Testing of tissue specimens obtained from SARS-CoV-2 nasopharyngeal swab-positive donors

Risk for transmission of SARS-CoV-2 through allogeneic human tissue transplantation is unknown. To further evaluate the risk of virus transmission, tissues were obtained from deceased donors who had tested positive for SARS-CoV-2 RNA via nasopharyngeal swab. This study evaluated an array of human tissues recovered for transplantation, including bone, tendon, skin, fascia lata, vascular tissues, and heart valves. Tissue samples and plasma or serum samples, if available, were tested for viral RNA (vRNA) using a real time PCR system for the presence of virus RNA. All samples were tested in quadruplicate for both subgenomic (sgRNA) and genomic (gRNA) RNA encoding the SARS-CoV-2 nucleocapsid gene. Amplification of a cellular housekeeping gene served as the positive control for every sample. A total of 47 tissue samples from 17 donors were tested for SARS-CoV-2 RNA. Four donors had plasma or serum available for paired testing. SARS-CoV-2 RNA was not detected from any tissue or plasma/serum sample tested. Based on these findings, risk of transmission through the transplantation of tissue types studied from SARS-CoV-2 infected donors is likely to be low.

Low rate of detection of SARS-CoV-2 RNA in deceased tissue donors

Given the possibility for disease transmission, this study was performed to determine whether there is detectable SARS-CoV-2 viral RNA in the blood of deceased tissue donors. A retrospective analysis of blood samples from eligible deceased tissue donors from Oct 2019 through June 2020 was performed. Plasma aliquots were initially tested with a SARS-CoV-2 NAT Assay; positive samples were further tested using an alternate NAT and an antibody assay. The proportion of donors with confirmed RNAemia and 95% confidence intervals were computed. Of donor samples collected in 2019, 894 yielded valid results, with 6 initially positive, none of which confirmed positive by alternate NAT. Of donor samples collected in 2020, 2562 yielded valid initial NAT results, with 21 (0.8%) initially positive. Among those, 3 were confirmed by alternate NAT, 17 were not confirmed, and 1 had an invalid alternate NAT result. The rate of SARS-CoV-2 RNAemia in deceased tissue donors is approximately 1 per 1000, and it is unknown whether this RNAemia reflects the presence of infectious virus. Given these results, the risk of transmission through tissue is thought likely to be low.

Pre-frontal stimulation does not reliably increase reward responsiveness

Depression is the leading cause of disability worldwide and its effects can be fatal, with over 800,000 people dying by suicide each year. Neuromodulatory treatments such as transcranial magnetic stimulation (TMS) are being used to treat depression. Despite its endorsement by two regulatory bodies: NICE (2016) and the FDA (2008), there are major questions about the treatment efficacy and biological mechanisms of TMS. Ahn et al.'s (2013) justified the use of TMS in a clinical context in an important study indicating that excitatory TMS increases reward responsiveness. A pseudo-replication of this study by Duprat et al., (2016) also found a similar effect of active TMS, but only with the addition of an exploratory covariate to the analyses-trait reward responsiveness. Here we replicate Ahn et al.'s (2013) key study, and to test the reliability of the effects, and their dependency on trait reward responsiveness as described by Duprat et al., (2016). Using excitatory and sham TMS, we tested volunteers using the probabilistic learning task to measure their reward responsiveness both before and after stimulation. We also examined affect (positive, negative) following stimulation. Irrespective of TMS, the task was shown to be sensitive to reward responsiveness. However, we did not show TMS to be effective in increasing reward responsiveness and we did not replicate Ahn et al., (2013) or Duprat et al., (2016)'s key findings for TMS efficacy, where we provide evidence favouring the null. Moreover, exploratory analyses suggested following active stimulation, positive affect was reduced. Given our findings, we question the basic effects, which support the use of TMS for depression, particularly considering potential deleterious effects of reduced positive affect in patients with depression.

372. Detection of SARS-CoV-2 RNAemia in Deceased Tissue Donors

Background

Tissue donors are evaluated for communicable disease in order to minimize the risk of transmission to recipients. Although there are data suggesting SARS-CoV-2 viremia across a wide spectrum of illness, prevalence in deceased tissue donors and the potential for transplant transmission are unknown.

Methods

Eight tissue banks participated in a retrospective analysis of samples from eligible deceased tissue donors from Oct 2019 through June 2020, one participant in Canada and the remainder located in the United States. All four Census regions of the continental US and all major racial-ethnic groups were represented. EDTA or sodium citrate plasma aliquots were tested in singlicate with the Research Use Only Procleix SARS-CoV-2 Assay on the Procleix Panther System, which uses transcription-mediated nucleic acid amplification (TMA) technology for detection of the SARS-CoV-2 RNA. Plasma (or if unavailable, serum) aliquots were sent to Grifols for an alternate SARS-CoV-2 nucleic acid amplification (NAT) test to verify reactivity and also sent for antibody testing using the emergency use authorization Ortho VITROS Immunodiagnostic Products Anti-SARS-CoV-2 Total test. The VITROS assay uses immunometric technology for qualitative measurement of total antibody (IgG, IgA and IgM) to SARS-CoV-2. The proportion of donors with confirmed RNAemia (i.e., presence of SARS-CoV-2 RNA in plasma or serum) and 95% confidence intervals were computed.

Results

Of 3,455 donor samples with valid final results, 26 (0.76%) were initially positive for SARS-CoV-2 RNA; of these, 3 were confirmed by alternate NAT. Of donor samples collected in 2019 0.00% (95% CI: 0.00%,0.43%) were confirmed RNAemic, while of those collected in 2020, 0.12% (0.04%,0.34%) were confirmed RNAemic. One of 26 initial positive, and none of the three samples confirmed by alternate NAT, tested positive for anti-SARS-CoV-2 Spike antibodies by serology. Infectivity studies are pending on one sample with sufficient available volume.

Conclusion

The rate of SARS-CoV-2 RNAemia in deceased tissue donors is approximately 1 per 1,000, and it is unknown whether this RNAemia reflects the presence of infectious virus. Given these results, the risk of transmission through tissue is most likely to be low.

