Accuracy of 3-dimensional color Doppler-derived flow volumes with increasing image depth.

OBJECTIVES: We and others have reported on the use of digital color Doppler sonography from real-time 3-dimensional (3D) echocardiography and its use in accurately calculating cardiac flow volumes, namely stroke volume (SV) and, hence, cardiac output. However, in some patients, image depth is higher than average, and this may affect the accuracy of volume calculation. We sought to investigate the impact of image depth and the accompanying change in signal strength, spatial resolution, and pulse repetition frequency on the accuracy of SV calculation from 3D color Doppler data in an in vitro model. METHODS: A tube model of the left ventricular outflow tract was constructed from plastic tubing and connected to a pulsatile pump. The volume flowing through the tube was imaged using a 3D echocardiography system. Stroke volumes from the pump were computed from the DICOM data using commercially available software and compared with a reference standard of timed volumes with the use of a graduated measuring cylinder over a range of depth settings and SVs. RESULTS: There was good correlation between the 3D-derived SVs and the reference cylinder measures over all depths from 4 to 16 cm at 1-cm increments with a tube diameter of 17 mm, a pump rate of 60 beats/min, and SVs ranging from 20 to 70 mL. The average r(2) value for the 13 different depths was 0.976. However, the accuracy of the 3D method of volume calculation appeared to fall at depths greater than 13 cm, especially at higher SVs. CONCLUSIONS: Stroke volume calculation from real-time 3D color Doppler data in this in vitro study shows that at depths greater than approximately 13 cm, accuracy decreases, especially at higher SVs. This may be due to decreased resolution and the reduced frame rate at these depths. At shallower depths, volume calculation form the 3D Doppler data appears very accurate.     

Phenytoin-Oxacillin Interactions in Normal and Uremic Sera

Displacement of phenytoin (90% bound to albumin) by other strongly albumin-bound drugs such as salicylate and valproic acid may result in an increase in pharmacologically active free concentrations. The antibiotic oxacillin is also strongly bound to albumin and is often administered to patients receiving phenytoin. Oxacillin at a concentration of 15 μg/ml caused no significant displacement of phenytoin in a serum pool prepared from patients receiving phenytoin. However, a significant increase in the free phenytoin concentration was seen at an oxacillin concentration of 50 μg/ml. We also prepared a serum pool from uremic patients and another from patients with hypoalbuminemia and supplemented both of them with phenytoin. Significant increases in the free phenytoin concentration occurred with both 15- and 50-μg/ml concentrations of oxacillin. In one hypoalbuminemic patient receiving both phenytoin and intravenous high-dose oxacillin, the free phenytoin fraction was 22.5% before oxacillin therapy, 24.1% 12 hours after first dose of oxacillin, and 27.2% after 60 hours, indicating the possibility of in vivo displacement of phenytoin by oxacillin. We conclude that the phenytoin-oxacillin interaction is not significant at lower dosages of oxacillin usually prescribed for oral therapy. However, the interaction may be significant at high concentrations of oxacillin, especially in patients with hypoalbuminemia or uremia.     

Consumption of dietary supplements in a liver transplant population.

The extensive use of alternative medicine products, herbal remedies, and vitamins in large doses has reached an all time high in the general public. Some agents are reported and advertised as immune stimulants and may interfere with patients suffering from immune modification, autoimmune diseases, or transplant recipients. In this report, we will present an investigation into the use of herbal remedies and vitamins in our liver transplant population. We performed an investigation using a questionnaire to determine the use of herbal products and vitamins in our liver transplant population. Medical records were reviewed for each liver transplant recipient that admitted to consuming herbal products or vitamins. Information collected included patient demographics, transplant related information, laboratory tests, outcomes, and herbs or vitamin products used. A total of 290 patients completed and returned the questionnaire. We found 156 admitting to taking more than a standard multivitamin and/or an herbal remedy. All patients were treated with steroids for allograft rejection and experienced a recurrence of amino transaminases following the removal of steroids. Further investigation into dietary supplements using a patient questionnaire form revealed that nearly 50% of patients admitted to using vitamins following transplantation, while 19% used herbal remedies combined with vitamins, most admitting to silymarin. One recipient was ingesting colostrum and required admission for the management of allograft rejection, while 5 patients had consumed large amounts of echinacea or CoEnzyme Q-10 and experienced elevations in their transaminases that resolved with discontinuation of the herb. The review also identified 4 patients with primary biliary cirrhosis and with transaminase elevation (mean values of aspartate aminotransferase and alanine aminotransferase levels of 88 and 95, respectively). All recipients were consuming vitamins, in particular high doses of vitamin E (tocopherol), more than 1 gram per day. All of the transplant recipients were instructed to discontinue all vitamin E products and the amino transaminases resolved over the following 30 to 60 days. In conclusion, this information reveals that a significant proportion of our liver transplant recipients consume herbal remedies. The results of this report suggest that transplant teams need to question each recipient about the use of herbal and vitamin remedies and educate them regarding the potential hazards.     

