In 2013, the American Academy of Clinical Toxicology and European Association of Poisons Centres and Clinical Toxicologists published a second update to their position statement on gastric lavage for GI decontamination (original 1997, 1st update 2004).
Bottom line: Gastric lavage generally causes more harm than good. It should not be thought of as a viable GI decontamination method.
Bonus: Dr. Leon Gussow (@poisonreview) reviews the position paper on his blog, The Poison Review, here: http://www.thepoisonreview.com/2013/02/23/gastric-lavage-fuggedaboutit/
Benson BE, et al. Position paper update: gastric lavage for gastrointestinal decontamination. Clin Toxicol 2013 Feb 18. [Epub ahead of print]
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