Metabolic acidosis in restraint-associated cardiac arrest: a case series

The mechanism of death in patients struggling against restraints remains a topic of debate. This article presents a series of five patients with restraint-associated cardiac arrest and profound metabolic acidosis. The lowest recorded pH was 6.25; this patient and three others died despite aggressive resuscitation. The survivor's pH was 6.46; this patient subsequently made a good recovery. Struggling against restraints may produce a lactic acidosis. Stimulant drugs such as cocaine may promote further metabolic acidosis and impair normal behavioral regulatory responses. Restrictive positioning of combative patients may impede appropriate respiratory compensation for this acidemia. Public safety personnel and emergency providers must be aware of the life threat to combative patients and be careful with restraint techniques. Further investigation of sedative agents and buffering therapy for this select patient group is suggested.

Immunization practices and beliefs of physicians in suburban Cook County, Illinois

This study was conducted to ascertain the vaccination beliefs and practices of physicians who provide care for low income children. Sixty-two (56.9%) of a sample of 109 physicians in suburban Cook County, Illinois responded to a mail survey. A majority of physicians reported a willingness to immunize during well child care, follow-up, and chronic illness visits; yet, a substantial lack of willingness to immunize given certain acute mild illnesses was reported. Twenty-six percent of providers did not routinely identify children who were behind in immunizations and only 16% had completed a chart audit in the past three years. Seventy-four percent were willing to provide all shots needed at a single visit. Misconceptions regarding true contraindications was found among the group. Missed well child visits were identified as the greatest barrier to complete immunization. Improvements in vaccination rates are expected if physicians utilize all types of medical encounters to monitor the immunization status of patients and provide vaccines using only true medical contraindications.

Ultrasonic imaging using a 5-MHz multilayer/single-layer hybrid array for increased signal-to-noise ratio

Conventional diagnostic ultrasound scanners are bulky and require significant amounts of electrical power during operation. Reducing the size, weight, and consumption of electrical power is made easier through the use of highly integrated compact transmit and receive electronics that may be incorporated in the transducer handle. This necessitates the use of low voltage transmitters and low power receive preamplifiers. Conventional scanners typically use approximately 100-V pulses during transmit; therefore, decreasing the transmit voltage to 15 V decreases the transmit sensitivity. Conventional receive electronics that are located at the scanner degrade the received signal-to-noise ratio (SNR) because the array element cannot efficiently drive the coaxial cable. Transmit sensitivity and received SNR can be radically improved using a multilayer/single-layer hybrid array making integration of electronics into the transducer handle more feasible. In this paper, we discuss the design, fabrication, and testing of a 5-MHz hybrid linear array. The hybrid array included 16 multilayer transmit elements (10 Omega impedance) and 24 single-layer receive elements at a half wavelength element pitch. Low voltage transmitters with an output resistance of 7 Omega and high impedance JFET preamplifiers using 15 V for biasing were located adjacent to the hybrid array in the transducer handle. The transmit sensitivity and received SNR of the hybrid array were compared with a conventional array using 50-Omega transmitters and receive preamplifiers at the scanner. The transmit sensitivity improved by 12.8 dB, and the received SNR improved by 7.8 dB, yielding an overall improvement of 20.6 dB, which compared well with predictions from the KLM model. Images of phantoms and in vivo images of the kidney obtained with the Siemens Model 1200 phased array system showed the increased SNR using the hybrid array. Estimates of penetration in tissue mimicking phantoms (alpha=0.5 dB/(cm MHz)) improved by 7 cm compared with the control.

Finite element analysis of a deformable array transducer

Deformable array transducers have previously been described to implement 2-D phase aberration correction of near-field aberrators with only a 1xN or 2xN array configuration. This transducer design combines mechanical phase correction using an actuator with electronic phase correction for a 2-D correction with significantly fewer elements than a full 2-D array. We have previously reported the fabrication and results of a 1x32 deformable array fabricated with a RAINBOW (Reduced And INternally Biased Wafer) actuator. Because of the complicated construction of deformable arrays, we propose to use finite element analysis (FEA) as a design tool for array development. In this paper, we use 2-D and 3-D FEA to model the experimental results of the deformable array as the first step toward development of a design tool. Because the deformable array combines a mechanical actuator with a medical ultrasound transducer, improvement in performance must consider both the ultrasound characterization along with the low frequency actuator characterization. For the ultrasound characterization, time domain FEA simulations of electrical vector impedance accurately predicted the measurements of single array elements. Additionally, simulations of pulse-echo sensitivity and bandwidth were also well matched to measurements. For the low frequency actuator characterization, time domain simulation of the low frequency vector impedance accurately predicted measurement and confirmed the fundamental flexure resonance of the cantilever configuration at 1.3 kHz. Frequency domain FEA included thermal processing effects and predicted actuator curvature arising during fabrication. Finally, frequency domain FEA simulations of voltage-induced displacement accurately predicted measured displacement.

Multi-layered PZT/polymer composites to increase signal-to-noise ratio and resolution for medical ultrasound transducers

Increasing transducer bandwidth and signal-to-noise ratio (SNR) is fundamental to improving the quality of medical ultrasound images. In previous work, the authors have proposed the use of multi-layer 1-3 PZT/epoxy composites to increase both but have encountered significant fabrication challenges. These difficulties include making the bond thickness between the layers extremely small relative to the ultrasound wavelength and aligning the posts of the composite to increase the coupling coefficient. The authors have routinely achieved a bond thickness of less than 5 mum but aligning the posts is more complicated. Finite element (PZFlex; Weidlinger, Assoc., New York, NY and Los Altos, CA) simulations show that the pulse-echo SNR and bandwidth degrade significantly with misalignment of the posts. Alignment of greater than 90% of the post pitch (i.e., tolerance of 10 to 20 mum) is required to obtain significant increases in SNR and bandwidth relative to conventional transducer arrays. This will be a difficult tolerance for large-scale production. Thus, the authors have developed a multi-layer composite hybrid array that will not require post alignment. This structure consists of a layer of 5 MHz 1-3 composite material on top of conventional 5 MHz PZT, which will provide greater SNR relative to conventional composites and increased bandwidth over multi-layer PZT. PZFlex simulations show that for a 2 MHz linear array element, the 2 layer hybrid structure increases the pulse-echo SNR by 7.5 dB over that from a single layer PZT element. Even without a matching layer, an increase in the -6 dB pulse-echo fractional bandwidth from 22% for the PZT element to 35% for the hybrid element was also predicted. Experimentally, in a 32 element array, the authors achieved an increase of 5.2 dB in SNR and an increased -6 dB bandwidth from 23 to 30%. In vitro and in vivo images showed corresponding improvements.

