Symptom resolution following a repeat concussion within the same athlete

INTRODUCTION

Repeat sport-related concussion (SRC) is anecdotally associated with prolonged recovery. Few studies have examined repeat concussion within the same athlete. We sought to explore differences in symptom burden and recovery outcomes in an individual athlete's initial and repeat SRC.

METHODS

A retrospective within-subject cohort study of athletes aged 12-23 years diagnosed with two separate SRCs from 11/2017-10/2020 was conducted. Primary outcomes were initial symptom severity and time-to-symptom-resolution. Secondary outcomes included return-to-learn (RTL) and return-to-play (RTP) duration.

RESULTS

Of 868 athletes seen, 47 athletes presented with repeat concussions. Median time between concussions was 244 days (IQR 136-395). Comparing initial to repeat concussion, no differences were observed in time-to-clinic (4.3 ± 7.3vs.3.7 ± 4.6 days, p = 0.56) or initial PCSS (26.2 ± 25.3 vs. 30.5 ± 24.1, p = 0.32). While a difference was observed in time-to-symptom resolution between initial/repeat concussion (21.2 ± 16.3 vs. 41.7 ± 86.0 days, p = 0.30), this did not reach statistical significance. No significant differences were observed in time-to-RTL (17.8 ± 60.6 vs. 6.0 ± 8.3 days, p = 0.26) and RTP (33.2 ± 44.1 vs. 29.4 ± 39.1 days, p = 0.75). Repeat concussion was not associated with symptom resolution on univariate (HR 1.64, 95% CI 0.96-2.78, p = 0.07) and multivariable (HR 0.85, 95% CI 0.49-1.46, p = 0.55) Cox regression.

CONCLUSION

No significant differences in symptom duration and RTP/RTL were seen between initial/repeat concussion.

Traumatic chest wall pyomyositis presenting with mediastinitis

Pyomyositis is an acute bacterial infection of the skeletal muscle that is commonly associated with localized abscess formation. It is estimated that pyomyositis accounts for up to 4% of all hospital admissions throughout Asia, tropical Africa, Oceania and the Caribbean Islands. However, there has been an increasing emergence of pyomyositis in temperate climates and high-income countries. Staphylococcus aureus is the most common organism implicated. Management requires a high index of clinical suspicion, prompt diagnosis and early management to prevent sequalae that can be fatal if left untreated. We describe an interesting case of pyomyositis in an otherwise fit and immunocompetent individual causing mediastinitis; a rare sequalae of the disease. Percutaneous drainage of his left pectoral abscess and a prolonged course of antibiotics provided complete clinical and radiological resolution of the disease despite mediastinal extension. Here we discuss aetiology, associations, pathophysiology and epidemiology of pyomyositis with associated sequalae of the disease.

Use of acute cognitive symptom cluster to predict return-to-learn duration following a sport-related concussion

OBJECTIVE

Adolescents sustaining sport-related concussion often experience difficulties with the return-to-learn (RTL) process. Whereas the initial symptom burden has predicted prolonged RTL, no studies have established a relationship between acute cognitive symptoms and RTL duration. The authors sought to evaluate the relationship between initial cognitive symptoms and RTL duration.

METHODS

A retrospective single-institution cohort study of adolescent athletes aged 12-23 years who were evaluated within 5 days of a diagnosed sport-related concussion between November 2017 and October 2020 was conducted. Athletes missing cognitive symptom ratings and RTL data were excluded. The primary exposure variable was the Cognitive Symptom Ratio (CSR), defined as total cognitive symptom cluster score divided by total Post-Concussion Symptom Scale (PCSS) score from the initial clinic visit. Primary and secondary outcomes were time to RTL and total length of care, respectively. Multivariable Cox proportional hazards modeling was used to assess the effect of CSR on RTL duration.

RESULTS

Of 653 athletes evaluated within 5 days of injury, 346 patients were included in the final cohort. Athletes reported a median initial PCSS score of 21 (interquartile range [IQR] 6-37) and a median cognitive symptom score of 4 (IQR 0-9). Most patients endorsed some degree of difficulty concentrating (n = 212, 61.3%). The median CSR was 0.18 (IQR 0.00-0.27). On multivariable regression analysis, a higher CSR was associated with prolonged RTL duration (HR 0.30, 95% CI 0.13-0.69, p = 0.004). When initial PCSS score was added to the model, the previously significant association between CSR and RTL was no longer significant (HR 0.67, 95% CI 0.29-1.59, p = 0.367). When dichotomized based on frequency distribution, a higher proportion of patients with low CSR achieved RTL by 7 days postinjury (82.2% vs 69.9%, p = 0.007), a difference not seen at 14 days (92.2% vs 87.3%, p = 0.133).

CONCLUSIONS

An acute ratio of cognitive symptoms may predict patients at increased risk for prolonged RTL and those with normal PCSS scores who may experience difficulties once resuming school activities.

Which Recommendations Are You Using? A Survey of Emergency Physician Management of Paroxysmal Atrial Fibrillation

Background

Both the Canadian Cardiovascular Society (CCS) and the Canadian Association of Emergency Physicians (CAEP) have published documents to guide atrial fibrillation (AF) management. In 2021, the CAEP updated its AF checklist. Prior to this update, the recommendations of the 2 organizations differed in several key areas, including the suggested cardioversion timeframe, the factors determining cardioversion eligibility, and anticoagulant initiation after cardioversion. Whether emergency physicians (EPs) are aware of, or adhering to, one, both, or neither of these documents is unknown.

Methods

We assessed document awareness, adherence, and EP practice using a piloted questionnaire administered to EPs at 5 emergency departments in 3 provinces.

Results

Of 166 survey recipients, 123 (74.1%) responded. The majority (64.7%) worked at an academic site, 38.8% identified as female, and median years in practice was 10.0. Most (93.1%) were aware of at least one of the documents; 45.7% were aware of both. Reported awareness was higher for the CCS (77.6%) vs the CAEP (61.2%) guidelines. Respondents varied in their adherence, with 40.5% using parts of both documents. Considerable practice variability occurred when recommendations conflicted. Despite its use not being recommended by either organization, half of respondents (50.0%) reported using the CHA2DS2-VASc score as their stroke-risk assessment tool.

Conclusions

Although most surveyed EPs were aware of at least one organization's AF documents, many reported using parts of both. When recommendations conflicted, EPs were divided in their decision-making. These findings emphasize the need to improve consensus between organizations and further improve knowledge translation.

Thiamine increases resident endoglin positive cardiac progenitor cells and atrial contractile force in humans: A randomised controlled trial

BACKGROUND

The heart has an intrinsic ability to regenerate, orchestrated by progenitor or stem cells. However, the relative complexity of non-resident cardiac progenitor cell (CPC) therapy makes modulation of resident CPCs a more attractive treatment target. Thiamine analogues improve resident CPC function in pre-clinical models. In this double blinded randomised controlled trial (identifier: ACTRN12614000755639), we examined whether thiamine would improve CPC function in humans.

METHODS AND RESULTS

High dose oral thiamine (one gram twice daily) or matching placebo was administered 3-5 days prior to coronary artery bypass surgery (CABG). Right atrial appendages were collected at the time of CABG, and CPCs isolated. There was no difference in the primary outcome (proliferation ability of CPCs) between treatment groups. Older age was not associated with decreased proliferation ability. In exploratory analyses, isolated CPCs in the thiamine group showed an increase in the proportion of CD34^-/CD105⁺ (endoglin) cells, but no difference in CD34^-/CD90⁺ or CD34⁺ cells. Thiamine increased maximum force developed by isolated trabeculae, with no difference in relaxation time or beta-adrenergic responsiveness.

