Gastric residual volume after split-dose compared with evening-before polyethylene glycol bowel preparation

Accepted Manuscript Gastric residual volume after split-dose compared with evening-before polyethylene glycol bowel preparation Deepak Agrawal, MD, MPH, Assistant Professor, Benjamin Elsbernd, MD, Amit Singal, MD, MS, Assistant Professor, Don Rockey, MD, Professor and Chairman PII:

S0016-5107(15)02872-2

DOI:

10.1016/j.gie.2015.08.081

Reference:

YMGE 9567

To appear in:

Gastrointestinal Endoscopy

Received Date: 14 April 2015 Accepted Date: 19 August 2015

Please cite this article as: Agrawal D, Elsbernd B, Singal A, Rockey D, Gastric residual volume after split-dose compared with evening-before polyethylene glycol bowel preparation, Gastrointestinal Endoscopy (2015), doi: 10.1016/j.gie.2015.08.081. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Title:

Authors:

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Deepak Agrawal MD, MPH Assistant Professor Division of Digestive and Liver Diseases University of Texas Southwestern

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Gastric residual volume after split-dose compared with evening-before polyethylene glycol bowel preparation

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Benjamin Elsbernd MD Internal Medicine Resident University of Texas Southwestern Amit Singal MD, MS Assistant Professor Division of Digestive and Liver Diseases University of Texas Southwestern

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Don Rockey MD Professor and Chairman Department of Medicine Medical University of South Carolina, Charleston. SC

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Corresponding Author: Deepak Agrawal MD POB1, 520P 5323 Harry Hines Blvd University Texas Southwestern Medical Center Dallas 75390 [email protected]

Author contributions

Deepak Agrawal: Study design, data collection and manuscript preparation Benjamin Elsbernd: Analysis and manuscript preparation Amit Singal: Statistical analysis and critical review of manuscript Don Rockey: Study design, data collection and critical review of manuscript

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Title Page

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Gastric residual volume after split-dose compared with evening-before polyethylene glycol bowel preparation

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Deepak Agrawal MD MPH, Benjamin Elsbernd MD, Amit G. Singal MD MS, Don Rockey MD

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From the Division of Digestive and Liver Diseases, University of Texas Southwestern Medical Center and the Department of Internal Medicine, Medical University of South Carolina

Correspondence to:

POB1, 520P 5323 Harry Hines Blvd

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Deepak Agrawal MD

Dallas 75390

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University Texas Southwestern Medical Center

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[email protected]

Conflicts of interest: The authors report no conflicts of interest

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Abstract Background and Aim: Split-dose bowel preparation for colonoscopy results in superior

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preparation quality. However, some endoscopy units remain hesitant to prescribe split-dose preparation given theoretical concerns about possible aspiration caused by gastric residual fluid when a second dose is given close to the time of endoscopy. Our aim was to compare gastric

preparation the evening before colonoscopy.

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residual volume (GRV) in patients taking split-dose bowel preparation and those taking

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Methods: We performed a prospective observational comparison of GRV among random inpatients undergoing same-day EGD and colonoscopy either after split-dose bowel preparations or after bowel preparation the prior evening.

Results: GRV was measured in 150 patients undergoing EGD and colonoscopy: 75 who

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completed split-dose bowel preparation 2 to 3 hours before endoscopy and 75 who completed the bowel preparation regimen the prior evening. The mean GRV 2 to 3 hours after the last ingestion of bowel preparation among split-dose group patients was 21 mL (SD ± 24 mL, range

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0-125 mL), which was not different from the mean GRV of 24 mL (SD ± 22 mL, range 0-135 mL)

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in patients who ingested the preparation the prior evening (p=0.08). GRV had no association with the presence of diabetes, gastroparesis, or opioid use. Conclusion: GRV is the same after a split preparation and fasting for 2 to 3 hours or after preparation with overnight fasting. The data suggest that the risk of aspiration is identical after either preparation technique, and thus that sedation for colonoscopy can be performed safely 2 hours after bowel prep ingestion.