Severe sepsis in the emergency department and its association with a complicated clinical course

OBJECTIVE

Infection severity as determined by clinical criteria has been recently classified and studied in hospitalized inpatients. The objective of the study was to use modified criteria to determine the clinical course associated with three levels of infection severity in infected patients admitted from the ED.

METHODS

This was a retrospective cohort study involving all patients 18 years of age and older admitted through the ED of an urban teaching hospital during a four-month period whose primary reason for requiring hospitalization was an infection that was recognized in the ED. ED records were reviewed for criteria used to classify patients by three levels of infection severity: no systemic inflammatory response syndrome, sepsis, and severe sepsis (SS). The relationships between these classifications as well as certain clinical characteristics and any complicated clinical course as measured by death and/or admission to an intensive care unit (ICU), and/or prolonged hospitalization, were analyzed.

RESULTS

Of 408 patients entered into the study, 138 (33.8%) fulfilled the criteria of SS in the ED. Patients with SS in the ED had a mortality of only 4.3%, though with an increased risk of dying compared with that of the other groups combined [relative risk (RR) = 11.64, 95% confidence interval (CI) = 1.43 to 96.53], an increased risk of ICU stay (RR = 7.65, 95% CI = 4.08 to 14.36), and an increased risk of prolonged hospitalization (RR = 1.99, 95% CI = 1.38 to 2.88). Although age over 60 years and several comorbid conditions also were identified by univariate analysis as risk factors, multivariate analysis revealed that only SS and diabetes mellitus (DM) were independent predictors of a complicated course. In the authors' institution, the positive predictive value (PPV) of SS for complicated clinical course was 0.48 and the negative predictive value (NPV) of no SS for no complicated course was 0.77. The PPV of [SS + DM] was 0.83, and the NPV of [SS, DM, or both] was also 0.83.

CONCLUSION

Although the strongest correlate of a complicated clinical course identified in the ED is SS as defined by the study criteria, its specificity and PPV are low. The mortality of ED patients with SS is much lower than the mortality rates reported for inpatients with SS. SS as defined by the study criteria is too sensitive and therefore lacks utility in the ED setting.

Total hip arthroplasty with use of second-generation cementing techniques. An eighteen-year-average follow-up study

In this report, we present the results of a further follow-up of a series of 140 consecutive patients (161 hips) who had had a primary total hip arthroplasty with insertion of a bead-blasted monoblock femoral component with use of so-called second-generation cementing techniques. The average age of the patients at the time of the arthroplasty was sixty-one years (range, twenty-one to eighty-five years). Sixty-seven patients (seventy-seven hips) died less than seventeen years after the index operation. The remaining seventy-three patients (eighty-four hips) were followed for an average of eighteen years (range, seventeen to twenty years). No patient was lost to follow-up. In the entire group of 161 hips, over the twenty-year span of the study, eight femoral components (5 percent) and twenty-eight acetabular components (17 percent) had been revised because of aseptic loosening. Of the seventy-seven hips in the sixty-seven patients who died, four had been revised because of aseptic loosening of the acetabular component only; one, because of aseptic loosening of the femoral component only; and one, because of aseptic loosening of both components. Of the eighty-four hips in the seventy-three patients who were alive at least seventeen years after the index arthroplasty, twenty-four hips (29 percent) in twenty-one patients had had revision of one or both components for any reason. Twenty-three acetabular components (27 percent) and six femoral components (7 percent) had been revised because of aseptic loosening. An additional two hips (2 percent) in two patients were loose according to radiographic criteria but had not been revised. Of the sixty-five all-polyethylene acetabular components that had been inserted with cement and were in patients who were alive at least seventeen years postoperatively, fifteen (23 percent) had been revised because of aseptic loosening. An additional seventeen cups (26 percent) were loose according to radiographic criteria. Thus, a total of thirty-two cups (49 percent) had been revised because of loosening or were loose but had not been revised at the time of the latest follow-up. The femoral components that had been inserted with use of second-generation cementing techniques fared better than did the acetabular components that had been inserted with these techniques during the same time-period. We found that assessment of all postoperative radiographs rather than only those that had been made immediately postoperatively increased the accuracy of the grading of the cement around the femoral component. Subsequent radiographs frequently had been made at different projections, which revealed new findings, consisting primarily of previously undetected voids, areas of thin cement, and defects in the cement mantle. Thus, we now use all available radiographs to determine the grade of the cement.

Severe acidosis and hyperdynamic circulation in a 39-year-old alcoholic

A case of acute fulminant cardiovascular beriberi, or "shoshin beriberi," is presented. Beriberi is classified as "dry" (neurologic) or "wet" (cardiovascular) and may be mixed. "Wet" beriberi refers to a spectrum of clinical manifestations ranging from a hyperdynamic state with high output cardiac failure to fulminant failure with collapsed peripheral circulation, lactic acidosis, and shock. Beriberi is probably much more common than previously recognized. Beriberi is caused by thiamine deficiency and should be suspected in alcoholics who present with unexplained lactic acidosis, a hyperdynamic state, high output cardiac failure, or cardiogenic shock without electrocardiographic (EKG) evidence of myocardial necrosis. Shoshin beriberi is rapidly fatal without immediate treatment with thiamine.