CONCLUSION

Thiamine does not improve proliferation ability of CPC in patients undergoing CABG, but increases the proportion of CD34^-/CD105⁺ cells. Having not met its primary endpoint, this study provides the impetus to re-examine CPC biology prior to any clinical outcome-based trial examining potential beneficial cardiovascular effects of thiamine.

Long-chain acylcarnitine 18:1 acutely increases human atrial myocardial contractility and arrhythmia susceptibility

Long-chain acylcarnitines (LCACs) are known to directly alter cardiac contractility and electrophysiology. However, the acute effect of LCACs on human cardiac function is unknown. We aimed to determine the effect of LCAC 18:1, which has been associated with cardiovascular disease, on the contractility and arrhythmia susceptibility of human atrial myocardium. Additionally, we aimed to assess how LCAC 18:1 alters Ca²⁺ influx and spontaneous Ca²⁺ release in vitro. Human right atrial trabeculae (n = 32) stimulated at 1 Hz were treated with LCAC 18:1 at a range of concentrations (1-25 µM) for a 45-min period. Exposure to the LCAC induced a dose-dependent positive inotropic effect on myocardial contractility (maximal 1.5-fold increase vs. control). At the 25 µM dose (n = 8), this was paralleled by an enhanced propensity for spontaneous contractions (50% increase). Furthermore, all LCAC 18:1 effects on myocardial function were reversed following LCAC 18:1 washout. In fluo-4-AM-loaded HEK293 cells, LCAC 18:1 dose dependently increased cytosolic Ca²⁺ influx relative to vehicle controls and the short-chain acylcarnitine C3. In HEK293 cells expressing ryanodine receptor (RyR2), this increased Ca²⁺ influx was linked to an increased propensity for RyR2-mediated spontaneous Ca²⁺ release events. Our study is the first to show that LCAC 18:1 directly and acutely alters human myocardial function and in vitro Ca²⁺ handling. The metabolite promotes proarrhythmic muscle contractions and increases contractility. The exploratory findings in vitro suggest that LCAC 18:1 increases proarrhythmic RyR2-mediated spontaneous Ca²⁺ release propensity. The direct effects of metabolites on human myocardial function are essential to understand cardiometabolic dysfunction.NEW & NOTEWORTHY For the first time, the fatty acid metabolite, long-chain acylcarnitine 18:1, is shown to acutely increase the arrhythmia susceptibility and contractility of human atrial myocardium. In vitro, this was linked to an influx of Ca²⁺ and an enhanced propensity for spontaneous RyR2-mediated Ca²⁺ release.

Human Atrial Fibrillation Is Not Associated With Remodeling of Ryanodine Receptor Clusters

The release of Ca²⁺ by ryanodine receptor (RyR2) channels is critical for cardiac function. However, abnormal RyR2 activity has been linked to the development of arrhythmias, including increased spontaneous Ca²⁺ release in human atrial fibrillation (AF). Clustering properties of RyR2 have been suggested to alter the activity of the channel, with remodeling of RyR2 clusters identified in pre-clinical models of AF and heart failure. Whether such remodeling occurs in human cardiac disease remains unclear. This study aimed to investigate the nanoscale organization of RyR2 clusters in AF patients – the first known study to examine this potential remodeling in diseased human cardiomyocytes. Right atrial appendage from cardiac surgery patients with paroxysmal or persistent AF, or without AF (non-AF) were examined using super-resolution (dSTORM) imaging. Significant atrial dilation and cardiomyocyte hypertrophy was observed in persistent AF patients compared to non-AF, with these two parameters significantly correlated. Interestingly, the clustering properties of RyR2 were remarkably unaltered in the AF patients. No significant differences were identified in cluster size (mean ∼18 RyR2 channels), density or channel packing within clusters between patient groups. The spatial organization of clusters throughout the cardiomyocyte was also unchanged across the groups. RyR2 clustering properties did not significantly correlate with patient characteristics. In this first study to examine nanoscale RyR2 organization in human cardiac disease, these findings indicate that RyR2 cluster remodeling is not an underlying mechanism contributing to altered channel function and subsequent arrhythmogenesis in human AF.

Starting, building and sustaining a program of research in emergency medicine in Canada

OBJECTIVE

To develop pragmatic recommendations for starting, building and sustaining a program of research in emergency medicine (EM) in Canada at sites with limited infrastructure and/or prior research experience.

METHODS

At the direction of the Canadian Association of Emergency Physicians (CAEP) academic section, we assembled an expert panel of 10 EM researchers with experience building programs of research. Using a modified Delphi approach, our panel developed initial recommendations for (1) starting, (2) building, and (3) sustaining a program of research in EM. These recommendations were peer-reviewed by emergency physicians and researchers from each of the panelist's home institutions and tested for face and construct validity, as well as ease of comprehension. The recommendations were then iteratively revised based on feedback and suggestions from peer review and amended again after being presented at the 2020 CAEP academic symposium.

RESULTS

Our panel created 15 pragmatic recommendations for those intending to start (formal research training, find mentors, local support, develop a niche, start small), build (funding, build a team, collaborate, publish, expect failure) and sustain (become a mentor, obtain leadership roles, lead national studies, gain influence, prioritize wellness) a program of EM research in centers without an established research culture. Additionally, we suggest four recommendations for department leads aiming to foster a program of research within their departments.

CONCLUSION

These recommendations serve as guidance for centres wanting to establish a program of research in EM.

Elevated myocardial fructose and sorbitol levels are associated with diastolic dysfunction in diabetic patients, and cardiomyocyte lipid inclusions in vitro

Diabetes is associated with cardiac metabolic disturbances and increased heart failure risk. Plasma fructose levels are elevated in diabetic patients. A direct role for fructose involvement in diabetic heart pathology has not been investigated. The goals of this study were to clinically evaluate links between myocardial fructose and sorbitol (a polyol pathway fructose precursor) levels with evidence of cardiac dysfunction, and to experimentally assess the cardiomyocyte mechanisms involved in mediating the metabolic effects of elevated fructose. Fructose and sorbitol levels were increased in right atrial appendage tissues of type 2 diabetic patients (2.8- and 1.5-fold increase respectively). Elevated cardiac fructose levels were confirmed in type 2 diabetic rats. Diastolic dysfunction (increased E/e’, echocardiography) was significantly correlated with cardiac sorbitol levels. Elevated myocardial mRNA expression of the fructose-specific transporter, Glut5 (43% increase), and the key fructose-metabolizing enzyme, Fructokinase-A (50% increase) was observed in type 2 diabetic rats (Zucker diabetic fatty rat). In neonatal rat ventricular myocytes, fructose increased glycolytic capacity and cytosolic lipid inclusions (28% increase in lipid droplets/cell). This study provides the first evidence that elevated myocardial fructose and sorbitol are associated with diastolic dysfunction in diabetic patients. Experimental evidence suggests that fructose promotes the formation of cardiomyocyte cytosolic lipid inclusions, and may contribute to lipotoxicity in the diabetic heart.

Outcomes of out of hospital cardiac arrest in First Nations and non-First Nations patients in Saskatoon

INTRODUCTION

One in nine (11.7%) people in Saskatchewan identify as First Nations. It is known that First Nations people have a higher burden of cardiovascular disease, but not whether outcomes of out of hospital cardiac arrest are different.

METHODS/METHODOLOGY

We reviewed pre-hospital and inpatient records of patients with out of hospital cardiac arrest between January 1st, 2015 and December 31st, 2017. The population consisted of patients aged 18 years or older with out of hospital cardiac arrest of presumed cardiac origin occurring in the catchment area of Saskatoon's emergency medical services (EMS). Variables of interest included age, gender, First Nations status, EMS response times, bystander cardiopulmonary resuscitation (CPR), and shockable rhythm. Outcomes of interest included return of spontaneous circulation (ROSC), survival to hospital admission, and survival to hospital discharge.

