Validating a pragmatic definition of shock in adult patients presenting to the ED.

OBJECTIVE: The importance of the early recognition of shock in patients presenting to emergency departments is well recognized, but at present, there is no agreed practical definition for undifferentiated shock. The main aim of this study was to validate an a priori clinical definition of shock against 28-day mortality. DESIGN, SETTING AND SUBJECTS: This prospective, observational, cross-sectional, single-center study was conducted in Hong Kong, China. Data were collected between July 1, 2012, and January 31, 2013. An a priori definition of shock was designed, whereby patients admitted to the resuscitation room or high dependency area of the emergency department were divided into 1 of 3 groups-no shock, possible shock, and shock. The primary outcome was 28-day mortality. Secondary outcomes were in-hospital mortality or admission to the intensive or coronary care unit. MEASUREMENTS AND MAIN RESULTS: A total of 111 patients (mean age, 67.2 ± 17.1 years; male = 69 [62%]) were recruited, of which 22 were classified as no shock, 54 as possible shock, and 35 as shock. Systolic blood pressure, mean arterial pressure, lactate, and base deficit correlated well with shock classifications (P < .05). Patients who had 3 or more positively defined shock variables had a 100% poor composite outcome rate (5 of 5). Patients with 2 shock variables had a 66.7% (4 of 6) poor composite outcome rate. CONCLUSIONS: A simple, practical definition of undifferentiated shock has been proposed and validated in a group of patients presenting to an emergency department in Hong Kong. This definition needs further validation in a larger population and other settings.

Learning profiles for noninvasive transcutaneous Doppler ultrasound.

OBJECTIVE: This study aimed to establish learning profiles for noninvasive transcutaneous Doppler ultrasound. MATERIALS AND METHODS: Four trainees attended a 2-h lecture, followed by a 15-min demonstration on a volunteer and a 30-min hands-on workshop in a small group setting. Then, they underwent hands-on practice on 50 participants without supervision. The skill acquisitions in terms of signal magnitude, signal quality, and measurement time of the trainees were evaluated through 50 assessments, and were compared with that of a trainer with extensive experience on the use of an ultrasonic cardiac output monitor acting as a 'gold standard'. The learning profile for each individual trainee was analyzed using the cumulative sum graphical method. RESULTS: Four trainees performed ultrasonic cardiac output monitor on 50 participants. All trainees attained proficiency after 18-36 assessments to achieve aortic signal magnitude and quality comparable with the trainer. It requires a minimum of nine assessments to obtain three aortic scans within 5 min with 95% success rates. Only half of the trainees achieved competence in pulmonary scans and the minimum number of assessments required was 36. A minimum of 22 assessments were required for three pulmonary scans within 10 min with 95% success rates. CONCLUSION: A substantial period of learning needs to be undertaken to achieve proficiency on the use of noninvasive transcutaneous Doppler ultrasound. Cumulative sum analysis is a useful tool for ongoing quality assessment during medical education and training in practical procedures on an individual basis.

Silole nanocrystals as novel biolabels.

A novel class of biofunctional silole nanocrystals with the potential to create highly sensitive immunoassay was firstly demonstrated. Biolabels were constructed by encapsulating nanocrystalline hexaphenylsilole [Ph2Si(CPh)4HPS] within ultrathin polyelectrolyte layers via the layer-by-layer (LbL) technique that provided an "interface" for the attachment of antibodies. A high ratio of fluorescent dyes to biomolecules (F/P ratio; 2.4 x 10(3)) was achieved without self-quenching problem. The aggregation-induced emission (AIE) feature offered silole biolabels the sensitivity 40- to 140-fold higher than that of a start-of-the-art immunoassay using directly fluorescent-labeled antibodies.

Age-specific non-invasive transcutaneous Doppler ultrasound derived haemodynamic reference ranges in elderly Chinese adults.