Ultrasonic imaging using optoelectronic transmitters

Conventional ultrasound scanners utilize electronic transmitters and receivers at the scanner with a separate coaxial cable connected to each transducer element in the handle. The number of transducer elements determines the size and weight of the transducer cable assembly that connects the imaging array to the scanner. 2-D arrays that allow new imaging modalities to be introduced significantly increase the channel count making the transducer cable assembly more difficult to handle. Therefore, reducing the size and increasing the flexibility of the transducer cable assembly is a concern. Fiber optics can be used to transmit signals optically and has distinct advantages over standard coaxial cable to increase flexibility and decrease the weight of the transducer cable for larger channel numbers. The use of fiber optics to connect the array and the scanner entails the use of optoelectronics such as detectors and laser diodes to send and receive signals. In transmit, optoelectronics would have to be designed to produce high-voltage wide-bandwidth pulses across the transducer element. In this paper, we describe a 48 channel ultrasound system having 16 optoelectronic transmitters and 32 conventional electronic receivers. We investigated both silicon avalanche photodiodes (APD's) and GaAs lateral photoconductive semiconductor switches (PCSS's) for producing the transmit pulses. A Siemens SI-1200 scanner and a 2.25 MHz linear array were used to compare the optoelectronic system to a conventional electronic transmit system. Transmit signal results and images in tissue mimicking of cysts and tumors are provided for comparison.

Radiologists' review of radiographs interpreted confidently by emergency physicians infrequently leads to changes in patient management

STUDY OBJECTIVE

To determine whether radiologists' review of radiographs is unwarranted when emergency physicians are confident in their interpretations.

METHODS

This was a prospective, descriptive study. Treating emergency physicians at a high-volume, urban teaching hospital and a moderate-volume nonteaching hospital indicated their confidence or lack of confidence in their plain-film radiographic study interpretations. All radiographs were then reviewed by radiologists according to the preexisting practice of each hospital. A total of 16,410 emergency department radiographic studies were included, comprising consecutive patients at each hospital. Charts of all discordant readings in the confident group were reviewed and judged clinically significant if treatment was altered. Charges for radiologic review of the confident ED interpretations were calculated.

RESULTS

The ED physicians were confident in 9,599 sets of radiographs out of a total of 16,410 (58%). Discordant interpretation rates for the "confident" and "not confident" groups were 1.2% and 3.1%, respectively (difference, 1.9%; 95% confidence interval [CI] of the difference, 1.44% to 2.36%). Review of the 118 discordant interpretations in the confident group demonstrated that 11 were significant. Few management changes were made as a result of radiologists' review of these radiographs. Total radiology review charges for the confident group were $215,338. Therefore the average radiology charge for each significant discordant interpretation was $19,576.

CONCLUSIONS

Of 9,599 sets of radiographs interpreted confidently by the emergency physicians in this study, there were 11 clinically significant discordant interpretations (0.1%). The standard practice of radiologists' review of all ED radiographs may not be justifiable.

Two-dimensional arrays for medical ultrasound using multilayer flexible circuit interconnection

The development of 2-D array transducers has received much recent interest. Unfortunately, fabrication of high density 2-D arrays is difficult due to the large number of electrical interconnections which must be made to the back side of the elements. A typical array operating at 2.2 MHz may have 256 or more connections within a 16.4 mm circular footprint. Interconnection becomes even more challenging as operating frequencies increase. To solve this problem, we have developed a multilayer flexible (MLF) circuit interconnect consisting of a polyimide dielectric with inter-laminar vias routing signals vertically and etched metal traces routing signals horizontally. A transducer is fabricated from an MLF by bonding a PZT chip to its surface and dicing the chip into individual elements, with the saw kerf extending partially into the top polyimide layer to ensure physical and electrical isolation of the elements. The KLM model was used to compare the performance of an MLF 2-D array to a conventional hand wired 2-D array. MLF and wire guide transducers were fabricated, each with 256 active elements, 0.4 mm interelement spacing, and 2.2 MHz center frequency. Vector impedance, pulse length, bandwidth, angular response, and cross-coupling were found to be comparable in both types of arrays. Using the MLF, however, fabrication time was reduced dramatically. More importantly, MLF technology may be used to increase 2-D array connection density beyond the limitations of current of hand wired fabrication techniques. Thus MLF circuits provide a means for the interconnection of current and future high frequency 2-D arrays.

Progress in two-dimensional arrays for real-time volumetric imaging

The design, fabrication, and evaluation of two dimensional array transducers for real-time volumetric imaging are described. The transducers we have previously described operated at frequencies below 3 MHz and were unwieldy to the operator because of the interconnect schemes used in connecting to the transducer handle. Several new transducers have been developed using new connection technology. A 40 x 40 = 1,600 element, 3.5 MHz array was fabricated with 256 transmit and 256 receive elements. A 60 x 60 = 3,600 element 5.0 MHz array was constructed with 248 transmit and 256 receive elements. An 80 x 80 = 6,400 element, 2.5 MHz array was fabricated with 256 transmit and 208receive elements. 2-D transducer arrays were also developed for volumetric scanning in an intra cardiac catheter, a 10 x 10 = 100 element 5.0 MHz forward-looking array and an 11 x 13 = 143 element 5.0 MHz side-scanning array. The-6dB fractional bandwidths for the different arrays varied from 50% to 63%, and the 50 omega insertion loss for all the transducers was about-64 dB. The transducers were used to generate real-time volumetric images in phantoms and in vivo using the Duke University real time volumetric imaging system, which is capable of generating multiple planes at any desired angle and depth within the pyramidal volume.

Successful use of propofol in refractory delirium tremens

Alcohol withdrawal is a common problem encountered by emergency physicians, with delirium tremens (DT) as the extreme manifestation. DT is a true medical emergency. Although benzodiazepines are the mainstay of therapy, some patients require massive amounts to control their symptoms. We report the successful use of propofol for DT refractory to benzodiazepines in a 42-year-old alcoholic man. We briefly discuss alcohol withdrawal, as well as the pharmacokinetics and adverse affects of propofol. The use of propofol in treating DT refractory to benzodiazepines has previously not been reported.

