BLOODLETTING

BLOODLETTING (also called Bleeding or Depletion, and including Phlebotomy or Venesection, Arteriotomy, Wet-cupping, Leeching, and Scarification) is a method of relieving the human system in states of general or local plethora by the abstraction of blood. General plethora is best treated, according to this method, by withdrawing a considerable quantity of blood from the arteries (arteriotomy) or veins (venesection). Local engorgement, or hyperæmia, of a part is usually treated by abstracting blood from the smallest-sized vessels, or capillaries, present in the skin, by the methods of scarification or leeching. In these cases, the removal of blood from the superficial textures diverts the blood-stream in part from underlying tissues, and thus reduces the tendency to inflammatory action in the deeper structures. In general bloodletting the object is to reduce the strength of the blood-stream throughout the whole system, and thus to diminish the acuteness of feverish conditions. The most usually employed method of accomplishing this is by the opening of one of the superficial veins of the arm, and allowing a sufficient quantity of blood to escape from the blood-vessel thus operated upon. The vein chosen for the operation is generally one of those near the front of the elbow-joint, which can be conveniently reached in this region without disturbing the patient, and which can be closed after the operation by applying a dressing with the elbow bent when the operation is completed. In performing the operation, it is first essential to make the vein stand out clearly under the skin, and to do so it is necessary to remember that the veins return the blood from the extremities to the trunk, and therefore that pressure must be applied constricting the arm above the elbow, thus causing the veins to swell from retardation of the blood-flow within their walls. A bandage is thus tied tightly around the middle of the upper-arm, and, as a result of its action, the veins in front of the elbow-joint commence to swell and stand out as blue cords, distinctly to be seen through the delicate skin of this region. Selecting the largest of these swollen veins, the operator places his left thumb upon it immediately below the point where he desires to open it. This prevents any backward flow of the blood in the vein, and renders it yet more distinct at the point where it is to be opened. Now taking a sharp lancet in his right hand, the surgeon pushes its point steadily downwards through the skin into the blue column that marks the position of the vein, taking care, however, only to divide its outer wall and not to transfix it completely. Having by this means made a slit about half an inch long in its outer wall, he withdraws the instrument and removes his left thumb from the vein. A steady flow of dark blood now takes place from the wound; this is received into a graduated glass vessel, by which the operator may gauge accurately the amount of blood removed. Should the flow of blood tend to diminish, the patient is requested to grasp some hard object tightly with the hand of the side operated upon, and an immediate increase will occur in the blood flowing from the wound. When a sufficiency of blood has been abstracted by this means, the operator places a large and firm pad of lint over the wounded vein, and bending the arm at the elbow to a right angle, bandages it firmly in that position, observing specially that the pad of lint is tightly pressed against the wound in the skin. When the bandaging is complete, and only then, the constricting band around the upper-arm may be removed. There is danger in removing it earlier, since air may enter at the wound in the vein; and, being sucked upwards into the chest, may cause sudden cessation of the heart's action, and a considerable risk of immediate death. On account of this danger, it is not advisable for unskilled persons to attempt the operation. When the bandage and pad are firmly applied, and when the constricting band is removed, the patient's arm is placed in a sling and kept at rest for a week, when the wound in the skin and the vein is generally healed, and the patient may be permitted to use his arm again without incurring any risk. In children the veins in the arm are too small to be operated on satisfactorily, hence the external jugular vein of the neck must be selected in such cases; but the danger of the entrance of air is still greater in this region than in the arm; the operation should therefore be reserved for very urgent cases, and only performed with the utmost caution. The amount of blood actually abstracted in bloodletting must depend on the age of the patient and the nature of the case. The operation would be scarcely necessary if less than a quarter of a pint is to be removed, and it is now rare to remove more than one pint at one operation, however severe the case in which it is employed. For the methods and effects of local bloodletting, see CUPPING and LEECH. For the bleeding of animals, see PHLEBOTOMY.