn criticized (114), but only to the extent of reducing the amount by 1/10. It may therefore be assumed that, according to the most recent work, the blood volume is from 5 to 6 litres, or, approximately, 8 to 10 pints.
It is a still more difficult matter for obvious reasons to estimate how much blood a man can lose and yet remain alive. This will depend partly on the power of physiological accommodation possessed by the individual in his vaso-motor system and tissue fluids and partly on the rapidity with which the bleeding takes place. Clinical observations have shown that after a moderate hæmorrhage, such as the withdrawal of 800 cc. of blood from a donor, the blood volume may be restored to normal within an hour. If, on the other hand, the hæmorrhage is excessive, a condition results in which the normal process of rapid restoration of volume fails, and the circulation remains in a dangerously depleted condition. The heart attempts to keep the blood pressure at an adequate level by an increase in its rate, but it is in effect attempting to circulate a small volume of fluid in a vascular system which has become too big for it. Imperfect oxygenation of the medullary and cerebral centres with exhaustion of the heart results, and this is accompanied by all the symptoms of anæmia which have been already described.
If the initial hæmorrhage be very rapid, death may result almost at once, since the physiological processes may have no time to act. On the other hand, a rapid hæmorrhage may under certain circumstances save the patient’s life, for the immediate syncope which results produces so great a fall in the blood pressure that hæmorrhage almost ceases and a clot may form in the lumen of the divided vessel. If the hæmorrhage be more gradual, the physiological compensation may at first be adequate to maintain the blood volume, but finally a point is reached at which this process fails and the patient then passes into the condition of acute anæmia.
The actual amount of blood therefore that must be lost to be fatal will vary according to circumstances. Experience shows that hæmorrhage may take place into the peritoneal or pleural cavities to the extent of two litres or even more, and it may be stated as a rough guess that 2·5 litres, that is to say, even as much as almost half the total blood volume, may be lost without immediate death resulting. This degree of depletion could not, however, be endured for long. A series of clinical observations made by Keith by the vital-red method upon the blood volume in soldiers suffering from the combined effects of hæmorrhage and wound shock showed that in the most serious cases the volume was below 65 per cent. of the normal, frequently even between 50 and 60 per cent. Serious symptoms followed a reduction to between 65 and 75 per cent. In patients without distressing symptoms the volume was never below 75 per cent. of the normal. There is direct evidence, therefore, that those patients who are most in need of treatment, such as a transfusion of blood, will probably have lost from 25 to 50 per cent. of their blood volume, that is to say, 1·5 to 3 litres in amount, and will need from 750 cc. to 1·5 litres to restore them to, or near to, the 75 per cent. level at which the compensatory processes can begin to regain their power.
It is thus possible to arrive at a theoretical basis on which an idea can be formed of the amount of blood that should be given in acute anæmia. Practical experience is in agreement with the theory, and it will now be easier to understand how it is that in treating acute anæmia no attempt need be made to replace the whole amount of blood that has been lost, or indeed anything approaching it. In an extreme case 2 to 3 litres of blood will have been lost and 1 litre or more will be needed to restore the blood volume to approximately 75 per cent. of the normal. A case of this sort, however, is fortunately not often to be met. One has already been described on [page 21]; this patient received altogether nearly 1,600 cc. of blood in two transfusions, and 1,000 cc. of normal saline were given in addition.
In most cases of severe hæmorrhage the patient has probably not lost more than 1,400 to 1,800 cc. of blood, and 600 to 800 cc. will be enough to restore the balance of the circulation. This is in practice the amount of blood that is commonly administered, and it is well within the limits of what a single blood donor can afford to lose. If a more definite standard be required, it may be laid down that in a single transfusion for acute anæmia 750 cc. of blood should be given. If, in an exceptional case, more than this is needed, a second transfusion should be performed with a similar amount taken from another donor. Sometimes it may happen that a patient already in extremis from loss of blood, needs a severe operation; in such a case a second transfusion may be given with great advantage at the conclusion of the operation. The first transfusion will restore the patient sufficiently to render the performance of an operation possible; the second will combat the additional shock and hæmorrhage which it has caused.