Gastrointestinal Ostomies in Children: A Primer for the Pediatrician

Despite the advancement of medical therapies in the care of the preterm neonate, in the management of short bowel syndrome and the control of pediatric inflammatory bowel disease, the need to create fecal ostomies remains a common, advantageous treatment option for many medically complex children.

Improved Outcomes in Eosinophilic Esophagitis with Higher Medication Possession Ratio

Eosinophilic esophagitis (EoE) disease activity can be caused by treatment non-adherence. Medication possession ratio (MPR) is an established metric of medication adherence. A higher MPR correlates with better outcomes in several chronic diseases, but MPR has not been investigated with respect to EoE. A retrospective cohort study was performed using an established EoE registry for the years 2005 to 2020. Treatment periods were identified, MPRs were calculated, and medical records were assessed for histologic remission (<15 eos/hpf), dysphagia, food impaction, stricture occurrence, and esophageal dilation that corresponded to each treatment period. In total, 275 treatment periods were included for analysis. The MPR in the histologic remission treatment period group was 0.91 (IQR 0.63-1) vs. 0.63 (IQR 0.31-0.95) for the non-remission treatment period group (p < 0.001). The optimal MPR cut-point for histologic remission was 0.7 (Sen 0.66, Spec 0.62, AUC 0.63). With MPRs ≥ 0.7, there were significantly increased odds of histologic remission (odds ratio 3.05, 95% confidence interval 1.79-5.30) and significantly decreased odds of dysphagia (OR 0.27, 95% CI 0.15-0.45), food impaction (OR 0.26, 95% CI 0.11-0.55), stricture occurrence (OR 0.52 95% CI 0.29-0.92), and esophageal dilation (OR 0.29, 95% CI 0.15-0.54). Assessing MPR before repeating an esophagogastroduodenoscopy may decrease unnecessary procedures in the clinical management of eosinophilic esophagitis.

Marching Band Injuries in Children Presenting to Emergency Departments in the United States, 2012-2021: A Trebling Tale

Marching band is both a sport and a performance art. Organized athletics like American football, soccer, and cheerleading all have established epidemiologic trends of injury, including stigmata from head trauma. Despite the potential for mild to severe injury, there is a paucity of data on marching band-related morbidity. We examined the National Electronic Injury Surveillance System from 2012 to 2021 to describe demographic information and injury patterns. There were an estimated 20 335 marching band injuries (95% confidence interval: 12 892-27 777). The majority of injuries occurred in females (70%), and those aged 14 to 18 years (85%). Fifty percent of all injuries occurred in the lower extremity, and soft tissue injuries were the most frequently observed diagnosis (49%). Mild traumatic brain injury accounted for 6% of all injuries. Of marching band injury, 98% did not require escalation of care. Based on these findings, we suggest targeted public health intervention by sports medicine teams.

Autoimmune gastritis as an unexpected cause of diarrhea in a young adult with type I diabetes: a case report

BACKGROUND

Type 1 diabetes mellitus (T1DM) is a lifelong diagnosis that involves immune-mediated damage of pancreatic beta cells and subsequent hyperglycemia, manifesting as: polyuria, polydipsia, polyphagia, and weight loss. Treatment of type 1 diabetes centers on insulin administration to replace or supplement the body's own insulin with the goal of achieving euglycemia and preventing or minimizing complications. Patients with T1DM are at risk for developing other autoimmune conditions, most commonly thyroid or celiac disease.

CASE PRESENTATION

A 20-year-old African American female with T1DM was referred by her endocrinologist to pediatric gastroenterology for 2 months of nocturnal, non-bloody diarrhea, left lower quadrant pain, and nausea; she was also being followed by neurology for complaints of lower extremity paresthesias and pain. The patient's initial lab-workup was remarkable for a low total Immunoglobulin A (IgA) level of < 6.7 mg/dL. As IgA deficiency is associated with an increased risk of celiac disease, the patient underwent upper and lower endoscopy, which was grossly unremarkable; however, histology revealed a pattern consistent with autoimmune gastritis. Subsequent serum evaluation was remarkable for an elevated fasting gastrin level and an elevated parietal cell antibody level without macrocytic anemia, iron deficiency, or vitamin B12 depletion. The patient was diagnosed with autoimmune gastritis (AIG) and subsequently initiated on parenteral B12 supplementation therapy with improvement in her neurologic and gastrointestinal symptoms.

CONCLUSION

This case illustrates the importance of recognition of red flag findings in a patient with known autoimmune disease. Following well-established health maintenance recommendations for individuals with T1DM ensures that common comorbidities will be detected. Autoimmune gastritis, while a rarer pathology in the pediatric population, deserves consideration in patients with pre-existing autoimmune conditions and new gastrointestinal or neurologic symptoms, as AIG can be associated with poor outcomes and risk of malignancy. Initial lab findings associated with an eventual diagnosis of AIG typically include anemia, iron deficiency, or Vitamin B12 deficiency. However, as demonstrated in this case, symptoms of AIG can rarely present before anemia or Vitamin B12 deficiency develops. To prevent permanent neurological damage, parenteral Vitamin B12 therapy must be considered even in the absence of Vitamin B12 deficiency, especially in those patients already experiencing neurological symptoms.

