Military anti-shock trousers

Military anti-shock trousers (or Pneumatic Anti-Shock Garments) are medical devices used to treat severe blood loss. They are also indicated for the stabilization of unstable pelvic fractures in the field prior to transport.

Usually called "MAST", and sometimes "pneumatic anti-shock garments" (PASG), they were invented by Lt. Col. Burton Kaplan during the Vietnam War. MAST look like a pair of trousers. They are opened and placed around the legs and pelvis of the patient. Each leg and the pelvic section may then be inflated, applying pressure to the lower half of the body The trousers can be used with sager traction splints and dressings already in place.

MAST are typically carried and used by emergency medical technicians and paramedics, although they are sometimes carried by fire department first responder trucks, and, in some states, first responders can apply and inflate them under direct medical control.

The exact way in which MAST help is uncertain. The most common theory is that the pressure decreases blood flow to the legs (thus increasing availability of blood to the rest of the body) and actually squeezes blood out of the lower body. It may be that increased perfusion to the brain and other organs also have indirect benefits.

There is some controversy over use of MAST. One question is whether the increased peripheral vascular resistance may reduce cardiac output or rupture existing clots. Due to these questions and several human studies that have shown no advantage to patients with a high degree of blood loss above the pelvis, MAST trousers are being used much less often now than they were the 1980s and early 1990s.

I. G. Roberts et al. sought to quantify the effect on mortality and morbidity of the use of MAST in patients following trauma, and published the data in the Cochrane Database of Systematic Reviews.