A two-dimensional array for B-mode and volumetric imaging with multiplexed electrostrictive elements

A 2:1 multiplexed 2-D array has been developed that has a sparse element pattern designed for real time volumetric imaging and an alternate element pattern designed for B-mode imaging. For volumetric imaging, a small aperture was used to provide a wide transmit beam, allowing multiple beams to be received simultaneously. For B-mode imaging, a larger aperture with a more narrow transmit beam was used to improve image quality. Sparse random element patterns were evaluated by beamplot and cyst image simulations. Using the alternate element pattern for B-mode imaging, simulated cyst contrast was improved by 28%. The multiplexed transducer was fabricated using an electrostrictive material in which array elements were activated and deactivated by a dc bias field. The transducer had a 3.4 MHz center frequency with 46% bandwidth, which was consistent with KLM simulations. The high dielectric constant of the electrostrictive material resulted in an element clamped capacitance of 14.3 pF versus 2 pF for a convention PZT element. An output off isolation of -35 dB was measured for transmit and -61 dB for receive. The array was integrated with the volumetric scanner and used to make real time images of a cyst phantom. The images showed improved cyst contrast using the alternate aperture for B-mode imaging.

Vastus-Psoas release for acetabular exposure in revision hip surgery

A technique is presented for wide exposure of the acetabulum for revision total hip arthroplasty surgery in the presence of a solidly fixed, modular, or monoblock femoral component without the need for trochanteric osteotomy. The technique involves release of the proximal portion of the vastus lateralis, vastus intermedius, and vastus medialis muscles and the iliopsoas tendon form the femur and placement of the femoral head/neck posterior to the acetabulum. The exposure afforded by this release usually precludes the need for trochanteric osteotomy and/or removal of a well-fixed femoral component in revision surgery that is being done for isolated loosening of acetabular components, thereby decreasing operative time, morbidity, and the risks of complication of trochanteric osteotomy.

Binary-optic smoothing with isotropic etching

Binary optics are an important part of modern optics, but they have some inherent problems because of their binary nature. The optics cannot achieve maximum efficiency unless the rms surface error can be reduced. A technique for smoothing jagged surfaces by use of isotropic etching is presented. We show that etching smoothes the binary nature and improves the optical efficiency.

Improved signal-to-noise ratio in hybrid 2-D arrays: experimental confirmation

2-D array transducers have shown significant promise for medical ultrasound over conventional linear arrays, at the cost of increasing the number of channels, difficulty of fabrication and array element impedance. The increase in element impedance reduces the power coupled to a 2-D array element from a conventional 50 omega source in transmit mode. If the array is sparse, which is typical of 2-D arrays, then the net power coupled into the front acoustic load is reduced when compared to a fully sampled aperture. Furthermore, the received signal-to-noise ratio (SNR), when measured through a nonideal amplifier, is degraded because the high impedance 2-D array transducer element cannot efficiently drive the coaxial cable. The reduction in transmit sensitivity and received SNR can be circumvented with the application of multilayer piezoelectric elements. The improvement in transmit occurs because the transducer impedance is better matched to the impedance of the source. In receive, multilayer elements allow more of the open circuit received voltage to fall across the input of the high impedance preamplifier. In this case, the same number of layers are used in transmit and receive. Recently, it has been suggested that separate optimization of the transmit channel and receive channel (a hybrid array) would further improve the pulse-echo SNR. In this paper, we fabricated and tested a hybrid array operating at 1 MHz using a multilayer transmit element and single layer receive element. A 7 omega transmitter and high impedance preamplifier were placed adjacent to the transmit and receive elements within the transducer assembly. The hybrid pulse-echo SNR improved by 26.4 dB over the conventional array. The experimental result showed good agreement with the KLM model. Furthermore, KLM simulations showed that as the operating frequency of the array increases, the overall improvement over the conventional array increases. For example, a 1.5-D array operating at 2 M Hz had an improvement of 30 dB whereas a 7.5 M Hz 1.5-D array showed an increase of approximately 38 dB. The separate optimization of the transmit and receive channel for 2-D arrays showed even greater improvement than for 1.5-D arrays. For example, a 2 MHz 2-D array had an improvement of over 44 dB.

Human peripheral mononuclear cell responses to UV damage are affected by radiation-induced changes in plasma

To evaluate the effects of environmental or therapeutic stress adequately, it is important to study cells or tissues under conditions that simulate as closely as possible the in vivo environment. To determine whether the responses of irradiated cells are significantly affected by radiation-induced changes in plasma, human mononuclear cells were isolated from peripheral blood and cultured in their autologous plasma. Freshly isolated cells were irradiated in phosphate-buffered saline. The plasma was irradiated separately. Irradiation of the plasma suppressed mitogen-induced DNA synthesis in unirradiated cells. For cells that were UV-damaged and subsequently stimulated with mitogen, DNA synthesis was enhanced by irradiation of the plasma. Medium in which irradiated cells had previously been incubated enhanced DNA, synthesis in unirradiated cells that had been mitogen stimulated but did not affect the UV-induced shutoff of DNA synthesis in replicating cells or unscheduled DNA synthesis in irradiated cells.

A ceramic system for delivering interleukin-2

Interleukin-2 (IL-2) is a potentially effective cytokine to be used for cancer treatment. Since keeping IL-2 doses at a low, continuous level is important to avoid side effects which accompany high IL-2 doses, a ceramic which release IL-2 could prove to be a beneficial method of drug delivery for cancer patients [1]. In vitro studies were performed to determine the optimal hydroxyapatite (HA) to IL-2 ratio for continuous release of IL-2 from HA using both a matrix and insert ceramic pellet. In the matrix pellet experiment, HA to IL-2 ratios of 25:1, 50:1 and 100:1 were tested by compressing a homogenous mixture of each variable in triplicate and placing each ceramic in 2.5 mL simulated body fluid (SBF) at 37 degrees C. The fluid was collected and replaced for each ceramic every two hours for 12 hours and at 24 hours. The collected fluid was then assayed for IL-2 content. Pellets consisting of 25:1 ceramic to drug ratio delivered almost the entire amount of IL-2 at the fastest rate. Composites of 100:1 IL-2 to HA delivered the least amount of IL-2 at the slowest rate. Release of IL-2 from the 50:1 ratio pellets was intermediate with respect to speed and amount of delivery. In the insert pellet experiment, similar laboratory procedures were used to show that 100:1 ratio insert pellets delivered IL-2 at a slower rate and in lesser amounts than 50:1 ratio insert pellets. Results of this study show that HA can deliver IL-2 at different rates by varying the ratio of HA to IL-2 in both matrix and insert ceramic pellets.

