Aviptadil: A multifaceted approach to mitigating hypoxemia in acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) is a severe and potentially life-threatening lung condition that often leads to Intensive Care Unit (ICU) admissions. Treating ARDS in the ICU involves providing essential support for proper oxygenation and ventilation, often requiring mechanical ventilation using high positive end-expiratory pressure (PEEP) to recruit alveoli. Strategies like prone positioning and extracorporeal membrane oxygenation (ECMO) may be necessary for stubbornly low oxygen levels. Addressing the underlying cause, if known, and employing additional therapies to prevent complications are also integral parts of the management. Despite advances in critical care, ARDS remains a formidable challenge with considerable risks of mortality and complications. Early recognition, immediate intervention, and comprehensive ICU care are pivotal in enhancing outcomes for ARDS patients. Ongoing research and clinical trials continue to explore innovative treatments and strategies to improve the prognosis of individuals with ARDS. In this series, we share our experience regarding the safe utilization of Aviptadil for treating ARDS arising from causes other than COVID-19.

Ulinastatin Add-on to Standard of Care in Critically Ill COVID-19 Patients: A Multicenter, Retrospective Study

AIM

To assess the impact on 30-day mortality with ulinastatin (ULI) used as add-on to standard of care (SOC) compared to SOC alone in coronavirus disease (COVID-19) patients requiring admission to the intensive care unit (ICU).

MATERIALS AND METHODS

In this multicentric, retrospective study, we collected data on clinical, laboratory, and outcome parameters in patients with COVID-19. Thirty-day mortality outcome was compared among patients treated with SOC alone and ULI used as add-on to SOC. Odds ratio (OR) and 95% confidence intervals (CI) were determined to identify the predictors of 30-day mortality.

RESULTS

Ninety-four patients were identified and enrolled in both groups with comparable baseline parameters. On univariate analysis, 30-day mortality was significantly lower in ULI plus SOC group than SOC alone group (36.2 vs 51.1%, OR 0.54, 95% CI 0.30-0.97, p = 0.040). The effect on mortality was more pronounced in patients who did not require intubation (10.9 vs 34.0%, OR 0.24, 95% CI 0.09-0.66, p = 0.006) and with early administration (within 72 hours of admission) of ULI (30.7 vs 57.9%, OR 0.32, 95% CI 0.11-0.91, p = 0.032). On multivariate analysis, only intubation predicted mortality (adjusted OR 10.13, 95% CI 3.77-27.25, p<0.0001) and the effect of ULI on survival was not significant (adjusted OR 0.58, 95% CI 0.22-1.52, p = 0.270).

CONCLUSION

Given the limited options for COVID-19 patients treated in ICU, early administration of ULI may be helpful, especially in patients not requiring intubation to improve the outcomes. Further, a large, randomized study is warranted to confirm these findings.

Nosocomial Infections in Extracorporeal Membrane Oxygenation

Extra corporeal membrane oxygenation (ECMO) has become an important modality in ICU for treating patients with severe hemodynamic and respiratory failure. It helps clinicians gain time for the primary disease to recover with definitive treatment, and aids in cardio pulmonary recovery of the patient. Most of the patients who require ECMO support are quite sick and fragile. Nosocomial infection is second most common complication after hemorrhage in ECMO patients.It affects about two-third of patients receiving ECMO. There is a lack of sufficient knowledge in this particular area. More focused efforts should be made in future to combat nosocomial infection in ECMO patients.

Noninvasive Respiratory Devices in COVID-19

How to cite this article: Mehta C, Mehta Y. Noninvasive Respiratory Devices in COVID-19. Indian J Crit Care Med 2022;26(7):770-772.

Adaptive design with bayesian informed interim decisions: application to a randomized trial of mechanical circulatory support

Background

Cardiovascular trials increasingly require large sample sizes and long follow-up periods. Several approaches have been developed to optimize sample size such as adaptive group sequential trials, samples size re-estimation based on the promising zone, and the win ratio. Traditionally, the log-rank or the Cox proportional hazards model is used to test for treatment effects, based on a constant hazard rate and proportional hazards alternatives, which however, may not always hold. Large sample sizes and/or long follow up periods are especially challenging for trials evaluating the efficacy of acute care interventions.

