- Email: [email protected]
619 Single-Electrode Colon Stimulation and Impedance Monitoring in an Intestinal Aganglionosis Model
617 Efficient Gene Delivery to the Enteric Nervous System by IV Delivery of AAV Vectors Sara E. Gombash Lampe, Christopher Cowley, Julie Fitzgerald, Christian Mueller, Fievos L. Christofi, Kevin Foust Gene therapy may be useful to treat and study the enteric nervous system (ENS). In this study, we characterized transduction efficiency and distribution in the myenteric and submucosal plexuses following intravenous (IV) injection of adeno-associated viral vectors (AAV) expressing GFP in mice. Neonate (P1) mice were injected with AAV9-CB-GFP (3 x 1011 vg) in the temporal vein and juvenile mice (P21) received tail vein injections (2 x 1012 vg). Mice were euthanized at 60-90 days of age, and the myenteric plexus was examined. GFP positive myenteric neurons were found along the entire GI tract in injected mice. Segmental examinations of myenteric neurons in the colon showed no oral-aboral bias. Neuronal transduction ranged from 21-57% depending on the region. GFP co-localized with interneurons, excitatory and sensory myenteric neurons. In contrast, GFP expression in VIP, nNOS and glial cells was absent. However, IV injection of AAV9 with a glial promoter (GFAP) drove GFP expression exclusively in glia. Neonate IV injections with AAV1, 5, and 6 containing the CB-GFP expression cassette produced little to no transgene expression in the myenteric plexus. However, AAV8-CB-GFP showed significantly higher neuronal transduction compared to AAV9 injected mice. AAV8-CB-GFP expressed in all ENS cell types examined including VIP and nNOS neurons and intraganglionic S100 glia. Characterization of AAV-CB-GFP transduction in submucosal neurons is ongoing. These data demonstrate that the ENS is efficiently targeted by AAV8 and AAV9 following IV delivery. Further, transgene expression can be customized with changes in the viral capsid and expression cassette.
619 Single-Electrode Colon Stimulation and Impedance Monitoring in an Intestinal Aganglionosis Model Yi-Kai Lo, Justin Wagner, Chih-Wei Chang, Joshua D. Rouch, James Dunn, Wentai Liu Background: Enteric neuromuscular dysfunction is the defining characteristic in the pathophysiology of Hirschsprung's disease, esophageal achalasia, Chagas disease, and gastroparesis. Medical therapies for these disorders are limited while surgical treatment may incur significant morbidity with variable outcomes. Electrical stimulation (ES) of intestine has been described with inconclusive clinical benefit. In this experimental series, we propose a novel strategy to stimulate aganglionic intestine while simultaneously monitoring myenteric impedance using the same electrode. Tissue impedance variation (TIV) provides a quantifiable feedback when ES is applied to intestinal tissue. Method: This experiment was performed in 12 adult female Lewis rats: 4 underwent jejunal segment isolation and benzalkonium chloride (BAC) aganglionosis induction, 4 underwent colonic segment isolation and BAC aganglionosis induction, and 4 underwent sham laparotomy. A customized versatile multichannel stimulator was used to bi-phasically current stimulate normal and aganglionic intestinal segments in the same rat. TIV of induced segmental contraction and subsequent relaxation were recorded through same electrodes. Stimulation strategies included a long pulse width (PW), high-intensity stimulus to generate smooth muscle (SM) contraction and a short-PW, lowintensity stimulus for impedance measurement. TIV was measured at several stimulus settings to determine the effective parameters to induce SM contraction among aganglionic and normal segments. Results: Extrinsic stimuli generated peristaltic waves of contraction in normal jejunum and colon; only local contraction at the stimulus sites in aganglionic jejunum and colon. At 10 kHz, tissue impedance varied from 3.7-6.25 k V, correlating with the degree of contraction observed grossly. Sequential contractions of aganglionic SM were generated by electrically stimulating and recording impedance at multiple sites longitudinally along the intestinal segment. The chronological multi-site impedance change represented the propagation of peristaltic wave of SM contraction. In all 8 aganglionic jejunal and colonic segements, cathodic-first biphasic stimuli, with 1 ms PW, 1 mA current intensity, and 100 Hz frequency were able to generate SM contraction. The speed of the peristaltic wave can be measured accordingly using impedance method. Conclusion: We report efficient stimulation parameters to generate intestinal SM contraction with a PW significantly shorter than previously reported. Our results demonstrate impedance measurement is a non-invasive effective technique to monitor SM contraction. This method permits further study of gastrointestinal tract electrophysiology in normal and diseased segments, and enables the development of implanted stimulators to treat disorders of enteric neuromuscular dysfunction.
