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Biomedical subjects

N Newman

Publications and source records attributed to N Newman.

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

Identification of factors responsible for postdialysis fatigue.

Ultrafiltration, diffusion, osmotic shifts, blood-membrane interactions, and psychological factors have all been implicated in the pathogenesis of postdialysis fatigue (PDF). To identify responsible factors, we performed a prospective, randomized, crossover analysis of fatigue scores (scale, 0 to 4) in 12 maintenance hemodialysis subjects with PDF. Fatigue scores were evaluated on nondialysis days (baseline) and after the following procedures on midweek treatment days: standard dialysis using either a 135- to 140-mEq/L sodium bath (routine hemodialysis) or a 150- to 155-mEq/L sodium bath (hypernatric hemodialysis); isolated ultrafiltration; isolated diffusion; and sham procedures with (isolated membrane) or without (recirculation) exposure to a dialysis membrane. Maximal fatigue scores are expressed as mean and 95% confidence intervals (CIs). The highest scores were recorded by patients who had just undergone routine hemodialysis (mean score, 2. 6; 95% CI, 1.7 to 3.4), isolated ultrafiltration (mean score, 2.1; 95% CI, 1.3 to 2.9), and isolated diffusion (mean score, 2.4; 95% CI, 1.5 to 3.2). There were no significant differences in fatigue scores between baseline periods and isolated membrane and recirculation procedures (mean score, 1.3; 95% CI, 0.4 to 2.2). Fatigue scores after hypernatric hemodialysis occupied an intermediate position (mean score, 1.7; 95% CI, 0.8 to 2.6). These results suggest that rapid hydraulic and molecular flux have a greater role in the pathogenesis of PDF than psychological stress and blood-membrane interactions. Use of a high-sodium bath may ameliorate PDF. We conclude that appropriate adjustments in both ultrafiltration and sodium profiling remain the most important means for controlling PDF in patients on short-duration hemodialysis.

Cross-Over Studies↗
PubMed1999

The association of opportunistic infections with the occurrence of trimethoprim/sulfamethoxazole hypersensitivity in patients infected with human immunodeficiency virus.

Hypersensitivity from trimethoprim/sulfamethoxazole (TMP/SMX) has been linked to a reactive nitroso intermediate from sulfamethoxazole metabolism, which may be altered in patients with human immunodeficiency virus (HIV) infection. The authors determined the clinical factors that are associated with TMP/SMX hypersensitivity in patients with HIV. In a case control study, 54 controls currently tolerating TMP/SMX prophylaxis were randomly matched by date of hypersensitivity reaction in case patients to 28 patients with a history of a rash consistent with erythema multiforme from TMP/SMX. Demographic data, coadministered medications, laboratory data, and histories of opportunistic infections were extracted on all patients. A highly significant association was observed between the number of opportunistic infections and the occurrence of TMP/SMX hypersensitivity (p < 0.001), despite comparability of CD4 counts between case patients and controls (p > 0.1). A tendency for protection from TMP/SMX hypersensitivity in blacks was also observed (p = 0.066). These observations suggest that the mechanisms by which HIV produces cellular immune dysfunction and alters drug detoxification may be linked.

AIDS-Related Opportunistic Infections↗
PubMed1998

The effect of cimetidine on the formation of sulfamethoxazole hydroxylamine in patients with human immunodeficiency virus.

Hypersensitivity reactions from trimethoprim/sulfamethoxazole are likely caused by a reactive nitroso intermediate formed from sulfamethoxazole hydroxylamine. This pilot study tested whether cimetidine inhibits the urinary excretion of sulfamethoxazole hydroxylamine. Ten outpatients infected with human immunodeficiency virus (HIV) and currently receiving trimethoprim/sulfamethoxazole prophylaxis were randomly selected from 59 eligible patients. Five received cimetidine 800 mg twice daily for 1 week and five served as controls. Two spot urine samples one week apart were obtained after a trimethoprim/sulfamethoxazole dose for all patients. Patients taking cimetidine had a significant decrease in excretion of sulfamethoxazole hydroxylamine relative to total excreted drug in the two urine samples compared with control patients. Cimetidine likely caused this decrease in sulfamethoxazole hydroxylamine excretion through inhibition of CYP3A4. Because of potential differences between HIV-infected patients and healthy subjects in oxidative metabolism, future studies of inhibitors of sulfamethoxazole hydroxylamine formation should be conducted in the HIV population.

Adult↗
PubMed1998

Postdialysis fatigue: lack of effect of a biocompatible membrane.