Purpose

We propose an adaptive design wherein using interim data, Bayesian computation of predictive power guides the increase in sample size and/or the minimum follow-up duration. These computations do not depend on the constant hazard rate and proportional hazards assumptions, thus yielding more robust interim decision making for the future course of the trial.

Methods

PROTECT IV is designed to evaluate mechanical circulatory support with the Impella CP device vs. standard of care during high-risk PCI. The primary endpoint is a composite of all-cause death, stroke, MI or hospitalization for cardiovascular causes with initial minimum follow-up of 12 months and initial enrolment of 1252 patients with expected recruitment in 24 months.

The study will employ an adaptive increase in sample size and/or minimum follow-up at the Interim analysis when ∼80% of patients have been enrolled. The adaptations utilize extensive simulations to choose a new sample size up to 2500 and new minimal follow-up time up to 36 months that provides a Bayesian predictive power of 85%.

Bayesian calculations are based on patient-level information rather than summary statistics therefore enabling more reliable interim decisions. Constant or proportional hazard assumptions are not required for this approach because two separate Piece-wise Constant Hazard Models with Gamma-priors are fitted to the interim data. Bayesian predictive power is then calculated using Monte-Carlo methodology. Via extensive simulations, we have examined the utility of the proposed design for situations with time varying hazards and non-proportional hazards ratio such as situations of delayed treatment effect (Figure) and crossing of survival curves. The heat map of Bayesian predictive power obtained when the interim Kaplan-Meier curves reflected delayed response shows that for this scenario an optimal combination of increased sample size and increased follow-up time would be needed to attain 85% predictive power.

Conclusion

A proposed adaptive design with sample size and minimum follow-up period adaptation based on Bayesian predictive power at interim looks allows for de-risking the trial of uncertainties regarding effect size in terms of control arm outcome rate, hazard ratio, and recruitment rate.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Abiomed, Inc Figure 1

GnRH agonist and hCG (dual trigger) versus hCG trigger for final follicular maturation: a double-blinded, randomized controlled study

STUDY QUESTION

Does co-administration of GnRH agonist and Human chorionic gonadotropin (hCG; dual trigger) in IVF cycles improve the number of mature oocytes and pregnancy outcome compared to hCG alone?

SUMMARY ANSWER

Using the dual trigger for final follicular maturation increases the number of oocytes, mature oocytes and number of blastocysts (total and top-quality) compared to triggering with hCG alone.

WHAT IS KNOWN ALREADY

hCG is used at the end of controlled ovarian hyperstimulation as a surrogate LH surge to induce final oocyte maturation. Recently, based on retrospective studies, the co-administration of GnRH agonist and hCG for final oocyte maturation (dual trigger) has been suggested to improve IVF outcome and pregnancy rates.

STUDY DESIGN, SIZE, DURATION

A single center, randomized controlled, double-blinded clinical trial between May 2016 and June 2018 analyzed by intention to treat (ITT).

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

One hundred and fifty-five normal responder patients were randomized either to receive hCG or dual trigger for final oocyte maturation. Data on patients age, BMI, AMH, number of oocytes retrieved, number of metaphase 2 (MII) oocytes, zygotes and blastocysts, clinical pregnancy rate and live birth rate were assessed and compared between the dual trigger group and the hCG group. We performed a planned interim analysis after the recruitment of 50% of the patients. Based on the totality of outcomes at the interim analysis we decided to discontinue further recruitment.

