THE PNEUMATIC TOURNIQUET IN SURGERY OF TH E LIMBS

Pneumatic tourniquets, often used to provide a bloodless operating fie ld, carry a risk of adverse effects. Limb exsanguination by gravitatio n is less aggressive than by mechanical means. Skin, muscles, nerves a nd vessels suffer maximally under tourniquet because of mechanical pre ssure, with both a sagittal force, responsible for compression and an axial force responsible for stretchening. All parts of the limb are th erefore affected by ischaemia. The restarting of circulation will also increase lesions at the microcirculatory level, responsible for the ' 'no reflow'' phenomena. Transient reperfusion intervals are not necess arily beneficial. These effects will significantly contribute to the p ost tourniquet sensory motor injuries. The tourniquet increases the ri sk of sepsis. Tourniquet release allows metabolites from the leg to en ter into the circulation, acid also carries a risk of pulmonary thromb oembolism. Carbon dioxide is eliminated by spontaneous hyperventilatio n under regional anaesthesia. If not eliminated by an increase of mech anical ventilation during general anaesthesia, it may raise intracrani al pressure in head trauma patients. Various chemotactic and cytolytic agents may cause lung injury. Mobilization of blood volume at tourniq uet placement and release may have detrimental haemodynamic effects in patients with coronary or cardiac insufficiency. The tourniquet incre ases arterial pressure after 20 to 25 minutes under general anaesthesi a. Regional anaesthesia is considered as the technique of choice for t he prevention of ''tourniquet hypertension'', closely linked to pain a nd relievable by local anaesthetics. Tourniquet modifies also the phar macokinetics of anaesthetic and other agents. It generates hyperthermi a, especially in children. Prospective and comparative studies did not show any advantage as far as duration of surgery and amount of blood loss are concerned. In order to minimize its side effects, the tourniq uet must be used within the frame of a strict procedure, with a well a dapted and regularly checked equipment. Duration of ischaemia should b e as short as possible and not continue for more than two hours, with a reperfusion of 15 minutes every hour. Local hypothermia seems to be a safe means for decreasing side effects.