RESULTS

In all, 372 patients sustained out of hospital cardiac arrest, of which 27 were status First Nations. There were no differences between First Nations and non-First Nations patients in terms of shockable rhythms (24% vs 26%; p = 0.80), ROSC (42% vs 41%; p = 0.87), survival to hospital admission (27% vs 33%; p = 0.53), and survival to hospital discharge (15% vs 12%; p = 0.54). First Nations patients with out of hospital cardiac arrest were significantly younger (mean age 46 vs. 65 years; p < 0.0001) and had shorter EMS response times (median times 5.3 vs. 6.2 min; p = 0.01) when compared to non-First Nations patients.

CONCLUSIONS

In Saskatoon, First Nations patients with out of hospital cardiac arrest appear to have similar survival rates when compared with non-First Nations patients. However, First Nations patients sustaining out of hospital cardiac arrest were significantly younger than their non-First Nations counterparts. This highlights a significant public health issue.

Inotropic and lusitropic, but not arrhythmogenic, effects of adipocytokine resistin on human atrial myocardium

The adipocytokine resistin is released from epicardial adipose tissue (EAT). Plasma resistin and EAT deposition are independently associated with atrial fibrillation. The EAT secretome enhances arrhythmia susceptibility and inotropy of human myocardium. Therefore, we aimed to determine the effect of resistin on the function of human myocardium and how resistin contributes to the proarrhythmic effect of EAT. EAT biopsies were obtained from 25 cardiac surgery patients. Resistin levels were measured by ELISA in 24-h EAT culture media (n = 8). The secretome resistin concentrations increased over the culture period to a maximal level of 5.9 ± 1.2 ng/mL. Coculture with β-adrenergic agonists isoproterenol (n = 4) and BRL37344 (n = 13) had no effect on EAT resistin release. Addition of resistin (7, 12, 20 ng/mL) did not significantly increase the spontaneous contraction propensity of human atrial trabeculae (n = 10) when given alone or in combination with isoproterenol. Resistin dose-dependently increased trabecula-developed force (maximal 2.9-fold increase, P < 0.0001), as well as the maximal rates of contraction (2.6-fold increase, P = 0.002) and relaxation (1.8-fold increase, P = 0.007). Additionally, the postrest potentiation capacity of human trabeculae was reduced at all resistin doses, suggesting that the inotropic effect induced by resistin might be due to altered sarcoplasmic reticulum Ca²⁺ handling. EAT resistin release is not modulated by common arrhythmia triggers. Furthermore, exogenous resistin does not promote arrhythmic behavior in human atrial trabeculae. Resistin does, however, induce an acute dose-dependent positive inotropic and lusitropic effect.

Acute interaction between human epicardial adipose tissue and human atrial myocardium induces arrhythmic susceptibility

Epicardial adipose tissue (EAT) deposition has a strong clinical association with atrial arrhythmias; however, whether a direct functional interaction exists between EAT and the myocardium to induce atrial arrhythmias is unknown. Therefore, we aimed to determine whether human EAT can be an acute trigger for arrhythmias in human atrial myocardium. Human trabeculae were obtained from right atrial appendages of patients who have had cardiac surgery (n = 89). The propensity of spontaneous contractions (SCs) in the trabeculae (proxy for arrhythmias) was determined under physiological conditions and during known triggers of SCs (high Ca²⁺, β-adrenergic stimulation). To determine whether EAT could trigger SCs, trabeculae were exposed to superfusate of fresh human EAT, and medium of 24 h-cultured human EAT treated with β_1/2 (isoproterenol) or β₃ (BRL37344) adrenergic agonists. Without exposure to EAT, high Ca²⁺ and β_1/2-adrenergic stimulation acutely triggered SCs in, respectively, 47% and 55% of the trabeculae that previously were not spontaneously active. Acute β₃-adrenergic stimulation did not trigger SCs. Exposure of trabeculae to either superfusate of fresh human EAT or untreated medium of 24 h-cultured human EAT did not induce SCs; however, specific β₃-adrenergic stimulation of EAT did trigger SCs in the trabeculae, either when applied to fresh (31%) or cultured (50%) EAT. Additionally, fresh EAT increased trabecular contraction and relaxation, whereas media of cultured EAT only increased function when treated with the β₃-adrenergic agonist. An acute functional interaction between human EAT and human atrial myocardium exists that increases the propensity for atrial arrhythmias, which depends on β₃-adrenergic rather than β_1/2-adrenergic stimulation of EAT.

Optimum Accuracy of Massive Transfusion Protocol Activation: The Clinician's View

Background

Massive transfusion protocols (MTP) aid in the efficient delivery of blood components to rapidly exsanguinating patients. Unfortunately, clinical gestalt and currently available clinical scoring systems lack the optimal accuracy to prevent blood product wastage (through over-activation), as well as individual patient morbidity and mortality (through under-activation). In order to help refine the MTP activation criteria and protocols, we surveyed clinicians on acceptable over- and under-activation rates for massive transfusions.

Methods

We surveyed Canadian content experts in their respective fields, using a snowball survey technique. Respondents were categorized into two groups: Group 1 was comprised of trauma and acute care specialists (TACS), while Group 2 was comprised of clinical and laboratory medicine specialists (CLMS). Between-group differences were examined using Fisher’s exact test and the likelihood ratio. Statistical significance was set at p < 0.05.

Results

We received responses from 35 clinicians in the TACS group and 10 clinicians in the CLMS group. About half (45.7%) of respondents in the TACS group considered an MTP overactivation rate of 5% - 10% acceptable (vs. 60% of the CLMS group; not significant (NS)). Approximately one-third (34.2%) of the respondents in the TACS group considered an MTP under-activation rate of less than 5% acceptable, whereas the majority (60%) of respondents in the CLMS group considered an under-activation rate of less than 5% acceptable (NS). A significantly greater proportion of respondents in the TACS group felt that an anticipated need for > 20 units of packed red blood cells within the next 24 hours was an acceptable criterion for MTP activation. Respondents in the CLMS group were more likely to consider “poor communication” as a reason for blood component wastage.

Conclusion

Similarities in acceptable MTP over- and under-activation rates were noted across specialties. Collaboration between involved parties is necessary for MTP protocol development to improve patient outcomes and reduce blood wastage.

How Robust Are Studies in the American Board of Emergency Medicine Maintenance of Certification Lifelong Learning and Self-assessment? An Examination of Fragility and Bias of Included Randomized Controlled Trials

OBJECTIVE

Critics have raised concerns regarding the validity of maintenance of certification (MOC) programs. We sought to examine the quality of the randomized controlled trials (RCTs) selected for the lifelong learning and self-assessment (LLS) component of the American Board of Emergency Medicine (ABEM) MOC program.

METHODS

We systematically reviewed the ABEM LLS reading lists from 2004 to 2017 to identify RCTs with dichotomous outcomes and superiority designs. A fragility index (FI) was calculated using Fisher's exact test for all statistically significant dichotomous outcomes. Bivariate correlation was performed to examine associations between the FI and RCT study characteristics. Each included study was evaluated with the Cochrane Collaboration risk-of-bias (ROB) tool.

RESULTS

Thirteen superiority RCTs with dichotomous outcomes were included in the 2004-2017 LLS reading lists. Ten had a statistically significant outcome, and the majority were robust and at low ROB. The median trial size was 511 patients (interquartile range [IQR] = 251-1,517), and the median FI was 10 (IQR = 7-18); i.e., if 10 patients in the treatment arm had not had events, the results would not have been statistically significant.