MAIN RESULTS AND THE ROLE OF CHANCE

One hundred and fifty-five patients were included in the study. The age (36 years versus 35.3 years P = NS), BMI (24 kg/m2 versus 23.7 kg/m2) and the AMH (20.1 pmol/l versus 22.4 pmol/l) were comparable between the two groups. Based on ITT analysis, the number of eggs retrieved (11.1 versus 13.4, P = 0.002), the MII oocytes (8.6 versus 10.3, P = 0.009), total number of blastocysts (2.9 versus 3.9, P = 0.01) and top-quality blastocysts transferred (44.7% versus 64.9%; P = 0.003) were significantly higher in the dual trigger group compared to the hCG group. The clinical pregnancy rate (24.3% versus 46.1%, OR 2.65 (1.43-1.93), P = 0.009) and the live birth rate per transfer (22% versus 36.2%, OR= 1.98 (1.05-3.75), P = 0.03) were significantly higher in the dual trigger group compared to the hCG group.

LIMITATIONS, REASONS FOR CAUTION

None.

WIDER IMPLICATIONS OF THE FINDINGS

The enhanced response observed with the dual trigger might lead to better IVF outcomes were it used more widely.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by TRIO Fertility. There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier: NCT02703584.

DATE OF TRIAL REGISTRATION

March 2016.

DATE OF FIRST PATIENT'S ENROLLMENT

May 2016.

REDUCE-IT: accumulation of data across prespecified interim analyses to final results

Background

REDUCE-IT (Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial), an event-driven trial, randomized 8,179 statin-treated patients with elevated triglycerides (TGs) and increased cardiovascular (CV) risk to icosapent ethyl (IPE); pure, stable prescription eicosapentaenoic acid, 4g/day or placebo. 1,612 primary endpoint events (CV death, nonfatal myocardial infarction [MI], nonfatal stroke, coronary revascularization, or hospitalization for unstable angina) projected 90% power to detect 15% relative risk reduction (5% 2-sided alpha). The key secondary composite endpoint was CV death, nonfatal MI, or nonfatal stroke. An independent data and safety monitoring committee (DMC) performed prespecified interim analyses (IAs) at ∼60% (IA1 31 May 2016 data cutoff; 2.9 y median primary endpoint follow-up) and ∼80% (IA2 01 May 2017; 3.7 y) of events; final analysis included 1,606 events (06 Sep 2018; 4.9 y median study follow-up).

Purpose

Explore REDUCE-IT efficacy and safety across prespecified IAs for insight into progression of robustness and consistency of conclusions.

Methods

The interim statistical analysis plan guided study continuation decisions by a prespecified decision-making process, including assessment of safety, treatment arm performance, primary composite endpoint formal analyses, and informal robustness analyses, with no futility or efficacy stopping requirements. Prior to DMC IA study continuation decisions, the need for a mature dataset to support the robustness of final efficacy and safety findings was discussed. Sponsor, Steering Committee, and Clinical Endpoint Committee were blinded throughout.

Results

Primary and key secondary endpoints achieved statistical significance at IA1 and IA2 that persisted at final analyses (p-value below final adjusted 2-sided alpha of 0.0437); hazard ratios also remained consistent and similar robustness was observed across individual endpoint components; clarity of findings across endpoints and subgroups improved with more events. Stopping for overwhelming efficacy was discussed at each IA; prior to IA study continuation recommendations, the DMC considered historical examples of failed CV outcome studies for TG-lowering and mixed omega-3 therapies, reflected on the potential for overestimating final demonstrated benefit using incomplete data, and weighed societal impacts of fuller datasets relative to patient therapy access.

Conclusions

Consistent, potent efficacy emerged early and persisted across the two prespecified interim and final analyses. The mature dataset demonstrated highly statistically significant reductions in the primary (25%; p=0.00000001) and key secondary (26%; p=0.0000006) endpoints and allowed robust analyses to support overall efficacy and safety conclusions. Allowing the REDUCE-IT dataset to fully mature provided clinicians with robust, consistent, and reliable data upon which to base clinical decisions for IPE in CV risk reduction.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): The study was funded by Amarin Pharma, Inc.

Impact of timing of randomization after an acute coronary syndrome and subsequent events in patients with type 2 diabetes mellitus: an analysis of the EXAMINE trial

Background

The timing of enrolment following an acute coronary syndrome (ACS) may influence cardiovascular (CV) outcomes and potentially treatment effect in clinical trials. Using a large contemporary trial in patients with type 2 diabetes mellitus (T2DM) post-ACS, we examined the impact of timing of enrolment on subsequent CV outcomes.

