Paediatric tracheostomy tubes: recent developments and our current practice.

OBJECTIVE: A variety of paediatric tracheostomy tubes are available. This article reviews the tubes in current use at Great Ormond Street Hospital for Children and Evelina London Children's Hospital. METHODS: This paper outlines our current preferences, and the particular indications for different tracheostomy tubes, speaking valves and other attachments. RESULTS: Our preferred types of tubes have undergone significant design changes. This paper also reports further experience with certain tubes that may be useful in particular circumstances. An updated sizing chart is included for reference purposes. CONCLUSION: The choice of a paediatric tracheostomy tube remains largely determined by individual clinical requirements. Although we still favour a small range of tubes for use in the majority of our patients, there are circumstances in which other varieties are indicated.

Coblation® intracapsular tonsillectomy (tonsillotomy) in children: A prospective study of 500 consecutive cases with long-term follow-up.

OBJECTIVES: Intracapsular tonsillectomy (tonsillotomy) has been used internationally, mainly in the management of obstructive sleep apnoea, rather than recurrent tonsillitis, with few published data evaluating its use for this latter indication. We present long-term prospective data from 500 paediatric cases undergoing Coblation® intracapsular tonsillectomy, for both obstructive and infective indications. DESIGN: Prospective case series, March 2013-January 2016, all with completed follow-up. SETTING: Tertiary paediatric otolaryngological practice. PARTICIPANTS: A total of 500 consecutive patients (6 months to 18 years, mean 5.1 years) undergoing Coblation® intracapsular tonsillectomy (with or without adenoidectomy), for obstructive and/ or infective indications, almost exclusively under the care of the senior author (DJT). MAIN OUTCOME MEASURES: Validated parent-reported T-14 tonsil symptom questionnaires were used in all cases pre- and postoperatively, including in the long term. Parents also recorded duration of analgesia, time to return to school, any complications and whether they would recommend the procedure. RESULTS: With a mean follow-up 7.4 months, symptom control has been excellent (mean total T-14 score (/70) 31.01 preoperatively, 2.68 postoperatively, P<.0000001), with similar trends for obstructive and infective domains. Two small secondary haemorrhages required readmission and observation only (0.4%); otherwise, no complications, delayed discharges or readmissions occurred; 12/500 (2.4%) have since undergone revision tonsil surgery, 10 for obstructive and 2 for infective symptoms, the majority in very young children, with revision adenoidectomy at the same time. More than 99% of parents would recommend the surgery. CONCLUSIONS: Our experience of this technique has been very positive, with excellent control of both obstructive and infective symptoms, and exceptionally low rates of complications. Further work will be required to allow conclusive demonstration of its advantages over extracapsular tonsillectomy.

Highlights from the International Transporter Consortium second workshop.

The Second International Transporter Consortium (ITC) Workshop was held with the purpose of expanding on previous white-paper recommendations, discussing recent regulatory draft guidance documents on transporter-drug interactions, and highlighting transporter-related challenges in drug development. Specific goals were to discuss additional clinically relevant transporters (MATEs, MRP2, BSEP) and best-practice methodologies and to re-evaluate ITC decision trees based on actual case studies. The outcome of the workshop will be a series of white papers targeted for publication in 2013.

Peri-operative complications after adenotonsillectomy in a UK pediatric tertiary referral centre.

