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And all of them agree for major trauma causing severe bleeding to an extremity a TQ is the appropriate first response.
Like I said, if you look at the wound and think you may need a TQ, you likely do. If you want to try some direct pressure while someone get the TQ ready, sure give it a shot, but do not delay a TQ for severe injuries.
Complication rate for TQ placement hovers around 1.5%. Certianly not high enough to worry about.
Some case studies show limb survival well outside 2 hours. Additionally you need to be alive to be worried about your potential for a prosthetic limb. If you wait for the patient to start showing SxS of shock you’ve already lost the battle. There are battlefield cases of patients who died in less than 10 minutes that a TQ would have likely saved.
Injuries requiring a TQ are thankfully pretty rare, but when a TQ is the answer, it’s likely the only answer.
I was always of the "anything can work" mentality until recently. I reached out to one of our forum experts on the matter and now have 3 CAT's. They are cheap enough, I keep one in my dry kit bag, one in my car and one on my bike. The bike was part of my decision to buy them, having not too long ago had a pretty serious bike crash. The only first aid I have on my bike, figured after a crash I'll either be out cold (cant do anything anyway) or all street pizza and joint separations (last time) or a "pumper". The first two, no emergency first aid really needed, but alone with a bleed, adding one seemed logical.
I can't stress enough the need for proper training (such as a Wilderness-EMT course) to know how to effectively respond in a medical emergency (and statistically thinking preparation for how to prevent/respond to a heart attack / car accident on the way to/from a dive site far more than a shark bite...)
With that said, I also second the sentiment expressed earlier about advances in medical technology in relation to purpose-built tourniquets (such as range at Tourniquets | Chinook Medical Gear, Inc.). ALL modern options avoid unnecessary degree of constriction while spreading the force applied over a wider area than some of the jury rigged options suggested.
Everyone should make their own choices, but for myself I carry a tourniquet spearfishing and/or when diving where tiger sharks (or other more "curious" sharks frequent, and more so with free diving than SCUBA because bubbles to a certain degree differentiate a diver from "normal prey"). I see no point preparing for an "attack" but I see value in preparing for a "bite" under certain circumstances. My personal rationale, based on some logic and a heavy dose of "feels right for me based upon totally subjective risk/reward ratio," is it's worth being prepared for a survivable case of a conflict over fish I shot spearfishing / mistaken identity / "taste test bite." My thinking is under those circumstances my chances of a "bite" increases from close to nothing to something above absolute zero, and IF biten it would most likely be to an extremity and therefore survivable if responded to quickly enough and the right way. None of my above thinking matters if not combined with adequate training, communication (phone/VHF/PLB/etc), AND transport to professional medical care (side note being get DAN insurance before getting a tourniquet though because in the USA seeing the bills for transport and the hospital would kill you from a heart attack if the shark didn't..)