Methods

EXAMINE was a randomized trial of alogliptin versus placebo in 5380 patients with T2DM and a recent ACS. The primary outcome was a composite of CV death, non-fatal myocardial infarction [MI], or non-fatal stroke. The median follow-up was 18 months. In this post hoc analysis, we examined the occurrence of subsequent CV events by timing of enrollment divided by tertiles of time from ACS to randomization: 8–34, 35–56, and 57–141 days.

Results

Patients randomized early (compared to the latest times) had less comorbidities at baseline including a history of heart failure (HF; 24.7% vs. 33.0%), prior coronary artery bypass graft (9.6% vs. 15.9%), or atrial fibrillation (5.9% vs. 9.4%). Despite the reduced comorbidity burden, the risk of the primary outcome was highest in patients randomized early compared to the latest time (adjusted hazard ratio [aHR] 1.47; 95% CI 1.21–1.74) (Figure 1). Similarly, patients randomized early had an increased risk of recurrent MI (aHR 1.51; 95% CI 1.17–1.96) and HF hospitalization (1.49; 95% CI 1.05–2.10).

Conclusion

In a contemporary cohort of T2DM with a recent ACS, early randomization following the ACS increases the risk of CV events including recurrent MI and HF hospitalization. This should be taken into account when designing future clinical trials.

Figure 1

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Takeda Pharmaceutical

Management of Coronavirus 2019

Coronavirus 2019 (COVID-19) disease is the most recent global public health problem. It is caused by SARS-CoV-2 (severe acute respiratory syndrome related coronavirus 2), which is a RNA virus with a high mutation rate, belonging to the genus Coronavirus . The objective of this communication is to provide an initial understanding regarding pathophysiology, clinical manifestations, management, and prevention of this devastating disease.

Experience with hemoadsorption (CytoSorb®) in the management of septic shock patients

BACKGROUND

Cytokines and inflammatory mediators are the hallmarks of sepsis. Extracorporeal cytokine hemoadsorption devices are the newer clinical support system to overcome the cytokine storm during sepsis.

AIM

To retrospectively evaluate the clinical outcomes of patients admitted in intensive care unit with septic shock with different etiologies.

METHODS

The laboratory parameters including biomarkers such as procalcitonin, serum lactate and C-reactive protein; and the hemodynamic parameters; mean arterial pressure, vasopressor doses, sepsis scores, cytokine levels and other vital parameters were evaluated. We evaluated these outcomes among survivors and non-survivors.

RESULTS

Of 100 patients evaluated, 40 patients survived. Post treatment, the vasopressors dosage remarkably decreased though it was not statistically different; 34.15% (P = 0.0816) for epinephrine, 20.5 % for norepinephrine (P = 0.3099) and 51% (P = 0.0678) for vasopressin. In the survivor group, a remarkable reduction of biomarkers levels; procalcitonin (65%, P = 0.5859), C-reactive protein (27%, P = 0.659), serum lactate (27%, P = 0.0159) and bilirubin (43.11%; P = 0.0565) were observed from baseline after CytoSorb^® therapy. A significant reduction in inflammatory markers; interleukin 6 and interleukin 10; (87% and 92%, P < 0.0001) and in tumour necrosis factor (24%, P = 0.0003) was also seen. Overall, 28 (28%) patients who were given CytoSorb^® therapy less than 48 h after onset of septic shock survived and the maximum duration of stay for 70% of these patients in intensive care unit was less than 15 d.

CONCLUSION

CytoSorb^® is a safe and well tolerated rescue therapy option in patients with septic shock. However, early (preferably within < 48 h after onset of septic shock) initiation could result in better clinical outcomes. Further randomized trials are needed to define the potential benefits of this new treatment modality.