Gastrointestinal Bleeding in the Neonate: Updates on Diagnostics, Therapeutics, and Management

Gastrointestinal bleeding (GIB) is a relatively uncommon presentation in the NICU. GIB in neonates includes a broad spectrum of disease morbidity, from minor reflux symptoms and growth failure to severe, clinically significant anemia requiring critical care resuscitation. Over the last several years, multiple diagnostic tools including fecal calprotectin and bedside ultrasonography have emerged and demonstrated utility in the early recognition of sources for GIB in neonates. Further evidence has continued to show that traditional medical therapy with intravenous proton pump inhibitors is well-tolerated, and that upper endoscopy has limited diagnostic and therapeutic value. Finally, additional research and quality improvement investigations are warranted to determine how best to prevent, recognize, and manage GIB in critical neonates.

Development and assessment of a low literacy, pictographic asthma action plan with clinical automation to enhance guideline-concordant care for children with asthma

OBJECTIVE

Asthma is characterized by reversible pulmonary symptoms, frequent hospitalizations, poor quality of life, and varied treatment. Parents with low health literacy (HL) is linked to poor asthma outcomes in children. Recent practice updates recommended inhaled corticosteroids for the management of persistent asthma, but guideline-concordant care is suboptimal. Our aim was to develop and assess an Asthma Action Plan (AAP) that could serve as an individualized plan for low HL families and facilitate guideline-concordant care for clinicians.

METHODS

We followed the National Institute of Health 5-step "Clear & Simple" approach to develop the Uniformed Services AAP. Our AAP included symptom pictographs (dyspnea, cough, sleep, activity) and guideline-concordant clinical automation tools. Caregivers assessed the pictograms for validity (transparency of ≥ 85%; translucency score ≥ 5; and ≥ 85% recall). Readability was assessed using 7 formulas. (<6th Grade was acceptable). Comprehensibility, design quality, and usefulness was assessed by caregivers using the Consumer Information Rating Form (CIRF) (>80% was acceptable). Understandability and actionability was assessed by medical librarians using the Patient Education Materials Assessment Tool-Printable (>80% was acceptable). Suitability was assessed by clinicians using the modified Suitability Assessment of Materials (SAM) instrument (>70% was superior).

RESULTS

All 12 pictograms were validated (N = 118 respondents). Readability demonstrated a 4th grade level. Overall CIRF percentile score = 80.4%. Understandability and Actionability = 100%. Suitability score = 75%.

CONCLUSIONS

Our AAP was formally endorsed by the Allergy & Asthma Network. The Uniformed Services AAP is a novel tool with embedded clinical automation that can address low HL and enhance guideline-concordant care.

The Uniformed Services Constipation Action Plan: An Effective Tool for the Management of Children with Functional Constipation

OBJECTIVE

To implement and to evaluate the effectiveness of the Uniformed Services Constipation Action Plan (USCAP) in our gastroenterology clinic for children with functional constipation.

STUDY DESIGN

This implementation science study included toilet-trained subjects aged 4 years and older who met the Rome IV criteria for functional constipation. Children were block randomized to receive either the USCAP or control. All clinic functional constipation plans recommended subjects continue pharmacotherapy for 4 months. Endpoints measured were clinical outcomes (resolution of functional constipation and achievement of a Pediatric Bristol Stool Form Scale [PBSFS] score of 3 or 4), patient-related outcomes (health-related quality of life [HRQoL] total scale score), and health confidence outcomes (Health Confidence Score [HCS]).

RESULTS

Fifty-seven treatment group subjects (44%) received a USCAP (52% male; mean age, 10.9 [4.9] years) compared with 73 controls (56%; 48% male; mean age,10.9 [5.3] years). A PBSFS score of 3 or 4 was achieved by 77% of the treatment group compared with 59% of controls (P = .03). Subjects from the treatment group were more likely than the controls to endorse adherence to the 4-month course of pharmacotherapy (P < .001). Subjects who received a USCAP had greater improvements in HRQoL total scale score by the end of the project (P = .04).

CONCLUSIONS

The USCAP is a simple, inexpensive tool that has the potential to improve global outcomes for functional constipation in children and should be recommended as standard clinical practice.

Development and Assessment of a Low Literacy, Pictographic Cyclic Vomiting Syndrome Action Plan

OBJECTIVE

To develop and assess an evidence-based, individualized Cyclic Vomiting Syndrome Action Plan (CVSAP) to optimize both preventative and acute care.

STUDY DESIGN

This implementation science project synthesized a combination of clinical practice guidelines, published literature, and clinical experience by a team of CVS clinicians to develop the CVSAP. The tool was developed to include validated pictograms and an automatic, embedded, weight-based dosing calculator to output acute management recommendations. The final version of the CVSAP was tested by patients/caregivers, readability calculators, medical librarians, and clinicians using validated metrics.

