How Safe Are Non-Pneumatic Tourniquets?

Pneumatic tourniquets are commonly used in surgery to safely establish a bloodless surgical field in a portion of a limb over a time period suitably long for the performance of a surgical procedure. It is estimated that at least 15,000 surgical procedures are performed each day on limbs with the benefit of pneumatic tourniquet systems. The introduction and widespread use of automatic tourniquet systems, with microcomputer control and improved pneumatic cuff designs, has greatly reduced the reported severity and number of tourniquet-related hazards and injuries^[1-3]. It is well established in the medical literature that the probability of tourniquet-related injuries increases as tourniquet pressure increases, and as the pressure gradients near the edges of tourniquet cuffs increase eg^{[2,4-8,10,13]}.

The widespread adoption and use of such automatic tourniquets employing microprocessor technology, together with improved designs of pneumatic tourniquet cuffs, has greatly improved the safety, accuracy and reliability of tourniquets in surgery. The resulting decrease in the number of reported hazards and incidents was accompanied by a reduction in risk class by the (US) FDA: in 1996, the FDA classified pneumatic tourniquets as Class I medical devices (indicating that they present minimal harm to the user and do not present a reasonable source of injury through normal use), and the FDA thereafter exempted pneumatic tourniquets from its (510k) pre-market notification and clearance procedures. Modern pneumatic tourniquets are used in an estimated 15,000 orthopaedic and non-orthopaedic surgical procedures daily in the US and elsewhere, facilitating surgery by reliably establishing a bloodless surgical field with relative safety.

Pneumatic tourniquets have recently been developed for military and emergency use, based on surgical designs proven to be safe and effective over many years. Such pneumatic devices are deployed in Afghanistan and Iraq and in other pre-surgical emergency settings. Pneumatic military tourniquets are more commonly used by medics than by individual soldiers in combat, but both types are designed to be suitable for rapid, one-handed self-application in the field. In a recent study, the early use of both types of military tourniquets (pneumatic and non-pneumatic) when shock was absent was strongly associated with saved lives, pre-hospital use was also strongly associated with lifesaving, and no limbs were lost due to use of these military tourniquets^[11]. In another paper reporting on the same study, pneumatic military tourniquets were rated 92% effective and non-pneumatic tourniquets were rated 79% effective^[14].

Fig. 1 Narrow, non-pneumatic strap tourniquet designed for one-handed self application in certain military settings.

The comparatively narrow, non-pneumatic tourniquet straps were developed to be very small in size and light in weight so they could be carried in backpacks by all soldiers, and were developed to be suitable for rapid one-handed self-application by wounded soldiers in combat situations. While effective in helping to stop potentially fatal arterial blood flow in combat, such narrow non-pneumatic tourniquet straps may produce hazardously high, inconsistent and uncontrolled pressures around limbs and may further produce high pressure gradients near the strap edges.

Very recently, it has been suggested by some that non-pneumatic tourniquets, including elastic bandages, elastic rings and non-elastic straps might be employed in pre-hospital civilian use and even in surgery, as they were in the 19th century. The uncritical acceptance and use of such non-pneumatic tourniquets in non-military settings and in surgery for extended periods, without investigation of applied pressure levels and applied pressure gradients and with limited evidence of their safety, may unnecessarily increase the incidence of tourniquet-related injuries in surgical patients to earlier levels, and may expose users in civilian settings to potential legal liability for non-military users.

Non-pneumatic tourniquet devices for stopping arterial bleeding may not be as safe as pneumatic tourniquets in civilian settings, where pneumatic tourniquets with proven safety and efficacy are available and where one-handed self-application is not an essential consideration. A recent study confirmed that non-pneumatic tourniquet straps and non-pneumatic elastic rings produce substantially higher applied pressures and higher pressure gradients when selected and used to stop arterial bloodflow according to manufacturer’s instructions (see Fig. 2 below)^[9].

Fig. 2 Applied pressures and pressure gradients typically produced by (a) a modern pneumatic surgical tourniquet cuff, (b) a non-pneumatic, non-surgical military tourniquet designed for self-application on the battlefield, and (c) a non-pneumatic elastic ring designed in an attempt to combine exsanguination and tourniquet functions. Higher levels of pressure and higher pressure gradients are associated with higher probabilities of patient injuries, eg^[2,4-8].

Such higher pressure levels and higher pressure gradients are associated in the clinical literature with higher probabilities of patient injuries. Additional caution is suggested by a recent anecdotal report of possible nerve, muscle, and soft tissue injuries associated with a commercial, non-pneumatic elastic ring recently developed for use as a surgical tourniquet and exsanguinator^[12].

Pneumatic military tourniquets have proven to be effective in stopping arterial bleeding in combat situations, as have narrow, light-weight non-pneumatic tourniquet straps^[11].

Fig. 3 Narrow, non-pneumatic elastic ring tourniquets produce substantially higher applied pressures and higher pressure gradients.

Fig. 4 Wide, pneumatic tourniquets have proven safety, lower pressures and lower pressure gradients.

For both of these types of military tourniquets, small size, light weight and the requirement that they be suitable for one-handed self-application are essential considerations. However, for civilian pre-hospital applications and civilian surgical applications these are not considerations. Thus to minimize potential legal liability, much further investigation is warranted before there is uncritical acceptance and use of non-pneumatic tourniquet straps, or non-pneumatic elastic tourniquet rings, when pneumatic tourniquets with proven safety, lower pressures and lower pressure gradients are available.