Hybrid multi/single layer array transducers for increased signal-to-noise ratio

In medical ultrasound imaging, two-dimensional (2-D) array transducers are necessary to implement dynamic focusing in two dimensions, phase correction in two dimensions and high speed volumetric imaging. However, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance, which decreases the transducer signal-to-noise ratio (SNR). We have previously shown that SNR is improved using transducers made from multi-layer PZT, due to their lower electrical impedance. In this work, we hypothesize that SNR is further increased using a hybrid array configuration: in the transmit mode, a 10 Omega electronic transmitter excites a 10 Omega multi-layer array element; in the receive mode, a single layer element drives a high impedance preamplifier located in the transducer handle. The preamplifier drives the coaxial cable connected to the ultrasound scanner. For comparison, the following control configuration was used: in the transmit mode, a 50 Omega source excites a single layer element, and in the receive mode, a single layer element drives a coaxial cable load. For a 5x102 hybrid array operating at 7.5 MHz, maximum transmit output power was obtained with 9 PZT layers according to the KLM transmission line model. In this case, the simulated pulse-echo SNR was improved by 23.7 dB for the hybrid configuration compared to the control. With such dramatic improvement in pulse-echo SNR, low voltage transmitters can be used. These can be fabricated on integrated circuits and incorporated into the transducer handle.

Primary total knee arthroplasty using the Genesis Total Knee Arthroplasty System: 3- to 6-year follow-up study of 105 knees

This prospective study analyzed data from 105 primary total knee arthroplasties performed in 90 patients using the Genesis Total Knee Arthroplasty System. The 34 men and 56 women with a mean age of 68.7 years (range, 41-86 years) were evaluated at a mean follow-up period of 4.25 years (range, 3-6 years). Fifty-five procedures (52%) used cemented femoral and tibial components, 49 (47%) used cementless femoral and cemented tibial components, and 1 (1%) used cementless femoral and tibial components. The preoperative mean pain and function scores were 50 (range, 12-79) and 41 (range, 5-80), respectively. At the most recent follow-up evaluation, the mean pain score increased to 97 (range, 67-100), and the mean function score increased to 88 (range, 40-100). Mean preoperative range of motion was 104 degrees (range, 50 degrees-130 degrees) and increased to 116 degrees (range, 80 degrees-130 degrees) at most recent follow-up evaluation. Clinically, there were 100 excellent results (95%). 4 good results (4%), and 1 poor result (1%).

Interobserver reliability and intraobserver reproducibility of the modified Ficat classification system of osteonecrosis of the femoral head

Anteroposterior and lateral plain radiographs of 116 osteonecrotic femoral heads were reviewed to assess the interobserver reliability and intraobserver reproducibility of the modified Ficat classification system. The radiographs were reviewed initially and then again six months later by three adult reconstructive surgeons, two general orthopaedic surgeons, two orthopaedic residents, and one musculoskeletal radiologist. All eight observers agreed on the classification of twenty hips (17 per cent) at both the first and the second review of the radiographs. Paired comparisons revealed a mean interobserver kappa reliability coefficient of 0.46 (range, 0.30 to 0.67) for the first review and 0.45 (range, 0.30 to 0.66) for the second. For all observers, the mean rate of perfect agreement between the first and the second review was 68 per cent (range, 56 to 80 per cent). The mean kappa value for intraobserver reproducibility was 0.59 (range, 0.44 [one of the residents] to 0.73 [one of the general orthopaedic surgeons]). No observer or pair of observers had excellent reproducibility or reliability (kappa > 0.75). The poor interobserver reliability and fair intraobserver reproducibility diminishes any meaningful comparison of studies in which the modified Ficat classification system has been used and illuminates the need for a more reliable and reproducible classification system.

Subjective assessment of fever by parents: comparison with measurement by noncontact tympanic thermometer and calibrated rectal glass mercury thermometer

STUDY OBJECTIVE

To assess the ability of parents to subjectively evaluate their children for fever and to compare their assessments with temperature measurements made with the use of a noncontact tympanic (NCT) or rectal glass mercury thermometer. A secondary goal was to assess how well a recently developed definition of fever for NCT thermometers, when used in the ear-equivalent mode (temperature of 37.7 degrees C or more), performed in a clinical situation.

METHODS

This 6-month prospective observational study employed a convenience sample of 180 children, aged birth to 4 years, who presented to the emergency department of a tertiary care children's hospital. Parents were asked to subjectively assess whether their child had a fever. The child's temperature was then measured with an NCT thermometer (three times in the rectal-equivalent mode and three times in the actual-ear mode). Both the subjective assessment and the NCT temperatures were compared with the rectal temperature measured by a rectal glass mercury thermometer.

RESULTS

The mean age of participants was 14.6 +/- 11.8 months (range, 2 days to 48 months); 56% were boys. The sensitivity of parental detection of fever by subjective means was 81.8% and the specificity 76.5%. The parent and the rectal glass thermometer agreed 79% of the time (95% confidence interval [CI], 73% to 85%). The sensitivity of the first temperature reading obtained with the NCT thermometer in rectal-equivalent mode was 74.7%, and the specificity was 96.3%. The NCT thermometer and the rectal glass thermometer agreed 84% of the time (95% CI, 78% to 89%). Use of the proposed definition of fever for NCT thermometers, when used in the ear-equivalent mode, caused sensitivity of a single measurement for fever to drop to 53.5%.