RESULTS

All pictograms met the criteria for inclusion in the CVSAP. A composite readability score of 5.32 was consistent with a fifth-grade level. Patients/caregivers (n = 70) judged the CVSAP to be of high quality with consumer information rating form rating of 84.2%. Six medical librarians rated the CVSAP to have 93% understandability and 100% actionability, and 33 clinicians completing the SAM generated a suitability rating of 87.5%.

CONCLUSIONS

The CVSAP visually highlights individualized care plan components to facilitate optimized preventative and acute CVS care. Further investigation will determine if CVSAP increases caregiver confidence and compliance in home management and improves quality of life and clinical outcomes for patients with CVS.

Development and assessment of a low-health-literacy, pictographic adrenal insufficiency action plan

OBJECTIVES

Adrenal insufficiency (AI) is an overall rare disorder characterized by the chronic need for pharmacotherapy to prevent threat to life. The Pediatric Endocrine Society has recommended the use of clinical action tools to improve patient education and help guide acute management of AI. We aimed to develop and assess an easy-to-use, patient-friendly, evidence-based, personalized pictogram-based adrenal insufficiency action plan (AIAP) to aid in the management of AI in children.

METHODS

Patients/caregivers (P/Cs) responded to surveys which measured the concepts of transparency, translucency, and recall in order to assess the pictograms. Readability was assessed using six formulas to generate a composite readability score. Quality was graded by P/Cs using the Consumer Information Rating Form (CIRF) (>80% rating considered acceptable). Understandability and actionability was assessed by medical librarians using the Patient Education Materials Assessment Tool-Printable (PEMAT-P) (>80% rating was acceptable). Suitability was evaluated by clinicians using the Suitability Assessment of Materials (SAM) instrument (>70% rating considered superior).

RESULTS

All pictograms met criteria for inclusion in the AIAP. Composite readability score=5.4 was consistent with a fifth-grade level. P/Cs (n=120) judged the AIAP to be of high quality with CIRF rating=85.2%. Three medical librarians rated the AIAP to have 100% understandability and 100% actionability. Thirty-three clinicians completing the SAM generated a suitability rating of 90.0%.

CONCLUSIONS

The AIAP visually highlights individualized care plan components to facilitate optimized preventative and acute AI care. Further investigation will determine if AIAP improves clinical outcomes for patients with AI.

Toilet Injuries Presenting to Emergency Departments, 2000-2019: A Different Game of Thrones

OBJECTIVE

Toilet training is a major developmental milestone. Unsupervised periods combined with immature gross and fine motor skills may lead to toddler injuries during toilet training. Our aim was to investigate toilet-related injuries (TIs) in children.

METHODS

Data from the National Electronic Injury Surveillance System were used to evaluate emergency department encounters of children ages 0 to 6 years with TI from 2000 to 2019.

RESULTS

There were an estimated 142,606 children (95% confidence interval, 115,599-168,613) who presented to the emergency department for TI. Toilets were involved in 95% of injuries, and other potty chairs (PCs) involved 5% of injuries. Children had higher odds of sustaining head injury while using a toilet versus PC (adjusted odds ratio = 1.91; 95% CI, 1.06-3.45).

CONCLUSIONS

Toilet-related injuries present a high burden of risk to young children. Our data support that the safest vessel for use in toilet training is a PC/training seat as opposed to the toilet.

Austere Foreign Body Injuries in Children and Adolescents: A Characterization of Penile, Rectal, and Vaginal Injuries Presenting to Emergency Departments in the United States From 2008 to 2017

BACKGROUND

Pediatric foreign body (FB) injuries to the nasal, aural, and/or oral cavities are well documented. Description of austere foreign body (AFB) injuries involving the rectum, vagina, or penis eludes the current pediatric literature. Austere FBs can be difficult to identify and have the potential to cause serious consequences. We aim to characterize AFB injuries by children and adolescents presenting to emergency departments (EDs) in the United States.

METHODS

The National Electronic Injury Surveillance System was queried to include subjects aged 0 to 25 years using a primary search term for diagnosis of foreign body from the period of January 2008 to January 2017. The consumer product and the body part involved (ie, rectal, vaginal, penile) were analyzed. Taylor series linearization generated national estimates. A trend analysis was performed using the Cochrane Armitage test of trend.

RESULTS

There were 27,755 (95% confidence interval, 21,170-34,338) national estimated childhood ED visits for suspected AFB injuries during 2008 to 2017 including an estimated 7756 vaginal FBs, 7138 penile FBs, and 8359 rectal FBs (RFBs). Over the timeline, there was a significant up trend in the frequency of annual RFBs (P < 0.01).

CONCLUSION

Austere FB injuries appear to cluster around age of 7 years. Most AFB injuries are able to be treated and released from the ED. It appears that RFB injury frequencies are rising and tend to require more frequent admission. Providers must be vigilant in the diagnosis and management of these potentially hazardous injury types.