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Introduction

Split-dose bowel preparation, in which a portion of bowel preparation is given the morning of

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the procedure, results in superior quality of bowel preparation and is better tolerated.1-8 Despite evidence-based recommendations supporting the use of a split-dose bowel

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preparation, adoption of this practice has been limited due to practical difficulties.9 For

example, some physicians, including many anesthesiology providers, mandate waiting 6 to 8

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hours after the last ingestion of bowel preparation in hopes of decreasing the aspiration risk. This necessitates either asking the patients to wake up at 2 to 3 AM or scheduling their procedure in the afternoon. Although some patients are willing to wake up in the middle of the night when told it helps clean the colon adequately and avoid repeating colonoscopy10, is it

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really necessary? This idea remains unpopular because one-third of patients may be unwilling to wake up early to complete split-dose preparation11.

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The American Society of Anesthesiologists (ASA) recommends a fasting period of 2 hours for clear liquids before administering sedation.12 Bowel preparations by their nature are clear

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liquids, although the guidelines do not specifically address this point. However, many anesthesiologists remain concerned about aspiration risk. With an increasing number of colonoscopies being performed using propofol by anesthesiology providers, a waiting time of 6 to 8 hours has become a de facto standard in many centers. To address this issue, we conducted a prospective study comparing gastric residual volume (GRV) among patients after split-dose bowel prep and those who took bowel prep the evening before colonoscopy.

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Methods

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Study Setting and Population Patients admitted to Parkland Memorial Hospital, the safety net health system of Dallas County, between March 2013 and June 2014, who required both upper endoscopy and colonoscopy on

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the same day were potentially eligible for the study. We excluded patients with active

gastrointestinal bleeding (ie, melena, hematemesis, or hematochezia) and those admitted to

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the intensive care unit. We intentionally did not exclude patients with medical conditions potentially associated with delayed gastric emptying such as diabetes, documented gastroparesis, and/or use of opioid medications.

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Patients received bowel preparation as recommended by the gastroenterology consulting service, and agreed upon by the anesthesiology provider (if applicable). If both sets of providers agreed to a 2-hour time interval for sedation after last ingestion of bowel preparation, patients

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were prescribed a split-dose preparation. If the providers involved with the procedure preferred to wait longer than 2 hours, the patients received standard bowel preparation. The

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standard preparation included at least 4 liters of polyethylene glycol (PEG) (GoLytley; Braintree Laboratories, Braintree, Mass) the evening before the procedure. The patients were then instructed to be “nil per os” (NPO, nothing by mouth) after midnight. The split-dose bowel preparation included 4L of PEG the evening before the procedures and an additional 1 L of PEG administered between 5AM and 6AM the morning of the procedure. The split-dose regimen that we used is different from the split-dose regimen described in earlier studies, which is

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typically administered 2L the evening before the procedure and 2L administered the morning of the procedure. The modification was necessary due to logistical difficulties and practical

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limitations. First, for us to implement the 2L + 2L split dose would have necessitated changes in Epic (our electronic medical record) as well as re-education of the hospital nursing staff. Our leadership felt that this would be feasible only if this regimen could be adapted for all patients

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undergoing colonoscopy, rather than only for patients undergoing colonoscopy with moderate sedation. We had already been using a 4L + 1L split-dose prep for patients who had history of

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prior inadequate preps and found that it worked very well, and thus used it for this study.

Upper endoscopy was performed between 8 and 9AM (2-3 hours after last ingestion of bowel prep). Patients in the split-dose group in whom EGD could not be performed within this time

excluded.

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Data Collection

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frame or those who did not finish a minimum 500 mL of the morning bowel preparation were

The GRV was measured, immediately after sedation and insertion of endoscope into the

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stomach, by suctioning all fluid through the suction channel of the endoscope, without addition of any water (including water used to cleanse the endoscope lens or irrigation). The suctioned fluid was collected in a calibrated container attached to the suction port of the endoscope. The volume of fluid collected was measured and recorded by the endoscopy nurse. Patient demographics, medical comorbidities and treatment, and indication for endoscopy were recorded for each patient from review of the electronic medical record. Patient

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demographics of interest included age and gender. Medical comorbidity data included history of diabetes, gastroparesis, and use of metoclopramide, erythromycin, or opioid medications.

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Patients were considered to have diabetes if they were taking any medication for diabetes as an outpatient and considered to have gastroparesis if the diagnosis had been confirmed by gastric emptying scan. Use of opioid medications was defined as patients administered

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scheduled opioid medications as inpatients. Indications for upper endoscopy and colonoscopy for each patient were noted. Any sedation-related difficulties or adverse events were recorded,

transfer to higher level of care.