Percutaneous tracheostomy

Percutaneous dilatational tracheostomy (PDT) is a commonly performed procedure in critically sick patients. It can be safely performed bedside by intensivists. This has resulted in decline in the use of surgical tracheostomy in intensive care unit (ICU) except in few selected cases. Most common indication of tracheostomy in ICU is need for prolonged ventilation. About 10% of patients requiring at least 3 days of mechanical ventilator support get tracheostomised during ICU stay. The ideal timing of PDT remains undecided at present. Contraindications and complications become fewer with increase in experience. Various methods of performing PDT have been discovered in last two decades. Preoperative work up, patient selection and post tracheostomy care form key components of a successful PDT. Bronchoscopy and ultrasound have been found to be useful procedural adjuncts, especially in presence of unfavorable anatomy. This article gives a brief overview about the use of PDT in ICU.

Retrospective study on prognostic importance of serum procalcitonin and amino-terminal pro-brain natriuretic peptide levels as compared to Acute Physiology and Chronic Health Evaluation IV Score on Intensive Care Unit admission, in a mixed Intensive Care Unit population

Background:

Timely decision making in Intensive Care Unit (ICU) is very essential to improve the outcome of critically sick patients. Conventional scores like Acute Physiology and Chronic Health Evaluation (APACHE IV) are quite cumbersome with calculations and take minimum 24 hours. Procalcitonin has shown to have prognostic value in ICU/Emergency department (ED) in disease states like pneumonia, sepsis etc. NTproBNP has demonstrated excellent diagnostic and prognostic importance in cardiac diseases. It has also been found elevated in non-cardiac diseases. We chose to study the prognostic utility of these markers on ICU admission.

Settings and Design:

Retrospective observational study.

Materials and Methods:

A Retrospective analysis of 100 eligible patients was done who had undergone PCT and NTproBNP measurements on ICU admission. Their correlations with all cause mortality, length of hospital stay, need for ventilator support, need for vasopressors were performed.

Results:

Among 100 randomly selected ICU patients, 28 were non-survivors. NTproBNP values on admission significantly correlated with all cause mortality (P = 0.036, AUC = 0.643) and morbidity (P = 0.000, AUC = 0.763), comparable to that of APACHE-IV score. PCT values on admission did not show significant association with mortality, but correlated well with morbidity and prolonged hospital length of stay (AUC = 0.616, P = 0.045).

Conclusion:

The current study demonstrated a good predictive value of NTproBNP, in terms of mortality and morbidity comparable to that of APACHE-IV score. Procalcitonin, however, was found to have doubtful prognostic importance. These findings need to be confirmed in a prospective larger study.

Management of refractory hypoxemia

Mechanical ventilation remains the cornerstone in the management of severe acute respiratory failure. Acute respiratory distress syndrome (ARDS) is the most common cause of respiratory failure. It is associated with substantial mortality, and unmanageable refractory hypoxemia remains the most feared clinical possibility. If hypoxemia persists despite application of lung protective ventilation, additional therapies including inhaled vasodilators, prone positioning, recruitment maneuvers, high-frequency oscillatory ventilation, neuromuscular blockade (NMB), and extracorporeal membrane oxygenation may be needed. NMB and prone ventilation are modalities that have been clearly linked to reduced mortality in ARDS. Rescue therapies pose a clinical challenge requiring a precarious balance of risks and benefits, as well as, in-depth knowledge of therapeutic limitations.

Epstein-Barr virus infection-Related hemophagocytic lymphohistiocytosis

We report a case of 27-year-old female diagnosed with hemophagocytic lymphohistiocytosis (HLH) following a recent Epstein-Barr virus (EBV) infection. A known case of relapsing remitting multiple sclerosis on corticosteroids for last 6 months presented to the critical care unit with fever, maculopapular rash and difficulty in breathing. A rapid and correct diagnosis with the precise treatment led to complete recovery of this patient. The HLH is a rare complication of primary EBV infection.

Pressure ulcer and patient characteristics--A point prevalence study in a tertiary hospital of India based on the European Pressure Ulcer Advisory Panel minimum data set

BACKGROUND

Pressure ulcers is a frequent problem in hospitalized patients. Several prevalence studies have been conducted across the globe. Little information is available regarding prevalence of pressure ulcers in India.