Disclosures

Melissa Greenwald, MD, Alamo Biologics (Consultant)Eurofins VRL Laboratories (Consultant)Right Cell Biologics (Consultant, Consultant Medical Director) Eduard Grebe, PhD, Gilead Sciences (Consultant)Sedia Biosciences Corporation (Consultant, Grant/Research Support)Vitalant (Employee) Alyce Linthurst Jones, PhD, LifeNet Health (Employee) Matthew Kuehnert, MD, American Association of Tissue Banks (Board Member)ICCBBA (Board Member)Musculoskeletal Transplant Foundation (Employee)

Avian Papilloma and Squamous Cell Carcinoma: a Histopathological, Immunohistochemical and Virological study

In this retrospective study, we describe the histopathological findings in seven papillomas and 45 squamous cell carcinomas (SCCs) from psittacine birds, raptors and domestic fowl. The age of affected birds ranged from 3 to 40 years, with median age significantly higher in psittacines (P = 0.014). The majority of tumours were located in the skin (24/52, 46.2%) or uropygial gland (10/52, 19.2%). Thirty of the SCCs (66.7%) were well differentiated and 15 (33.3%) were poorly-differentiated. SCCs exhibited a significantly higher degree of nuclear pleomorphism (P = 0.005) and a greater proportion were ulcerated (P = 0.001) compared with papillomas; however, there was no significant difference in mitotic count (MC) or inflammation score. The expression of cyclo-oxygenase (COX)-2 and E-cadherin was investigated by immunohistochemistry. The COX-2 total score (TS) was significantly higher in SCCs compared with papillomas (P = 0.002), but the difference between COX-2 TS of well- and poorly-differentiated SCCs was not significant. COX-2 labelling was predominantly cytoplasmic, but some tumours had concurrent membranous and/or perinuclear labelling. SCCs with membranous labelling had a significantly higher MC (P = 0.028). A significantly higher proportion of SCCs were negative for E-cadherin compared with papillomas (P = 0.042), but there was no significant difference between well- and poorly-differentiated SCCs. Fourteen papillomas and SCCs from psittacines were also tested by polymerase chain reaction for the presence of Psittacus erithacus papillomavirus 1 and Psittacid herpesvirus 1, but all samples tested negative. We demonstrate for the first time the expression of COX-2 and E-cadherin in avian tissues, and suggest that these markers may be useful in differentiating papillomas from SCCs, particularly when sample size is small.

An evaluation of methods for the isolation of nontuberculous mycobacteria from patients with cystic fibrosis, bronchiectasis and patients assessed for lung transplantation

BACKGROUND

RGM medium is an agar-based, selective culture medium designed for the isolation of nontuberculous mycobacteria (NTM) from the sputum of patients with cystic fibrosis (CF). We evaluated RGM medium for the detection of NTM in patients with CF (405 samples), bronchiectasis (323 samples) and other lung diseases necessitating lung transplantation (274 samples).

METHODS

In total, 1002 respiratory samples from 676 patients were included in the study. Direct culture on RGM medium, with incubation at two temperatures (30 °C and 37 °C), was compared with conventional culture of decontaminated samples for acid-fast bacilli (AFB) using both a solid medium (Löwenstein-Jensen medium) and a liquid medium (the Mycobacterial Growth Indicator Tube; MGIT).

RESULTS

For all three patient groups, significantly more isolates of NTM were recovered using RGM medium incubated at 30 °C than by any other method (sensitivity: 94.6% vs. 22.4% for conventional AFB culture; P < 0.0001). Significantly more isolates of Mycobacterium abscessus complex were isolated on RGM at 30 °C than by AFB culture (sensitivity: 96.1% vs. 58.8%; P < 0.0001). The recovery of Mycobacterium avium complex was also greater using RGM medium at 30 °C compared to AFB culture (sensitivity: 83% vs. 70.2%), although this difference was not statistically significant and a combination of methods was necessary for optimal recovery (P = 0.21).

CONCLUSIONS

In the largest study of RGM medium to date, we reaffirm its utility for isolation of NTM from patients with CF. Furthermore; we show that it also provides an effective tool for culture of respiratory samples from patients with bronchiectasis and other lung diseases.

Microscopic polyangiitis secondary to Mycobacterium abscessus in a patient with bronchiectasis: a case report

Background

Non-Tuberculous Mycobacterial–pulmonary disease (NTM-PD) is increasing in incidence and prevalence. Mycobacterium abscessus (M.abscessus) is a rapid growing multi-resistant NTM associated with severe NTM-PD requiring prolonged antibiotic therapy. Complications of therapy are common but reports on direct complications of active NTM-PD are rare. Vasculitis has been described as a rare complication of NTM-PD, most often in individuals with inherited immune defects. This case is the first to describe an ANCA positive vasculitide (Microscopic Polyangiitis) secondary to M.abscessus pulmonary disease.

Case presentation

A 70 year old female with bronchiectasis underwent a clinical decline associated with the growth of M.abscessus and was diagnosed with NTM-PD. Before treatment could be initiated she developed small joint arthralgia and a glove and stocking axonal loss sensorimotor neuropathy. Positive Perinuclear Anti-Neutrophil Cytoplasmic Antibodies (P-ANCA) and Myeloperoxidase-ANCA (MPO-ANCA) titres led to a diagnosis of microscopic polyangiitis. Further investigation revealed reduced interferon-gamma production but no other significant immune dysfunction.

Dual treatment with immunosuppressive therapy (Corticosteroids/Cyclophosphamide) for vasculitis and antimicrobial therapy for M.abscessus NTM-PD was initiated. Clinical stability was difficult to achieve with reductions in immunosuppression triggering vasculitic flares. One flare led to retinal vein occlusion with impending visual loss requiring escalation in immunosuppression to Rituximab infusions. An increase in immunosuppression led to a deterioration in NTM-PD necessitating alterations to antibiotic regimes. Adverse effects including alopecia and Achilles tendonitis have further limited antibiotic choices resulting in a strategy of pulsed intra-venous therapy to stabilise NTM-PD.

Conclusions

This is the first reported case of an ANCA positive vasculitis secondary to M.abscessus pulmonary disease. This rare but important complication had a significant impact on the patient adding to the complexity of an already significant disease and treatment burden. The potential role of reduced interferon-gamma production in this case highlights the importance of investigating immune function in those with mycobacterial infection and the intricate relationship between mycobacterial infection and immune dysfunction. Immune dysfunction caused by genetic defects or immunosuppressive therapy is a known risk factor for NTM-PD. Balancing immunosuppressive therapy with prolonged antimicrobial treatment is challenging and likely to become more common as the number of individuals being treated with biologics and immunosuppressive agents increases.

Should all patients with unexplained anaemia be screened for chronic lead poisoning?

The global prevalence of lead poisoning is declining. However, the prevalence of lead poisoning in patients with either microcytic or normocytic anaemia is unknown. Blood samples from anaemic patients residing in south-east London without an obvious cause for anaemia had their blood lead concentration (BLC) analysed.A batch of 988 samples was analysed for BLC using atomic absorption spectroscopy. Median haemoglobin was 10.3 g/dL (range: 4.2–10.9) in females, 10.6 g/dL (range: 5.2–11.4) in males and 10.7 g/dL (range: 6.7–10.9) in children. Median BLC was 2.63 μg/dL (0.21–24.0 μg/dL; 95th centile 7.54 μg/dL). Fifteen samples (1.5%) had a BLC>10.0 μg/dL, five samples (1%)>15.0 μg/dL and one sample (0.1%)>20.0 μg/L. In the 106 children, median BLC was 2.34 μg/dL (0.5–14.5 μg/dL; 95th centile 6.12 μg/ dL). Only one child (14.5 μg/L) had a BLC>10.0 μg/dL. There was a poor correlation between haemoglobin and BLC (r2=0.08).Routine screening for lead poisoning cannot be justified in all patients with unexplained anaemia, unless there is a history or clinical features to suggest lead toxicity. Additionally, we have shown that in this former high-risk area for lead exposure, there is a low point prevalence of significant lead poisoning, even in an anaemic population.

