It was once thought that suspension trauma patients should be kept in a sitting position once they reached the ground to avoid cardiac complications and potential arrest. Current data suggests that although possible, arrest is not a likely outcome and victims of suspension trauma should be treated in the same manner as other trauma patients.
Climber, cavers, etc. who may find themselves fully suspended in their harness without contact with a wall should consider wearing a full body harness (rather than a sit harness), carrying "foot slings" (to permit them to stand, engage the muscles of the lower legs, and relieve pressure on their femoral veins), and/or specially designed straps that support them in a horizontal (versus vertical) position. Those who have contact with a wall should push off the wall with their legs to reduce the pressure on their femoral veins and engage their leg muscles to decrease venous pooling in their legs. Ideally, any rappel or belay system should permit rapid lowering of a potential trauma victim.
If you haven't taken a course in wilderness medicine — or you are looking to recertify — please consider taking one from us, the Wilderness Medicine Training Center. Guides and expedition leaders should consider taking our Wilderness First Responder course.