Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

Does Intubation Prevent Aspiration of Stomach Contents?

ResearchBlogging.org
 

This is a study that looked at the rate of aspiration among patients intubated in the PH (PreHospital or EMS) setting and compared them to patients intubated in the ED = (Emergency Department) setting.
 


Image credit.
 

There is one huge difference between these settings – EMS was not authorized to use any form of chemically assisted intubation or RSI (Rapid Sequence Induction/Intubation). At the time of this study, the only drugs available to snow the patient would have been morphine, midazolam (Versed) and/or diazepam (Valium).

One of the reasons for using RSI is to prevent aspiration. If the hurl muscles are paralyzed, will there be a technicolor yawn?
 

Tracheal aspirates were obtained using a standard Leukens trap as soon as endotracheal tube position was confirmed using visualization, auscultation, and end-tidal CO2. If no aspirate could be obtained, 3 mL of normal saline solution was instilled into the endotracheal tube. Each patient was ventilated for several breaths and the sample was then collected. Tracheal aspirates were collected and marked with a study number, and no further patient identifiers other than the study number were used after this point.[1]

 

This was a good way to make this unbiased, but I would have liked to see a repeat of the ED test about 15 and again at about 30 minutes after the original intubation. In Philadelphia, it would be reasonable to expect that the packaging and transport of patients would result in a similar time from intubation to sample collection. A review of the documented times could give a better estimate of the time from intubation to the time of the collection of the pepsin assay sample.

Would this difference in time from intubation to sample collection affect the results?

This is a variable that can be controlled for, so this variable should be controlled for.

How much is cost a factor?

I don’t know, but we draw conclusions from bunches of studies that have asterisks next to them to describe the variables that might have affected the results, when we should be drawing conclusions from much fewer studies that do not need these asterisks.
 

Of the 148 patients intubated in the ED, 33 (22%) had positive pepsin assays, as opposed to 10 (50%) of the 20 patients intubated in the PH setting (OR, 3.5; 95% CI, 1.34-9.08; χ2 P = .008). No patient was excluded owing to inability to obtain a tracheal aspirate.[1]

 

How many of the PH patients aspirated after the endotracheal tube was placed?

How many of the PH patients aspirated during the intubation?

How many of the PH patients aspirated before the intubation?

These are things we really want to know, because there are plenty of people who promote the myth that intubation prevents aspiration.

In a randomized study, with endotracheal tubes and extraglottic airways on the trucks on even days (or odd days), would the incidence of aspiration be lower with intubation or with only BVM ventilation?
 

It is important to note that there is no way of knowing whether the aspiration occurred immediately before, during, or after the actual act of ETI. However, it has been shown that pepsin’s activity in lung secretions diminishes over time, with pepsin testing losing much of its sensitivity after 30 to 60 minutes[14]. Thus, we can be fairly certain that the aspiration events occurred in the peri-intubation period.[1]

 

More than double the rate of aspiration of stomach contents with EMS intubation, but . . .

Would it be better without EMS intubation?

Would it be better with EMS intubation with RSI?

Would it be better with extraglottic airways?

We do not know.

A lot of people will claim that an extraglottic airway will not prevent aspiration, but . . .

Endotracheal tubes do not show any signs of preventing aspiration.
 

Although it is possible that the ETI skills of the paramedics were less than those of the ED staff, it is equally possible that the absence of adjunctive medications (such as RSI medications) may account for some, if not all, of the increase in aspiration rates in the PH setting.[1]

 

The number of PH intubations was very low, so this may be a statistical variation among a very low number of patients. The number of ED intubations was much larger and agrees with a larger study of ED intubations and aspiration performed by the same authors several years earlier.
 

Results: Tracheal aspirates were obtained from 225 patients. The pepsin assay was positive for aspiration in 57 of these patients (25.3%). Only 22 of these 57 patients (38.6%) were deemed definitely or likely to have aspirated by the intubating physician. Of the 105 patients thought unlikely or definitely not to have aspirated clinically, 21 patients (20%) tested positive for aspiration.[2]

 

How good is our opinion of whether aspiration is likely?

Horrible.

Even doctors, working in the much more controlled setting of the ED, do not recognize when aspiration is present or when aspiration is happening.

Even in the more ideal setting of the ED, intubation does not prevent aspiration.

Footnotes:

[1] Aspiration of gastric contents: association with prehospital intubation.
Ufberg JW, Bushra JS, Karras DJ, Satz WA, Kueppers F.
Am J Emerg Med. 2005 May;23(3):379-82.
PMID: 15915418 [PubMed – indexed for MEDLINE]

Free Full Text Download in PDF format from IEP.org.

[2] 128 Incidence of Aspiration after Emergency Endotracheal Intubation and Association with Clinical Suspicion
Joseph S Bushra, Jacob W Ufberg, David J Karras, Friedrich Kueppers;
Temple University School of Medicine: Philadelphia, PA
Academic Emergency Medicine 2002; 9:405. abstract issue

Free Full Text Download in PDF format from Academic Emergency Medicine

Ufberg, J., Bushra, J., Karras, D., Satz, W., & Kueppers, F. (2005). Aspiration of gastric contents: association with prehospital intubation The American Journal of Emergency Medicine, 23 (3), 379-382 DOI: 10.1016/j.ajem.2005.02.005

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Comments

  1. Thank you for the useful post Rogue.

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