AAV9 mediated GFP expression in green. HuD, a myenteric neuron marker, is in red.
618 Effect of Anesthesia in Colon Motility: Prospective Study of Children With Intractable Constipation Undergoing Colon Manometry Ricardo A. Arbizu, Nicole Heinz, Maureen Amicangelo, Samuel Nurko, Leonel Rodriguez Introduction: Constipation is amongst the most common complaints to pediatricians and pediatric gastroenterologists. Colon manometry (CM) is a useful test to evaluate the pathophysiology of defecation disorders. Currently there is no standardization on its performance with some centers doing the study after anesthesia and others 24 hours later. Information on the effect of anesthesia in colon motility is limited, and its effect on CM interpretation is controversial. Methods: Prospective study evaluating the effect of anesthesia on colon motility and CM interpretation in children with intractable constipation. All patients received a bowel preparation the day before the study and underwent anesthesia with propofol (no narcotics) for catheter placement (6 also received rocuronium). Study started at least 1 hour after anesthesia with patient fully awake. CM was performed on the day of the catheter placement and repeated the next day. Study included an hour of fasting followed by meal and bisacodyl challenges and was interpreted as normal when gastrocolonic (GC) response to a meal and fully propagated high amplitude propagating contractions (HAPCs) were observed. To evaluate the effect of anesthesia on colon motility we compared the motility index of both days on each study phase (fasting, post-prandial and bisacodyl challenge) for left, right and whole colon. To evaluate the effect of anesthesia on CM interpretation we compared the GC response to a meal, quality and quantity of HAPCs and proportions of studies interpreted as normal between both days. Results: A total of 32 children were included, median age was 10.5 years (range 1.5-18 years) and 16 were female. We observed a significant effect of anesthesia in all the colon motility parameters (Table 1). We also found a higher number of HAPCs on day 2 vs. day 1 (10 vs. 6.5, p<0.001) and although we found no significant difference in the presence of HAPCs (p=0.15) between both days, we observed HAPCs on day 2 in 4/5 of the patients with absent HAPCs on day 1 and 3 of those 4 patients demonstrating fully propagated HAPCs on day 2. We found a higher proportion of normal HAPCs on day 2 vs. day 1 (25/32 or 78% vs. 17/32 or 53%, p=0.002). A total of 8/32 (25%) patients with an abnormal study on day 1 were interpreted as normal on day 2. We found no effect of rocuronium on colon motility and study interpretation but
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we found a higher median anesthesia time among those with no HAPCs on day 1 compared to those with HAPCs. All patients with normal study on day 1 remained normal on day 2. Conclusions: Anesthesia has a significant effect in colon motility leading to an incorrect interpretation of the CM as abnormal in up to 25% of patients. CM should be repeated the next day on those patients with an abnormal study on the day of the catheter placement under anesthesia. Table 1. Effect of Anesthesia on Colon Motility
AGA Abstracts
Table 1. Table of Measures
620 Nausea Complicating Recurrent Abdominal Pain in Childhood Predicts Functional GI Disorders, Disability, Depression and Anxiety in Young Adulthood: Results of a Prospective Cohort Study Alexandra Russell, Amanda L. Sherman, Lynn S. Walker Background and Aim: Nausea is common among children with functional abdominal pain (FAP); however, little is known about its co-morbidities and prognosis. Recent studies link chronic nausea to an increased incidence of somatic complaints, anxiety, and social disability in children, but there are no prospective studies on the outcome for these patients in young adulthood. The purpose of this study was to better characterize the short and long term impact of nausea on the wellbeing of children and adolescents with FAP. Methods: Participants were enrolled in a large IRB approved prospective study of FAP in pediatric patients evaluated for chronic abdominal pain at the Vanderbilt Pediatric Gastroenterology Clinic and found to have no organic diagnosis for abdominal pain, age 8-16 years. Patients were defined as having clinically significant nausea if they reported experiencing nausea or upset stomach "a lot" or "a whole lot" within the past two weeks. Validated questionnaires were used to assess abdominal pain, gastrointestinal and somatic symptoms, family stress, self-esteem, and depression at baseline (Table 1). These measures were repeated at follow-up, in addition to measures for anxiety and the Rome III