CONCLUSION

Parental subjective assessment of fever agreed with the presence of fever as measured by rectal glass thermometer in 79% of cases. Specificity was improved with the use of the NCT thermometer. The recently proposed definition for fever for NCT thermometers, when they are used in the ear-equivalent mode, does not appear to be validated by the current data.

Novel azole derivatives are antagonists at the inhibitory GABA receptor on the somatic muscle cells of the parasitic nematode Ascaris suum

The somatic muscle cells of the parasitic nematode Ascaris suum possess GABA receptors that gate chloride conductances in a similar fashion to the mammalian GABAA receptor subtype. These receptors mediate muscle relaxation and are the site of action of the anthelmintic piperazine. The properties of this receptor differ from the properties of the GABA-gated chloride receptors in the mammalian host, in particular they are not as sensitive to mammalian GABA receptor antagonists such as bicuculline and picrotoxin. Using two-electrode intracellular electrophysiological recording techniques from Ascaris muscle cells, we have tested the potency of a series of azole derivatives for their ability to block the chloride-dependent GABA response. The lead compound, SN606078, 2-(2,6-dichloro-4-trifluoromethylphenyl)-4-(4,5-dicyano-1H-imidazo l-2-yl)-2H- 1,2,3-triazole, and 4 structurally related compounds reversibly blocked the conductance increase elicited by 30 microM GABA with IC50s of less than 10 microM. SN606078 (10 microM) decreased the slope of the dose-response curve for GABA, suggesting a non-competitive mechanism of action. In two-electrode voltage clamp experiments, 10 microM SN606078 blocked the outward current elicited by 20 microM GABA in a voltage-dependent manner with 72 +/- 2% inhibition at -20 mV and 49 +/- 6% inhibition at -40 mV. These observations indicate that SN606078 may act as an open-channel blocker of the GABA-gated chloride channel in A. suum.

Genes that regulate apoptosis in the mouse thymus

Elimination of self-reactive T lymphocytes occurs during T-cell development in the thymus by a process known as negative selection. The mechanism that drives negative selection is apoptosis. To identify genes that regulate apoptosis in the mouse thymus, a library of negatively selected T cells was constructed and, by subtractive screening, several differentially regulated genes were isolated. Two transcripts that are repressed during cell death were identified, in addition to two induced transcripts. Further experiments demonstrated that cell death in thymocytes can occur via several induction pathways and each pathway appears to be regulated by a unique cascade of genes.

An evaluation of the safety and efficacy of fluconazole in the treatment of onychomycosis

Sixteen subjects were enrolled in this open-label noncomparative study to evaluate the safety and efficacy of fluconazole as a single daily dose for a period of 6 months. Liver function enzymes were monitored to assess safety. An adverse function questionnaire was used on a monthly basis to assess patient tolerance. A visual analogue scale was used to assess efficacy of treatment. After 6 months of fluconazole, all subjects experienced improvement in the appearance of their nails. None of the subjects evidenced any elevation in liver function enzymes. Adverse reactions were limited and consistent with other studies involving fluconazole. Fluconazole proved to be safe and efficacious in the treatment of onychomycosis. Further studies are needed to determine a cost-effective dosing regimen for the treatment of onychomycosis with fluconazole.

Phase aberration correction in two dimensions using a deformable array transducer

Phase aberrations due to tissue inhomogeneities degrade medical ultrasound images by disrupting the ultrasound beam focus. Currently, phase correction algorithms are implemented by adjusting the electronic phase delays uses to steer and focus the ultrasound beam. This means that a two-dimensional array is necessary to completely correct two-dimensional aberrations in tissue. However, two-dimensional arrays are a complex option due to their large number of elements and poor sensitivity. Instead of using a full two-dimensional array, a new technique is proposed, similar to one used in adaptive optics, which used a deformable transducer of significantly fewer channels for two-dimensional phase correction. Phase correction in azimuth is achieved by altering the electronic phase delay of the element. However, phase correction in elevation is achieved by tilting the element in elevation with a piezoelectric actuator. Comparison of simulations of the new phase correction transducer versus the conventional phase correction technique have shown that a deformable 1 x N or 2 x N transducer can approach the image quality of a 4 x N two-dimensional array or greater. A prototype 1 x 32 array with eight low frequency piezoelectric actuators has been constructed such that every four ultrasonic transducer elements in azimuth are mounted on one independently controlled actuator. This prototype transducer was used to test the ability of a deformable array to produce real time phased array scans and to simulate on-line phase correction by tilting the elements in the elevation direction.

Core decompression of the osteonecrotic femoral head

The results in 114 hips of ninety-two patients who had osteonecrosis of the femoral head were assessed after treatment with core decompression. The average duration of follow-up was three years and four months (range, two years to six years and six months). The average age of the patients was forty-one years (range, fifteen to sixty-seven years). The presumed risk factors were the use of corticosteroids (thirty-seven hips), excessive use of alcohol (thirty-two hips), trauma (seven hips), and various other factors (seven hips). No specific risk factor was identified for thirty-one hips, and the osteonecrosis was considered to be idiopathic. The preoperative evaluation consisted of clinical assessment, magnetic resonance imaging, and radiographic staging according to a modification of the system of Ficat. Thirty-two hips were in stage I; thirty-eight, in stage IIA; twenty-five, in stage IIB (transition stage, with a crescent sign); and nineteen, in stage III. Clinical failure was defined as the performance of a subsequent operation. Over-all, sixty-four hips (56 percent) failed clinically. Fifty-seven were treated with a hip replacement; four, with a femoral osteotomy; and three, with a vascularized fibular graft. Clinical failure was seen in five (16 percent) of the thirty-two hips in stage I, twenty (53 percent) of the thirty-eight hips in stage IIA, twenty (80 percent) of the twenty-five hips in stage IIB, and in all nineteen of the hips in stage III.(ABSTRACT TRUNCATED AT 250 WORDS)

Human skin permeability enhancement by lauric acid under equilibrium aqueous conditions