Characterization of voltage-gated and calcium-activated potassium currents in toadfish saccular hair cells

Patch clamp methods were used to study calcium activated (IKCa) and voltage-gated (IK) potassium currents in enzymatically disassociated hair cells from the saccule of the toadfish Opsanus tau. In one population of hair cells, tetraethylammonium bromide (TEA) blocked all outward current, leaving only an inward calcium current (ICa). This current blocked by TEA was also blocked by barium (5 mM) and cadmium (0.2 mM) but only partially blocked by zero external calcium. In the majority of the cells, after TEA (25 mM) was used to block IKCa, a second outward current remained. This current was resistant to block by apamin, barium (5 mM) and cadmium (0.2 mM). Its kinetics of activation and deactivation were considerably slower than those of IKCa. Because of the current/voltage characteristics, its resistance to block by the above agents and voltage-gated activation, this current was termed IK. Study of the rates of activation and deactivation of the two currents in hair cells exhibiting either fast or slow total outward current activation showed that these two kinetic parameters were linked in a cell, i.e., cells with fast IKCa kinetics exhibit faster IKCa kinetics than cells with slower IKCa kinetics. Cell attached and inside out recordings showed a high conductance channel with short open times and a lower conductance channel with longer open times active over the same voltage ranges as those seen in whole cell recordings. Since these two currents with quite different but linked kinetics are active over the same voltage range, their co-existence may be of some importance to sensory coding in the hair cells.     

Information Rx: Prescribing Good Consumerism and Responsible Citizenship

Recent medical informatics and sociological literature has painted the image of a new type of patient--one that is reflexive and informed, with highly specified information needs and perceptions, as well as highly developed skills and tactics for acquiring information. Patients have been re-named "reflexive consumers." At the same time, literature about the questionable reliability of web-based information has suggested the need to create both user tools that have pre-selected information and special guidelines for individuals to use to check the individual characteristics of the information they encounter. In this article, we examine suggestions that individuals must be assisted in developing skills for "reflexive consumerism" and what these particular skills should be. Using two types of data (discursive data from websites and promotional items, and supplementary data from interviews and ethnographic observations carried out with those working to sustain these initiatives), we examine how users are directly addressed and discussed. We argue that these initiatives prescribe skills and practices that extend beyond finding and assessing information on the internet and demonstrate that they include ideals of consumerism and citizenship.     

Potential role of female sex hormones in the pathophysiology of migraine

Clinical evidence indicates that female sex steroids may contribute to the high prevalence of migraine in women, as well as changes in the frequency or severity of migraine attacks that are in tandem with various reproductive milestones in women's life. While female sex steroids do not seem to be involved in the pathogenesis of migraine per se, they may modulate several mediators and/or receptor systems via both genomic and non-genomic mechanisms; these actions may be perpetuated at the central nervous system, as well as at the peripheral (neuro)vascular level. For example, female sex steroids have been shown to enhance: (i) neuronal excitability by elevating Ca(2+) and decreasing Mg(2+) concentrations, an action that may occur with other mechanisms triggering migraine; (ii) the synthesis and release of nitric oxide (NO) and neuropeptides, such as calcitonin gene-related peptide CGRP, a mechanism that reinforces vasodilatation and activates trigeminal sensory afferents with a subsequent stimulation of pain centres; and (iii) the function of receptors mediating vasodilatation, while the responses of receptors inducing vasoconstriction are attenuated. The serotonergic, adrenergic and gamma-aminobutyric acid (GABA)-ergic systems are also modulated by sex steroids, albeit to a varying degree and with potentially contrasting effects on migraine outcome. Taken together, female sex steroids seem to be involved in an array of components implicated in migraine pathogenesis. Future studies will further delineate the extent and the clinical relevance of each of these mechanisms, and will thus expand the knowledge on the femininity of migraine.     

Dental fear, communication, and behavioural management problems in children referred for dental problems

BACKGROUND: Knowledge about the influence of the interaction between child, parent, and dentist and the referral pattern is very limited. AIM: This study intended to assess to what extent the pathways of Rachman could clarify why a child is being referred to a specialist in paediatric dentistry and if other aspects in the interaction between child, parent, and dentist play a role in the referral. DESIGN: The referral letters of 500 children referred to a Special Dental Care Centre in Amsterdam were examined. All parents filled out the Children's Fear Survey Schedule-Dental Subscale, on behalf of the child. Information about interaction and the referral was collected from the referral letter and a semistructured interview with the parent and dentist separately. RESULTS: Eighty pairs of parents and dentists of referred children participated in a semistructured interview. Child factors seem to contribute the most to the referral. For the cause of referral the pathways of Rachman and communication were often combined. CONCLUSIONS: Apart from fear acquisition, as implied in Rachman's pathways, the interaction between child, dentist, and parent also contributes to the referral of a child to a specialist clinic in paediatric dentistry.