diagnostic criteria. Results: The study sample included 878 pediatric FAP patients; 396 had follow up data 8.7±3.3 years after initial subspecialty evaluation. At initial evaluation, 398 (45%) children had significant nausea. Patients with nausea were slightly older (p=0.001) and experienced significantly more frequent and intense abdominal pain (p<0.0005) than those without nausea. They also reported more gastrointestinal symptoms (p<0.0005), somatic symptoms (p<0.0005), family stress (p=0.046), depression (p<0.0005), functional disability (p<0.0005), and lower self-esteem (P<0.0005). In adolescence and young adulthood, these patients continued to have worse gastrointestinal (p<0.0005) and somatic symptoms (p=0.003) than patients without nausea. At follow up, FAP patients with a history of nausea also reported greater functional disability (p=0.003), anxiety (p=0.009), and depression (p=0.02), and were more likely to meet diagnostic criteria for current irritable bowel syndrome (33% vs. 24%; p=0.036) and functional dyspepsia (25% vs 16%; p=0.034) and for current or lifetime anxiety disorders (58% vs. 46%; p=0.019). Conclusions: Children with chronic abdominal pain and nausea experience increased morbidity in both the short and long term. Its impact on their lives is pervasive, effecting not just gastrointestinal symptoms but also mental health and daily functioning. Pediatricians and gastroenterologists need to be aware that FAP patients with nausea may need more intensive treatment and follow up to improve outcomes. This research was supported by RO1 HD23264.
AGA Abstracts
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631 The Association Between Physician Beliefs, Characteristics and Adenoma Detection Rate: Believing in Your Outcomes Katharine A. Germansky, Ateev Mehrotra, Stephen Strotmeyer, Katie Dean, Robert E. Schoen, Daniel Leffler Background: Adenoma detection rate (ADR) is a key quality indicator of colonoscopy and prior work has documented wide variation in ADR across physicians. Although there is much speculation, what drives the variation in ADR is unknown. Our aim was to create a novel survey to evaluate the relationship between physicians' beliefs and characteristics and their ADR. Methods: We conducted open ended interviews with content experts including gastroenterologists, internists and health care policy experts on potential drivers of ADR. Interviews were conducted until saturation was reached and no further novel content generated. Concepts included three preliminary domains: fund of knowledge, technical skill, and conscientiousness. We developed a series of survey questions specific to colonoscopy around these and performed cognitive debriefing in a mixed panel of academic and private practice gastroenterologists. We also assessed conscientiousness items derived from the Neo PI-R personality inventory. We surveyed 21 gastroenterologists at one academic center and compared responses to ADR's. All survey development and administration took place between June and November 2014. ADR was calculated in consecutive first screening colonoscopies performed over a 9 month period. Survey Characteristics: Responses returned with good item separation. We identified five domains including Coping Under Pressure, Dedication, Conscientiousness, Cognitive versus Technical Interest, and Confidence. Internal consistency within each domain as demonstrated by the Cronbach's a was 0.802, 0.795, 0.546, 0.407, and 0.299, respectively. None of these domains were significantly correlated with ADR but there were expected trends with Pearson correlations ranging from 0.320 to 0.040. Results: The median number of colonoscopies per gastroenterologist was 53 (range 5-309) and mean ADR was 0.24 (range 0.07-0.40). Average number of screening/surveillance colonoscopies performed per week ranged from 1-60, and years in practice ranged from 3-40. 81% of respondents had never received formal feedback on their ADR. Gastroenterologists who believed more strongly that ADR is an important quality measure had significantly higher ADR's (p = 0.037). Respondents who answered that ADR is a fair or poor metric had a mean ADR of 0.22 versus 0.30 in those who reported ADR to be a good, very good or excellent metric. Endoscopists that reported being more comfortable with larger sessile polyp removals found more adenomas overall. Conclusions: Belief that ADR is an important quality indicator and comfort with polypectomy for large sessile lesions are predictors of higher adenoma detection rates. If confirmed in larger cohorts, this survey may be useful to predict colonoscopy quality in settings where ADR is not available and may suggest novel targets for interventions aimed at ADR improvement.
