Tourniquet (The turnstile) - withers

Given some theses that can be found by pseudo professionals on social networks, it is interesting to give some explanations.

In fact, too many things are said, without argumentation, and by persons, whom we will not name directly, but who will recognize themselves. It is necessary to be able to make the difference between supplying material and providing a donor of lessons, even of doctrine .

Tourniquet - tourniquet

The principle of the tourniquet is to interrupt the blood circulation downstream of its place of application, to stop bleeding. For this, it must exert sufficient pressure on the skin, as well as the underlying structures, to occlude the arterial circulation. This pressure is called Arterial Occlusion Pressure (AOP).

POA is proportional to limb diameter, systolic pressure (Psys) and diastolic pressure (Pdia).

The POA is inversely proportional to the width of the withers. The more the tourniquet is wide, the less pressure to apply is important.

Graham's formula allows to calculate the POA, according to the following formula (13): POA = (Psys - Pdia) x limb circumference / 3xl tourniquet of the withers + Pdia (mmHg)

This pressure can be exerted by several means:

-a strip of tissue tight at its maximum around the member.

a rigid rod system making it possible to exert additional pressure by further shortening the web of fabric: said turnstile system.

- an inflatable cuff, such as the tension cuff system.

- a tight elastic link until the bleeding stops, like the system used during a blood test or an infusion set.

Compartmental syndrome, or ischemia-reperfusion syndrome:

The ischemia induced by the setting of a tourniquet involves multiple physiological mechanisms, including vasodilation associated with capillary hyperpermeability. These mechanisms are amplified with the length of the tourniquet.

When the tourniquet is dropped, if it has remained in place for a long time, these reactions cause a large, progressive and prolonged increase in the volume of the limb by increasing the size of the muscular bundles. The member can reach up to 150% of its normal size.

This increase of volume in the muscular compartments is very badly tolerated, because of the inextensibility of these boxes. The consequences are serious, and clinically, the pain is very intense, not relieved by the usual therapies.

This pain results from a progressive decrease of the local blood flow by compression of the vessels by the oedematous muscle bundles. Complete interruption causes limb ischemia. Nervous lesions can also appear, according to the same mode. The treatment is then based on the realization of fasciotomy of discharge, consisting of incising the muscular compartments to quickly lower their pressure.