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| The Surgical Technologist | JANUARY 2022 16 This article is intended to provide the surgical technologist the knowledge on the correct application of the SET, model selection, documentation of pressure and the contraindica- tions as well as with the Esmarch bandage and compari- son of both. The article also reviews the biomechanics and physiology of applying a tourniquet (SET or pneumatic) to a limb. The decision on which tourniquet to use is the sur- geon’s, but the surgical technologist should be prepared to safely assist in applying the SET if this option is requested. H I S T O R Y Performing bloodless limb surgery was first described in 1873 by Johannes Friedrich August von Esmarch (1823- 1908) 1 using a long bandage, now called the Esmarch ban- dage. Still used to date, when wrapped tightly around the limb from distal to proximal, it expels the blood from the limb into the central circulation. This procedure is called exsanguination. In its original application, the Esmarch ban- dage was wrapped several additional times at the proximal end of the limb to also block the return of arterial blood into the limb to act as a tourniquet. While this method is still occasionally used in ORs, it is now recognized to apply inconsistent, often excessive, pressure on the soft tissues. In 1904, Harvey Cushing, the well-known neurosurgeon who was concerned about tissue damage from the tight Esmarch bandage, first described the pneumatic tourniquet using compressed gas source. 2 Despite many shortcomings and complications, 3, 28, 29 the Esmarch bandage together with the pneumatic tourniquet are the most widely used method for achieving bloodless surgical field in the US and glob- ally. Recently, a review of the use of pneumatic tourniquets and military tourniquets, 19 advanced the hypothesis that individualizing the cuff pressure can reduce the incidence of tourniquet-induced adverse events including nerve dam- age. This article aims to broaden the surgical technologist’s knowledge and understanding on the newer methods of safely and effectively providing a bloodless limb surgical field for orthopedic, plastic and vascular surgeries, as well as the biomechanics and physiology of tourniquet-tissue interactions. In recent years, more hospitals and surgical centers in the US are using a novel device that expels the blood from the limb, blocks the blood re-entry and provides a sterile surgical field in one action. The generic name of this free- standing elastic device is the Surgical Exsanguination Tour- niquet (SET). 4 T H E S E T A N D I T S A P P L I C A T I O N O N T H E O P E R A T E D L I M B The SET is supplied sterile-packed in dual peel-back pouch- es. The device consists of a silicone circular ring (torus) wrapped around with an elastic tubular stockinet made from woven cotton and spandex and with straps that end w i t h a p l a s t i c handle (Figure 1). The SET is placed on the tips of the f ingers or toes while an assis- tant stabilizes the hand/foot. When the handles are pulled proximally along the axis of the limb, the torus rolls upon itself along the limb while the sterile stockinet unrolls on the limb. Once the SET has been rolled up the limb to reach its final position, the straps either can be cut away or wrapped around the limb. The correct sequence of preparation for applying the SET is to first disinfect the skin to about 10 cm (4”) above the anticipated final position of the ring and drape the proximal portion of the limb so that the edge of the drape is about 4-5 cm below the anticipated final ring position. After a timeout is performed and the patient is properly draped for the procedure, the SET is applied, typi- cally by the surgeon with the help of one or two assistants. M O D E L S E L E C T I O N There are four basic SET sizes: small, medium, large and extra large. In addition, there are two special models: Model F for the forearm and Model A for the ankle. The medium and the large SET models are available at 3 levels of tight- ness; the least tight models are suitable for patients with low blood pressure, ie, <130 mm Hg systolic (typically children) and the tightest models are suitable for patients whose BP may rise up to 190 mm Hg. The medium tightness is for patients whose highest anticipated systolic BP during the operation is not more than 160 mm Hg. With each SET unit there is a small envelope with a color-coded measuring tape. Measuring the limb circum- ference at the site the surgeon decides to place it will imme- diately show which size to use. SET sizes range from 14 cm to 85 cm. The best practice is to base model selection on the ruler and sizing. If sizes overlap, it is recommended to Figure 1. The application of the SET.