Congesting veins with a tourniquet is done to make the veins more palpable and easier to puncture. Tourniquets create pressure on surface veins without affecting arterial blood circulation. In order to prevent hindrance of the animal's pulse and other blood related factors, it is important that the veins are neither too drastically congested nor for too long.
Depending on the animal species, various tourniquets are available that differ greatly in material and manipulation.
Tourniquets for Small Animals
Tourniquets that allow for fine congestion and that are easy to manipulate often find more use in small animal medicine. Depending on the animal's size and the user's preference, these are mostly rubber or latex tourniquets that take the shape of a thin tube, which can either be tightly knotted or they can be equipped with a special latching mechanism. These can also include tourniquets from human medicine that consist of an elastic band and a plastic or metal latching mechanism. These tourniquets are particularly easy to manipulate; usually with only a single hand.
Tourniquets for Large Animals
The tourniquets used in large animal medicine need to be extra durable because they cannot tear, yield too greatly, nor can they be too short. For these reasons, chain tourniquets are often used for large animals like cows, horses or bulls. Witte tourniquets (chain tourniquets) are extremely durable, can be easily cleaned and reliably congest larger veins.
Tourniquets are to be applied above the vein; often even above the nearest joint above the puncture point. For cats and dogs, the veins on the front or hind legs are most often punctured. The tourniquet is then applied above the elbow. In order to prevent bleeding and haematomas after drawing blood, the congestion should be loosened before the cannula is removed. With intravenous injections and infusions, the tourniquet should be loosened as soon as the cannula is properly positioned.