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including witnessed aspiration or vomiting, use of reversal agent, prolonged recovery time, or

The study was approved by the Institutional Review Board (IRB) at UT Southwestern Medical

Statistical Analysis

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Center and all patients signed written informed consent.

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Our primary outcome of interest was GRV. In a post-hoc power calculation, we found 96 patients (48 in each group) would provide 90% power, with an alpha of 0.05, to demonstrate

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non-inferiority, assuming a non-inferiority margin of 15 mL. Including 150 patients (75 in each group) would provide 90% power to demonstrate non-inferiority assuming a margin of 12 mL. We used the Fisher exact test and Wilcoxon rank-sum test for categorical and continuous variables, respectively, to identify covariates associated with GRV. Multivariate logistic regression was then performed using variables significant on univariate analysis as well as variables of a priori clinical importance. Statistical significance was defined as p≤ 0.10 for

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univariate and p< 0.05 for multivariate analyses. All data analyses were conducted using Stata 11.0 (College Station, Tex).

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Results Patient Characteristics

In total, 161 patients were included in the study. Eighty-six patients were given split-dose bowel

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preparation, of whom 11 drank less than 500 mL of the preparation or the EGD and

colonoscopy could not be performed within 3 hours. Therefore, 75 patients from the split-dose

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group were included in the final analysis and compared with 75 consecutive patients who completed the bowel prep the evening before the procedure. The mean (± SD) age of the cohort was 61 years ± 12 years and 51% were male. There were 22 patients with a history of diabetes, 7 with a history of gastroparesis and 28 patients with periprocedure use of opioids (18

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taking hydromorphone, 6 morphine, 4 hydrocodone). Patient demographics, other comorbid diseases, and medications were similar in the 2 groups, with the exception that patients who

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completed the bowel preparation the night before had a higher mean age (64 ± 12 vs 58 ± 12 years) (p 0.005) (Table 1). The indications for the bidirectional endoscopy were as would be

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expected, and were similar in both groups. Patients in the split-dose group underwent procedures with moderate sedation, whereas those in the standard bowel preparation group had sedation administered by an anesthesiology provider. (The practice of anesthesiology providers at our institution was such that they agreed to be involved in procedures only after a minimal fasting time of 6 hours after bowel preparation, due to fear of aspiration.)

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Gastric Residual Volume The mean (± SD) gastric residual volume (GRV) in patients receiving split-bowel prep was 21 mL

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± 24 mL and for those receiving bowel preparation the evening before and then fasting overnight, was 24 mL ± 22 mL (Figure 1). Although GRV was higher in the standard bowel-prep group, this difference did not reach statistical significance (p=0.08). Furthermore, the median

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gastric residual volume in both groups was only 20 mL, and these small volumes are unlikely to have clinical significance. Among patients who received the split-dose preparation, there was

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no difference in GRV at 2, 2.5, and 3 hours, with mean ± SD GRV of 27 ± 29 mL, 16 ± 26 mL, and 17 ± 14 mL, respectively (p = 0.27) (Figure 2).

We also evaluated whether diabetes, gastroparesis, or use of opioids might affect GRV. There

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was no difference in the GRV among those with a history of diabetes (p = 0.08), gastroparesis (p=0.28), use of opioids (p=0.62), or those without these comorbidities (Figure 3). There was no difference in the GRV among those with these comorbidities in the split-dose group compared

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with those with these comorbidities in the overnight group (p=0.3).

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No patient in either group had any evidence of aspiration or other endoscopy-related adverse events during their procedures.

Discussion Here, we have shown that the GRV 2-3 hours after ingestion of bowel preparation in inpatients is trivial and same as in patients fasting overnight. Further, the use of narcotics, presence of

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diabetes, or gastroparesis did not appear to alter GRV. These findings suggest that it is as safe to undergo colonoscopy 2 to 3 hours after the last ingestion of bowel preparation as it is to wait

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for 8 hours or longer. This implies that there is no need to adhere to the impractical practice of asking patients to wake up in the middle of the night to take the second portion of a split-dose

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prep due to concern for aspiration.