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619 Single-Electrode Colon Stimulation and Impedance Monitoring in an Intestinal Aganglionosis Model Yi-Kai Lo, Justin Wagner, Chih-Wei Chang, Joshua D. Rouch, James Dunn, Wentai Liu Background: Enteric neuromuscular dysfunction is the defining characteristic in the pathophysiology of Hirschsprung's disease, esophageal achalasia, Chagas disease, and gastroparesis. Medical therapies for these disorders are limited while surgical treatment may incur significant morbidity with variable outcomes. Electrical stimulation (ES) of intestine has been described with inconclusive clinical benefit. In this experimental series, we propose a novel strategy to stimulate aganglionic intestine while simultaneously monitoring myenteric impedance using the same electrode. Tissue impedance variation (TIV) provides a quantifiable feedback when ES is applied to intestinal tissue. Method: This experiment was performed in 12 adult female Lewis rats: 4 underwent jejunal segment isolation and benzalkonium chloride (BAC) aganglionosis induction, 4 underwent colonic segment isolation and BAC aganglionosis induction, and 4 underwent sham laparotomy. A customized versatile multichannel stimulator was used to bi-phasically current stimulate normal and aganglionic intestinal segments in the same rat. TIV of induced segmental contraction and subsequent relaxation were recorded through same electrodes. Stimulation strategies included a long pulse width (PW), high-intensity stimulus to generate smooth muscle (SM) contraction and a short-PW, lowintensity stimulus for impedance measurement. TIV was measured at several stimulus settings to determine the effective parameters to induce SM contraction among aganglionic and normal segments. Results: Extrinsic stimuli generated peristaltic waves of contraction in normal jejunum and colon; only local contraction at the stimulus sites in aganglionic jejunum and colon. At 10 kHz, tissue impedance varied from 3.7-6.25 k V, correlating with the degree of contraction observed grossly. Sequential contractions of aganglionic SM were generated by electrically stimulating and recording impedance at multiple sites longitudinally along the intestinal segment. The chronological multi-site impedance change represented the propagation of peristaltic wave of SM contraction. In all 8 aganglionic jejunal and colonic segements, cathodic-first biphasic stimuli, with 1 ms PW, 1 mA current intensity, and 100 Hz frequency were able to generate SM contraction. The speed of the peristaltic wave can be measured accordingly using impedance method. Conclusion: We report efficient stimulation parameters to generate intestinal SM contraction with a PW significantly shorter than previously reported. Our results demonstrate impedance measurement is a non-invasive effective technique to monitor SM contraction. This method permits further study of gastrointestinal tract electrophysiology in normal and diseased segments, and enables the development of implanted stimulators to treat disorders of enteric neuromuscular dysfunction.
AAV9 mediated GFP expression in green. HuD, a myenteric neuron marker, is in red.
