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Postoperative Gastrointestinal Telemetry with an Acoustic Biosensor Predicts Ileus vs. Uneventful GI Recovery

Journal of Gastrointestinal Surgery Aims and scope

Abstract

Background

Postoperative ileus (POI) can worsen outcomes, increase cost, and prolong hospitalization. We previously found that a disposable, non-invasive acoustic gastrointestinal surveillance (AGIS) biosensor distinguishes healthy controls from patients recovering from abdominal surgery. Here, we tested whether AGIS can prospectively predict which patients will develop POI in a multicenter study.

Study Design

AGIS is a disposable device embedded with a microphone that adheres to the abdominal wall and connects to a computer that measures acoustic intestinal rate (IR), defined as motility events/minute. We applied AGIS for 60 min before and continuously after abdominal surgery. Clinicians blinded to AGIS recordings clinically separated patients into those with vs. without POI. We used receiver operating characteristic curve analysis to calculate sensitivity, specificity, and negative predictive value (NPV) of AGIS to predict POI.

Results

There were 28 subjects; nine developed POI. Median IR was 3.01/min and 4.46/min between POI and non-POI groups, respectively (P = 0.03). AGIS predicted POI onset with a sensitivity, specificity, and NPV of 63, 72, and 81 %, respectively.

Conclusion

Non-invasive, abdominal, acoustic monitoring prospectively predicts POI. Surgeons may use AGIS to rule out POI with over 80 % certainty; this offers added confidence to advance feeding earlier in those for whom it is safe.

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Grant Support

None to declare.

Conflicts of Interest

This study was conducted with funding from the Principal Investigators (B.S. and W.K.). The technology described in this study is managed by the UCLA Office of Intellectual Property (OIP) and the Cedars-Sinai Technology Transfer Office. At the time of this study, UCLA submitted a patent application and was evaluating university in-licensing options. The authors did not receive outside funding to conduct this study. This is an interim report of an ongoing study per ClinicalTrials.gov: https://clinicaltrials.gov/ct2/show/NCT02065583

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Correspondence to Brennan Spiegel.

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Primary Discussant

John T. Mullen, M.D. (Boston, MA)

Thank you Dr. Kaneshiro for your excellent presentation. You and your co-authors are to be congratulated for building on your prior work demonstrating that gastrointestinal telemetry with an Acoustic Gastro-Intestinal Surveillance (AGIS) biosensor distinguishes healthy controls from patients recovering from abdominal surgery with or without postoperative ileus (POI). In this prospective, multicenter study, you and your colleagues show that AGIS can prospectively predict POI with approximately 80 % certainty. I have three questions for you:

1) In order to obtain reliable and actionable data from AGIS, do the recordings need to be captured continuously, thus committing the patient to being connected to this device at all times, or can brief snapshots provide data that is just as reliable? Is it difficult for patients to ambulate with this device?

2) Is there any correlation between the intestinal rate as measured by AGIS and the more traditional clinical signs we look for to determine whether a patient has an ileus or not, such as the presence of bowel sounds on auscultation or the passage of flatus or a bowel movement?

3) At my medical center, there is certainly a huge push to shorten length of stay while at the same time minimizing readmissions. I can see how this instrument might aid the clinician in determining which patients can be safely fed and discharged early after surgery, even as soon as POD#2. However, we cannot afford to be wrong 20 % of the time. Are efforts underway to devise a different algorithm with better discrimination between the POI and non-POI groups?

Closing Discussant

Dr. Kaneshiro

1. Thank you for the thoughtful questions. No, the recordings do not need to be performed continuously in an uninterrupted manner to yield useful data. However, the more data captured the better, as the predictive algorithms do require multiple data points over multiple days to establish patterns. We have not currently determined the minimum data necessary to make these decisions and that is something we are investigating.

Patients can easily ambulate with the low-profile sensors, similar to ambulating with EKG leads. They simply need to disconnect the wires from the sensors when ambulating and plug them back in when they return, where AGIS resumes recording.

2. The main focus of our current study is to predict POI, however we are also collecting data points such as presence of bowel sounds, flatus and bowel movements for all the study patients and that is something we certainly intend to look at. Given the fact that there is no universally accepted definition of POI, we are defining POI by the outcomes that seem clinically most important such as ability to advance diets, avoid severe symptoms and decreased hospitalizations and costs.

In regards to the question specifically about capturing the presence of bowel sounds by clinicians, the device has the ability to measure sounds of a spectrum wider than the human ear can perceive, so it can potentially show meaning in acoustic signals captured by the device that physicians have been unable to hear with a stethoscope.

3. Although 100 % would certainly be better, we feel that the 80 % accuracy and 80 % NPV are quite good as an additional piece of information that clinicians can use. The device is not necessarily meant to be a stand-alone test, but rather an adjunctive piece of information to help assist the gestalt of clinicians. Currently with ERAS protocols, the default appears to be leaning towards feeding and this device could help to assist with feeding with more confidence.

As far as a different algorithm, as we continue to recruit more patients and data points, we will look for other predictive patterns that could be used to update our current algorithm which already appears to show utility.

Presentations

This study was presented in the SSAT Distinguished Abstract Plenary session of the 2015 Digestive Disease Week (DDW) in Washington, DC. It has not been presented or submitted for publication elsewhere.

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Kaneshiro, M., Kaiser, W., Pourmorady, J. et al. Postoperative Gastrointestinal Telemetry with an Acoustic Biosensor Predicts Ileus vs. Uneventful GI Recovery. J Gastrointest Surg 20, 132–139 (2016). https://doi.org/10.1007/s11605-015-2956-3

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  • DOI: https://doi.org/10.1007/s11605-015-2956-3

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