An in vitro method was developed to investigate the enhancement of hydrocortisone transport across human stratum corneum (SC) by a model enhancer, lauric acid, in aqueous solutions under equilibrium conditions with respect to the enhancer. In contrast to classical (i.e., nonequilibrium) loading techniques, in which the enhancer is applied only to the donor side of SC either in pure form or in an organic solvent while enhancer-free aqueous buffers are placed in the receptor phase, this method allowed the investigation of pH effects, concentration effects, and reversibility of both enhancer uptake and enhancement of drug transport under thermodynamically well-defined conditions. The SC-buffer partition coefficients for lauric acid were linear with concentration and sigmoidal with pH, suggesting that both the neutral species and laurate anion partition into SC. Comparisons of partition coefficients in delipidized and untreated SC as a function of pH indicated that the uptake of lauric acid in neutral form is governed primarily by the lipid domain, whereas the protein domain accounts for anion uptake. The effects of lauric acid on skin permeability were > 80% reversible upon extraction of the enhancer from the membrane. However, the degree of enhancement of hydrocortisone permeability was nonlinearly dependent on the equilibrium concentration of lauric acid in either the aqueous buffer or the membrane, exhibiting thresholds in the appearance of enhancement with concentration. The enhancer concentration necessary to achieve isoenhancement of about 6-fold varied from approximately 1 x 10(-5) M at pH < pKa to approximately 1 x 10(-2) M at high pH (pH > 8) demonstrating the higher influence of the free acid species.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimization of signal-to-noise ratio for multilayer PZT transducers

In medical ultrasound imaging, two-dimensional (2-D) array transducers are desirable to implement dynamic focusing and phase aberration correction in two dimensions as well as volumetric imaging. Unfortunately, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance near the resonance frequency. This results in poor signal-to-noise ratio (SNR) of the array elements. It has previously been demonstrated that transducers made from multilayer PZT ceramics have lower electrical impedance and greater SNR than comparable single layer elements. A simplified circuit model has been developed to optimize the SNR for multilayer ceramic (MLC) transducers. In this model, an electronic transmitter excites the array element and in the receive mode, the element drives a coaxial cable load terminated by a high impedance preamplifier. The transducer impedance is Zt/N2, where N is the number of piezoelectric layers. Maximum transmit signal is obtained when N = Ntx such that the transducer impedance, Zt/Ntx2, is matched to the source impedance. Maximum receive signal is obtained when N = Nrx such that the transducer impedance, Zt/Nrx2, is matched to the coaxial cable reactance. For maximum pulse-echo signal, the transducer should be designed with N = square root of Ntx Nrx, the geometric mean of Ntx and Nrx. Using this optimization technique, a 1.5-D array was designed with 3 layers for maximum pulse-echo SNR. Results of simulations from the simplified circuit analysis were consistent with those of the KLM model. The 3 layer array was fabricated as well as a single layer control array. The measured transmit signal and receive signal agreed with the simulation results.

Physiologic responses of cardiac patients to supine, recumbent, and upright cycle ergometry

Physiological responses were compared in nine stable male cardiac patients (mean +/- standard error (SE): age, 68.3 +/- 8.1 years; height, 172.7 +/- 3.9cm; weight, 72.8 +/- 14.5kg) during stationary cycling in the supine, recumbent, and upright positions. A discontinuous exercise protocol was performed in which each stage included 3 minutes of exercise and 1 minute of recovery. Each subject's workload started at 150kgm.min-1 and increased by 150kgm.min-1 per stage until volitional fatigue. Testing sessions were randomized and performed 1 week apart. Subjects continued their normal medication regimen. All subjects were participants in a community-based cardiac rehabilitation program. Dependent variables were assessed at two different intensities; submaximal (300kgm.min +/- 1) and maximal. A two-way repeated measures ANOVA found no significant differences in systolic blood pressure (SBP), diastolic blood pressure (DBP), minute ventilation (VE), respiratory exchange ratio (R), rate pressure product (RPP), and rating of perceived exertion (RPE) at submaximal (300kgm.min +/- 1) and maximal exercise efforts. Heart rate (HR) was significantly lower (p < or = .05) in the supine position compared with either the upright or recumbent positions during the submaximal workload. In addition, oxygen uptake (VO2) was significantly lower in the supine position at the submaximal workload (p < or = .05) compared with both upright and recumbent. No difference in HR or VO2 was observed at maximal exercise. Regressions of HR on VO2 showed similar slopes and intercepts for supine, recumbent, and upright ergometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient transfection assays to examine the requirement of putative cell death genes

In conclusion, this chapter provides a convenient and efficient method for the detection and analysis of transiently transfected cells. Such strategies allow a fast and simple analysis of the requirement for particular genes that have been identified as being induced during apoptosis. Our experience has been that, when screening for "cell death genes," it is easy to isolate genes induced during apoptosis but far more difficult to determine the requirement for any given gene. These protocols have rendered such determinations much simpler to perform.

Cardiac ultrasound phantom using a porcine heart model

A beating cardiac phantom has been developed using an excised porcine heart for use as a training tool in echocardiography. The heart is fixed with a formalin-based preservation method, housed in an optically transparent Lexan chamber, and undergoes hydraulic pumping to circulate a blood-mimicking fluid. The cardiac phantom has been used for a period of four months to produce images of excellent quality with ventricular wall motion typical of human subjects.

The genetic data environment an expandable GUI for multiple sequence analysis

An X-Windows-based graphic user interface is presented which allows the seamless integration of numerous existing biomolecular programs into a single analysis environment. This environment is based on a core multiple sequence editor that is linked to external programs by a user-expandable menu system and is supported on Sun and DEC workstations. There is no limitation to the number of external functions that can be linked to the interface. The length and number of sequences that can be handled are limited only by the size of virtual memory present on the workstation. The sequence data itself is used as the reference point from which analysis is done, and scalable graphic views are supported. It is suggested that future software development utilizing this expandable, user-defined menu system and the I/O linkage of external programs will allow biologists to easily integrate expertise from disparate fields into a single environment.