Development and Implementation of DIGEST: The Digital Interactive Gastroenterology Education Suite for Trainees

INTRODUCTION

Clinical clerkship curricula should exist to provide rotating learners on subspecialty rotations with consistent exposure to specific topics geared toward the discipline of interest, such as pediatric gastroenterology (GI). We aim to describe our experience developing and implementing DIGEST: the Digital Interactive Gastroenterology Education Suite for Trainees, a novel, online GI curriculum delivered to virtual, rotating learners during the coronavirus (COVID-19) pandemic stay-at-home order.

MATERIALS AND METHODS

A general needs assessment in 2019 identified a lack of standardized educational experience amongst the rotating learners on pediatric GI service. The COVID-19 pandemic compelled us to transition our curriculum from our institution's secure share drive to the GOOGLE classroom. A program evaluation was undertaken and included learner responses to content and confidence questionnaires and a health care professions education (HPE) expert's response to a course quality assessment rubric.

RESULTS

Feasibility-the final DIGEST product was free of charge to create but incurred direct and indirect costs of time and training on behalf of the authors. Acceptance-7 possible learners participated and responded to the questionnaires (100% response rate). Learners reported a superior learning experience and increased confidence with DIGEST. An HPE expert reported that the course design of DIGEST met or exceeded expectations in all categories.

CONCLUSIONS

DIGEST is a novel pediatric GI curriculum for rotating learners that could be rapidly deployed, or adapted, for a wide range of clinical disciplines within the Military Health System.

Design and Assessment of a Mobile Health Care Solution for the Military Pediatrician: The DHA Pediatrics App

INTRODUCTION

Mobile health technology design and use by patients and clinicians have rapidly evolved in the past 20 years. Nevertheless, the technology has remained in silos of practices, patients, and individual institutions. Uptake across integrated health systems has lagged.

MATERIALS AND METHODS

In 2015, the authors designed a mobile health application (App) aimed at augmenting the capabilities of clinicians who care for children within the Military Health System (MHS). This App incorporated a curated, system-based collection of Clinical Practice Guidelines, access to emergency resuscitation cards, call buttons for local market subspecialty and inpatient teams, links to residency academic calendars, and other web-based resources. Over the next 5 years, three Plan-Do-Study-Act cycles facilitated multiple enhancements for the App which eventually transitioned from the Android/iOS stores to a web browser. The "People At the Centre of Mobile Application Development" tool which has validity evidence captured user experience. The team assessed the App's global effectiveness using Google Analytics. A speed test measured time saved and accuracy of task completion for clinicians using the App compared to non-users. Finally, MHS medical librarians critiqued the App using a questionnaire with validity evidence. The Walter Reed National Military Medical Center Institutional Review Board reviewed the study and deemed it exempt.

RESULTS

Clinician respondents (n = 68 complete responses across six MTFs, 51% graduate medical trainees representing a 7.4% response rate of active duty pediatrician forces) perceived the App to have appropriate qualities of efficiency, effectiveness, learnability, memorability, errors, satisfaction, and cognitive properties following App use in clinical practice. Google Analytics demonstrated more than 1,000 unique users on the App from May 1, 2020 to January 20, 2021. There were 746 instances (26% of all sessions) when a user navigated between more than one military treatment facility. App users were faster and more accurate at task completion during a digital scavenger hunt. Medical librarians measured the App to have acceptable usefulness, accuracy, authority, objectivity, timeliness, functionality, design, security, and value.

CONCLUSIONS

The App appears to be an effective tool to extend a clinician's capabilities and inter-professional communication between world-wide users and six MHS markets. This App was designed-and used-for a large health care network across a wide geographic footprint. Next steps are establishing an enduring chain of App champions for continued updates and sharing the App's code with other military medical disciplines and interested civilian centers.

Development and Assessment of a Pictographic Pediatric Constipation Action Plan

OBJECTIVE

To assess the Uniformed Services Constipation Action Plan (USCAP) as an evidence-based, personalized, clinical action tool with pictograms to aid clinicians and families in the management of functional constipation.

STUDY DESIGN

The USCAP facilitates the management functional constipation by using a health literacy-informed approach to provide instructions for pharmacotherapies and lifestyle modifications. This study included part 1 (pictogram validation) and part 2 (assessment). For part 1, pictogram transparency, translucency, and recall were assessed by parent survey (transparency ≥85%, mean translucency score ≥5, recall ≥85% required for validation). For part 2, the USCAP was assessed by parents, clinical librarians, and clinicians. Parental perceptions (n = 65) were assessed using the Consumer Information Rating Form (17 questions) to gauge comprehensibility, design quality and usefulness. Readability was assessed by 5 formulas and a Readability Composite Score was calculated. Clinical librarians (n = 3) used the Patient Education Materials Assessment Tool to measure understandability (19 questions) and actionability (7 questions) (>80% rating was acceptable). Suitability was assessed by clinicians (n = 34) using Doak's Suitability Assessment of Materials (superior ≥70% rating).