BACKGROUND: Whilst there is a presumption in medicine that ageing adversely affects cardiovascular function, it is unknown if resting haemodynamics are compromised in the elderly, and if so, to what degree. This study was intended to answer several questions; whether age-related changes in haemodynamics occur; whether there was a difference between the haemodynamics of ageing subjects with and without mild chronic disease; whether there was a difference in haemodynamics as measured from either the aortic or the pulmonary valve; and to establish reference ranges for this population. METHODS: Chinese adults aged over 60 years were divided into three age bands of 61-70, 71-80 and over 80 years. The haemodynamic parameters were measured using a non-invasive Doppler ultrasound-based instrument, the Ultrasonic Cardiac Output Monitor (USCOM). RESULTS: One hundred and sixty-five subjects (48.5% males) were recruited. 78 (47.3%) had no known disease whilst 87 (52.7%) had mild chronic illness. A total of 21 individual haemodynamic parameters were measured or calculated for each subject. There were no significant differences in stroke volume (SV), cardiac output (CO), systemic vascular resistance (SVR) or in body surface area (BSA)-indexed parameters, SV index (SVI), cardiac index (CI) and SVR index (SVRI) across age groups, or in other indexed haemodynamic parameters. No significant differences in indexed haemodynamics were found between those subjects with and those without mild chronic disease. Small, statistically significant, but clinically insignificant, differences (< 5%) were found between the aortic and pulmonary valve measurements for SV, SVI and heart rate. CONCLUSIONS: Ageing does not have any significant effect on resting haemodynamics in the elderly population studied. Mild chronic disease does not adversely affect resting haemodynamics in this population. GENERAL SIGNIFICANCE: Reference ranges were established for 21 haemodynamic parameters, as measured by USCOM, for an elderly Chinese population but not for non-Chinese populations.

Evidence-based point-of-care diagnostics: current status and emerging technologies.

Point-of-care (POC) diagnostics brings tests nearer to the site of patient care. The turnaround time is short, and minimal manual interference enables quick clinical management decisions. Growth in POC diagnostics is being continuously fueled by the global burden of cardiovascular and infectious diseases. Early diagnosis and rapid initiation of treatment are crucial in the management of such patients. This review provides the rationale for the use of POC tests in acute coronary syndrome, heart failure, human immunodeficiency virus, and tuberculosis. We also consider emerging technologies that are based on advanced nanomaterials and microfluidics, improved assay sensitivity, miniaturization in device design, reduced costs, and high-throughput multiplex detection, all of which may shape the future development of POC diagnostics.

Label-free fluorescent probing of G-quadruplex formation and real-time monitoring of DNA folding by a quaternized tetraphenylethene salt with aggregation-induced emission characteristics.

Biosensing processes such as molecular beacons require non-trivial effort to covalently label or mark biomolecules. We report here a label-free DNA assay system with a simple dye with aggregation-induced emission (AIE) characteristics as the fluorescent bioprobe. 1,1,2,2-Tetrakis[4-(2-bromoethoxy)phenyl]ethene is nonemissive in solution but becomes highly emissive when aggregated. This AIE effect is caused by restriction of intramolecular rotation, as verified by a large increase in the emission intensity by increasing viscosity and decreasing temperature of the aqueous buffer solution of 1,1,2,2-tetrakis[4-(2-triethylammonioethoxy)phenyl]ethene tetrabromide (TTAPE). When TTAPE is bound to a guanine-rich DNA strand (G1) via electrostatic attraction, its intramolecular rotation is restricted and its emission is turned on. When a competitive cation is added to the G1 solution, TTAPE is detached and its emission is turned off. TTAPE works as a sensitive poststaining agent for poly(acrylamide) gel electrophoresis (PAGE) visualization of G1. The dye is highly affinitive to a secondary structure of G1 called the G-quadruplex. The bathochromic shift involved in the G1 folding process allows spectral discrimination of the G-quadruplex from other DNA structures. The strong affinity of TTAPE dye to the G-quadruplex structure is associated with a geometric fit aided by the electrostatic attraction. The distinct AIE feature of TTAPE enables real-time monitoring of folding process of G1 in the absence of any pre-attached fluorogenic labels on the DNA strand. TTAPE can be used as a K+ ion biosensor because of its specificity to K+-induced and -stabilized quadruplex structure.

Biofunctional organic nanocrystals for quantitative detection of pathogen deoxyribonucleic acid.