GRV has been used as a surrogate marker for risk of aspiration because a higher GRV likely

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increases the probability of fluid refluxing into the lungs. However, the actual volume of retained fluid that increases risk of aspiration remains undefined. GRV ≥25 mL is often used as a critical value for patients.14 This value was extrapolated from an experiment in 1974, in which direct injection of 0.4 mL/kg of acidified content into the bronchus of a rhesus monkey resulted

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in pulmonary adverse events. For a 60 kilogram human, this translates into a volume of 25 mL. The assumptions made in derivation of this often quoted number have been challenged in many studies15, 16, and most now agree that the GRV that poses an aspiration risk is likely much

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higher than 25 mL. This is further supported by our observation that many patients who fast overnight have GRV >25 mL. Because overnight fasting is the accepted standard, we compared

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GRV in patients who ingested bowel prep the morning of colonoscopy with GRV in those who fasted overnight.

We found no significant differences between GRV in the split-dose group and those who took the bowel preparation the prior evening. A prior study also found no significant differences in GRV between patients receiving split-dose bowel prep and those that took the bowel prep the

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prior evening.17 However, the mean time between last fluid ingestion and endoscopy in the split-dose group was 5.1 hours (SD 2.5; range 2-14 hours). This long mean time may explain

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why some anesthesiology providers remain hesitant to shorten their recommended fasting interval before sedation. In our study, endoscopies in the split-dose group were performed only 2 to 3 hours after last ingestion of prep. A second notable difference between these 2 studies is

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that the previous study included mostly outpatients, whereas all subjects in the current study were inpatients. This is important because inpatient status has been raised as a concern for

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delayed emptying, and an increased aspiration risk.18 Additionally, in an attempt to make our study more practical and generalizable, our study intentionally included patients with comorbidities such as those with known gastroparesis.

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Although the mean GRV was less than 25 mL in both groups, GRV ranged from 0 mL to 135 mL. There were 5 patients with volume >100 mL, with patients in both groups being equally likely to have GRV > 100 mL. Of these 5 patients, 2 had history of diabetes mellitus and one of these

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of opioids.

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was also prescribed metoclopramide. None of the patients had history of gastroparesis or use

In our study, there were no sedation-related adverse events among these 5 patients. Some studies even suggest ingestion of fluids may promote gastric emptying by causing gastric distension and ensuing gastric contraction.19 Because it remains unproven what gastric volume causes aspiration risk, endoscopists should remain cautious and suction any excess fluid seen in the stomach to decrease aspiration risk, especially in a deeply sedated patient.

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Furthermore, we found no association between GRV and conditions associated with delayed

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gastric emptying such as diabetes, gastroparesis, and narcotic use. This is important given a recent survey of 109 chiefs and directors of anesthesiology at academic institutions found 72% preferred to wait longer before endoscopy in patients with a history of diabetes.20 Prior studies

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also do not substantiate longer wait intervals in diabetics.17, 21 This is not surprising because gastroparesis in diabetes is relatively uncommon, occurring in only 1% of type 2 diabetics and

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5% of type 1 diabetics over a 10-year time period.22 Even in patients with established gastroparesis, the gastric emptying time for liquids is prolonged by only a few minutes and continues to be much shorter than the 2-hour fasting recommendation for patients.23 Similarly, opioids also prolong liquid gastric emptying time by only a few minutes (~ 20 minutes for half

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the liquid to empty)—well under 2 hours24 and hence clinically inconsequential.

Although our data suggest it is safe to administer sedation 2 to 3 hours after ingestion of bowel

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prep, there may be reasons to wait longer. For example, a patient scheduled for an outpatient procedure may need a longer time interval to avoid using the restroom on the way to the

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hospital. Also, there is evidence that quality of bowel preparation is optimal 4 to 6 hours after the morning dose of prep solution.25, 26 However, having the option to perform colonoscopy 2 hours after bowel prep can make scheduling easier (especially for inpatients), is optimal when patients are given rapid bowel prep before urgent colonoscopy, and may be preferred by some patients.