Clostridium perfringens type-D enterotoxaemia in cattle: the diagnostic significance of intestinal epsilon toxin

The aims of this study were to describe 42 cases of Clostridium perfringens type-D enterotoxaemia in cattle seen between 2003 and 2014 and to determine the diagnostic value of detecting epsilon toxin in bovine intestinal content. All cases in the series had histological brain changes considered pathognomonic for C. perfringens type-D enterotoxaemia in sheep and goats and the epsilon toxin of C. perfringens was concurrently detected in the intestinal contents of 15 (36 per cent) cases. The data from the case series indicate that intestinal epsilon toxin has a sensitivity of 56 per cent compared with histology of the brain for diagnosis of bovine C. perfringens type-D enterotoxaemia. The diagnostic specificity of detecting epsilon toxin in bovine intestinal content was investigated by screening intestinal contents of 60 bovine carcases submitted for postmortem examination. Epsilon toxin was detected in 11 (18 per cent) carcases but no pathognomonic histological brain change was found in any. The specificity of intestinal epsilon toxin was estimated to be 80.4 per cent. These studies demonstrate that for a definitive diagnosis of C. perfringens type-D enterotoxaemia in cattle histological examination of the brain is essential as the presence of epsilon toxin in the intestinal contents alone is neither sensitive nor specific enough.

Serotonin toxicity from antidepressant overdose and its association with the T102C polymorphism of the 5-HT2A receptor

Serotonin toxicity results from serotonin excess in the central nervous system from serotonergic drugs. Previous studies suggest an association between T102C polymorphism of the serotonin 2A (5-hydroxytryptamine 2A) receptor gene and serotonergic adverse effects with serotonergic drugs. We aimed to determine whether there is an association between the T102C polymorphism and serotonin toxicity in patients taking serotonergic drug overdoses. Ninety-five patients presenting with serotonergic drug overdoses were examined for serotonin toxicity and had blood collected for DNA analysis. A diagnosis of serotonin toxicity was made in 14 patients (15%) based on the Hunter Serotonin Toxicology Criteria. Four of the 14 patients (29%) with serotonin toxicity had the C/C genotype compared with 20/81 (25%) without serotonin toxicity. There were no differences in age or sex, but the median defined daily dose taken by patients with serotonin toxicity was 27 (14-84) compared with 18 (2-136) in patients without serotonin toxicity (P=0.06). There was no association between serotonin toxicity and the T102C polymorphism in patients taking a serotonergic drug overdose.

UK guidance document: treatment of metastatic breast cancer

Although there have been major improvements in the management of breast cancer, with a rapidly falling death rate despite an increasing incidence of the disease, metastatic breast cancer remains common and the cause of death in nearly 12 000 women annually in the UK. Numerous treatment options are available that either target the tumour or reduce the complications of the disease. Clinical decision making depends on knowledge of the extent and biology of the disease and available drug options, an understanding of the functional status, and also the wishes and expectations of the individual patient. In addition, the organisation of services and support of the patient are essential components of high-quality care. The National Institute for Health and Clinical Excellence (NICE) has produced guidelines for the treatment of advanced breast cancer, which in some areas have perhaps failed to appreciate the complexity of patient management. This guidance document aims to provide succinct practical advice on the treatment of metastatic breast cancer, highlight some limitations of the NICE guidelines, and provide suggestions for management where available data are limited.

Delay times between harvesting or collection of food products and consumption for use in radiological assessments

From a radiological protection point of view, the inclusion of delay times when carrying out assessments of dose from consumption of foods should be considered. A review of delay times has been carried out to update a report published in 1983, to take account of changes and modernisations in industrial food processes, together with changes in diet and popularity of different foods in the United Kingdom. The new review considered more foods and data for existing foods have been reconsidered to check whether manufacturing processes or procedures have changed the shelf-life of any products. For some foods there have been changes made to the recommended delay times because of changes in manufacture or handling of the fresh foodstuff. A discussion is also included on the appropriate use of delay times in dose assessments.

Management of cardiac health in trastuzumab-treated patients with breast cancer: updated United Kingdom National Cancer Research Institute recommendations for monitoring

More women are living with and surviving breast cancer, because of improvements in breast cancer care. Trastuzumab (Herceptin®▾) has significantly improved outcomes for women with HER2-positive tumours. Concerns about the cardiac effects of trastuzumab (which fundamentally differ from the permanent myocyte loss associated with anthracyclines) led to the development of cardiac guidelines for adjuvant trials, which are used to monitor patient safety in clinical practice. Clinical experience has shown that the trial protocols are not truly applicable to the breast cancer population as a whole, and exclude some women from receiving trastuzumab, even though they might benefit from treatment without long-term adverse cardiac sequelae. Consequently, five oncologists who recruited patients to trastuzumab trials, some cardiologists with whom they work, and a cardiovascular lead general practitioner reviewed the current cardiac guidelines in the light of recent safety data and their experience with adjuvant trastuzumab. The group devised recommendations that promote proactive pharmacological management of cardiac function in trastuzumab-treated patients, and that apply to all patients who are likely to receive standard cytotoxic chemotherapy. Key recommendations include: a monitoring schedule that assesses baseline and on-treatment cardiac function and potentially reduces the overall number of assessments required; intervention strategies with cardiovascular medication to improve cardiac status before, during, and after treatment; simplified rules for starting, interrupting and discontinuing trastuzumab; and a multidisciplinary approach to breast cancer care.

Doctors' knowledge of the appropriate use and route of administration of antidotes in the management of recreational drug toxicity

BACKGROUND

Specific antidotes (eg, naloxone, flumazenil, cyproheptadine and benzodiazepines) are available for the management of certain recreational drug-induced toxicities. Some controversies surround the use of some of these antidotes, especially flumazenil in benzodiazepine toxicity. There are no previously published data on doctors' knowledge of the use of these specific antidotes.

METHODS

A questionnaire survey was designed to determine internal/emergency medicine doctors' knowledge of the appropriate use of antidotes in the management of clinical scenarios of acutely poisoned patients. For nine simulated clinical scenarios of acute toxicity from recreational drugs (benzodiazepines, cocaine, N-methyl-L-(3,4-methylene-dioxyphenyl)-2-aminopropane (MDMA)-induced serotonin toxicity and opioids), they were asked to indicate whether the suggested antidote and route of administration were correct.