RESULTS

All 12 pictograms demonstrated appropriate transparency, translucency, and recall. Parental perceptions reflected appropriate comprehensibility, design quality, and usefulness. The Readability Composite Score was consistent with a fifth-grade level. Clinical librarians reported acceptable understandability and actionability. Clinicians reported superior suitability.

CONCLUSIONS

The USCAP met all criteria for clinical implementation and future study of USCAP implementation for treating children with chronic functional constipation.

Pediatric Ingestions of Christmas Past, Present, and Future: A Review of Holiday Trends, 1997 to 2015

During the observance of Christmas, many families display decorations, which increases the risk of unfettered access and subsequent ingestion of small objects by children in the home. Our aim was to characterize the epidemiology of Christmas foreign body ingestion (CFBI) by children. National Electronic Injury Surveillance System data from 1997 to 2015 were obtained for children aged 0 to 17 years who presented to United States Emergency Departments matching "ingested" for "artificial Christmas trees"; "Christmas tree lights"; "Christmas tree stands or supports"; "Christmas decorations, nonelectric"; and "Christmas decorations, electric" (excluding tree lights). An estimated 22 224 children (95% confidence Interval = 18 107-26 340) presented to the emergency department for CFBI over the study period. Children aged 2 years and younger ingested Christmas objects most frequently ( P < .001). CFBI visits demonstrated a seasonal trend ( P < .001). Christmas decoration ingestions are a frequent reason for children to present to the ED, which require dedicated awareness for appropriate diagnosis and care.

Fashionably Late: A Case of Delayed Cutaneous Manifestations in Juvenile Dermatomyositis

Juvenile dermatomyositis (JDM) is a rare, but well recognized multi-systemic inflammatory myopathy in children defined by proximal muscle weakness and distinctive skin lesions, that if recognized and treated early result in decreased morbidity and mortality. The 1975 criteria established by Bohan and Peter center around the propensity for early development of heliotrope and Gottron’s lesions in combination with specific laboratory abnormalities, and are still the leading diagnostic tool. The following case demonstrates a toddler with an atypical presentation of JDM in which delayed dermatologic manifestations hindered initial diagnosis. A previously healthy 2 years and 11 months old female presented to the emergency department with a 7-month history of bilateral knee pain and progressive muscular weakness. Initial evaluation yielded a diagnosis of idiopathic rhabdomyolysis but progressive deterioration prompted additional workup. During her course of care, the patient required admission at numerous facilities for specialty procedures including swallow studies, electromyography, Nissen fundoplication with G-tube insertion, and eventual muscle biopsy, resulting in pathology clinching the diagnosis. Post-diagnosis the development of a heliotrope and malar rash ensued, 11 months after commencement of original presentation. As the Bohan and Peter criteria of 1975 can help to aid in diagnosis of JDM for textbook presentations, atypical cases such as ours suggest that revision to current diagnostic criteria needs to be established. Also, with many pediatric rheumatologists opting for less invasive methods than muscle biopsy to aid in diagnosis, in combination with the heterogeneous nature of currently tracked serous markers, the risk for delayed or missed diagnosis is amplified. As prior research has demonstrated, early diagnosis leads to better outcomes for children battling JDM. Therefore, it is vital that criteria be revised and additional research be conducted for more sensitive and specific markers to help aid in early diagnosis of JDM.

Fidget Spinner Ingestions in Children-A Problem that Spun Out of Nowhere

The Consumer Product Safety Risk Management System's injury and potential injury database records 13 cases of fidget spinner ingestion since 2016. In addition to a database query, we report 3 additional cases of fidget spinner ingestion to describe patient presentations and subsequent management strategies.

Bridging burn care education with modern technology, an integration with high fidelity human patient simulation

OBJECTIVE

The Advanced Burn Life Support (ABLS) program is a burn-education curriculum nearly 30 years in the making, focusing on the unique challenges of the first 24h of care after burn injury. Our team applied high fidelity human patient simulation (HFHPS) to the established ABLS curriculum. Our hypothesis was that HFHPS would be a feasible, easily replicable, and valuable adjunct to the current curriculum that would enhance learner experience.

METHODS

This prospective, evidenced-based practice project was conducted in a single simulation center employing the American Burn Association's ABLS curriculum using HFHPS. Participants managed 7 separate simulated polytrauma and burn scenarios with resultant clinical complications. After training, participants completed written and practical examinations as well as satisfaction surveys.

RESULTS

From 2012 to 2013, 71 students participated in this training. Simulation (ABLS-Sim) participants demonstrated a 2.5% increase in written post-test scores compared to traditional ABLS Provider Course (ABLS Live) (p=0.0016). There was no difference in the practical examination when comparing ABLS-Sim versus ABLS Live. Subjectively, 60 (85%) participants completed surveys. The Educational Practice Questionnaire showed best practices rating of 4.5±0.7; with importance of learning rated at 4.4±0.8. The Simulation Design Scale rating for design was 4.6±0.6 with an importance rating of 4.4±0.8. Overall Satisfaction and Self-Confidence with Learning were 4.4±0.7 and 4.5±0.7, respectfully.