OBJECTIVES: Adenoidectomy and/or tonsillectomy are commonly performed in tertiary pediatric hospitals for the management of obstructive sleep apnea, often in children with significant comorbidities. This study examines the peri-operative course of a large series of complex patients undergoing such surgery at a major pediatric centre, reporting particularly cases of respiratory compromise requiring intensive care admission, both electively and unplanned. METHODS: This study was conducted by the pediatric ENT department at Great Ormond Street Hospital. All children undergoing adenoidectomy and/or tonsillectomy from July 2003 to December 2010 were included in this study. This involved a retrospective review of the case notes and hospital databases, with particular emphasis on those children requiring admission to the pediatric intensive care unit. RESULTS: A total of 1735 consecutive admissions for adenoidectomy and/or tonsillectomy (1627 individual patients aged 4-197 months, median 46 months) were included between 2003 and 2010 (998 adenotonsillectomies, 182 tonsillectomies and 555 adenoidectomies). In this group, 999/1627 patients (61.4%) had a diagnosis of sleep disordered breathing or sleep apnea, including 258 who had polysomnography. 407/1627 (25.0%) had no specific comorbidities which were felt likely to influence their surgical outcome. Established high risk factors included age less than 24 months (292), Down syndrome (99), neuromuscular problems (314), craniofacial abnormalities (94), storage diseases (23), morbid obesity (20), cardiovascular disease (133), respiratory disease (261), hemoglobinopathy (76) and coagulophathy (34). 300/1735 admissions were day cases and 1082/1735 were observed for one night. 353/1735 required more than one night in hospital (294 for two to three nights). 7/1735 had primary hemorrhage necessitating return to the operating room, all after tonsillectomy. 41/1735 (38 with major comorbidities) required peri-operative intensive care admission, mostly for respiratory support. Of these, 7 were admitted pre-operatively to intensive care, and 17 were planned post-operative transfers. Only 17/1735 required unanticipated post-operative admission to intensive care. Odds ratio analysis suggested a significantly higher chance of PICU admission in children with particular comorbidities (Down Syndrome, cardiac disease, obesity, cerebral palsy, craniofacial anomalies, mucopolysaccharidoses and hemoglobinopathy) when compared to children without comorbidities. Adenotonsillectomy was associated with a higher risk of PICU admission than adenoidectomy alone, but patient age less than 24 months was not associated with significantly higher rates of PICU admission. There were no peri-operative mortalities in this cohort. CONCLUSIONS: The peri-operative course was largely uneventful for the majority of children undergoing surgery during this period, particularly given the high prevalence of sleep apnea and other risk factors in this cohort. Major complications were uncommon, with 2.4% of these selected, typically high risk cases requiring peri-operative intensive care admission. Importantly, only 1% of all admissions required unanticipated transfer to intensive care. This has informed changes in peri-operative management in this unit, with implications for other pediatric tertiary referral centres.

Choosing a paediatric tracheostomy tube: an update on current practice.

OBJECTIVES: A variety of paediatric tracheostomy tubes are available. This article reviews those in current use at Great Ormond Street Hospital. METHODS: We outline our preferences and the particular indications for the different tubes, speaking valves and other attachments. RESULTS: Practice has changed significantly in recent years. One product has been re-sized by its manufacturer; others are no longer commonly used. An updated sizing chart is included for reference purposes, together with manufacturers' contact details. CONCLUSIONS: The choice of paediatric tracheostomy tube is driven by clinical requirements. A small range of tubes are suitable for the majority of children, but some will require other varieties in specific circumstances.

Suction diathermy for adenoidectomy: complications and risk of recurrence.

OBJECTIVES: When introduced, suction coagulation was initially utilised for haemorrhage control following curettage of the adenoid pad. More recently the whole procedure has been performed using the technique. This study aims to report post-operative haemorrhage rates and risk of recurrence in adenoidectomy performed solely by suction diathermy in children. METHODS: A retrospective study of 1411 consecutive paediatric patients. Surgery was performed using suction diathermy. No patients were excluded. All patients were followed up. RESULTS: There were no cases of post-operative haemorrhage. 1.7% of patients remained symptomatic and underwent revision adenoidectomy. None required a third procedure. CONCLUSIONS: Re-growth of adenoid tissue may occur despite visualisation of the nasopharynx at the time of surgery. The incidence of re-growth is similar to that reported in patients undergoing conventional adenoidectomy by curettage. Post-operative haemorrhage was not encountered in children having adenoidectomy by suction diathermy. The authors suggest suction diathermy as the most appropriate method for adenoidectomy in children.

The nasopharyngeal prong airway: an effective post-operative adjunct after adenotonsillectomy for obstructive sleep apnoea in children.

OBJECTIVES: Obstructive sleep apnoea is a common childhood disorder. Adenotonsillar enlargement is most commonly implicated, with adenotonsillectomy representing an effective treatment in the majority of cases. Such children may develop respiratory compromise post-operatively, sometimes necessitating admission to the intensive care unit. We describe insertion of a nasopharyngeal "prong" airway and evaluate its benefits after adenotonsillectomy for obstructive sleep apnoea and milder forms of sleep-disordered breathing. METHODS: The prong is easily fashioned from a paediatric endotracheal tube. It is inserted once surgery is complete, remaining in situ overnight. We retrospectively examine its elective use over an 18-month period in selected children considered to be at high risk of post-operative respiratory compromise. Existing practice over the preceding 18-month period is also examined, by way of comparison. RESULTS: Forty-three children underwent adenotonsillectomy for sleep-disordered breathing/OSAS in the 18 months prior to introduction of the prong. Ten were considered "high risk" cases: post-operative intensive care beds were pre-booked for these, but none were eventually required. During the subsequent 18 months, 60 children underwent adenotonsillectomy for the same indication. Seventeen "high risk" cases received the prong post-operatively. No intensive care beds were pre-booked and all children were managed safely on the ENT ward, with minimal intervention. CONCLUSIONS: Use of a nasopharyngeal prong significantly improves the post-operative course of selected children who are at high risk of respiratory compromise after adenotonsillectomy. This largely avoids the need for medical intervention and intensive care admission.

