I don't know, someting is odd here. If this was some hyper-toxic Aussie elapid, where a few mg are enough to kil you, then I could believe it (there are documented cases of it happening), but with a puff adder?
Put simply, puff adder venom is not that potent drop for drop or dried crystal for dried crystal - to kill someone, you need something of the order of 50-100 mg of dried venom. 8 vials of SAIMR is the sort of dose you would use for a serious bite that injects a large amount of venom (being a tropical antivenom, SAIMR is both cheap and effective, with a reasonable dosage requirement, unlike our First World Wonders of Technology, like Wyeth dishwater or Yes-I-am-happy-to-remortgage-my-house-CroFab).
Let's take this further: how much venom is contained dried in a shed fang? How much of that is dissolved and absorbed into the flesh in the seconds that the fang was stuck in the skin? Surely only a very tiny fraction of what would be injected in a bite - only a few mg at most.
I have seen snake handlers impale themselves on freshly shed fangs of Bothrops spp., still covered in fresh venom, and suffer nothing more than a mildly swollen digit for a few hours - I have a very hard time understanding how a normal person would get a major envenomation from a puff adder in this way.
I am not doubting that the incident took place, but if it did as described, then there is some extra angle to it that we are missing so far.
A bit of arithmetic on the amount of venom in a fang:
- According to the diagram of a rattlesnake fang longitudinal section in Klauber's epic volume, the diameter of the venom canal in a fang is about 1/20th the length of the fang.
- Let's assume a puff adder fang with a venom canal 1 mm across and 20 mm long (generous, to be sure). The volume of the venom canal would be the radius squared times pi times the length of the fang, or 0.25 * 3.14 * 20 = 15.7 cubic millimetres - call it 16 - that is to say 16 microlitres. If this entire volume of the fang canal was full of liquid venom when the fang was shed (and obviously lost externally, not digested), then the 16 microlitres of venom would weigh approx 16 milligrams. In general, approx. 1/4 of the wet weight of the venom is solids, i.e., the 16 milligrams of wet venom would dry into 4 milligrams of dry venom, i.e., a very small fraction of the usual venom yield of 100-200 mg.
- Taking it further, how much of these 4 mg would be absorbed into tissues from a fang that is accidentally poked into the skin? Anyone who has ever had to wash dried-on spitting cobra venom off their gogges or camera lens knows that venom, once dried, is not that easily or quickly dissolved. Moreover, if the entire venom canal was full of dried venom, the inner parts, away from the two orifices, would be out of reach of the tissue fluids that might dissolve it. So, my guess is that less than half of the venom that might possibly be in the fang would ever get into the wound, or in this example 2 mg - compared to a lethal dose of 50-100 mg.
Given that the 8 vials of SAIMR antivenom for puff adder bites (likely to have injected at least 10s if not 100s of mg of venom ) would be considered a large dose, this simply does not compute. Either the patient had some sensitivity reaction (does that make sense from the symptoms?) and the antivenom was given in error, or we are missing something else here.
There have been documented cases of serious envenomation from puncture wounds from dried Australian elapid skulls, so the concept as a whole is not absurd, but this particular case raises more questions than it can answer.
Cheers,
WW