CONCLUSIONS

The majority of RCTs included in the LLS are robust and at low ROB.

The thyroid hormone-αvβ3 integrin axis in ovarian cancer: regulation of gene transcription and MAPK-dependent proliferation

Ovarian carcinoma is the fifth common cause of cancer death in women, despite advanced therapeutic approaches. αvβ3 integrin, a plasma membrane receptor, binds thyroid hormones (L-thyroxine, T4; 3,5,3'-triiodo-L-thyronine, T3) and is overexpressed in ovarian cancer. We have demonstrated selective binding of fluorescently labeled hormones to αvβ3-positive ovarian cancer cells but not to integrin-negative cells. Physiologically relevant T3 (1 nM) and T4 (100 nM) concentrations in OVCAR-3 (high αvβ3) and A2780 (low αvβ3) cells promoted αv and β3 transcription in association with basal integrin levels. This transcription was effectively blocked by RGD (Arg-Gly-Asp) peptide and neutralizing αvβ3 antibodies, excluding T3-induced β3 messenger RNA, suggesting subspecialization of T3 and T4 binding to the integrin receptor pocket. We have provided support for extracellular regulated kinase (ERK)-mediated transcriptional regulation of the αv monomer by T3 and of β3 monomer by both hormones and documented a rapid (30-120 min) and dose-dependent (0.1-1000 nM) ERK activation. OVCAR-3 cells and αvβ3-deficient HEK293 cells treated with αvβ3 blockers confirmed the requirement for an intact thyroid hormone-integrin interaction in ERK activation. In addition, novel data indicated that T4, but not T3, controls integrin's outside-in signaling by phosphorylating tyrosine 759 in the β3 subunit. Both hormones induced cell proliferation (cell counts), survival (Annexin-PI), viability (WST-1) and significantly reduced the expression of genes that inhibit cell cycle (p21, p16), promote mitochondrial apoptosis (Nix, PUMA) and tumor suppression (GDF-15, IGFBP-6), particularly in cells with high integrin expression. At last, we have confirmed that hypothyroid environment attenuated ovarian cancer growth using a novel experimental platform that exploited paired euthyroid and severe hypothyroid serum samples from human subjects. To conclude, our data define a critical role for thyroid hormones as potent αvβ3-ligands, driving ovarian cancer cell proliferation and suggest that disruption of this axis may present a novel treatment strategy in this aggressive disease.

Heated humidified high-flow nasal cannula therapy in children

Heated humidified high-flow nasal cannula therapy (HHHFNC) was originally described as a mode of respiratory support in premature neonates and is now increasingly used in the management of acute respiratory failure in older infants and children. Heating and humidification of gas mixtures allow comfortable delivery of flow rates that match or exceed the patient's inspiratory flow rate. Emerging evidence from observational studies suggests that the use of HHHFNC therapy may be associated with reduced work of breathing, improved ventilation efficiency and a decreased need for intubation in children with respiratory insufficiency. There are several proposed mechanisms of action, and the potential for provision of unpredictable positive distending pressure has caused concern. Randomised controlled trial evidence comparing clinical outcomes with those achieved using other forms of respiratory support is, however, awaited. We review the proposed mechanisms of actions, indications, advantages and complications of HHHFNC therapy in children and describe our approach to its use in the paediatric ward environment.

Relationship between nitric oxide- and calcium-dependent signal transduction pathways in growth hormone release from dispersed goldfish pituitary cells

Nitric oxide (NO) and Ca(2+) are two of the many intracellular signal transduction pathways mediating the control of growth hormone (GH) secretion from somatotropes by neuroendocrine factors. We have previously shown that the NO donor sodium nitroprusside (SNP) elicits Ca(2+) signals in identified goldfish somatotropes. In this study, we examined the relationships between NO- and Ca(2+)-dependent signal transduction mechanisms in GH secretion from primary cultures of dispersed goldfish pituitary cells. Morphologically identified goldfish somatotropes stained positively for an NO-sensitive dye indicating they may be a source of NO production. In 2h static incubation experiments, GH release responses to the NO donor S-nitroso-N-acetyl-d,l-penicillamine (SNAP) were attenuated by CoCl2, nifedipine, verapamil, TMB-8, BHQ, and KN62. In column perifusion experiments, the ability of SNP to induce GH release was impaired in the presence of TMB-8, BHQ, caffeine, and thapsigargin, but not ryanodine. Caffeine-elicited GH secretion was not affected by the NO scavenger PTIO. These results suggest that NO-stimulated GH release is dependent on extracellular Ca(2+) availability and voltage-sensitive Ca(2+) channels, as well as intracellular Ca(2+) store(s) that possess BHQ- and/or thapsigargin-inhibited sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPases, as well as TMB-8- and/or caffeine-sensitive, but not ryanodine-sensitive, Ca(2+)-release channels. Calmodulin kinase-II also likely participates in NO-elicited GH secretion but caffeine-induced GH release is not upstream of NO production. These findings provide insights into how NO actions many integrate with Ca(2+)-dependent signalling mechanisms in goldfish somatotropes and how such interactions may participate in the GH-releasing actions of regulators that utilize both NO- and Ca(2+)-dependent transduction pathways.

The Relevance of the Irrelevant Beginning

There are many paradoxes associated with the concept of infinity. I would like to set forth and comment on one which, though well-known in principle, I have not seen stated in the following form.

Isolation of highly cytolytic MDV strains from Germany and Spain

Four serotype 1 Marek's disease virus (MDV) strains were isolated from Marek's disease (MD) outbreaks in Germany and Spain and their virulence was tested in SPF White Leghorn chickens. Two of the isolates from Germany (MR48/1-2 and /2-8) induced early mortality from cytolytic MD in 25% of the chickens whereas one isolate from Germany (MR48/3-16) caused early mortality in 58% of the inoculated chickens. Histological examination showed severe depletion of the lymphoid tissue of the bursa of Fabricius and the thymus, consistent with the cytolytic phase of MD. AH surviving chickens later developed acute MD in the form of multiple visceral tumours. Inoculation of SPF chickens with various doses of the isolate MR36 8/1C (Spain) caused early mortality in up to 69% of the chickens and acute MD in 92 to 100% of the chickens surviving the cytolytic phase of the disease.

Acute hemodynamic changes after rapid intravenous bolus dosing of dexmedetomidine in pediatric heart transplant patients undergoing routine cardiac catheterization

BACKGROUND

Dexmedetomidine is a highly selective α(2)-adrenoceptor agonist with sedative, anxiolytic, and analgesic properties that has minimal effects on respiratory drive. Its sedative and hypotensive effects are mediated via central α(2A) and imidazoline type 1 receptors while activation of peripheral α(2B)-adrenoceptors result in an increase in arterial blood pressure and systemic vascular resistance. In this randomized, prospective, clinical study, we attempted to quantify the short-term hemodynamic effects resulting from a rapid i.v. bolus administration of dexmedetomidine in pediatric cardiac transplant patients.

METHODS

Twelve patients, aged 10 years or younger, weighing ≤40 kg, presenting for routine surveillance of right and left heart cardiac catheterization after cardiac transplantation were enrolled. After an inhaled or i.v. induction, the tracheas were intubated and anesthesia was maintained with 1 minimum alveolar concentration of isoflurane in room air, fentanyl (1 μg/kg), and rocuronium (1 mg/kg). At the completion of the planned cardiac catheterization, 100% oxygen was administered. After recording a set of baseline values that included heart rate (HR), systolic blood pressure, diastolic blood pressure, central venous pressure, systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery wedge pressure, and thermodilution-based cardiac output, a rapid i.v. dexmedetomidine bolus of either 0.25 or 0.5 μg/kg was administered over 5 seconds. The hemodynamic measurements were repeated at 1 minute and 5 minutes.