Long-term outcome of laparoscopic mesh rectopexy for solitary rectal ulcer syndrome.

OBJECTIVE: To determine the long-term outcome of laparoscopic mesh rectopexy for solitary rectal ulcer syndrome (SRUS). PATIENTS AND METHODS: A retrospective review of 11 patients who underwent laparoscopic mesh rectopexy for refractory SRUS between 1993 and 1996. All patients were followed up initially with rigid sigmoidoscopy and seven were involved in long-term evaluation (follow-up at 71-106 months, median 89 months) involving a sickness impact profile questionnaire. RESULTS: Complete endoscopic healing of the ulcer was demonstrated in all 11 patients up to one year postoperatively but one suffered recurrence later. Of seven assessed long-term, none experienced endoscopic recurrence. Six continued to enjoy a significant reduction in symptoms and an improved quality of life. One had persistent problems and demonstrated little symptomatic improvement. CONCLUSION: Laparoscopic mesh rectopexy offers a minimally invasive option for selected patients who remain severely symptomatic despite maximal conservative therapy for SRUS, with demonstrable ulcer healing and long-term improvement in symptoms and quality of life. Larger studies are required to fully evaluate its efficacy compared to 'conventional' surgical options.

Molecular cloning, expression, and characterization of CYP2D17 from cynomolgus monkey liver.

The cynomolgus monkey is a species used in drug-safety evaluation and biotransformation studies by the pharmaceutical industry. Relatively little is known, however, about the catalytic activities and specificities of cytochromes P450 (CYP) in this species. As a first step in characterizing monkey CYPs, a cDNA was cloned by reverse-transcriptase PCR from cynomolgus monkey liver mRNA using oligonucleotide primers based on the human CYP2D6 sequence. The full-length cDNA (called CYP2D17) encoded a 497-amino-acid protein that is 93% identical to human CYP2D6 and 90% identical to marmoset CYP2D19. The CYP2D17 cDNA was cloned into a baculovirus expression vector, and microsomes prepared from CYP2D17-infected insect cells were used to determine the catalytic properties of the recombinant enzyme. The recombinant CYP2D17 results were compared to data generated with monkey liver microsomes, human liver microsomes, and recombinant CYP2D6 and demonstrated catalytic similarity using probe substrates and inhibitors. Recombinant CYP2D17 catalyzed the oxidation of bufuralol to 1'-hydroxybufuralol and dextromethorphan to dextrorphan, reactions shown to be mediated by CYP2D6 in humans; the apparent K(m) values for bufuralol and dextromethorphan were 1 and 0.8 microM, respectively. Moreover, both of these reactions were more strongly inhibited by quinidine than by quinine. A more complete understanding of the substrate specificities and activities of monkey CYPs will be advantageous in delineating species differences in metabolite profiles and metabolic activation of new chemical entities in the pharmaceutical industry.

Expression and characterization of canine cytochrome P450 2D15.

CYP2D15 is the canine ortholog of human CYP2D6, the human CYP2D isoform involved in the metabolism of drugs such as antiarhythmics, adrenoceptor antagonists, and tricyclic antidepressants. Similar to human, canine CYP2D15 is expressed in the liver, with detectable levels in several other tissues. Three different CYP2D15 cDNA clones were obtained by RT-PCR from dog liver RNA. Two clones corresponded to variant full-length CYP2D15 cDNAs (termed CYP2D15 WT2 and CYP2D15 V1); the third was identified as a splicing variant missing exon 3 (termed CYP2D15 V2). Recombinant baculoviruses were constructed containing full-length cDNAs and used to express CYP2D15 WT2 and CYP2D15 V1 in Spodoptera frugiperda (Sf9) cells with expression levels of up to 0.14 nmol/mg cell protein. As with human CYP2D6, the recombinant CYP2D15 enzymes exhibited bufuralol 1'-hydroxylaseand dextromethorphan O-demethylase activities whencoexpressed with rabbit NADPH:P450 oxidoreductase. For bufuralol 1'-hydroxylase, apparent Km values were 4.9, 3.7, and 2.5 microM and the Vmax values were 0.14, 0.034, and 0.60 nmol/min/mg protein for dog liver microsomes, CYP2D15 WT2, and the variant CYP2D15 V1, respectively. For dextromethorphan O-demethylase, apparent Km values were 0.6, 0.6, and 2.0 microM and the Vmax values were 0.18, 0.034, and 0.057 nmol/min/mg protein for dog liver microsomes, CYP2D15 WT2, and the variant CYP2D15 V1, respectively. The human CYP2D6-specific inhibitor quinidine and the rat CYP2D1-specific inhibitor quinine were both shown to be inhibitors of bufuralol 1'-hydroxylase activity for dog liver microsomes, CYP2D15 WT2, and the CYP2D15 V1 variant with nearly equal potency. Thus, the dog expresses a CYP2D ortholog possessing enzymatic activities similar to human CYP2D6, but is affected by the inhibitors quinine and quinidine in a manner closer to that of rat CYP2D1.