CONCLUSIONS

Integrating HFHPS with the current ABLS curriculum led to higher written exam scores, high levels of confidence, satisfaction, and active learning, and presented an evidenced-based model for education that is easily employable for other facilities nationwide.

Residues of veterinary drugs at injection sites

Residues of veterinary drugs have potential implications for human food safety and international trade in animal-derived food commodities. A particular concern is the slow depletion of residues of some injectable formulations from the site of administration. Licensing authorities have adopted different approaches to the human food safety assessment of injection site residues. European agencies apply the maximum residue limit (MRL) for muscle to muscle at the injection site and specify a withdrawal period sufficient to ensure the ingestion of a 300 g portion of muscle, if comprised entirely of injection site tissue, does not exceed the acceptable daily intake. The agencies in Australia, Canada and the USA also exclude injection site residues from the MRL-setting process. These agencies evaluate the risk to consumers posed by potential acute manifestations resulting from the infrequent ingestion of injection site residues based on acute dietary exposure considerations. While all of these approaches protect the safety of consumers, the adoption of different approaches has potential implications for residue surveillance programs in the international trade in meat. In particular, when an exporting country establishes standards for residues at injection sites based on acute dietary exposure considerations and the importing country assesses these residues against the MRL for muscle, the unnecessary condemnation of meat and disruption to market access may result. The latter may represent a potential economical impost to the exporting country. An internationally harmonized approach to the risk analysis of residues of veterinary drugs at injection sites, which protects the safety of consumers and facilitates the international trade in meat, is needed.

N-and O-acetylation of aromatic and heterocyclic amine carcinogens by human monomorphic and polymorphic acetyltransferases expressed in COS-1 cells

Human monomorphic and polymorphic arylamine acetyltransferases (EC 2.3.1.5) were expressed in monkey kidney COS-1 cells and used to study the N- and O-acetylation of a number of carcinogenic amines and their N-hydroxy metabolites. The monomorphic enzyme N-acetylated the aromatic amines, 2-aminofluorene and 4-aminobiphenyl, and also O-acetylated their N-hydroxy derivatives. None of the food-derived heterocyclic amines (Glu-P-1, PhIP, IQ, MeIQx) were substrates and their N-hydroxy metabolites were poorly O-acetylated by this isozyme. By contrast, the polymorphic acetyltransferase catalyzed the N-acetylation of both aromatic amines, and to a lesser extent, Glu-P-1 and PhIP. However, all six N-hydroxy amine substrates were readily O-acetylated to form DNA-bound adducts by the polymorphic isozyme. These data suggest that, for the heterocyclic amine carcinogens, rapid acetylator individuals will be predisposed to their genotoxicity.

Direct O-acetylation of N-hydroxy arylamines by acetylsalicylic acid to form carcinogen-DNA adducts

Acetylsalicylic acid (aspirin) has been shown to acetylate a number of drugs and biological macromolecules. Since enzymatic O-acetylation of N-hydroxy arylamines is regarded as an important activation step for DNA adduct formation, we initially examined the ability of aspirin to serve as an acetyl donor for this reaction, using rabbit liver cytosol. Instead, a direct non-enzymatic reaction was observed. Arylamine-DNA binding was enhanced from 3- to 25-fold at pH 7 by addition of aspirin to reactions containing the N-hydroxy derivatives of 2-aminofluorene (AF), 4-aminobiphenyl, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, but not for 2-amino-3-methylimidazo[4,5-f]quinoline or 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole. Further studies with N-hydroxy-AF showed that reaction rates were first order with respect to both aspirin (0.1-10 mM) and N-hydroxy-AF (0.01-0.1 mM) concentrations. In contrast, aspirin had no effect on reactions conducted at pH 5 where N-hydroxy-AF is known to undergo protonation and react with DNA to form high levels of N-(deoxyguanosin-8-yl)-AF. N-Acetylation of AF by aspirin under these conditions was also negligible. However, the formation of the adduct from N-hydroxy-AF occurred at high yield (64-82%) at pH 7 with either DNA or 2'-deoxyguanosine. HPLC analyses showed only an aspirin-dependent loss of N-hydroxy-AF and concomitant adduct formation, with no detectable formation of solvolysis products. This indicated that the reaction proceeds to a significant extent only upon addition of the nucleophile, and suggests the formation of an O-tetrahedral intermediate that is in equilibrium with both the N-hydroxy derivative and the reactive N-acetoxy arylamine. Thus, the apparent O-acetylation of certain N-hydroxy arylamines selectively by aspirin offers a convenient route for the synthesis of arylamine-DNA adducts. The potential biological significance of this reaction in vivo is also discussed.