Tumor necrosis factor-alpha (TNF-alpha) has been shown to have somnogenic properties. Plasma levels of this cytokine have been found to increase significantly during dialysis with a bioincompatible (cuprophane) membrane in patients with postdialysis fatigue (PDF). We conducted a crossover study with random assignment to ascertain whether a biocompatible membrane might attenuate the increase of TNF-alpha and severity of PDF. Sixteen patients on maintenance hemodialysis underwent dialysis with either cuprophane (n = 8) or polymethylmethacrylate (PMMA; n = 8) membranes for 1 week and then switched to the opposite membrane during the second week. Predialysis and postdialysis measurements of plasma TNF-alpha levels were performed during the first and last dialysis treatments of each week. A fatigue score was determined from the sum of duration of fatigue and sleep within 6 hours of the completion of dialysis. TNF-alpha levels increased by an average of 18.3% during dialysis with cuprophane membranes but only 2.4% with PMMA membranes (P = 0.04). Despite this, fatigue scores remained unaltered (approximately 4 of 6). Hence, the biocompatible membrane, PMMA, failed to alleviate PDF. This suggests that dialytic stimulation of TNF-alpha plays no substantial role in the pathogenesis of PDF.

Biocompatible Materials↗
PubMed1998

Preoperative smoking habits and postoperative pulmonary complications.

OBJECTIVE: To examine the effect of preoperative smoking behavior on postoperative pulmonary complications. DESIGN: Prospective cohort study. SETTING: The Veterans Administration Medical Center, Syracuse, NY. PARTICIPANTS: Patients scheduled for noncardiac elective surgery (n=410). MEASUREMENTS AND RESULTS: Smoking status was determined by self-report. Postoperative pulmonary complications were determined by systematic extraction of medical record data. Postoperative pulmonary complications occurred in 31 of 141 (22.0%) current smokers, 24 of 187 (12.8%) past smokers, and 4 of 82 (4.9%) never smokers. The odds ratio (OR) for developing a postoperative pulmonary complication for current smokers vs never smokers was 5.5 (95% confidence interval [CI], 1.9 to 16.2) and 4.2 (95% CI, 1.2 to 14.8) after adjustment for type of surgery, type of anesthesia, abnormal chest radiograph, chronic cough, history of pulmonary disease, history of cardiac disease, history of COPD, education level, pulmonary function, body mass index, and age. Current smokers who reported reducing cigarette consumption prior to surgery were more likely to develop a complication compared with those who did not (adjusted OR=6.7, 95% CI, 2.6 to 17.1). CONCLUSIONS: Current smoking was associated with a nearly sixfold increase in risk for a postoperative pulmonary complication. Reduction in smoking within 1 month of surgery was not associated with a decreased risk of postoperative pulmonary complications.

Confidence Intervals↗
PubMed1997

Anticonvulsant usage is associated with an increased risk of procarbazine hypersensitivity reactions in patients with brain tumors.

BACKGROUND: Procarbazine usage in brain tumors has a high incidence of hypersensitivity reactions compared with its use in other malignancies. Procarbazine oxidation to a reactive intermediate is enhanced by phenobarbital. Patients with primary brain tumors would have a preferential exposure to anticonvulsants compared to patients with other malignancies. OBJECTIVE: To determine whether anticonvulsant exposure is associated with procarbazine hypersensitivity reactions in patients with primary brain tumors. METHODS: This retrospective cohort study included 83 patients with primary brain tumors who were treated with procarbazine between 1981 and 1996 at a university hospital-based regional oncology center. Data were extracted by chart review. The data collected included age, sex, race, tumor type, smoking, alcohol usage, and all concomitant medications, as well as creatinine, aspartate aminotransferase, total bilirubin, and anticonvulsant serum levels. Anticonvulsant exposure was determined by the presence of detectable serum levels. Cases of procarbazine hypersensitivity reactions were identified through a review of progress notes. RESULTS: There were 20 patients with procarbazine hypersensitivity reactions. A significant association between the exposure to anticonvulsants and the development of procarbazine hypersensitivity reactions was found (p = 0.05). In addition, there was a significant dose-response association between the development of procarbazine hypersensitivity and the presence of therapeutic anticonvulsant serum levels (p = 0.03). CONCLUSIONS: Concomitant exposure to anticonvulsants is associated with procarbazine hypersensitivity reactions, possibly though a reactive intermediate generated by CYP3A isoform induction. All patients in this cohort received enzyme-inducing anticonvulsants. New anticonvulsants devoid of this property are available. These data support trials that use these newer agents for the prophylaxis of seizures in patients with brain tumors who are to receive procarbazine.

Adult↗
PubMed1996

Can the computerized physical examination differentiate normal subjects from abnormal subjects with benign mechanical low back pain?

