On the Shoulders of Giants
NG tubes are just mean if they don't help patients.
Don't do this noxious procedure to patients if it doesn't help them. This systematic review identified three retrospective studies that were useful to determine whether NG tube aspiration, +/- lavage, helped differentiate an upper or lower GI source of bleeding in patients with melena or hematochezia but without hematemesis. They found the prevalence of an upper GI bleed (UGIB) ranged from 32-74%. "[Sensitivity of NG aspiration] ranged from 42% to 84%, the specificity from 54% to 91%, and negative likelihood ratio from 0.62 to 0.20."
Let's do an example of a mid-range value from each of these numbers
- Pre-test probability (or prevalence), 53%
- Negative LR, 0.41
- Post-test probability for UGIB, 31.6% (calculation here).
In this scenario, there remains a roughly 1 in 3 chance of an UGIB source with negative NG aspiration - and they still need an EGD.
NG tube aspiration or lavage for UGI bleeding is unhelpful as a diagnostic tool. It's a noxious procedure that is best avoided for this indication. See this for an in-depth review of this article.
Acad Emerg Med. 2010 Feb;17(2):126-32. doi: 10.1111/j.1553-2712.2009.00609.x.
1Department of Emergency Medicine, State University of New York, Downstate Medical Center, Brooklyn, New York, USA. email@example.com
The utility of nasogastric aspiration and lavage in the emergency management of patients with melena or hematochezia without hematemesis is controversial. This evidence-based emergency medicine review evaluates the following question: does nasogastric aspiration and lavage in patients with melena or hematochezia and no hematemesis differentiate an upper from lower source of gastrointestinal (GI) bleeding?
MEDLINE, EMBASE, the Cochrane Library, and other databases were searched. Studies were selected for inclusion in the review if the authors had performed nasogastric aspiration (with or without lavage) in all patients with hematochezia or melena and performed esophagogastroduodenal endoscopy (EGD) in all patients. Studies were excluded if they enrolled patients with history of esophageal varices or included patients with hematemesis or coffee ground emesis (unless the data for patients without hematemesis or coffee ground emesis could be separated out). The outcome was identifying upper GI hemorrhage (active bleeding or high-risk lesions potentially responsible for hemorrhage) and the rate of complications associated with the nasogastric tube insertion. Quality of the included studies was assessed using standard criteria for diagnostic accuracy studies.
Three retrospective studies met our inclusion and exclusion criteria. The prevalence of an upper GI source for patients with melena or hematochezia without hematemesis was 32% to 74%. According to the included studies, the diagnostic performance of the nasogastric aspiration and lavage for predicting upper GI bleeding is poor. The sensitivity of this test ranged from 42% to 84%, the specificity from 54% to 91%, and negative likelihood ratios from 0.62 to 0.20. Only one study reported the rate complications associated with nasogastric aspiration and lavage (1.6%).
Nasogastric aspiration, with or without lavage, has a low sensitivity and poor negative likelihood ratio, which limits its utility in ruling out an upper GI source of bleeding in patients with melena or hematochezia without hematemesis.
(c) 2010 by the Society for Academic Emergency Medicine.
PMID: 20370741 [PubMed - indexed for MEDLINE]