Back in the old days, it was recommended that for a snake bite you cut an X and suck the venom out. That is no longer recommended, however, they still sell suction devices such as the Sawyer Extractor that you are supposed to place over the bit and then suck the venom out. (There is at least one answer here that recommends them for scorpions as well).
Is there any studies of scientific evidence that these types of devices would be helpful?
There are two studies I could find on this,
Conclusion
The Sawyer Extractor pump removed bloody fluid from our simulated snakebite wounds but removed virtually no mock venom, which suggests that suction is unlikely to be an effective treatment for reducing the total body venom burden after a venomous snakebite.
Suction for venomous snakebite A study of “mock venom” extraction in a human model
Conclusion.-No benefit was demonstrated from Extractor use for artificial rattlesnake envenomation in our animal study. The skin necrosis noted in 2 Extractor-treated extremities suggests that an injury pattern may be associated with the device.
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In our controlled study evaluating the Extractor, there was no difference in swelling, which is the most common outcome following pit viper envenomation, after artificial envenomations in a porcine model. However, our study and others suggest that there may be a specific injury pattern associated with the device. Although most authorities have previously agreed that the Extractor could be beneficial and would probably cause no harm, our study suggests the opposite may be true.
In other words, these are not a good idea.