Snake Bite Reading

Wentworth

Bear Mears
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Hi all,

I picked up one of the Setopress bandages that Thrud posted about recently. It seems really good. One bandage is almost enough to cover a leg from toe to hip with 1/3 overlap on each wrap.

I did a bit of googling on the pressure that the bandage needs to be under for pressure immobilisation and the specs listed for setopress.

When the brown rectangles are pulled into squares, it's meant to be 40mmhg.

For a snakebite to the leg, I read that the pressure should be 55mmhg to 70mmhg. Not to say that the setopress isn't good for pressure immobilisation, just that I'd have to pull it tighter with each wrap than you would to make the brown rectangles squares. It's still a great length, good quality bandage and I'll be keeping it in the first aid kit.

The article that I was browsing is this one (downloads as a PDF):
resus.org.au/download/9_4_envenomation/guideline-9-4-8-aug11.pdf

They look at all of the work done on PIT and snake bites. An interesting bit was this:

Of the 12 studies that were identified examining the effect of PIT for the first‐aid treatment
of Australian snakebite, 5 were animal studies, 3 examined the ability of people to
administer the treatment, one was an observational study of presentations of viper
envenomation in Myanmar (of limited value in the Australian context, as there are no
Australian vipers) and the remaining 3 were the only clinical trials in humans (all were non‐
randomised, small and used different ‘mock’ venoms).


I'm not surprised to read there were no human volunteers for proper snake venoms.

I know we have some medical forum members like Thrud and Swampy who might be able to shed some more light on how effective PIT is against snake bites and if there is more up to date info. I wonder if first aiders generally apply enough pressure, enough overlap, whether the bites are generally dry bites, whether they would have been fine anyway etc. Maybe it's a case of anything is better than nothing.
 

Aussie123

Never Alone In The Bush
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Interesting article.

I discussed pressure with a GP friend (who hikes and camps). I recall his comments were that most people never need to apply a bandage are really don't know how tight to make it;
consequently most bandages were either too tight or too loose (not specifically talking snake bite but any bandage application).

He was quite a fan of the setopress because it gave a guideline which anyone could follow and get right all the way up the length of the bandage.

He also thought that the "high pressure" setting of the setopres was about the right pressure for a bite.


I'm one of those people who never needs to apply bandages so I'm very unsure what is "correct".
Having a setopress gives me some confidence (perhaps misplaced ?) that I'll be doing the right thing if ever needed ...
 

Bloffy13

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Something is far better than nothing. I'd rather have this than nothing. Sounds a good bit of kit. I dont carry a specific snake bite kit as that is only one of the needs I might need this sort of bandage for. Might have to look into this.
Cheers
Bloffy
 

Thrud

Richard Proenneke
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I think there are a number of potential issues with trying to get a pressure toward the upper limit 70mmHg as suggested.
It is difficult to judge accurately and whilst the majority of us have a BP of 120(systolic)/80(diastolic)mmHg, some will have a lower (diastolic) BP which could potential lead to compromised venous return if the bandage was above this pressure. Left in place this would result in(potentially) venous gangrene, although that would take some time to develop and should be recognised by increasing pain(of course the bite and effect thereof, might also be the cause of pain).

The other issue is in stressful situations there is a great tendency to overdo things and wrap the bandage too tight.

Finally and most importantly, a bandage that was too tight, would have to be released to save the limb; it is difficult to judge where the bandage constricts the most and as such the entire bandage might have to be re-done. This would potentially be a lethal move as the increase in blood supply would(if a blood transmitted venom) be washed back( sit on your hand for a few minutes then watch what happens to the colour compared to the other side after the blood returns)

The beauty of the Setopress is that it puts you into the right ballpark with the visual indicator as a too loose bandage can be dangerously ineffective. Once the Setopress is in place, you can then look at the finger or toe tips for colour, press the pulp and see how quickly the colour returns. Compare with the victims other side, if it is the same colour, the you have not done it properly, if it is white and stays white, you have done it too tight and if it looks slightly pinker than normal and when you prod it it takes about 2-3 secs for the blood to return you are in the right zone.

If the bandage is too loose then you can apply a second bandage over the top of it, if too tight then you would either have to start gradually loosening from above, or apply a second bandage from above down whilst simultaneously undoing the tight bandage a bit at a time(again, not easy to do with one person).

To practice, I would suggest holding your finger with a tissue wrapped around the base and varying the pressure so you can get a rough idea of the colour spectrum for the different pressures.(don't do this if you have vascular disease!!!) then practice on a full limb to get the same colour.
 
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Bushdoc

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I made this suggestion years ago! Pressure dressing bandages for pressure ulcers had the circle/oval device...the pressure required 40-70mmHg was the same as that for snakebite.
Snakebite tightness = 'as tight as you would for a sprained ankle'.
MJA 1994 Christmas edition showed a nice study proving you need pressure AND immobilisation to make it work.
eg. bite to hand: bandage, NO WALKING, as the isotopes tested still spread (simulated venom).
Original article was Sutherland's piece in the Lancet in 1979, proving tourniqets were bunkum for Aussie snakes.
 
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