Metabolism of azoxy derivatives of procarbazine by aldehyde dehydrogenase and xanthine oxidase.

Procarbazine, a 1,2-disubstituted hydrazine, is employed therapeutically in the treatment of Hodgkin's disease and a limited number of other neoplasias. The isomeric azoxy metabolites of procarbazine have recently been identified as the precursors of species responsible for both the anti-cancer efficacy and toxic effects mediated by this drug. This study demonstrates that cytosolic enzymes are involved in the metabolism of the azoxy metabolites of procarbazine. Two azoxy procarbazine oxidase activities were resolved by diethylaminoethyl (DEAE)-cellulose chromatography. The activity which did not bind to this column was purified to homogeneity and was identified as a phenobarbital-inducible form of cytosolic aldehyde dehydrogenase. This protein fraction was shown to metabolize only the azoxy 2 procarbazine isomer to yield N-isopropy-p-formylbenzamide (ALD) in a reaction which did not require NAD+ as cofactor. The ALD product formed was also a substrate for a subsequent NAD(+)-dependent reduction reaction catalyzed by that purified protein. The azoxy 2 procarbazine isomer and ALD were shown to be potent inhibitors of both the dehydrogenase and esterase activities of aldehyde dehydrogenase. The second azoxy procarbazine oxidase activity which was retained by the DEAE-cellulose column co-eluted with xanthine oxidase activity. Both the xanthine dehydrogenase/oxidase and azoxy procarbazine oxidase activities of this protein fraction were inhibited by allopurinol, a specific inhibitor of xanthine dehydrogenase. Xanthine dehydrogenase/oxidase was partially purified by an alternative procedure and was shown to metabolize both the azoxy 2 procarbazine isomer and ALD, ultimately producing N-isopropylterephthalamic acid. The ability of xanthine oxidase to metabolize azoxy 2 procarbazine and ALD was confirmed using commercial, purified milk xanthine oxidase.

Induction of microsomal NADPH-cytochrome P-450 reductase and cytochrome P-450IVA1 (P-450LA omega) by dehydroepiandrosterone in rats: a possible peroxisomal proliferator.

Dehydroepiandrosterone (DHEA) is a naturally occurring C19-steroid that is found in the peripheral circulation of mammals, including humans. The feeding of DHEA to rodents has been shown to inhibit chemical carcinogenesis in colon, liver, and lung. Therefore, the effect of DHEA on hepatic enzyme activities that are associated with carcinogen metabolism was assessed. Microsomal NADPH-cytochrome P-450 reductase activity and the content of cytochrome b5 were induced 1.8- and 1.4-fold, respectively, upon feeding male Sprague-Dawley rats a synthetic diet containing 0.45% DHEA (w/w). No significant changes in total content of microsomal cytochrome P-450 or the activities of microsomal NADH-cytochrome b5 reductase and cytosolic or microsomal NAD(P)H-quinone oxidoreductase were noted at day 7 of feeding. Cytosolic glutathione S-transferase activity was decreased to 68% of control activity. Administration of DHEA p.o. or by i.p. injection for 5 days led to the same extent of induction of NADPH-cytochrome P-450 reductase activity. Maximal induction of this flavoprotein reductase was noted between days 3 and 4 of feeding or at a dose of 80-120 mg/kg i.p. A small but statistically significant increase in total microsomal cytochrome P-450 was observed after DHEA administration i.p. Rats fed DHEA had a slower growth rate compared with rats fed control diet, whereas rats treated with DHEA i.p. had growth rates identical to those of controls. The liver weights of rats given DHEA by p.o. or i.p. routes were increased significantly compared to those of control rats. Pair feeding of rats with DHA-containing or control diets served to demonstrate that the levels of induction of hepatic microsomal NADPH-cytochrome P-450 reductase and at least one form of cytochrome P450 (P-450IVA1) were the same as those seen in livers of rats fed DHEA ad libitum. This finding suggested that the induction of the flavoprotein and at least one form of the cytochrome was not due to caloric restriction. The increase in NADPH-cytochrome P-450 reductase content of liver microsomes prepared from rats either fed or treated i.p. with DHEA was also observed by Western blotting techniques. DHEA did not appear to induce any of the major forms of rat liver microsomal cytochrome P-450 that are normally increased by either phenobarbital, beta-naphthoflavone, or dexamethasone pretreatment of rats in vivo. However, the measurement of androstenedione and testosterone metabolism in vitro showed pronounced decreases in the 16 alpha-hydroxylase activities of liver microsomes following DHEA feeding.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytotoxicity and DNA damage caused by the azoxy metabolites of procarbazine in L1210 tumor cells.