Advances in nanotechnology have had significant impacts in the field of biodiagnostics. In this study, we describe the novel application of dissolvable, organic and biofunctional nanocrystals for the quantitative detection of a PCR product. Fluorescein diacetate (FDA), a fluorogenic precursor of fluorescein, was milled in a solution of a polymeric surfactant to create a stable, nanosized colloid with an interface for coupling streptavidin molecules. The application of these particulate labels for the quantitative detection of biotinylated human papillomavirus (HPV) DNA, amplified in a standard PCR procedure, was demonstrated. After the affinity reaction, the FDA molecules were dissolved and concomitantly converted into fluorescein. This approach resulted in a high selectivity, short incubation times and a sensitivity up to 147 times greater than obtained from state-of-the-art, directly fluorescent-labeled streptavidins. This innovative method offers rapid detection of small amounts of nucleic acids because less target material and thus fewer PCR cycles are required.

A highly sensitive fluorescent immunoassay based on avidin-labeled nanocrystals.

Nanocrystals of the fluorogenic precursor fluorescein diacetate (FDA) were applied as labels in order to improve on the assay sensitivity achieved in our previous studies. Each FDA nanocrystal can be converted into approximately 2.6x10(6) fluorescein molecules, which is useful for improving immunoassay sensitivity and limits of detection. NeutrAvidin was simply adsorbed onto the surface of the FDA nanocrystals, which were coated with distearoylglycerophosphoethanolamine (DSPE) modified with amino(poly(ethylene glycol))(PEG(2000)-Amine) as an interface for coupling biomolecules. This can be applied to detect different kinds of analytes that are captured by corresponding biotinylated biomolecules in different bioanalytical applications. The applicability of the NeutrAvidin-labeled nanocrystals was demonstrated in an immunoassay using the labeled avidin-biotin technique. Biotinylated antibody and FDA-labeled avidin were applied to the assay sequentially. The performance was compared with the traditional sandwich-type assay for mouse immunoglobulin G detection. Following the immunoreaction, the nanocrystals were released by hydrolysis and dissolution instigated by adding a large volume of organic solvent/sodium hydroxide mixture. The limit of detection was lower (by a factor of 2.5-21) and the sensitivity was (3.5-30-fold) higher than immunoassays using commercial labeling systems (FITC and peroxidase). This study shows that using fluorescent nanocrystals in combination with the avidin-biotin technique can enhance assay sensitivity and provide a lower limit of detection without requiring long incubation times as in enzyme-based labels.

Nanocrystal biolabels with releasable fluorophores for immunoassays.

A novel signal amplification technology based on a new class of biofunctional fluorescent nanocrystals holds promise to improve the sensitivity and the limits of detection of immunoassays. A two-step approach without layer-by-layer techniques is described to encapsulate the fluorogenic precursor fluorescein diacetate (FDA) nanocrystals (107-nm average size) followed by conjugation of the antibody. Distearoylphosphatidylethanolamine (DSPE) modified with amino(poly(ethylene glycol)) (PEG(2000)Amine) is coated on the surface of the FDA nanocrystals to provide a interface for the antibody coupling. Anti-mouse antibodies are attached to the nanocrystalline FDA biolabels by adsorption. A high molar ratio of fluorescent molecules to biomolecules (2.8 x 10(4)) is achieved in this nanocrystal biolabel system. The analytical performance of the nanocrystal-based label system is evaluated in a model sandwich immunoassay for the detection of mouse IgG. After separation of the nonbound antibody nanocrystal labels, fluorophores are released by hydrolysis and dissolution of the nanocrystalline FDA. Due to the release of the fluorophores (fluoresceins) into a large volume of organic solvent/sodium hydroxide mixture, self-quenching is suppressed. The FDA[DSPE-PEG(2000)Amine]-modified biolabels have a highly stable colloidal suspension with minimized nonspecific interactions. The limit of detection was lowered by a factor of 5-28, and the sensitivity was 400-2700-fold higher compared with a state-of-the-art immunoassay using directly fluorescent-labeled antibodies. Our approach provides high sensitivity and low limits of detection without the need for long incubation times, making it an interesting alternative in biolabel technology.