RESULTS

42 physicians of all grades completed the questionnaire. The mean correct score was 5.4 (SD 1.1) (median 6, interquartile range 5-7). The percentages correct for the various clinical scenarios were 68.3% for opioid toxicity, 81% for benzodiazepine toxicity, 28.6% for MDMA-induced serotonin toxicity and 70.2% for cocaine toxicity. Doctors were more likely to record an answer of "unsure" for the use of cyproheptadine in ST serotonin toxicity (28.6%) compared with the use of the other antidotes (1.4%; p<0.001).

CONCLUSION

Knowledge of the appropriate use of antidotes in recreational drug toxicity is not consistent, with poorer knowledge on the use of newer antidotes such as cyproheptadine in serotonin toxicity. Education is required both to increase overall knowledge on the use of specific antidotes in the management of recreational drug-induced toxicity, as well as focusing on newer antidotes such as cyproheptadine.

Decellularization reduces calcification while improving both durability and 1-year functional results of pulmonary homograft valves in juvenile sheep

OBJECTIVE

The juvenile sheep functional valve chronic implant calcification model was used to compare long-term calcification rates, functional performance, and durability for 3 types of right ventricular outflow tract implants: classically cryopreserved homografts and 2 decellularized pulmonary valved conduits.

METHODS

Fifteen juvenile sheep were randomly assigned to one of 3 study arms and underwent pulmonary valve replacement. The arms included the following: (1) cryopreserved ovine pulmonary valves; (2) cryopreserved, decellularized, saline (1 degrees C-10 degrees C)-stored ovine pulmonary valves; and (3) cryopreserved, decellularized, glycerolized (-80 degrees C) stored ovine pulmonary valves. Animal growth, serial echocardiographic results (with valve performance assessment), dimensions, and tissue-specific calcification measurements were compared with pre-explant angiographic analysis and right ventricular outflow tract pressure measurements, cardiac magnetic resonance imaging, specimen radiographic analysis, gross explant pathology, and histopathology. Parametric and nonparametric statistical analysis were performed.

RESULTS

All but 2 study animals receiving implants thrived postoperatively, with similar growth rates, explant valve dimensions, ventricular functions, cardiac output, and indices during the study. As determined by means of echocardiographic analysis, 3 animals in arm 1 (and one in arm 2) had leaflet dysfunction. Valve regurgitation was recognized in 1 survivor each from both arms 1 and 2. Although 1 arm 1 animal died with calcified subacute bacterial endocarditis, and the other 4 had leaflet and conduit wall calcification by the time of death, no arm 2 or arm 3 animals demonstrated leaflet calcium, and no arm 3 and only 1 arm 2 animals had calcium in the conduit wall over the entire year, as determined with any measurement method. All cryopreserved conduit walls had calcium by 20 weeks, whereas only 1 of 10 decellularized conduits (arms 2 plus 3) had wall calcium.

CONCLUSION

Cryopreserved-decellularized-glycerolized valves retained normal valve function, with absent leaflet and minimal wall calcifications 1 year postoperatively, as opposed to classically cryopreserved allografts. These results might be predictive of the prolonged durability and functionality of a cryopreserved-decellularized-glycerolized allograft valve.

Improvement in the management of acutely poisoned patients using an electronic database, prospective audit and targeted educational intervention

PROBLEM

The need to improve the clinical assessment and management of acutely poisoned patients presenting to an NHS hospital emergency department (ED).

DESIGN

Creation of an electronic clinical toxicology database to prospectively collect all aspects of clinical information on poisoned-patient presentations. Systematic analysis of collated information to identify shortfalls in patient assessment and management. Bimonthly audit meetings, and design and implementation of educational interventions to address identified shortfalls. Ongoing audit to demonstrate continued improvement in patient care.

BACKGROUND AND SETTING

ED in tertiary-level inner-city London teaching hospital. Study conducted by staff from the ED and clinical toxicology service.

KEY MEASURES FOR IMPROVEMENT

Demonstration of overall reduction in the incidence of predefined shortfalls in patient assessment and management during 12-month study period.

STRATEGIES FOR IMPROVEMENT

Targeted educational lectures and case-based clinical scenarios addressing identified deficiencies in the knowledge required to effectively manage poisoned patients. Weekly case-based anonymised feedback report sent electronically to staff involved in caring for poisoned patients.

EFFECTS OF CHANGE

Implementation of targeted teaching of ED staff and regular electronic distribution of teaching cases. Between the first and second 6 months of the study, there was a significant increase in the proportion of presentations for which clinical management was graded as "good" (77.6% to 89.4%, p<0.0001) and a significant reduction in the proportion of "major" (9.9% to 5.8%, p = 0.012) and "minor" (12.6% to 4.8%, p<0.0001) shortfalls.

LESSONS LEARNT

Systematic collection of clinical information, using a dedicated electronic database and subsequent review and audit of collated data by interested clinicians, enabled design and implementation of targeted educational interventions to address shortfalls in patient management. This process has led to significant improvements in the clinical care of acutely poisoned patients presenting to the ED.

Mechanical properties of completely autologous human tissue engineered blood vessels compared to human saphenous vein and mammary artery

We have previously reported the initial clinical feasibility with our small diameter tissue engineered blood vessel (TEBV). Here we present in vitro results of the mechanical properties of the TEBVs of the first 25 patients enrolled in an arterio-venous (A-V) shunt safety trial, and compare these properties with those of risk-matched human vein and artery. TEBV average burst pressures (3490+/-892 mmHg, n=230) were higher than native saphenous vein (SV) (1599+/-877 mmHg, n=7), and not significantly different from native internal mammary artery (IMA) (3196+/-1264 mmHg, n=16). Suture retention strength for the TEBVs (152+/-50 gmf) was also not significantly different than IMA (138+/-50 gmf). Compliance for the TEBVs prior to implantation (3.4+/-1.6%/100 mmHg) was lower than IMA (11.5+/-3.9%/100 mmHg). By 6 months post-implant, the TEBV compliance (8.8+/-4.2%/100 mmHg, n=5) had increased to values comparable to IMA, and showed no evidence of dilation or aneurysm formation. With clinical time points beyond 21 months as an A-V shunt without intervention, the mechanical tests and subsequent lot release criteria reported here would seem appropriate minimum standards for clinical use of tissue engineered vessels.

Can medical students identify recreational drugs by name?

BACKGROUND

Recreational drug toxicity is a common reason for presentation to the Emergency Department. Knowledge of recreational drug names is important to allow targeted assessment of patients presenting with recreational drug toxicity.

AIMS

To assess final year medical student knowledge of proper and street names for recreational drugs.

DESIGN

Questionnaire survey of final year medical students attending a revision lecture.

METHODS

There were two questionnaires used in this study. The first contained either proper names of recreational drugs or names sounding similar to recreational drugs or licensed pharmaceutical products; students were asked to identify which of these were recreational drugs. The second contained street names of recreational drugs and the students were asked to identify which recreational drug the street name referred to.