618 Effect of Anesthesia in Colon Motility: Prospective Study of Children With Intractable Constipation Undergoing Colon Manometry Ricardo A. Arbizu, Nicole Heinz, Maureen Amicangelo, Samuel Nurko, Leonel Rodriguez Introduction: Constipation is amongst the most common complaints to pediatricians and pediatric gastroenterologists. Colon manometry (CM) is a useful test to evaluate the pathophysiology of defecation disorders. Currently there is no standardization on its performance with some centers doing the study after anesthesia and others 24 hours later. Information on the effect of anesthesia in colon motility is limited, and its effect on CM interpretation is controversial. Methods: Prospective study evaluating the effect of anesthesia on colon motility and CM interpretation in children with intractable constipation. All patients received a bowel preparation the day before the study and underwent anesthesia with propofol (no narcotics) for catheter placement (6 also received rocuronium). Study started at least 1 hour after anesthesia with patient fully awake. CM was performed on the day of the catheter placement and repeated the next day. Study included an hour of fasting followed by meal and bisacodyl challenges and was interpreted as normal when gastrocolonic (GC) response to a meal and fully propagated high amplitude propagating contractions (HAPCs) were observed. To evaluate the effect of anesthesia on colon motility we compared the motility index of both days on each study phase (fasting, post-prandial and bisacodyl challenge) for left, right and whole colon. To evaluate the effect of anesthesia on CM interpretation we compared the GC response to a meal, quality and quantity of HAPCs and proportions of studies interpreted as normal between both days. Results: A total of 32 children were included, median age was 10.5 years (range 1.5-18 years) and 16 were female. We observed a significant effect of anesthesia in all the colon motility parameters (Table 1). We also found a higher number of HAPCs on day 2 vs. day 1 (10 vs. 6.5, p<0.001) and although we found no significant difference in the presence of HAPCs (p=0.15) between both days, we observed HAPCs on day 2 in 4/5 of the patients with absent HAPCs on day 1 and 3 of those 4 patients demonstrating fully propagated HAPCs on day 2. We found a higher proportion of normal HAPCs on day 2 vs. day 1 (25/32 or 78% vs. 17/32 or 53%, p=0.002). A total of 8/32 (25%) patients with an abnormal study on day 1 were interpreted as normal on day 2. We found no effect of rocuronium on colon motility and study interpretation but
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we found a higher median anesthesia time among those with no HAPCs on day 1 compared to those with HAPCs. All patients with normal study on day 1 remained normal on day 2. Conclusions: Anesthesia has a significant effect in colon motility leading to an incorrect interpretation of the CM as abnormal in up to 25% of patients. CM should be repeated the next day on those patients with an abnormal study on the day of the catheter placement under anesthesia. Table 1. Effect of Anesthesia on Colon Motility
AGA Abstracts
Table 1. Table of Measures
620 Nausea Complicating Recurrent Abdominal Pain in Childhood Predicts Functional GI Disorders, Disability, Depression and Anxiety in Young Adulthood: Results of a Prospective Cohort Study Alexandra Russell, Amanda L. Sherman, Lynn S. Walker Background and Aim: Nausea is common among children with functional abdominal pain (FAP); however, little is known about its co-morbidities and prognosis. Recent studies link chronic nausea to an increased incidence of somatic complaints, anxiety, and social disability in children, but there are no prospective studies on the outcome for these patients in young adulthood. The purpose of this study was to better characterize the short and long term impact of nausea on the wellbeing of children and adolescents with FAP. Methods: Participants were enrolled in a large IRB approved prospective study of FAP in pediatric patients evaluated for chronic abdominal pain at the Vanderbilt Pediatric Gastroenterology Clinic and found to have no organic diagnosis for abdominal pain, age 8-16 years. Patients were defined as having clinically significant nausea if they reported experiencing nausea or upset stomach "a lot" or "a whole lot" within the past two weeks. Validated questionnaires were used to assess abdominal pain, gastrointestinal and somatic symptoms, family stress, self-esteem, and depression at baseline (Table 1). These measures were repeated at follow-up, in addition to measures for anxiety and the Rome III diagnostic criteria. Results: The study sample included 878 pediatric