PURPOSE

The aim was to identify the prevalence of pressure ulcers in one of the tertiary hospital in northern India and the factors associated with its development.

DESIGN

A cross sectional point prevalence study.

INSTRUMENTS

European Pressure Ulcer Advisory Panel (EPUAP) data collection form.

METHODS

Ethics approval was obtained prior to start of the study. Total of 358 patients were enrolled in the study. All patients above 18 years of age admitted in intensive care units and wards were included in the study. Patients admitted in emergency, day care, coronary care unit were excluded because of their short duration of hospital stay (varies from 24 to 72 h usually). All patients admitted before midnight on the predetermined day were included. The Braden scale was used to identify the risk of developing pressure ulcers. European Pressure ulcer advisory panel (EPUAP) minimum data set was used to collect prevalence data.

RESULTS

The overall prevalence rate was 7.8%.The sacrum and heel were more commonly affected. Grade III pressure ulcers were the most common (42.8%).

CONCLUSION

The pressure ulcer prevalence rate in our hospital was lower than that published in international studies. Severe forms of pressure ulcers were commonly encountered This data provides background information that may help us in developing protocols for applying effective practices for prevention of pressure ulcers.

Flexible bronchoscopic removal of a three piece foreign body from a child's bronchus

Foreign body aspiration can be a life-threatening event especially in young children because they have smaller diameters of airway lumen, moreover, the delay in the diagnosis and subsequent therapeutic intervention can further increase the risk of morbidity.(1, 2) A retained foreign body can result in inflammatory response and granulation tissue formation around the object which make the foreign body removal difficult.(3) In such situations surgical intervention is usually needed but with interventional pulmonology modalities we can restrict the need for surgery.(4) Rigid bronchoscopy under general anaesthesia is the gold standard of diagnosis and management of foreign body aspiration.(1) However, nowadays flexible bronchoscopy is more widely available and most pulmonary physicians are trained in its use so it can be used to remove such foreign bodies. We hereby report a case of a neglected foreign body which remained in the bronchus of a child for 11 days, successfully removed by flexible bronchoscopy.

Complication after abdominoperineal resection of the rectum

Treatment of rectal cancer commonly involves pre-operative short-term external beam radiotherapy along with curative surgery. We describe a case that was treated with the standard multi-modality treatment but developed some very unusual complications.

How to achieve balloon stability in aortic valvuloplasty using rapid ventricular pacing

Balloon aortic valvuloplasty is now the treatment of choice for congenital aortic stenosis. Balloon stability may be difficult to achieve and this may result in a suboptimal result or even valve damage. We describe the technique of rapid ventricular pacing as a safe and effective option for achieving balloon stability during aortic valvuloplasty.

Power and sample size for ordered categorical data

We propose a new method for computing power and sample size for linear rank tests of differences between two ordered multinomial populations. The method is flexible in that it is applicable to any general alternative hypothesis and for any choice of rank scores. We show that the method, though asymptotic, closely approximates existing exact methods. At the same time it overcomes the computational limitations of the exact methods. This advantage makes our asymptotic approach more practical for sample size computations at the planning stages of a large study. We illustrate the method with data arising from both proportional and non-proportional odds models in the two ordered multinomial setting.

Vocal cord dysfunction presenting as refractory asthma

Vocal cord dysfunction is a rare variety of upper airway obstruction characterized by typical laryngoscopic features and may mimic an acute asthma attack. The case presented in this report pertains to a 15-year-old girl who had repeated acute episodes of dyspnoea and wheezing and remained non-responsive to corticosteroids and inhaled bronchodilators requiring endotracheal intubations for adequate control. Laryngoscopic findings were consistent with vocal cord dysfunction. She was treated with a tracheostomy and psychological support.

Langerhans cell histiocytosis of the orbit

Langerhans cell histiocytosis (LCH) accounts for less than 1% of all orbital tumours. Though rare, orbital involvement in LCH is not uncommon. Most reports so far have been in Western literature. We report here a case of LCH of orbit with intracranial extension. To the best of our knowledge, this is the first case of single system multifocal LCH reported from India.