RESULTS

One hundred and thirty-five students completed the questionnaire 1. The mean total score (+/-SD) of correct answers was 7.15 +/- 2.26 (range 2-13) out of a maximum of 15. One hundred and fifteen students completed questionnaire 2. The mean total score (+/-SD) of correctly identified street names was 11.0 +/- 2.6 (range 0-17) out of a maximum of 24. No individual student was able to correctly identify all the street names for the recreational drugs listed in the survey.

CONCLUSION

We have shown that final year medical students have variable knowledge of both the proper and street names of recreational drugs. There is a need for improved education of medical students in the names of recreational drugs and the sources of information available to assist them in identifying what drugs an individual has taken.

Severe hypokalaemic metabolic alkalosis following ingestion of gaviscon®

INTRODUCTION

Uncommon metabolic abnormalities in the emergency department could be a result of drug overdose due to uncommon agents.

CASE REPORT

A 35-year-old male presented to the emergency department with a Glasgow Coma Scale (GCS) of 3/15 and a normal pulse rate and blood pressure. Subsequent questioning after recovery revealed he had ingested 2 L of Gaviscon over the preceding 48 hours. He had normal haematology, liver, and renal function during admission. The electrocardiogram showed T wave inversion in the inferior leads on admission. Arterial blood gas on air was: pH 7.54, HCO3 50 mmol/L (50 meq/L), Chloride 66 mmol/L, anion gap was 19, pO2 11 kPa (82.5 mmHg), and pCO2 8 kPa (60 mmHg). Serum sodium was 127 mmol/L and serum potassium was 1.6 mmol/L. His GCS improved within one hour of admission with supportive care, and his serum potassium and bicarbonate improved within 24 hours. He subsequently made a full recovery. Discussion. Bicarbonate ingestion in the form of Gaviscon(R) and vomiting made this patient alkalotic, and simple supportive care provided effective management with a complete recovery.

CONCLUSION

This case illustrates how a severe metabolic alkalosis can result from a significant ingestion of Gaviscon, and that such presentations can give rise to diagnostic dilemma.

Review of trends in the UK population dose

The Radiation Protection Division of the Health Protection Agency (HPA-RPD), formerly the National Radiological Protection Board, has periodically reported the doses to members of the public and workers in the UK from all sources of radiation. This paper is a review of the doses reported in these publications from the 1970s to 2000 or later. The paper aims to present how the estimated doses received by the UK population have changed over this time period, and where possible from earlier years as well, from all sources of radiation. It was not possible to directly compare the doses reported in the earlier reports. There have been changes in the type of doses estimated, the dosimetry (in particular the definition of effective dose) and improvements made in the measurement of natural background doses. In these cases the earlier reported doses have been recalculated using modern dosimetry so that the doses can be compared. The occupational doses reported in this paper are for those workers involved in the civil nuclear power production industry, industrial radiography or from the medical use of radiation sources. For workers it was found that the individual and collective dose has decreased significantly over this time through the introduction of legislation, the improvement in technology and better working practices. Members of the public are exposed to radiation following the atmospheric testing of nuclear weapons, discharges from UK civil nuclear sites and from diagnostic radiology as well as from natural sources. Exposure to anthropogenic sources has decreased over the period considered in this paper. However, the dose to the UK population as a whole, presented as a per caput dose to a population of 55 million, has not changed significantly as it is dominated by the constant level of exposure to natural sources of radiation.

Nutrition, synchronization, and management of beef embryo transfer recipients

A commercially viable cattle embryo transfer industry was established during the early 1970s. Initially, techniques for transferring cattle embryos were exclusively surgical. However, by the early 1980s, most embryos were transferred nonsurgically. For an embryo transfer program to be effective, numerous factors need to be in place to ensure success. Nutrition, estrous cycle control, and recipient management are all responsible for the success or failure in fertility for a given herd. Utilization of body condition scores is a practical method to determine nutritional status of the recipient herd. Prepartum nutrition is critical to ensure that cows calve in adequate body condition to reinitiate postpartum estrous cycles early enough to respond to synchronization protocols. Estrus synchronization for embryo transfer after detected estrus or for fixed-time embryo transfer without estrus detection are effective methods to increase the number of calves produced by embryo transfer. In addition, resynchronization of nonpregnant recipients effectively ensures that a high percentage of recipients will return to estrus during a 72 h interval and are eligible for subsequent embryo transfers. Numerous additional factors need to be assessed to ensure that the recipient herd achieves its reproductive potential. These factors include assessing the merits of nulliparous, primiparous, or multiparous cows, ensuring that facilities allow for minimal stress, and that the herd health program is well-defined and followed. Numerous short- and long-term factors contribute to recipients conceiving to a transferred embryo, maintaining the embryo/fetus to term, delivering the calf without assistance and raising and weaning a healthy calf.

Paracetamol availability and recent changes in paracetamol poisoning: is the 1998 legislation limiting availability of paracetamol being followed?

OBJECTIVE

To determine the degree of adherence to legislation introduced in 1998 restricting the availability of over the counter paracetamol.

DESIGN

A prospective observational study.

SETTING

An emergency department in an inner city London teaching hospital. Pharmacy and non-pharmacy outlets in south London.

MAIN OUTCOME MEASURES

(1) The source of paracetamol ingested by 107 patients presenting with an acute paracetamol overdose (2001-2003) and (2) the ability to purchase paracetamol from pharmacy and non-pharmacy outlets in a manner contravening paracetamol pack size legislation (2004).

RESULTS

Potentially toxic amounts of paracetamol in excess of pack size restrictions were purchased in 70% (17 of 24) of outlets. Forty six per cent of patients who had ingested a potentially toxic dose of paracetamol obtained the tablets in a manner contravening the 1998 legislation.

CONCLUSION

Legislation limiting the availability of over the counter paracetamol is not being adhered to in south London. A significant number of patients ingesting a potentially toxic dose of paracetamol report purchasing the tablets in a manner contravening the legislation. Studies that attempt to assess the impact of the legislation need to be interpreted in the context of these results. Measures to enforce current legislation may help to reduce the severity of paracetamol poisoning in the UK.

Variations in radiation exposures of adults and children in the UK

Members of the UK population receive radiation doses from a number of sources including cosmic radiation, from uranium, thorium and their decay products, particularly radon, and from medical sources. On average, members of the UK population receive an effective dose of about 200 mSv over their lifetime. This results in a risk of fatal cancer of about 1%. However, the radiation dose is not the same to all individuals. Some components give doses that vary systematically from one region to another. Doses may also vary greatly from one individual to another. The rate at which the dose is accumulated may vary as the individual ages. Different organs and tissues do not necessarily receive the same dose. This paper discusses these factors and attempts to quantify them. Cosmic rays deliver doses which vary little across the body or between individuals. Terrestrial gamma rays also deliver more or less uniform whole-body doses, but the difference between individuals can be greater. Radionuclides in food deliver doses which vary both across the body and between individuals. These variations are even more marked in the case of doses from radon and from medical exposures.