FAP patients; 396 had follow up data 8.7±3.3 years after initial subspecialty evaluation. At initial evaluation, 398 (45%) children had significant nausea. Patients with nausea were slightly older (p=0.001) and experienced significantly more frequent and intense abdominal pain (p<0.0005) than those without nausea. They also reported more gastrointestinal symptoms (p<0.0005), somatic symptoms (p<0.0005), family stress (p=0.046), depression (p<0.0005), functional disability (p<0.0005), and lower self-esteem (P<0.0005). In adolescence and young adulthood, these patients continued to have worse gastrointestinal (p<0.0005) and somatic symptoms (p=0.003) than patients without nausea. At follow up, FAP patients with a history of nausea also reported greater functional disability (p=0.003), anxiety (p=0.009), and depression (p=0.02), and were more likely to meet diagnostic criteria for current irritable bowel syndrome (33% vs. 24%; p=0.036) and functional dyspepsia (25% vs 16%; p=0.034) and for current or lifetime anxiety disorders (58% vs. 46%; p=0.019). Conclusions: Children with chronic abdominal pain and nausea experience increased morbidity in both the short and long term. Its impact on their lives is pervasive, effecting not just gastrointestinal symptoms but also mental health and daily functioning. Pediatricians and gastroenterologists need to be aware that FAP patients with nausea may need more intensive treatment and follow up to improve outcomes. This research was supported by RO1 HD23264.
AGA Abstracts
X : 55624$1AGA 03-28-15 04:55:56 PDFd : 55624B : e
631 The Association Between Physician Beliefs, Characteristics and Adenoma Detection Rate: Believing in Your Outcomes Katharine A. Germansky, Ateev Mehrotra, Stephen Strotmeyer, Katie Dean, Robert E. Schoen, Daniel Leffler Background: Adenoma detection rate (ADR) is a key quality indicator of colonoscopy and prior work has documented wide variation in ADR across physicians. Although there is much speculation, what drives the variation in ADR is unknown. Our aim was to create a novel survey to evaluate the relationship between physicians' beliefs and characteristics and their ADR. Methods: We conducted open ended interviews with content experts including gastroenterologists, internists and health care policy experts on potential drivers of ADR. Interviews were conducted until saturation was reached and no further novel content generated. Concepts included three preliminary domains: fund of knowledge, technical skill, and conscientiousness. We developed a series of survey questions specific to colonoscopy around these and performed cognitive debriefing in a mixed panel of academic and private practice gastroenterologists. We also assessed conscientiousness items derived from the Neo PI-R personality inventory. We surveyed 21 gastroenterologists at one academic center and compared responses to ADR's. All survey development and administration took place between June and November 2014. ADR was calculated in consecutive first screening colonoscopies performed over a 9 month period. Survey Characteristics: Responses returned with good item separation. We identified five domains including Coping Under Pressure, Dedication, Conscientiousness, Cognitive versus Technical Interest, and Confidence. Internal consistency within each domain as demonstrated by the Cronbach's a was 0.802, 0.795, 0.546, 0.407, and 0.299, respectively. None of these domains were significantly correlated with ADR but there were expected trends with Pearson correlations ranging from 0.320 to 0.040. Results: The median number of colonoscopies per gastroenterologist was 53 (range 5-309) and mean ADR was 0.24 (range 0.07-0.40). Average number of screening/surveillance colonoscopies performed per week ranged from 1-60, and years in practice ranged from 3-40. 81% of respondents had never received formal feedback on their ADR. Gastroenterologists who believed more strongly that ADR is an important quality measure had significantly higher ADR's (p = 0.037). Respondents who answered that ADR is a fair or poor metric had a mean ADR of 0.22 versus 0.30 in those who reported ADR to be a good, very good or excellent metric. Endoscopists that reported being more comfortable with larger sessile polyp removals found more adenomas overall. Conclusions: Belief that ADR is an important quality indicator and comfort with polypectomy for large sessile lesions are predictors of higher adenoma detection rates. If confirmed in larger cohorts, this survey may be useful to predict colonoscopy quality in settings where ADR is not available and may suggest novel targets for interventions aimed at ADR improvement.
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