Computational tools for exact conditional logistic regression

Logistic regression analyses are often challenged by the inability of unconditional likelihood-based approximations to yield consistent, valid estimates and p-values for model parameters. This can be due to sparseness or separability in the data. Conditional logistic regression, though useful in such situations, can also be computationally unfeasible when the sample size or number of explanatory covariates is large. We review recent developments that allow efficient approximate conditional inference, including Monte Carlo sampling and saddlepoint approximations. We demonstrate through real examples that these methods enable the analysis of significantly larger and more complex data sets. We find in this investigation that for these moderately large data sets Monte Carlo seems a better alternative, as it provides unbiased estimates of the exact results and can be executed in less CPU time than can the single saddlepoint approximation. Moreover, the double saddlepoint approximation, while computationally the easiest to obtain, offers little practical advantage. It produces unreliable results and cannot be computed when a maximum likelihood solution does not exist.

An exact trend test for correlated binary data

The problem of testing a dose-response relationship in the presence of exchangeably correlated binary data has been addressed using a variety of models. Most commonly used approaches are derived from likelihood or generalized estimating equations and rely on large-sample theory to justify their inferences. However, while earlier work has determined that these methods may perform poorly for small or sparse samples, there are few alternatives available to those faced with such data. We propose an exact trend test for exchangeably correlated binary data when groups of correlated observations are ordered. This exact approach is based on an exponential model derived by Molenberghs and Ryan (1999) and Ryan and Molenberghs (1999) and provides natural analogues to Fisher's exact test and the binomial trend test when the data are correlated. We use a graphical method with which one can efficiently compute the exact tail distribution and apply the test to two examples.

Power comparisons for tests of trend in dose-response studies

The Cochran-Armitage test for trend is a popular statistical procedure for detecting increasing or decreasing probabilities of response when a categorical exposure is ordered. Such associations may arise in a variety of biomedical research settings, particularly in dose-response designs such as carcinogenicity experiments. Previously, computing limitations mandated the use of the asymptotic trend test, but with the availability of new algorithms, increased computing power, and appropriate software the exact trend test is now a practical option. Nevertheless, the exact test is sometimes criticized on the grounds that it is conservative. In this paper we investigate the implications of this conservatism by comparing the true type I error and power of three alternative tests of trend - the asymptotic test, the exact test and an admissible exact test proposed by Cohen and Sackrowitz. The computations are performed by an extension to the network algorithm of Mehta et al. This allows us to make precise power comparisons between the tests under any given design without resorting to simulation. We show how this tool can guide investigators in choosing the most appropriate test by considering the design of two-year carcinogenicity studies carried out by the National Toxicology Program. We additionally compare the tests for various other combinations of sample sizes and number of groups or levels of exposure. We conclude that the asymptotic test, while more powerful where it is valid, generally does not preserve the type I error. This violation of the a priori testing level can be greatly affected by imbalance in the data or unequal spacing of dose levels.

Tracheal duplication as a cause of congenital stridor

A six-week-old child with tracheal duplication presenting with congenital stridor is being reported. To the best of our knowledge, a tracheal web or tracheal duplication (as the present condition may be named) has not been described as a causative factor of infantile stridor.

A case of motor neurone disease with sleep apnoea syndrome

A case of a 63-year-old patient with motor neurone disease (amyotrophic lateral sclerosis) with central sleep apnoea syndrome is being reported. His sleep architecture was fragmented with a high apnea-hypopnea index of 65 per hour and maximum oxygen-desaturation of 78 percent. Total correction of sleep pattern with nasal non-invasive ventilation (BiPAP-ST) was demonstrated.

Bilioma secondary to choledocholithiasis

Bilioma secondary to choledocholithiasis is rare. We report a patient in whom a large common bile duct stone was responsible for leak from the infraduodenal segment of the bile duct. Choledochotomy with extraction of stone followed by T-tube drainage of the bile duct and evacuation of the bilioma resulted in complete recovery.