Recellularization of decellularized allograft scaffolds in ovine great vessel reconstructions

BACKGROUND

Decellularized allograft tissues have been identified as a potential extracellular matrix (ECM) scaffold on which to base recellularized tissue-engineered vascular and valvular substitutes. Decreased antigenicity and the capacity to recellularize suggest that such constructs may have favorable durability. Detergent/enzyme decellularization methods remove cells and cellular debris while leaving intact structural protein "scaffolds." Allograft pulmonary artery tissues decellularized with an anionic detergent/enzyme methodology were tested in a long-term implantation model that used arterial wall repairs in the great vessels of juvenile sheep.

METHODS

Twelve test sheep were implanted (n = 4) for each of three different scaffold protocols that compared traditional dimethylsulfoxide cryopreservation, cryopreservation followed by decellularization, and decellularization of fresh tissue. Four additional sheep served as controls (n = 2 sham, n = 2 fresh tissue). Patches were fashioned and implanted into pulmonary artery and aortic defects. Panel reactive antibodies (PRA) were measured over time (10 to 20 weeks). Explant histopathology determined recellularization morphology as well as calcium, collagen, and elastin distribution within explanted tissue.

RESULTS

Unlike traditionally cryopreserved tissues, the decellularized tissues contained no residual cells or cellular debris before implantation, which correlated with measurable reductions in PRA. Decellularized explants demonstrated time-dependent migration of recipient cells through matrix, typically staining positive for alpha-smooth muscle actin with no calcification.

CONCLUSIONS

The properties demonstrated seem consistent with characteristics necessary for implantable tissue-engineered scaffolds. The decellularization method described appears to create a biologically suitable ECM scaffold for in vivo migration of phenotypically appropriate cells while avoiding antigenicity and calcification.

Review of the radiation exposure of the UK population

Since 1974 the National Radiological Protection Board (now the Radiation Protection Division of the Health Protection Agency) has produced reviews of the levels of exposure to ionising radiation in the UK, from sources of natural and artificial origin. The latest review (Watson et al 2005 Ionising Radiation Exposure of the UK Population: 2005 Review HPA-RPD-001 (Chilton: HPA-RPD)) in the series gives estimates of annual doses based predominantly on data collected for the years 2001-2003. The overall average annual dose is rounded to 2.7 mSv, and the average annual dose from natural radiation is found to be 2.2 mSv. The overall average annual dose is slightly increased over that found in the previous, 1999, review. This increase is mainly due to a larger contribution from medical irradiation.

Metaraminol (Aramine) in the management of a significant amlodipine overdose

OBJECTIVE

To report a patient with a significant amlodipine self-poisoning who failed to clinically respond to conventional treatment and was managed with metaraminol (Aramine).

PATIENT

A 43-year old male presenting after ingestion of 560 mg amlodipine, who failed to respond clinically to treatment with fluid resuscitation, calcium salts, glucagon and norepinephrine/epinephrine inotropic support.

MAIN RESULTS

Following a loading bolus of 2 mg and intravenous infusion (83 microg/min) of metaraminol (Aramine) there was improvement in his blood pressure, cardiac output and urine output.

CONCLUSIONS

This is the first case report of the beneficial use of metaraminol (aramine) in the management of significant amlodipine poisoning unresponsive to conventional therapy.

Dietzia strain X: a newly described Actinomycete isolated from confluent and reticulated papillomatosis

Confluent and reticulated papillomatosis (CRP) is a rare skin disorder. To date its aetiology remains uncertain. The possibility of an infectious aetiology has been supported by case reports of therapeutic response to antibiotic therapy. We have isolated and identified a previously unknown Dietzia strain, an Actinomycete, from skin scrapings of a 17-year-old boy with CRP. We propose that this organism may be the aetiological agent of CRP. Further investigations are necessary to determine the potential role of this Actinomycete in the pathogenesis of CRP.

Naloxone in opioid poisoning: walking the tightrope

Acute opioid intoxication and overdose are common causes of presentation to emergency departments. Although naloxone, a pure opioid antagonist, has been available for many years, there is still confusion over the appropriate dose and route of administration. This article looks at the reasons for this uncertainty and undertakes a literature review from which a treatment algorithm is presented.

Measuring plasma salicylate concentrations in all patients with drug overdose or altered consciousness: is it necessary?

BACKGROUND

Salicylate self poisoning is potentially fatal. Plasma salicylate concentrations can be used to guide management when taken in the context of clinical features of toxicity and acid base status. Previous studies in the USA and Hong Kong have shown that routine measurement of plasma salicylate concentrations in all overdose patients is inappropriate, but there have been no previous studies in the UK.

METHODS

A retrospective case note study from 1 February 2001 to 31 January 2002 was undertaken at the emergency department of St. Thomas' Hospital, London. Records were reviewed and information on demographic data, history, details of salicylate overdose, and documentation of clinical features of salicylate toxicity recorded.

RESULTS

In total, 722 patient episodes were identified, of which 596 case notes were available and appropriate for inclusion in this study. Plasma salicylate concentrations (range 15-428 mg/l) were detectable in 50 patients (three notes not available), of whom 38 had given a positive history. The history of salicylate poisoning had a sensitivity of 81% (95% confidence interval (CI) 67 to 91%) and the predictive value of a negative history of salicylate ingestion in not detecting salicylate concentrations was 98% (95% CI 97 to 99%). Insufficient information on clinical features of salicylate toxicity was recorded in 569 patients (including 35 patients who had a history of salicylate ingestion).

CONCLUSION

History of salicylate ingestion has a high sensitivity and negative predictive value with respect to the detection of plasma salicylate concentrations. However, current practice indicates that insufficient information is obtained from patients about the clinical features of toxicity. Routine measurement of plasma salicylate concentrations is not required unless there is (a) a positive history of ingestion of salicylates or (b) a reduced level of consciousness or other reason limiting the validity of the history obtained, together with clinical features consistent with salicylate poisoning.

Acute poisoning: understanding 90% of cases in a nutshell

The acutely poisoned patient remains a common problem facing doctors working in acute medicine in the United Kingdom and worldwide. This review examines the initial management of the acutely poisoned patient. Aspects of general management are reviewed including immediate interventions, investigations, gastrointestinal decontamination techniques, use of antidotes, methods to increase poison elimination, and psychological assessment. More common and serious poisonings caused by paracetamol, salicylates, opioids, tricyclic antidepressants, selective serotonin reuptake inhibitors, benzodiazepines, non-steroidal anti-inflammatory drugs, and cocaine are discussed in detail. Specific aspects of common paediatric poisonings are reviewed.

Evaluation of the high specificity Screening Program (C-20-1) of the Frequency Doubling Technology (FDT) perimeter in clinical practice

AIMS

To compare the efficacy of the high specificity Frequency Doubling Technology (FDT) Perimeter Screening Program (C-20-1) to standard threshold automated perimetry in the diagnosis of open-angle glaucoma.