RESULTS

There were 6 patients in each group. Investigation suggested that systolic blood pressure, diastolic blood pressure, systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery wedge pressure, and systemic vascular resistance all increased at 1 minute after rapid i.v. bolus for both doses and decreased significantly to near baseline for both doses by 5 minutes. The transient increase in pressures was more pronounced in the systemic system than in the pulmonary system. In the systemic system, there was a larger percent increase in the diastolic pressures than the systolic pressures. Cardiac output, central venous pressure, and pulmonary vascular resistance did not change significantly. HR decreased at 1 minute for both doses and was, within the 0.5 μg/kg group, the only hemodynamic variable still changed from baseline at the 5-minute time point.

CONCLUSION

Rapid i.v. bolus administration of dexmedetomidine in this small sample of children having undergone heart transplants was clinically well tolerated, although it resulted in a transient but significant increase in systemic and pulmonary pressure and a decrease in HR. In the systemic system, there is a larger percent increase in the diastolic pressures than the systolic pressures and, furthermore, these transient increases in pressures were more pronounced in the systemic system than in the pulmonary system.

Chain arrangements in the gel state and the transition temperatures of phosphatidylcholines

Measures of chain length, inequivalence of chain length, and chain position have been incorporated into a parameter, D, which we call the "relative chain inequivalence." D has been calculated for a number of saturated phosphatidylcholines (PC) containing one type of chain (homoacid PC), saturated PC containing two different acyl chains (heteroacid PC), and heteroacid PC containing one saturated and one unsaturated chain. The gel to liquid-crystalline transition temperatures and D are related in a regular pattern, which suggests similarity of chain packing in the gel. This pattern may have useful predictive value.

Tetraiodothyroacetic acid (tetrac) and nanoparticulate tetrac arrest growth of medullary carcinoma of the thyroid

CONTEXT

Tetraiodothyroacetic acid (tetrac) blocks angiogenic and tumor cell proliferation actions of thyroid hormone initiated at the cell surface hormone receptor on integrin alphavbeta3. Tetrac also inhibits angiogenesis initiated by vascular endothelial growth factor and basic fibroblast growth factor.

OBJECTIVE

We tested antiangiogenic and antiproliferative efficacy of tetrac and tetrac nanoparticles (tetrac NP) against human medullary thyroid carcinoma (h-MTC) implants in the chick chorioallantoic membrane (CAM) and h-MTC xenografts in the nude mouse.

DESIGN

h-MTC cells were implanted in the CAM model (n = 8 per group); effects of tetrac and tetrac NP at 1 microg/CAM were determined on tumor angiogenesis and tumor growth after 8 d. h-MTC cells were also implanted sc in nude mice (n = 6 animals per group), and actions on established tumor growth of unmodified tetrac and tetrac NP ip were determined.

RESULTS

In the CAM, tetrac and tetrac NP inhibited tumor growth and tumor-associated angiogenesis. In the nude mouse xenograft model, established 450-500 mm(3) h-MTC tumors were reduced in size over 21 d by both tetrac formulations to less than the initial cell mass (100 mm(3)). Tumor tissue hemoglobin content of xenografts decreased by 66% over the course of administration of each drug. RNA microarray and quantitative real-time PCR of tumor cell mRNAs revealed that both tetrac formulations significantly induced antiangiogenic thrombospondin 1 and apoptosis activator gene expression.

CONCLUSIONS

Acting via a cell surface receptor, tetrac and tetrac NP inhibit growth of h-MTC cells and associated angiogenesis in CAM and mouse xenograft models.

Arginase is overactive in psoriatic skin

BACKGROUND

Psoriatic keratinocytes are poorly differentiated and hyperproliferative. Low concentrations of nitric oxide (NO) induce keratinocyte proliferation, while high concentrations induce differentiation. The NO-producing enzyme inducible NO synthase is overexpressed in psoriatic skin, but so is arginase. The overexpressed arginase competes for arginine, the common substrate for both enzymes, and may reduce NO production.

OBJECTIVES

To determine whether arginase activity is elevated in psoriatic skin and whether exogenous NO will improve psoriatic plaques.

METHODS

Tape strips were taken from healthy skin of eight control subjects and nonlesional skin of eight patients with psoriasis and L-arginine, L-citrulline and L-ornithine concentrations measured by high-performance liquid chromatography. In a second study, four psoriatic patients with a pair of similar symmetrical plaques were treated with an NO donor and vehicle control. Plaques were scored for size, erythema, induration and scaling at the start and after 6 weeks of treatment.

RESULTS

Ornithine, the end-product of arginase, was at higher concentrations in nonlesional psoriatic than in healthy skin (mean +/- SEM 2.08 +/- 0.98 vs. 1.13 +/- 0.44 microg mg(-1) protein; P = 0.0002). Arginine, its substrate, was at lower concentrations. Topical application of an NO donor improved psoriatic plaques clinically [mean +/- SD reduction in severity from baseline score (100%) to 35% +/- 16% in active NO donor and to 93% +/- 10% in control].

CONCLUSIONS

Arginase is overactive in psoriatic skin, leading to a relative increase in the consumption of arginine. We therefore hypothesize a relative decrease in NO synthase-derived NO production. NO donors may be effective topical treatments for psoriasis.

Tetraidothyroacetic acid (tetrac) and tetrac nanoparticles inhibit growth of human renal cell carcinoma xenografts

Renal cell carcinoma is the most lethal of the common urologic malignancies, with no available effective therapeutics. Tetrac (tetraiodothyroacetic acid) is a deaminated analogue of L-thyroxine (T(4)) that blocks the pro-angiogenesis actions of T(4) and 3, 5, 3'-triiodo-L-thyronine as well as other growth factors at the cell surface receptor for thyroid hormone on integrin alphavbeta3. Since this integrin is expressed on cancer cells and also on endothelial and vascular smooth cells, the possibility exists that Tetrac may act on both cell types to block the proliferative effects of thyroid hormone on tumor growth and tumor-related angiogenesis. To test this hypothesis, we determined the effect of Tetrac on tumor cell proliferation and on related angiogenesis of human renal cell carcinoma (RCC). We used two models: tumor cell implants in the chick chorioallantoic membrane (CAM) system and xenografts in nude mice. To determine the relative contribution of the nuclear versus the plasma membrane action of Tetrac, we compared the effects of unmodified Tetrac to Tetrac covalently linked to poly (lactide-co-glycolide) as a nanoparticle (Tetrac NP) that acts exclusively at the cell surface through the integrin receptor. In the CAM model, Tetrac and Tetrac NP (both at 1 microg/CAM) arrested tumor-related angiogenesis and tumor growth. In the mouse xenograft model, Tetrac and Tetrac NP promptly reduced tumor volume (p<0.01) when administered daily for up to 20 days. Animal weight gain was comparable in the control and treatment groups. Overall, the findings presented here provide evidence for the anti-angiogenic, and anti-tumor actions of Tetrac and Tetrac NP and suggest their potential utility in the treatment of renal cell carcinoma.

