What Is the Purpose of A...
Highlights
- What is the purpose of an NG tube in bowel obstruction? (View Tweet)
- I'm sorry to say, but if you answered A, C, or D, you are wrong. And if you don't know the purpose of the tube, how you can possibly know if it is needed?
NG tubes are intended to remove air from the stomach. (View Tweet)
- A popular blogger attempted to summarize the data on NG tubes, noting that in Fonseca et al, "almost 2/3rds of the patients who had an NG placed had minimal drainage, indicating the procedure could not possibly help the majority of patients."
https://t.co/XPcOBqH9hM (View Tweet)
- The implication - or frank assertion - that NG tubes are there to drain liquid demonstrates a lack of understanding of the core function of an NG tube. In fact, in a well functioning and demonstrably therapeutic NG tube, the important function is not seen and not measured. (View Tweet)
- Before NG tubes were popularized, enteral obstruction was a catastrophe. Survival of these patients was essentially a coin flip, with a mortality of 60% reported in 1908 and 44% in 1932.
https://t.co/8R6vIhDY1Y (View Tweet)
- What changed, and brought mortality down to <5% in the 1960s was dissemination of the work of Wangensteen. The Wangensteen drain worked so well that "how to" manuals were published, similar to today's sonography-phantom building guides.
https://t.co/0ijEj2vogr (View Tweet)
- But the Wangensteen drain is just a nasogastric tube, and you are still presuming the NG tube's job is to remove liquid enteric content. And Wangensteen would remind you that it is not. (View Tweet)
- Why does fluid accumulate in the obstructed bowel? Why does it distend? The function of bowel is to absorb fluid; that it should fail in this function with stasis, and fluid accumulate, should be puzzling. Shouldn't obstructed bowel be empty, since contents can be absorbed? (View Tweet)
- The answer is elegantly demonstrated in animal studies. Ligate the ileum of a dog, and it will die quickly of its bowel obstruction. Ligate the ileum AND the esophagus however, and it will not. At least, not right away; on average, they'll live 36 days!
https://t.co/zuTVHicPDY (View Tweet)
- Swallowed air is the answer. Bowel absorbs fluid, not air. As air is swallowed, the surface to volume ratio of the bowel shrinks; absorption decreases, fluid accumulates, pressure builds, and venous congestion results in ischemia. The bowel first and the patient second, die. (View Tweet)
- Wangensteen went further, inducing various obstructions and analyzing the composition of the aspirated gases to determine their origin. (View Tweet)
- While 68% of gas is atmospheric air, 22% of bowel gas seemed to have diffused out of the static blood, and only 10% originated from food decomposition. Thus, in a closed loop obstruction which can't entrain air, dangerous gas still accumulates.
https://t.co/ETGsx0B8Bl (View Tweet)
- An NG tube with "minimal drainage" is referencing the measurable liquid effluent. The liquid is not, as it turns out, the important part. Bowel can handle liquid. What the NG tube is draining is air. We don't measure and don't see it. (View Tweet)
- Evidence Based Medicine's hierarchy of evidence places multiple trials second only to meta analysis in primacy. There are multiple trials proving this concept from the last century. There is no reason to think our GI tract functions differently from other large mammals with SBO. (View Tweet)
- "NG tubes cause pain."
Yes. They are not there for pain control. (View Tweet)
- "NG tubes cause aspiration."
Yes. They are not there for aspiration prevention. At least not primarily. (View Tweet)
- "NG tubes don't shorten the duration of the obstruction!"
Yes. They aren't supposed to. They are there to keep the bowel alive while you wait it out or plan to operate. You can wait weeks to months in fact, as long as air isn't entrained. (View Tweet)
- "NG tubes don't drain gut contents!"
Well, wrong. They do. Just not the liquid part you measure in the collection cannister. And that's not the important part anyways; the bowel is fully capable of absorbing its own secretions! (View Tweet)
- "But this is all really old, and therefore outdated."
Wangensteen can answer that himself: (View Tweet)
- “There exists a feeling among many physicians and students that anything over 10 years old has no pertinence. ... If you only look forward, it’s tantamount to having a physician with total amnesia. How good would he be?"
https://t.co/919f6liIO0 (View Tweet)
- @rbarbosa91 @JordanNotta @BradleyNori @CANUCSurg
Tagging a small number of people who might care about this stuff! (View Tweet)