METHODS

A total of 100 consecutively presenting patients attending a glaucoma clinic who volunteered for the study (approximately 30% of whom were attending for an initial visit) were examined with the FDT C-20-1 Screening Program and with the Humphrey Field Analyzer (HFA) SITA Fast algorithm and Program 24-2.

RESULTS

Of the patients, 17 were excluded due to unreliable visual field results or non-glaucomatous ocular abnormalities. In all, 10 patients were diagnosed as normal, 54 with open-angle glaucoma, eight with ocular hypertension, and 11 as glaucoma suspects. Of the 54 glaucomatous patients, 45 exhibited high-tension glaucoma and nine normal tension glaucoma. Perimetry with the HFA gave a sensitivity of 81.5% for the combined category of glaucoma and glaucoma suspect and a specificity of 83.3% for the combined category of normal and ocular hypertension. Perimetry with the FDT gave a sensitivity of 74.5% and a specificity of 85.2% compared to that of the HFA.

CONCLUSION

In the detection of glaucoma, Program C-20-1 of the FDT perimeter exhibits high specificity. It exhibits low sensitivity for the detection of mild loss but high sensitivity for advanced field loss relative to Program 24-2 and the SITA Fast algorithm of the HFA.

Responsive brushes and gels as components of soft nanotechnology

Progress in the development of generic molecular devices based on responsive polymers is discussed. Characterisation of specially synthesised polyelectrolyte gels, "grafted from" brushes and triblock copolymers is reported. A Landolt pH-oscillator, based on bromate/ sulfite/ferrocyanide, with a room temperature period of 20 min and a range of 3.1 < pH < 7.0, has been used to drive periodic oscillations in volume in a pH responsive hydrogel. The gel is coupled to the reaction and changes volume by a factor of at least 6. A continuously stirred, constant volume, tank reactor was set-up on an optical microscope and the reaction pH and gel size monitored. The cyclic force generation of this system has been measured directly in a modified JKR experiment. The responsive nature of polyelectrolyte brushes, grown by surface initiated ATRP, have been characterised by scanning force microscopy, neutron reflectometry and single molecule force measurements. Triblock copolymers, based on hydrophobic end-blocks and either polyacid or polybase mid-block, have been used to produce polymer gels where the deformation of the molecules can be followed directly by SAXS and a correlation between molecular shape change and macroscopic deformation has been established. The three systems studied allow both the macroscopic and a molecular response to be investigated independently for the crosslinked gels and the brushes. The triblock copolymers demonstrate that the individual response of the polyelectrolyte molecules scale-up to give the macroscopic response of the system in an oscillating chemical reaction.

Prototype anionic detergent technique used to decellularize allograft valve conduits evaluated in the right ventricular outflow tract in sheep

BACKGROUND AND AIM OF THE STUDY

Biodegradable polymeric materials or extracellular matrix scaffolds are used in tissue-engineered heart valve designs, with the expectation of replicating the anatomic, histological and biomechanical characteristics of semi-lunar valves. The study aim was to evaluate the extent of in-vivo recellularization and the explant pathology findings of a prototype anionic, non-denaturing detergent and endonuclease technique used to decellularize allograft (homograft) valve conduits implanted in the right ventricular outflow tract (RVOT) of sheep, and to identify possible risks associated with tissue-engineered heart valve conduits based on decellularized allograft semilunar valve scaffolds.

METHODS

Valve conduits were decellularized using a solution of N-lauroylsarcosinate and endonucleases, rinsed in lactated Ringers solution, and stored in an antibiotic solution at 4 degrees C until implanted. Explanted valves and unimplanted controls were examined macroscopically, radiographically (for calcification) and histologically using immunohistochemistry (IHC), routine and special histological stains, transmission electron microscopy (TEM) and polarized light microscopy (evaluation of collagen crimp).

RESULTS

Cells and cellular remnants were uniformly absent in the decellularized cusps, but occasional focal sites of arterial wall smooth muscle cells and to a greater extent subvalvular cardiac myocytes were variably retained. The trilaminar histological structure of the cusp was preserved. Valve conduit-related pathology consisted of intracuspal hematoma formation, collagen fraying, thinning of the conduit wall, and inflammatory cells associated with cardiac myocyte remnants. Cuspal calcification was not seen, but elastic fibers in the conduit wall and retained subvalvular cardiac myocyte remnants were liable to calcification. Fibrous sheath formation was present on the luminal surface of the conduit and extended over the cuspal surfaces to a variable extent. Myofibroblast-like cells repopulated the conduit wall and the basal region of the cusp. Re-endothelialization was variably present on the cuspal surfaces.

CONCLUSION

Explant pathology findings showed that in-vivo recellularization occurred, but was focally limited to regions of the arterial wall and cusp base. Safety concerns related to detergent and endonuclease use were identified. Methods to eliminate the potential for structural deterioration and enhance the rate and extent of recellularization of valve conduit tissue are required. Pathology findings showed implantation of valve conduits in the RVOT of juvenile sheep for 20 weeks to be a reliable animal model for the initial in-vivo assessment of decellularized valves. A 20-week period may be insufficient however to evaluate the long-term safety and effectiveness of a tissue-engineered valve conduit, as these depend on effective and phenotypically appropriate recellularization accompanied by sustained cell viability and function.

Hepatocellular damage from non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for the management of rheumatological disorders, and as analgesics and antipyretics. Hepatotoxicity is an uncommon, but potentially lethal complication, which usually occurs within 12 weeks of starting therapy. It can occur with all NSAIDs, but appears to be more common with diclofenac and particularly sulindac. Female patients aged >50 years, with autoimmune disease, and those on other potentially hepatotoxic drugs, appear to be particularly susceptible. Liver function test abnormalities generally settle within 4-6 weeks of stopping the causative drug. However, some patients may develop acute liver failure and successful orthotopic liver transplantation may be undertaken in such patients. Recent in vitro animal studies have shown that the mechanism of diclofenac toxicity relates both to impairment of ATP synthesis by mitochondria, and to production of active metabolites, particularly n,5-dihydroxydiclofenac, which causes direct cytotoxicity. Mitochondrial permeability transition (MPT) has also been shown to be important in diclofenac-induced liver injury, resulting in generation of reactive oxygen species, mitochondrial swelling and oxidation of NADP and protein thiols. Physicians and hepatologists must be vigilant to the hepatotoxic potential of any NSAID, as increased awareness, surveillance and reporting of these events will lead to a better understanding of the risk factors and the pathophysiology of NSAID-related hepatotoxicity.

Paracetamol overdose: an evidence based flowchart to guide management

A flowchart for the management of patients with paracetamol poisoning is presented to help clinicians in the emergency department.

An evidence based flowchart to guide the management of acute salicylate (aspirin) overdose

OBJECTIVE

To develop a flowchart to be used as a tool to guide clinicians step by step through the management of salicylate poisoning.

