Enhancement_Articles

Table of Contents
The Theory Behind the Use of PASG
Indications and Contraindications
Application of PASG
Inflation of PASG
Deflation of PASG

The Theory Behind the Use of PASG
It is thought that use of inflated pneumatic anti-shock garments (PASG)-also called military anti-shock trousers (MAST)-aids in the treatment of patients in hemorrhagic shock by auto-transfusion. Blood from the lower extremities is, according to this theory, "transfused" back into the thorax and the core organs by compression of the vasculature in the lower extremities. In essence, PASG reduce the amount of hoses available for the blood to travel through by squeezing them shut. The pressure created by the PASG causes blood to be squeezed from the lower extremities into the vasculature of the upper body and the core organs. It is hoped that this shunting of blood results in a restored perfusing blood pressure by increasing peripheral vascular resistance (PVR).
Although PVR is an important component in the maintenance of systemic blood pressure, it has a negative proportional effect on cardiac output. Increasing PVR leads to decreasing cardiac output, which is the opposite of what a bleeding patient needs. Increasing PVR can also rupture clots, leading to increased bleeding. Finally, once the PASG are deflated, blood trapped in the lower extremities is allowed to re-enter the circulation, and patients can enter a state of instant acidosis. The use of PASG remains very controversial, and local protocols must be followed to ensure proper use.

Indications and Contraindications
PASG may be considered an effective tool for the treatment of circulatory collapse secondary to perceived hypovolemias such as:
· Septic shock
· Neurogenic shock
· Anaphylactic shock
· Extremity fractures or amputations
· Stabilization of femoral or pelvic fractures
· Cardiac arrest in which no pulses are generated by CPR
EMS systems usually establish their own protocols listing contraindications, which can fall under two categories: absolute and relative. Absolute contraindications include situations in which a treatment should never be used. Relative contraindications include situations in which a treatment could have a negative impact, but the benefits of treatment could outweigh the negative impact. In those cases, care providers must exercise judgment. Most EMS systems agree that an absolute contraindication to using PASG involves any compromise of breathing, as with pulmonary edema. The minute a patient shows signs and symptoms of any breathing difficulty, the use of PASG must be stopped immediately. Relative contraindications to the use of PASG include:
· Cardiogenic shock
· Internal bleeding of the chest
· Impaled objects in the abdomen
· Third trimester of pregnancy
· Evisceration

Application of PASG
The decision to apply PASG should be based on the type of shock being experienced as well as the type of injury to the patient. For example, the use of PASG can make the use of other equipment-for example, Hare traction splints, rigid splints, or bleeding control measures-cumbersome if not impossible. Possible application methods include:
· Trouser method: The rescuers apply the PASG as though they are a pair of pants. One rescuer places his or her arms up through the PASG legs to grab the patient's ankles while the other rescuers help slide the PASG up over the patient. This method should never be used when there is any possibility of a spinal injury.
· Log roll method: The PASG are placed on a backboard and the patient is logrolled onto the board and PASG. Once the patient is centered over the alignment markings of the PASG, wrap the legs and abdomen with the appropriate compartments and begin inflating them according to protocol.
· Diaper method: The rescuers roll the inner edges and the anterior abdominal section of the PASG toward the center of the garment and then slide the pants underneath the patient, in the same way that they would slip a sheet underneath a patient. This method involves little movement of the patient and may be preferred when dealing with a hip injury.

Inflation of PASG
PASG should be used when the patient's systolic pressure falls below 100 mm Hg. The legs must be inflated individually before the abdominal portion is inflated. The stopcocks must be closed before inflation, with only one open at a time to fill the compartment. The compartments should be filled until either a systolic blood pressure of 100 mm Hg is reached or until the Velcro begins to pull apart.

Deflation of PASG
Deflation should rarely, if ever, be done in the prehospital setting, and then should be done only following a direct physician order. Before deflation takes place, the hospital needs to be able to correct the problem for which the PASG were initially used.