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Biomedical subjects

S W Smith

Publications and source records attributed to S W Smith.

At least 37 records · Page 2Linked to original sources
PubMed1999

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.

Acidosis↗
PubMed1998

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.

Attitude of Health Personnel↗
PubMed1998

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.

Adult↗
PubMed1998

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.

Cardiac Volume↗
PubMed1998

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.

Fiber Optic Technology↗
PubMed1998

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.

Adult↗
PubMed1997

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.

Adult↗
PubMed1997

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%).

Aged↗
PubMed1997

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.

Acetabulum↗
PubMed1997

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.

Cell Division↗
PubMed1997

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.

Humans↗
PubMed1997

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.

Image Processing, Computer-Assisted↗
PubMed1997

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.

Biocompatible Materials↗
PubMed1996

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.

Animals↗