Distribution of acetyltransferase activities in the intestines of rapid and slow acetylator rabbits

Epidemiological studies have shown that there is a significantly greater proportion of the rapid acetylator phenotype in patients with colorectal tumors than in controls; phenotype-related differences in bioactivation of dietary or environmental amines in the intestinal epithelium have been suggested as a mechanism for this effect. In the present study, we have used hepatic and intestinal cytosols to compare N-acetyltransferase (NAT1 and NAT2), O-acetyltransferase (OAT) and arylhydroxamic acid N,O-acyltransferase (AHAT) distribution in rapid and slow acetylator rabbits. The ratio (rapid/slow) for p-aminobenzoic acid acetylation (a selective substrate for NAT1) was 6 in liver, 1.7-2 in small intestine and 1.3-1.5 in large intestine while the ratio of sulfamethazine acetylation (a selective substrate for NAT2) was 150 in liver, 16-22 in small intestine and 1.8-2.5 in large intestine. The ratios (rapid/slow) for DNA binding of N-hydroxy-3,2'-dimethyl-4-aminobiphenyl and N-hydroxy-4-aminobiphenyl (primarily substrates for OAT) were 82-84 in liver, 13-20 in small intestine and 3.8-5.3 in large intestine and for DNA binding of N-hydroxy-2-acetylamidofluorene (a substrate for AHAT), the ratio was 432 in liver, 32-161 in small intestine and 8.8-13.5 in large intestine. The data show also that NAT1 activity is uniformly distributed along the intestinal tract whereas NAT2 activity is highest in the small intestine. In addition, hepatic and intestinal OAT and AHAT but not NAT1 activities in the rabbit intestine are similarly distributed to activities for NAT2, suggesting that NAT2, OAT and AHAT activities are properties of a single protein in the rapid acetylator phenotype. Moreover, OAT and AHAT activities were much higher in tissues from the rapid than the slow phenotype. The data support the hypothesis that phenotype-dependent metabolic activation of N-OH heterocyclic or aromatic amines to reactive acetoxy metabolites may be involved in the etiology of colorectal cancer.

Immunological evidence for N-acetyltransferase isozymes in the rabbit

An immunological evaluation of N-acetyltransferase (NAT) (EC 2.3.1.5) in liver, duodenum, lung, and kidney of the rabbit is described. Polyclonal antibodies to hepatic NAT isolated from rapid acetylator rabbits were raised in a goat and utilized for immunoblot analyses and enzyme inhibition studies. Immunoblot analyses demonstrated that hepatic and duodenal cytosols from rapid but not slow acetylator rabbits contained an immunoreactive 33-kDa protein. No immunoreactivity was observed for lung or kidney cytosols from either rapid or slow acetylators. The inhibition of sulfamethazine and p-aminobenzoic acid acetylation by polyclonal antibodies was investigated using cytosols from rapid and slow acetylator rabbits. With rapid acetylator cytosols, maximal inhibition of hepatic, duodenal, and lung NAT activities was 94.4 +/- 9.0%, 92.5 +/- 8.5%, and 28.3 +/- 2.4%, respectively, for sulfamethazine (500 mM) acetylation and 90.1 +/- 8.0%, 80.2 +/- 6.4%, and 26.7 +/- 3.1%, respectively, for p-aminobenzoic acid (500 microM) acetylation. Using 25 microM p-aminobenzoic acid as substrate, maximal inhibition of NAT activity was 32.0 +/- 2.1% with liver cytosol and 5.8 +/- 0.16% with duodenal cytosol, whereas no inhibition of lung NAT activity was observed. Kidney NAT activity was not inhibited by the polyclonal antibodies. With slow acetylator cytosols, no inhibition of NAT activities was observed. It is concluded that at least two NATs are present in liver, duodenum, and lung of rapid acetylator rabbits. Furthermore, the principal NAT in liver and duodenum is immunologically related to the minor form of lung NAT and is antigenically distinct from kidney NAT of rapid acetylators. Hepatic, duodenal, lung, and kidney NAT(s) of slow acetylator rabbits is (are) immunologically distinct from the major hepatic NAT in rapid acetylators. The data support the model in which the hepatic polymorphism in rabbits is caused by the total lack of the major rapid acetylator hepatic NAT in the phenotypic slow acetylator animal. These observations may have significant implications in the organ-specific toxicities of carcinogens that undergo metabolic activation via N-acetylation.

Metabolism of drugs and other xenobiotics in the gut lumen and wall

Metabolism in the gut lumen and wall can decrease the bioavailability and the pharmacological effects of a wide variety of drugs. Bacterial flora in the gut, the environmental pH and oxidative or conjugative enzymes present in the intestinal epithelial cells can all contribute to the process. Bacterial biotransformation is greatest in the colon, while gut wall metabolism is generally highest in the jejunum and decreases distally. Gut wall metabolism may be induced or inhibited by dietary or environmental xenobiotics or by co-administered drugs. Recent evidence suggests that some drugs, food-derived mutagens and other xenobiotics can be metabolized by gut flora and/or gut wall enzymes to reactive species which may cause tumors.