Location of the amino acid differences in the S1 spike glycoprotein subunit of closely related serotypes of infectious bronchitis virus

Four UK strains of three different serotypes were found to differ by only 2-3% of their S1 amino acids. The S1 sequences were also very similar to those of three Dutch isolates (D207, D274 and D3896), the greatest difference between two of the seven isolates being 4.4%. The few amino acid differences between the seven isolates were located largely between residues 19-122 and 251-347 of the mature S1 subunit. The seven isolates could be differentiated using 16 monoclonal antibodies in an enzyme-linked immunosorbent assay. Some virus neutralizing (VN) antibody-inducing epitopes were common to all seven isolates even though the strains had been differentiated into three serotypes by polyclonal sera. The results indicate that the most antigenic of the VN antibody-inducing epitopes are formed by very few amino acids and that these occur in the first and third quarters of the S1 subunit. We suggest that serology-based epizootiological studies of IBV should, therefore, be augmented by the inclusion of nucleic acid sequencing and/or monoclonal antibody analysis.

Biochemical analysis of the interaction of calcium with toposome: A major protein component of the sea urchin egg and embryo

We have investigated the biochemical and functional properties of toposome, a major protein component of sea urchin eggs and embryos. Atomic force microscopy was utilized to demonstrate that a Ca(2+)-driven change in secondary structure facilitated toposome binding to a lipid bilayer. Thermal denaturation studies showed that toposome was dependent upon calcium in a manner paralleling the effect of this cation on secondary and tertiary structure. The calcium-induced, secondary, and tertiary structural changes had no effect on the chymotryptic cleavage pattern. However, the digestion pattern of toposome bound to phosphatidyl serine liposomes did vary as a function of calcium concentration. We also investigated the interaction of this protein with various metal ions. Calcium, Mg(2+), Ba(2+), Cd(2+), Mn(2+), and Fe(3+) all bound to toposome. In addition, Cd(2+) and Mn(2+) displaced Ca(2+), prebound to toposome, while Mg(2+), Ba(2+), and Fe(3+) had no effect. Collectively, these results further enhance our understanding of the role of Ca(2+) in modulating the biological activity of toposome.

A survey of Alberta physicians' use of and attitudes toward face masks and face shields in the operating room setting

BACKGROUND

There is little evidence that surgical mask use by physicians in the operating room (OR) reduces surgical site infections (SSIs), but masks do protect the wearer from potentially infectious splashes. Face shields offer even more protection because they cover the eyes, but they may be perceived as offering less protection to the patient than do masks. The objectives of this study were to ascertain if there were predictors to determine which OR physicians are continuing to use masks and what their reasons are for doing so, and which OR physicians would accept face shields and their reasons for doing so.

METHODS

We surveyed the province of Alberta's surgeons, general practice (GP) surgeons, anesthesiologists, and GP anesthetists to determine how many physicians in the OR wear surgical masks, their reasons for wearing surgical masks (ethical, legal, protection of the patient, protection of the wearer), and if they believe that face shields offer more protection to the patient or to the wearer. We also sought to examine which demographic factors affected their responses. The data were examined with chi(2) analysis to assess the relationships of age and practitioner type, and for various outcome variables. A significance level of P < .05 was accepted as statistically significant.

RESULTS

The sex of the physician did not affect his/her responses. Older physicians believe that the OR team has an ethical and legal responsibility to wear surgical masks; masks are worn to prevent the spread of disease, not because it is tradition to do so; masks protect the wearer more than do face shields; and wearing face shields alone will subject the patient to higher rates of SSIs. Surgeons are more likely than are anesthesiologists to wear surgical masks in the OR and wear a surgical mask and a face shield if the patient has risk factors for a blood borne infection.

CONCLUSIONS

According to our survey, age and profession were the most important variables that affected the potential use of surgical masks and face shields. Younger OR physicians likely would be amenable to using face shields in addition to masks in the OR to protect themselves from exposure to blood or bodily fluids.

Expression of chicken interleukin-2 by turkey herpesvirus increases the immune response against Marek's disease virus but fails to increase protection against virulent challenge

As Marek's disease virus continues to evolve towards greater virulence, more efficacious vaccines will be required in the future. We expressed chicken interleukin-2 (IL-2) from a turkey herpesvirus (HVT) in an attempt to increase the efficacy of HVT as a vaccine against Marek's disease. The recombinant IL-2/HVT was safe for in ovo vaccination, although it replicated less in the birds compared with the parent HVT strain. Expression of IL-2 increased the neutralizing antibody response against HVT but did not increase the protection against virulent Marek's disease virus challenge.

Interaction of toposome from sea-urchin yolk granules with dimyristoyl phosphatidylserine model membranes: a 2H-NMR study

The yolk granule is the most abundant membrane-bound organelle present in sea urchin eggs and embryos. The major protein component of this organelle, toposome, accounts for approximately 50% of the total yolk protein and has been shown to be localized to the embryonic cell surface. Extensive characterization in several laboratories has defined a role for toposome in mediating membrane-membrane interactions. The current study expands the analysis of toposome-membrane interaction by defining toposome-induced changes to the lipid bilayer. The effect of toposome on the biophysical properties of phosphatidyl serine (PS) multibilayers was investigated using deuterium nuclear magnetic resonance and perdeuterated dimyristoyl PS (DMPS-d(54)). Toposome was found to have little effect on DMPS-d(54) chain orientational order in both the gel and liquid-crystalline phases. Timescales for DMPS-d(54) reorientation were investigated using quadropole echo decay. Echo decay times were sensitive to toposome in the liquid-crystalline phase but not in the gel phase. Additional information about the perturbation of bilayer motions by toposome was obtained by analyzing its effect on the decay of Carr-Purcell-Meiboom-Gill echo trains. Collectively, these results suggest that toposome interacts peripherally with DMPS bilayers and that it increases the amplitude of lipid reorientation, possibly through local enhancement of bilayer curvature.

Pro-angiogenesis action of thyroid hormone and analogs in a three-dimensional in vitro microvascular endothelial sprouting model

AIM

Our laboratory has recently demonstrated the pro-angiogenesis effects of thyroid hormone in the chick chorioallantoic membrane model.

METHODS

Generation of new blood vessels from existing vessels was promoted two- to three-fold by either L-thyroxine (T4) or 3,5,3'-triiodo-L-thyronine (T3) at total hormone concentrations of T7-T9 M.

RESULTS

T4-agarose, a formulation of thyroid hormone that does not cross the cell membrane, produced a potent pro-angiogenesis effect comparable to that obtained with T3 or T4. In the present investigation, T3, T4, T4-agarose, and basic fibroblast growth factor, each added to vascular endothelial growth factor, produced comparable pro-angiogenesis effects in the in vitro three-dimensional human microvascular endothelial sprouting model. The pro-angiogenesis effect of the thyroid hormone analogs was blocked by PD 98059, an inhibitor of the mitogen-activated protein kinase (MAPK; ERK1/2) signal transduction cascade. A specific avb3 integrin antagonist (XT199) also inhibited the pro-angiogenesis effect of either thyroid hormone analogs or T4-agarose. Tetrac, a thyroid hormone analog that blocks cell surface-initiated actions of T4 and T3, inhibited the pro-angiogenesis response of thyroid hormone.

CONCLUSIONS

T4, T3, and T4-agarose are pro-angiogenic in the three-dimensional human microvascular endothelial sprouting model, an action that is initiated at the plasma membrane, involves avb3 integrin receptors, and is MAPK-dependent.

Preparation and physical characterization of a novel marine oil emulsion as a potential new formulation vehicle for lipid soluble drugs

Emulsions often contain vegetable oils such as soybean oil. In this study, a 10% (w/w) of marine mammal oil emulsion was prepared. The effect of a group of emulsifying agents on the stability of the 10% of seal oil emulsion was examined. The emulsifying agents studied were hydrogenated castor oil coated with various polyoxyethylene derivatives. It was found that 2.5% of HCO-40 resulted in the most stable seal oil emulsion. The size of the emulsified droplets defined by their diameters was found to be around 240-270 nm. The initial zeta-potential and pH value of the emulsion were found to be around -27 mV and 3.5, respectively, which decreased over time, to about -31 mV and 2.4, respectively. This is believed to be a result of the hydrolysis of triacylglycerides into free fatty acids in the emulsion. The effect of various amounts of Crodasinic LS-30, a negatively charged surfactant, and Incroqal Behenyl TMS, a positively charged surfactant, on the emulsion was investigated. It was shown that Crodasinic LS-30 had very little effect on the particle size, zeta-potential and pH, while the effect of Incroquat Benhenyl TMS was found to be dependent upon the concentration of the surfactant used.