Procarbazine, a chemotherapeutic hydrazine, is thought to be metabolized to an alkylating species similar to methyl carbonium ion by multistep reactions involving cytochrome P-450, monoamine oxidase, and cytosolic enzymes. The DNA-damaging and cytotoxic potential of procarbazine and its metabolites in murine L1210 leukemia tumor cells in vitro was determined using alkaline elution techniques and extrapolation of growth curves. Neither procarbazine nor any of the chemical degradation products (except for the aldehyde derivative at high concentrations) caused significant amounts of DNA strand breakage. The primary enzymatic oxidation product, azo-procarbazine, did not produce strand breakage. However, exposure of the cells to either of the two isomers of azoxy-procarbazine led to significant DNA damage and cytotoxicity. DNA damage included both single-strand breaks and alkali-labile sites. At equimolar concentrations, the azoxy 2 isomer of procarbazine caused 14 to 20 times more DNA damage than did the azoxy 1 metabolite. When cell growth is expressed as percentage survival of L1210 cells, the azoxy 2 isomer was approximately 7-fold more toxic than the azoxy 1 metabolite. The other metabolites tested showed little or no cytotoxicity. L1210 cells were shown to contain little or no cytochrome P-450 or monoamine oxidase activity, which may account for the lack of toxicity of the parent drug or the primary oxidative metabolite, azo-PCZ, to these cells. The conversion of procarbazine to the azoxy-procarbazine isomers in vivo must occur in cells which contain these enzymes, such as liver. However, the azoxy isomers of procarbazine were metabolized in L1210 cells, presumably leading to the DNA or cytotoxic damage observed.

Effects of induction on the metabolism and cytochrome P-450 binding of harman and other beta-carbolines.

1. The metabolism of harman by liver microsomes from non-induced, phenobarbitone (PB)-induced and 3-methylcholanthrene (MC)-induced mice was investigated. Initial reaction rates for harman disappearance were measured and showed a 4-fold induction by PB and a 10.6-fold induction by MC. 2. The major metabolite formed with each microsomal preparation was identified as 6-hydroxyharman. 3. Microsomal cytochrome P-450 binding was measured for harman and other beta-carbolines and both Type I and Type II binding spectra were observed, being dependent upon the mode of induction.

Metabolism of the beta-carbolines, harmine and harmol, by liver microsomes from phenobarbitone- or 3-methylcholanthrene-treated mice. Identification and quantitation of two novel harmine metabolites.

This study extends an investigation of the metabolism of the beta-carbolines, harmine and harmol, by untreated, phenobarbitone-induced, or 3-methylcholanthrene (MC)-induced mouse liver microsomes to identify two MC-inducible metabolites of harmine and to quantitate their rates of formation using 3H-labeled substrate. An HPLC system was devised to separate harmine and its metabolites. The major metabolite with MC-induced microsomes was identified by mass spectroscopy and by NMR to be 6-hydroxy-7-methoxyharman and was produced at an initial reaction rate of 11 nmol/min/mg of microsomal protein (27-fold induction). The other novel metabolite, 3- or 4-hydroxy-7-methoxyharman (the position of the hydroxyl group could not be definitively assigned by NMR) was produced at an initial reaction rate of 3.8 nmol/min/mg of microsomal protein (32-fold induction) which was similar to the rate of formation of the other metabolite, harmol, determined previously. All three metabolites were further metabolized to unidentified metabolites. Protein binding of [3H]harmine and [3H]harmol was measured and shown to be metabolism dependent. It was also noted that the alkali conditions used for optimal extraction stimulated the protein binding.