In vivo mechanisms for the enhanced acetylation of sulfamethazine in the rabbit after hydrocortisone treatment

The administration of hydrocortisone (HC; 75 mg/kg i.v. daily for 10 days) to rabbits significantly increased the metabolic clearance (Clm) of sulfamethazine (SMZ) from 1.92 +/- 0.05 to 2.85 +/- 0.06 liters/hr/kg (P less than 0.01). However, p.o. availability of SMZ was similar before (0.42 +/- 0.06) and after (0.39 +/- 0.03) steroid treatment. Furthermore, total liver blood flow as measured by the radioactive microsphere technique was increased (P less than 0.01) from 3.64 +/- 0.15 to 5.12 +/- 0.54 liters/hr/kg by HC treatment. Estimates of presystemic intestinal extraction and hepatic extraction were derived. These data predicted that intestinal extraction ranged from 0.11 to 0.15 in untreated rabbits and from 0.11 to 0.16 in HC-treated rabbits. Moreover, intestinal clearance was shown to contribute less than 4% to Clm of SMZ on both study days. By comparison, estimates of hepatic extraction ranged from 0.51 to 0.53, and from 0.54 to 0.56 in untreated and HC-treated rabbits, respectively. Based on the concept of a well-stirred, perfusion-limited model of hepatic elimination, the HC-induced increases in hepatic enzyme activity and blood flow were shown to make comparable contributions to the increase in hepatic clearance. It is concluded that the liver is the major site of SMZ acetylation in untreated and HC-treated, rapid acetylator rabbits. Furthermore, the increase in Clm of SMZ observed in vivo after HC treatment is attributable primarily to increases in hepatic N-acetyltransferase activity and liver blood flow.

Effect of intra-articular glucocorticoids on the disposition of sulphadimidine in chronic osteoarthritis patients

1. The disposition of sulphadimidine (15 mg kg-1 orally) was investigated in six chronic osteoarthritis patients (four slow and two fast acetylators) prior to and 4 days following intra-articular administration of glucocorticoids. 2. The mean (+/- s.e. mean) renal clearance of sulphadimidine was increased from 0.03 +/- 0.01 to 0.07 +/- 0.02 ml min-1 kg-1 (P = 0.01) following the administration of intra-articular steroid. 3. Mean metabolic clearance and volume of distribution data were similar on the two study days. However, two of the slow acetylators showed marked increases (63% and 193%) in metabolic clearance following steroid treatment.

Measurement of organ blood flow in the rabbit

A surgical procedure to facilitate the radioactive microsphere technique for simultaneously measuring cardiac output and its regional distribution has been developed. The procedure allows the use of either anesthetized or conscious rabbits. Organ blood flows in untreated and saline-treated conscious rabbits and saline-treated anesthetized rabbits were quantified and compared. First, comparison of data from the untreated and saline-treated conscious rabbits demonstrated a significantly lower hepatic blood flow in the untreated animals. Moreover, liver blood flow in the untreated animals was markedly less than literature values. Since the untreated rabbits were not handled on a regular basis prior to the blood flow study, it is suggested that anxiety may have caused the redistribution of splanchnic circulation. Secondly, comparison of the data from the conscious and anesthetized saline-treated rabbits demonstrated that total liver blood flow was similar and in agreement with literature values. Hence, either the conscious or anesthetized animal can be used to estimate liver blood flow. By contrast, blood flow to the kidney and caecum was significantly altered by anesthesia (propanidid: nitrous oxide: halothane), indicating that blood flow to these organs is best studied in the placid conscious rabbit.

Induction of sulfamethazine acetylation by hydrocortisone in the rabbit

Daily intravenous administration of hydrocortisone (HC) to rabbits resulted in a marked time-dependent increase in the metabolic clearance of sulfamethazine (SMZ). Kinetic analysis of the plasma concentration-time profiles for SMZ indicated that HC treatment significantly increased the rate of acetylation of SMZ without altering the renal clearances or volumes of distribution for either parent drug or the N-acetyl metabolite N-acetylsulfamethazine (NASMZ). Total body clearance of NASMZ was also unaltered. Doses of HC ranging from 25 to 150 mg/kg were equally effective in enhancing the in vivo acetylation rate of SMZ. Moreover, the induction of SMZ acetylation was reversible when treatment with the steroid was terminated. The in vitro rate of SMZ acetylation was measured in the cytosol of various organs from controls and rabbits treated with HC for 10 days. HC did not alter the Michaelis-Menten parameters for N-acetyltransferase (NAT) activity in kidney, lung, or gut. Similarly, the Km for SMZ acetylation in liver cytosol was not affected by the steroid. However, the Vmax estimates of hepatic NAT activity were significantly increased after HC treatment. At 0.5 mM SMZ and variable [acetyl-CoA], Vmax increased 3-fold from 82 +/- 20 to 244 +/- 43 mumol/min/organ, while at 0.5 mM acetyl-CoA and variable [SMZ], Vmax increased 2.8-fold from 75 +/- 19 to 208 +/- 41 mumol/min/organ. This increase was primarily due to a 69% increase in liver weight since Vmax expressed per mg of cytosolic protein was similar in both groups. The endogenous acetyl CoA concentrations were significantly increased by HC in liver and lung, but not in gut and kidney.(ABSTRACT TRUNCATED AT 250 WORDS)