A chemical method for the convenient surface functionalisation of polymers

A method for the application of carbenes as reactive intermediates for surface modification of polymeric substrates has been developed; the efficacy of the process has been demonstrated by irreversible dyeing of polystyrene, polythene, nylon, silica, and controlled pore glass, and to a limited extent, polytetrafluoroethylene.

Oestrogen inhibits resveratrol-induced post-translational modification of p53 and apoptosis in breast cancer cells

Resveratrol, a naturally occurring stilbene, induced apoptosis in human breast cancer MCF-7 cells. The mechanism of this effect was dependent on mitogen-activated protein kinase (MAPK, ERK1/2) activation and was associated with serine phosphorylation and acetylation of p53. Treatment of MCF-7 cells with resveratrol in the presence of 17β-oestradiol (E₂) further enhanced MAPK activation, but E₂ blocked resveratrol-induced apoptosis, as measured by nucleosome ELISA and DNA fragmentation assays. E₂ inhibited resveratrol-stimulated phosphorylation of serines 15, 20 and 392 of p53 and acetylation of p53 in a concentration- and time-dependent manner. These effects of E₂ on resveratrol action were blocked by ICI 182,780 (ICI), an inhibitor of the nuclear oestrogen receptor-α (ER). ICI 182,780 did not block the actions of resveratrol, alone. Electrophoretic mobility studies of p53 binding to DNA and of p21 expression indicated that E₂ inhibited resveratrol-induced, p53-directed transcriptional activity. These results suggest that E₂ inhibits p53-dependent apoptosis in MCF-7 cells by interfering with post-translational modifications of p53 which are essential for p53-dependent DNA binding and consequent stimulation of apoptotic pathways. These studies provide insight into the complex pathways by which apoptosis is induced by resveratrol in E₂-depleted and -repleted environments.

Multidimensional subgroups in migraine: differential treatment outcome to a pain medicine program

OBJECTIVE

The present study compared two different approaches for deriving patient profiles on their ability to predict treatment outcome to a pain medicine program for migraine headache.

DESIGN/METHODS

Using visual analog scale measures of pain intensity and functional limitations and the Beck Depression Inventory (BDI), as a measure of depression, 235 migraine patients were classified into statistical clusters. The same patients were also classified using the Multidimensional Pain Inventory (MPI) algorithm into three subgroups: Adaptive copers (AC), characterized by lower reported levels of pain intensity, life interference, and distress, as well as higher levels of perceived life control; interpersonally distressed (ID), characterized by more intermediate levels of pain, distress, and interference, with a predominant perception of inadequate support and punishing responses from significant others; and dysfunctional (Dys), characterized by high levels of pain severity, life interference, and distress and low levels of perceived life control and activity.

RESULTS

The results of the K-cluster analysis yielded a three-cluster solution: The low impact cluster, was characterized by low pain, low functional limitations and low depression and showed significant reductions in pre-to-posttreatment pain; the moderate impact cluster displayed higher levels of pain and functional limitations and low depression and showed only slight pre-to-posttreatment pain reduction; and the high impact cluster displayed the highest levels of pain, functional limitations, and depression and showed significant increases in pre-to-posttreatment pain. Unlike the K-clustered groups, MPI subgroups failed to differentially predict treatment outcome. When the K-clustered groups were crosstabulated with the MPI subgroups, the predictive validity of the MPI subgroups was enhanced.

CONCLUSION

This study questions the validity of the MPI subgroup classification algorithm. The results indicate that the K-clustering approach is more useful than the MPI in deriving meaningful patient clusters that differentially predict treatment outcome in a migraine population.

Endogenous hypothalamic somatostatins differentially regulate growth hormone secretion from goldfish pituitary somatotropes in vitro

Using Southern blot analysis of RT-PCR products, mRNA for three different somatostatin (SS) precursors (PSS-I, -II, and -III), which encode for SS(14), goldfish brain (gb)SS(28), and [Pro(2)]SS(14), respectively, were detected in goldfish hypothalamus. PSS-I and -II mRNA, but not PSS-III mRNA, were also detected in cultured pituitary cells. We subsequently examined the effects of the mature peptides, SS(14), gbSS(28), and [Pro(2)]SS(14), on somatotrope signaling and GH secretion. The gbSS(28) was more potent than either SS(14) or [Pro(2)]SS(14) in reducing basal GH release but was the least effective in reducing basal cellular cAMP. The ability of SS(14), [Pro(2)]SS(14), and gbSS(28) to attenuate GH responses to GnRH were comparable. However, gbSS(28) was less effective than SS(14) and [Pro(2)]SS(14) in diminishing dopamine- and pituitary adenylate cyclase-activating polypeptide-stimulated GH release, as well as GH release resulting from the activation of their underlying signaling cascades. In contrast, the actions of a different 28-amino-acid SS, mammalian SS(28), were more similar to those of SS(14) and [Pro(2)]SS(14). We conclude that, in goldfish, SSs differentially couple to the intracellular cascades regulating GH secretion from pituitary somatotropes. This raises the possibility that such differences may allow for the selective regulation of various aspects of somatotrope function by different SS peptides.

Role of Ca2+ stores in dopamine- and PACAP-evoked growth hormone release in goldfish

Growth hormone (GH) secretion, evoked by either pituitary adenylate cyclase-activating polypeptide (PACAP) or dopamine (DA), is dependent on both voltage-sensitive calcium channels (VSCC) and cAMP signaling in goldfish. We further characterized the involvement of Ca2+ in evoked release by PACAP and DA, by examining the sensitivity of evoked GH release to perturbations of Ca2+ signaling. Both VSCC and calmodulin/calmodulin-dependent kinase are involved in PACAP signaling as had been shown for DA. In spite of this apparent dependence on VSCC, blockade of TMB-8 but not ryanodine-sensitive intracellular Ca2+ stores inhibited both PACAP- and DA-evoked GH release. Using sarcoplasmic/endoplasmic reticulum Ca-ATPases (SERCA) inhibitors, we found BHQ blocked, whereas thapsigargin (Tg) enhanced stimulated GH release, suggesting that Tg-sensitive SERCA may counteract these cAMP-mobilizing neuroendocrine regulators by sequestering [Ca2+]i. As GH secretion stimulated by two endogenous gonadotropin-releasing hormones is not affected by Tg, it appears that distinct multiple Ca2+ stores mediate the hormone releasing response to different neuroendocrine regulators.

