Tourniquet, an instrument for compressing the main artery of the thigh or arm, either for the purpose of preventing too great a loss of blood in amputation, or to check dangerous haemorrhage from accidental wounds, or to stop the circulation through an aneurysm. For the last purpose special forms of tourniquet are required, which do not compress the whole limb.
The common tourniquet consists of three parts—viz. (1) a pad to compress the artery; (2) a strong band which is buckled round the limb; and (3) a bridge-like contrivance over which the band passes, with a screw whose action raises the bridge and consequently tightens the band. The best kind of pad is a small firm roller bandage, about an inch thick; it must be placed lengthways over the main artery so as to compress it against the bone, and must be secured in its place by a turn of bandage, over which the band of the tourniquet must be applied. This band must first be tightly buckled, and the pressure must be then quickly increased to the necessary extent (viz. till the circulation through the limb is completely arrested) by the action of the screw, which should always be opposite the buckle of the band.
The credit of the invention of this most useful instrument is usually ascribed to the French surgeon Morel, who, in 1674, used a stick passed beneath a bandage, and turned round so as to twist it up to the requisite degree of tightness, as a means of preventing the undue loss of arterial blood in amputations of the limbs—a rough but by no means ineffectual form of tourniquet, which may often be usefully extemporised in cases of emergency at the present time (see Vol. I. p. 702). Mr Young of Plymouth, in 1679, described a similar apparatus. A much improved screw tourniquet was invented by Petit in 1718, the same in principle as that described above. Many surgeons now use in preference a strong elastic band, wound two or three times round the limb—a method first introduced by Esmarch.