Improved cardiac anthropomorphic phantom

An improved cardiac sonographic phantom is described that simulates the anatomy of the human heart for applications as a low cost quality assurance and training tool in echocardiography. The major new feature in the phantom is the development of a polyurethane sponge left ventricle, which mimics the myocardium during sonographic imaging while undergoing hydraulic pumping. The left ventricle, including prosthetic mechanical mitral and aortic valves, is housed in an optically transparent Lexan chamber or in a tissue mimicking polyurethane rubber torso. Additional new features include a port for transesophageal imaging, and an adjustable calibrated stroke volume on the piston pump, which can serve as a standard for echocardiographic stroke volume measurement. B-scans of the phantom show excellent image quality in all three standard echocardiographic views as well as in transesophageal scanning.

Two-dimensional random arrays for real time volumetric imaging

Two-dimensional arrays are necessary for a variety of ultrasonic imaging techniques, including elevation focusing, 2-D phase aberration correction, and real time volumetric imaging. In order to reduce system cost and complexity, sparse 2-D arrays have been considered with element geometries selected ad hoc, by algorithm, or by random process. Two random sparse array geometries and a sparse array with a Mills cross receive pattern were simulated and compared to a fully sampled aperture with the same overall dimensions. The sparse arrays were designed to the constraints of the Duke University real time volumetric imaging system, which employs a wide transmit beam and receive mode parallel processing to increase image frame rate. Depth-of-field comparisons were made from simulated on-axis and off-axis beamplots at ranges from 30 to 160 mm for both coaxial and offset transmit and receive beams. A random array with Gaussian distribution of transmitters and uniform distribution of receivers was found to have better resolution and depth-of-field than both a Mills cross array and a random array with uniform distribution of both transmit and receive elements. The Gaussian random array was constructed and experimental system response measurements were made at several ranges. Comparisons of B-scan images of a tissue mimicking phantom show improvement in resolution and depth-of-field consistent with simulation results.

Apoptotic signals delivered through the T-cell receptor of a T-cell hybrid require the immediate-early gene nur77

Engagement of the T-cell antigen receptor (TCR) on immature thymic T cells induces death by apoptosis. Although several lines of evidence indicate that apoptosis requires de novo gene expression, little is known about the molecular pathways that mediate this response. Here we show that nur77 (refs 4-7), a zinc-finger transcription factor, is expressed in response to TCR engagement in immature T cells and T-cell hybrids. Antisense inhibition of nur77 expression prevents apoptosis in TCR-stimulated cells. nur77 is also expressed in response to mitogens, but in this case transcription is regulated by 5' upstream elements that are distinct from those used for induction of apoptosis. In addition, polyadenylation is only observed on nur77 transcripts found in condemned cells. These data support a role for nur77 in cell death that may be distinct from that of activation.

Multilayer piezoelectric ceramics for two-dimensional array transducers

In medical ultrasound imaging, 2-D array transducers have become essential to implement dynamic focusing and phase-correction in the elevation dimension as well as real-time volumetric scanning. Unfortunately, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance near resonance. These elements have poor sensitivity because their impedance is much higher than the electrical impedance of the transmit and receive circuitry. Sensitivity can be improved by using an N layer structure of PZT ceramic with the layers connected acoustically in series and electrically in parallel. For the multilayer ceramic (MLC), the damped capacitance is multiplied by a factor of N(2) and the electrical impedance by 1/N(2) compared to a single layer element of the same dimensions. A 3x43 phased-array transducer has been fabricated using 3 layer PZT-5H material. Each element had a thickness of 0.66 mm and an area of 0.37x3.5 mm. The MLC was manufactured using thick film technology with plated-through vias to electrically interconnect the electrode layers. The completed transducer was compared to a single layer control array of similar dimensions. With a light epoxy backing and a lambda/4 matching layer, the MLC array elements had an impedance of 100 Omega at series resonance of 2.25 MHz, compared to 800 Omega for the control elements. The lower impedance of the MLC elements resulted in a minimum round-trip insertion loss of 24.0 dB, compared to an 34.1 dB for the control array elements. These results were consistent with KLM modeling. B-scan images were made of cysts in a tissue-mimicking phantom and of the left kidney in vivo. The images clearly showed a higher signal-to-noise ratio for the MLC array compared to the control. As a result, 2-D arrays made of multilayer ceramics can be used to form images at a higher frequency and greater range than single layer arrays.

Salt and mesophase formation in aqueous suspensions of lauric acid

The solubility and solution behavior of lauric acid (LA) and its 1:1 acid soap (potassium hydrogen dilaurate) were investigated at 32 degrees C over a pH range of 2.5-8.5 and at varying KCl concentrations to examine the self-association of this long-chain carboxylic acid under these conditions. LA's solubility in water exhibited the classical pH dependence of a monocarboxylic acid with no evidence of self-association. In 0.1 M KCl between pH 6.3 and pH 7.3, filtered samples were turbid, suggesting the presence of high molecular weight aggregates (mesophase), which could be removed by ultrafiltration. The apparent LA solubility vs pH profile in ultrafiltered samples was consistent with a solid phase consisting of either the free acid (pH < 6.5) or potassium hydrogen dilaurate (pH > 6.5), again with no evidence of self-association to form low molecular weight species (dimers, etc.). Quasi-elastic light scattering (QLS) studies and mannitol trapping experiments indicated that vesicles were present in samples containing mesophase. The mesophase composition was characterized and a mass-action law for mesophase formation was developed to describe the apparent LA solubility versus pH in the mesophase region in terms of three parameters. The index of cooperativity, theta, indicated that the mesophase consists of approximately 25 molecules of LA with an acid:anion ratio, rho, of 1.7. The standard free energy of mesophase formation per mole of monomer was determined to be -6.3 kcal/mol. The aggregate size determined thermodynamically is several orders of magnitude less than that of the mesophase particle size determined by QLS measurements, suggesting that the LA monomer concentration in equilibrium with mesophase may be governed by a small unit domain of the vesicle. These observations may have a bearing on the thermodynamics of self-assembly of lipid bilayer membranes.