METHODS

A comprehensive literature search was carried out.

RESULTS

The evidence base was used to develop a management flowchart that guides the clinician through the three main steps in caring for the patient with salicylate poisoning: preventing further absorption, assessing the severity of poisoning and, where appropriate, increasing elimination.

CONCLUSIONS

Salicylate poisoning can result in severe morbidity and mortality and this flowchart provides an evidence based guideline that will guide clinicians through the management of patients presenting to the emergency department with salicylate poisoning.

Survival of enterococci during hospital laundry processing

Much remains to be elucidated about the epidemiology of nosocomial enterococcal infections. Enterococci are, however, known to be relatively thermotolerant, and several studies have shown that under laboratory conditions many strains are able to survive the time/temperature combinations of the UK Department of Health recommendations for the decontamination of used linen (HSG(95)18). We therefore wished to investigate the efficacy of decontamination of enterococci from hospital linen in working hospital laundries. The thermotolerance of 40 strains of Enterococcus faecalis and Enterococcus faecium was first determined. Reduction by a factor of greater than 10(5) was achieved in only two of 40 strains after 3 min at 71 degrees C or 10 min at 65 degrees C, the time/temperature combinations specified by the Department of Health for the disinfection of used linen. During experimental challenge of 10 working hospital laundries, however, we demonstrated successful decontamination of laundry artificially contaminated with enterococci. This was shown to take place during the washing stage. Our study suggests that, despite the relative thermotolerance of enterococci, the time/temperature combinations specified in HSG(95)18 should be adequate for their decontamination in hospital laundries.

Measuring plasma paracetamol concentrations in all patients with drug overdose or altered consciousness: does it change outcome?

OBJECTIVE

To assess whether measuring plasma paracetamol concentrations in all patients with drug overdose or collapse (altered consciousness) changes outcome.

METHOD

A retrospective survey was performed of all patients attending the Accident and Emergency Department at Guy's Hospital, London over a 12 month period who had plasma paracetamol concentrations measured (it is hospital policy that patients presenting after any drug overdose, or with a collapse/altered consciousness have a plasma paracetamol concentration).

RESULTS

A total of 440 patients were identified who had plasma paracetamol concentrations measured, of whom 411 were eligible for the study. Altogether 115 patients presented after a collapse and paracetamol was detected in four of these. A total of 296 patients presented after a drug overdose-136 denied overdose with a paracetamol containing product and paracetamol was not detected in any of these 136 cases. Of the remaining 160 patients who gave a positive history for overdose with paracetamol, 122 presented within 24 hours and 94 had detectable paracetamol values with 16 cases above the treatment line, 12 presented more than 24 hours after ingestion, and 26 presented with a staggered overdose. One patient died as a result of paracetamol overdose.

CONCLUSIONS

This is the first study in the United Kingdom to evaluate the clinical value of routine paracetamol levels in patients presenting to the emergency department after any overdose or a collapse. Taking blood samples for plasma paracetamol estimation in patients who deny taking paracetamol is of little clinical value. However, there is the potential for missing significant paracetamol poisoning in patients presenting with collapse and so screening with a plasma paracetamol concentration is clinically justified in these patients. Such an approach can only be justified in a country in which paracetamol poisoning is prevalent, such as the United Kingdom.

The Humphrey optical coherence tomography scanner: quantitative analysis and reproducibility study of the normal human retinal nerve fibre layer

BACKGROUND/AIMS

To determine the reproducibility of the Humphrey optical coherence tomography scanner (OCT), software version 5.0, for measurement of retinal nerve fibre layer (RNFL) thickness in normal subjects and to compare OCT measurements with published histological thickness of the human RNFL.

METHODS

Three independent measurements were obtained at each session for one eye from 15 normal subjects with a mean age of 30.8 (SD 10.9) years. Scans were taken in the peripapillary retina using the default setting (1.74 mm radius from centre of the optic disc) and were repeated 1 week later. Additional scans were obtained at the optic nerve head (ONH) margin overlying the scleral rim, for comparison with available histological data on the human RNFL.

RESULTS

For the 1.74 mm circular scan, the mean coefficient of variation (COV) for the global RNFL thickness measurement was 5% (SD 3%). This increased to 8% (3%) for quadrant measurements and to 9% (3%) with further subdivision into 12 segments. Significant differences (p<0.05) between sessions were only found when the data were divided into segments. The mean RNFL thickness for the 1.74 mm scan was 127.87 (9.81) microm. The RNFL was maximal at the superior disc pole, 161.44 microm (14.8), and minimal at the temporal pole, 83.1 (12.8) microm. Peak thickness values occurred superior temporal and inferior temporal to the vertical axis. RNFL thickness for every sector of the disc was greatest at the margin of the optic disc (mean 185.79 microm; SD 32.61). Although the variation in RNFL thickness around the disc follows published histology data, the OCT underestimates RNFL thickness by an average of 37% (SD 11; range 21-48%).

CONCLUSION

The OCT provides reproducible measurement of the retinal structures that are consistent with the properties of the RNFL. However, comparison with available studies of RNFL thickness in the human suggests that in its present form, the OCT underestimates RNFL thickness. Further refinement of this technology is required to improve the accuracy with which the OCT measures retinal nerve fibre layer thickness.

Freeze tolerance in the gray treefrog: cryoprotectant mobilization and organ dehydration

Freeze tolerance in the frog Rana sylvatica is supported by nonanticipatory mobilization of cryoprotectant (glucose) and redistribution of organ water. Other freeze-tolerant frogs may manifest these responses but differences exist. For example, the gray treefrog (Hyla versicolor) accumulates mostly glycerol as opposed to glucose. The current study reports additional novel features about cryoprotection in H. versicolor. Frogs were acclimated to low temperature for 12 weeks and frozen for 3 days at -2.4 degrees C. Some frogs were then thawed at 3 degrees C for 4 hr. Calorimetry revealed that frozen frogs had 53.9% +/- 11.1% of their body water in ice, and all frogs recovered following this procedure. Plasma glucose was low prior to the onset of freezing (1.1 +/- 0.9 micromol/ml) and it was 20x higher in postfreeze frogs. Constituting nearly 30% of plasma solute, glycerol was 117.2 +/- 13.6 micromol/ml prior to freezing and it remained equally high in postfreeze frogs. Liver water content was moderately lower in frozen frogs when compared to controls (62.9% +/- 3.7% vs. 68.6% +/- 1.7%), whereas postfreeze frogs excessively hydrated their livers (75.7% +/- 2.1%). Less-pronounced changes were seen in muscle water content. H. versicolor can mobilize its major cryoprotectant, glycerol, in response to extended cold acclimation, which is unique in comparison to other freeze-tolerant frogs, and it experiences only moderate organ dehydration during freezing. This species conforms with other freeze-tolerant frogs, however, by mobilizing glucose as a direct response to tissue freezing.