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We recognize potential limitations of our study. First, patients were not randomized, and this could have led to bias. However, we intentionally chose to use a pragmatic approach as would

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be practiced in real life situations. The data also suggest that the patient groups were similar with regard to all clinical features, except age and method of sedation. Because age has been shown to not affect gastric emptying time27, we doubt that a difference in age has any effect on

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the interpretation of our findings. Conscious sedation was provided to the split-dose group in contrast to anesthesia for those in the overnight fasting group due to the preference of

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anesthesiology providers at our institution to wait at least 4 hours after the last ingestion of bowel prep. One reason for this is that many anesthesiologists consider PEG to be a full liquid rather than a clear liquid20. The type of sedation administered unlikely has any impact on gastric emptying, especially because sedation was administered just before the procedure. A

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second limitation is that endoscopists were not blinded to the type of bowel preparation taken by patients. To avoid bias in measuring GRV, the amount of fluid collected in the suction container was recorded by the endoscopy nurse rather than the endoscopist. A further point is

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that, we used a “modified” split-dose preparation where patients ingested 4L PEG the evening before and 1L PEG the morning of the procedure rather than the more widely used split-dose of

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2L the evening before and 2L the morning of the procedure. Apart from logistic reasons, our rationale for this was several-fold. First, other practioners3, 13 have described 3L + 1L or 2L + 1L split-dose regimens, similar to what we used, and found them to be effective. Additionally, we had already been using a 4L + 1L split-dose prep in some patients, and found it to be excellent, and thus used it for our study. Finally, our experience is that the 4L + 1L split-dose prep regimen is better tolerated than the 2L + 2L prep because patients are required to drink only 1L in the

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morning of the procedure. We would emphasize that using only 1L versus 2L of preparation the morning of the procedure is not likely to affect the generalizability of our results because the volume of ingested fluid has been reported to be less important than type or timing of

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ingestion of fluid12.

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Although we included patients with a history of diabetes in our study, hemoglobin A1c or other measures of diabetic control were not available in many patients and thus not reported.

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However, there appears to be poor correlation between gastric emptying time and HbA1c levels. We measured blood glucose levels at the time of the procedure, which has been shown to be a better determinant of gastric emptying in diabetics.28 We intentionally studied inpatients - and this could limit the generalizability of our findings. Notwithstanding, we believe

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the results of our study should be generalizable to outpatients because patients admitted to the hospital would be expected to have more comorbidities than outpatients that could theoretically hinder gastric emptying. We also note that we did not study low volume split-

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dose preparations. However, even typical low volume preparations administer around 1L of fluid in the morning of the procedure, and thus our results may be applicable to these bowel

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preparations. Finally, we did not study GRV sooner than 2 hours after the last ingestion of preparative material. Because gastric emptying is typically very rapid, it is possible that GRVs are low as soon as 30 minutes to 1 hour after the last ingestion of preparation.

In summary, our data indicate that bowel preparation given up to 2 hours before endoscopy leads to the same (trivial) GRV as does bowel preparation given the night before an overnight

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fast. The data thus suggest the risk for aspiration is low, and support the American Society of Anesthesiologists recommendations that clear liquids, including bowel preparations, can be

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taken up to 2 hours before sedation. We propose that physicians need not wait longer than 2 hours after the last ingestion of bowel preparation out of concern for aspiration to proceed

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with endoscopy.

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Figure Legends

Figure 1. Gastric residual volume (GRV) in patients receiving split-dose bowel preparation and those receiving bowel preparation the prior evening. The horizontal lines indicate the mean

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GRV.

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Figure 2. Gastric Residual Volume (GRV) in patients 2, 2.5, and 3 hours after ingestion of bowel prep compared with patients who fasted overnight. Some dots represent multiple patients.

Figure 3. Gastric Residual Volume (GRV) in all patients with diabetes, gastroparesis, those

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taking opioids, and with all 3 conditions versus those without these conditions.

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Tables

Split-dose

before

preparation

Age (years)

64 ± 12

58 ± 12

Sex (% males)

56

51

Diabetes

10

12

Gastroparesis

3

4

Opioid use

15

Mean glucose (diabetics)

116 ± 21

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P = 0.65

p = 1.00

P = 0.13

25

P = 0.86

13

P = 1.00

5

4

P = 1.00

1

7

P = 0.02

8

3

P = 0.21

24

23

P = 1.00

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GI bleed (including melena)

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Other UGI conditions + screening

P = 0.62

132 ± 26

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Abnormal Imaging

P = 0.005

p = 0.83

Anemia

IBD

P value

13

Indications for procedures

Abdominal Pain

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Preparation the evening

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Table 1.

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GRV – gastric residual volume ASA- American Society of Anesthesiologists PEG – Polyethylene glycol NPO – nil per os mL – Milliliter L – Litre IRB – Institutional Review Board

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1. 2. 3. 4. 5. 6. 7.

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Acronyms used