Comparison of the mechanisms of nongenomic actions of thyroid hormone and steroid hormones

Steroids and thyroid hormone are thought primarily to act via binding to hormone-specific nuclear receptor superfamily members. The nuclear ligand-receptor complexes then initiate transcriptional activity. Actions of steroids and iodothyronines that are nongenomic or extranuclear in mechanism have been recognized recently and new insights into such mechanisms are available. Despite their distinct structures and biologic effects, the two families of hormones have similarities in the mechanisms of their nongenomic actions. That is, both steroids and thyroid hormone appear to interact with specific cell surface G protein-coupled receptors and to activate signal transducing kinases such as those involved in the mitogen-activated protein kinase (MAPK) pathway. Much is known about the ability of certain steroids such as estrogen and mineralocorticoids to increase [Ca2+]i acutely and stimulation of the MAPK cascade by L-T4 appears to depend upon a hormone-induced increase in [Ca2+]i via phosphoinositide pathway activation. At least in the case of iodothyronines, hormone activation of the MAPK pathway modulates the cellular activities of certain cytokines and growth factors. One of the two cell surface estrogen receptors (ERs) may be an expression of the same transcript as that for nuclear ER, whereas the mineralocorticoid and progesterone-binding proteins in the plasma membrane appear to be products of genes different from those of nuclear receptors. Iodothyronine structure-activity relationships at the plasma membrane binding site for thyroid hormone suggest that the cell surface receptor for T4 that also binds 3,5,3'-triiodo-L-T3 is different from the nuclear T3 receptor (TR). There are interfaces of nongenomic and genomic mechanisms for both steroids and thyroid hormone. For example, by nongenomic mechanisms, estrogen and thyroid hormone can promote serine phosphorylation, respectively, of nuclear ER and TR. Transcriptional activity of the nuclear receptor proteins can be altered by such phosphorylation.

A randomized multicenter study of remifentanil compared with halothane in neonates and infants undergoing pyloromyotomy. I. Emergence and recovery profiles

Pyloric stenosis is sometimes associated with hemodynamic instability and postoperative apnea. In this multicenter study we examined the hemodynamic response and recovery profile of remifentanil and compared it with that of halothane in infants undergoing pyloromyotomy. After atropine, propofol, and succinylcholine administration and tracheal intubation, patients were randomized (2:1 ratio) to receive either remifentanil with nitrous oxide and oxygen or halothane with nitrous oxide and oxygen as the maintenance anesthetic. Pre- and postoperative pneumograms were done and evaluated by an observer blinded to the study. Intraoperative hemodynamic data and postanesthesia care unit (PACU) discharge times, PACU recovery scores, pain medications, and adverse events (vomiting, bradycardia, dysrhythmia, and hypoxemia) were recorded by the study's research nurse. There were no significant differences in patient age or weight between the two groups. There were no significant differences in hemodynamic values between the two groups at the various intraoperative stress points. The extubation times, PACU discharge times, pain medications, and adverse events were similar for both groups. No patient anesthetized with remifentanil who had a normal preoperative pneumogram had an abnormal postoperative pneumogram, whereas three patients with a normal preoperative pneumogram who were anesthetized with halothane had abnormal pneumograms after.

IMPLICATIONS

The use of ultra-short-acting opioids may be an appropriate technique for infants less than 2 mo old when tracheal extubation after surgery is anticipated.

A randomized multicenter study of remifentanil compared with halothane in neonates and infants undergoing pyloromyotomy. II. Perioperative breathing patterns in neonates and infants with pyloric stenosis

Although former preterm birth infants are at risk for postoperative apnea after surgery, it is unclear whether the same is true of full-term birth infants. We evaluated the incidence of apnea in 60 full-term neonates and infants undergoing pyloromyotomy both before and after anesthesia. All subjects were randomized to a remifentanil- or halothane-based anesthetic. Apnea was defined by the presence of prolonged apnea (>15 s) or frequent brief apnea, as observed on the pneumocardiogram. Apnea occurred before surgery in 27% of subjects and after surgery in 16% of subjects, with no significant difference between subjects randomized to remifentanil or halothane anesthesia. This apnea was primarily central in origin, occurred throughout the recording epochs, and was associated with severe desaturation in some instances. Of the subjects with normal preoperative pneumocardiograms, new onset postoperative apnea occurred in 3 (23%) of 13 subjects who received halothane-based anesthetics versus 0 (0%) of 22 subjects who received remifentanil-based anesthetics (P = 0.04). Thus, postoperative apnea can follow anesthesia in otherwise healthy full-term infants after pyloromyotomy and is occasionally severe with desaturation. New-onset postoperative apnea was not seen with a remifentanil-based anesthetic.

IMPLICATIONS

Abnormal breathing patterns can follow anesthesia in infants after surgical repair of pyloric stenosis. Occasionally, these patterns can be associated with desaturation. New-onset postoperative apnea was not seen with a remifentanil-based anesthetic.

Pharmacokinetics of remifentanil in anesthetized pediatric patients undergoing elective surgery or diagnostic procedures

Remifentanil hydrochloride is an ultra-short-acting opioid that undergoes rapid metabolism by tissue and plasma esterases. We aimed to characterize the pharmacokinetics and determine the hemodynamic profile of remifentanil after a single-bolus dose in children aged 0 to 18 yr. Forty-two children undergoing elective surgical procedures received remifentanil 5 microg/kg infused over 1 min. Patients were divided into age groups as follows: young infants (< or =2 mo), older infants (> 2 mo to < 2 yr), young children (2 to < 7 yr), older children (7 to < 13 yr), adolescents (13 to < 16 yr), and young adults (16 to < 18 yr). Arterial blood samples were collected and analyzed by mass spectroscopy to determine remifentanil pharmacokinetic profiles. Hemodynamic measurements for remifentanil's effect were made after the infusion. Methods of statistical analysis included analysis of variance and linear regression, with significance at P < or = 0.05. Complete remifentanil pharmacokinetic data were obtained from 34 patients. The volume of distribution was largest in the infants < 2 mo (mean, 452 mL/kg) and decreased to means of 223 to 308 mL/kg in the older patients. There was a more rapid clearance in the infants < 2 mo of age (90 mL. kg(-1). min(-1)) and infants 2 mo to 2 yr (92 mL. kg(-1). min(-1)) than in the other groups (means, 46 to 76 mL. kg(-1). min(-1)). The half-life was similar in all age groups, with means of 3.4 to 5.7 min. Seven subjects (17%) developed hypotension related to the remifentanil bolus. Remifentanil showed an extremely rapid elimination similar to that in adults. The fast clearance rates observed in neonates and infants, as well as the lack of age-related changes in half-life, are in sharp contrast to the pharmacokinetic profile of other opioids. Remifentanil in a bolus dose of 5 microg/kg may cause hypotension in anesthetized children.

IMPLICATIONS

The pharmacokinetics of remifentanil were studied in children from birth to 18 yr. Remifentanil was found to have age-related changes in clearance and volume of distribution, but not half-life. The increased clearance observed in young infants is in contrast to other opioids.

Paediatric trainees and the transportation of critically ill neonates: experience, training and confidence

AIM

To study the experience of, training in, and confidence in the transportation of critically ill neonates amongst paediatric trainees in one UK region.

DESIGN

An anonymized questionnaire was sent to all middle grades with paediatrics National Training Numbers from the Trent region.

RESULTS

The response rate was 78%. Less than half (45%) of the respondents reported receiving any training in the transportation of neonates, either in the UK or abroad; 45% (30/66) of the trainees reported having performed 10 or fewer neonatal transfers. The self-perceived confidence for transporting neonates was scored on a 10-point scale, to produce a "confidence score", the median score being 7 (IQ range 5, 8). Both as a group and individually, the trainee paediatricians were more confident in transporting neonates than older infants or children (p < 0.0001). Using multiple analysis of covariance, it was found that the most important and significant variables affecting the "confidence scores" for the inter-hospital transportation of critically ill neonates were receipt of any relevant transport training, and the current frequency of transports performed.

CONCLUSIONS

Many training-grade paediatricians lack both the experience and training in transporting critically ill neonates, factors that were found to affect their confidence in transferring sick neonates. As the overwhelming majority of neonatal transports in the UK are still arranged by individual units and performed by training-grade paediatricians, concerns regarding both the safety and effectiveness of the current service provision for the inter-hospital transfer of critically ill neonates remain valid.