Inconsistencies among physicians in the evaluation of benign low back conditions make standardization desirable. A computerized physical examination device was used to evaluate low back pain patients and compare their results with a normative database obtained from a selection of healthy subjects. A high-resolution motion analysis system tracked the movement of skin markers placed on the midline and pelvis. Surface electromyography electrodes placed above L(5) collected data from multifidus. From the kinematics of skin markers during flexion extension with lifts up to 32 kg, and lateral bending with lifts up to 4.6 kg, the following parameters were estimated: lumbosacral angle and elongation, contribution of each lumbar segment to the lordosis reduction, relative pelvic/spine motion and trunk velocity. First, the average normal value for each estimated parameter was determined using 40 normal subjects. For each subject, the difference between his parameter and the normal was processed by an expert system generating a normality index varying from zero (perfect abnormal) to one (perfect normal). To develop the expert system's rules, a preliminary group of 20 very abnormal subjects were used, such that the normality index separated them from the normals. For validation, a set of 29 WCB sprain patients and another set of 42 discogram positive were selected. Each subject was tested and his computerized normality index calculated without any clinicians' input. The computerized normality index was compared with the clinicians' evaluation which was taken to be the gold standard. The Receiver Operating Characteristic technique was used to quantify the discrepancies. Results show that the expert system can detect clinically abnormal subjects with accuracy (sensitivity 83-91% and specificity >/=90%) while providing quantitative information on workers' functional capacities.

Journal Article↗
PubMed1996

Clinical improvement of photoaged skin with 50% glycolic acid. A double-blind vehicle-controlled study.

BACKGROUND: Although there is increasing interest in the use of glycolic acid in the treatment of photoaged skin, to our knowledge, no controlled study has been done to assess the efficacy or the mode of this agent. OBJECTIVE: The purpose of this study was to determine whether 50% glycolic acid can improve photoaged skin and to study the histological basis for this improvement. METHODS: Forty-one volunteers were recruited into this double-blind vehicle-controlled study. Glycolic acid (50%) or vehicle was applied topically for 5 minutes to one side of the face, forearms, and hands, once weekly for 4 weeks. Punch biopsies were taken at pretherapy and at 5 weeks for histologic study. RESULTS: Significant improvement noted included decrease in rough texture and fine wrinkling, fewer solar keratoses, and a slight lightening of solar lentigines. Histology showed thinning of the stratum corneum, granular layer enhancement, and epidermal thickening. Some specimens showed an increase in collagen thickness in the dermis. CONCLUSION: The results of this study demonstrate that the application of 50% glycolic acid peels improves mild photoaging of the skin.

Adult↗
PubMed1995

A database for estimating normal spinal motion derived from noninvasive measurements.

STUDY DESIGN: A database for estimated normal spinal motion was derived using a noninvasive, high-resolution, computer-aided system, which tracks the motion of skin markers strategically placed on the spine. Forty normal subjects, selected from hundreds of possible subjects according to rigorous inclusion/exclusion criteria, were tested on the system. OBJECTIVES: Patterns of estimated spinal motion were analyzed as a function of load, age, and sex, confirming a correlation between the movement of spinal segments and the motion of skin markers. SUMMARY OF BACKGROUND DATA: The Workers Compensation Board of Quebec funded and supervised the experiments necessary to establish a normative reference database for a high-resolution motion analysis system that permits a noninvasive assessment of spinal function. A previous study examined the correlation between the movements of the skin markers and the underlying bony structures for trunk flexion. Skin movement cannot be random and contains information characterizing both the spine and its surrounding soft tissues. METHODS: A noninvasive dynamic imaging system was used to measure normal spinal function under free movement. A high-resolution three-dimensional camera system collected basic kinematic data from strategically placed skin markers over the lumbar spine while the activity of paraspinal muscles was being recorded with surface electromyography. The measurements were analyzed for consistent, specific patterns recognizable as normal lumbar spine skin motion and reflecting normal lumbar spine function. A comparison was made with previous radiographic studies to confirm the correlation between the motion of skin markers and lumbar spine function. RESULTS: Lumbar skin marker motion patterns in normal subjects were consistent and varied little with load; gender had no effect except in the initial phase of a movement. There was less mobility but similar coordination in older subjects. No inconsistencies with previous radiologic investigations were found for sagittal and lateral plane movement.

Adolescent↗
PubMed1993

Examining motion in the cervical spine. I: Imaging systems and measurement techniques.

Instruments for measuring mobility in the cervical spine range from plumb-lines and inclinometers to sophisticated optoelectronic systems. In order to investigate the need and possible uses for an enhancement to a new diagnostic instrument, we examine some of the available diagnostic systems suitable for cervical motion analysis. These should be of practical use in a clinical setting for the diagnosis of soft tissue injuries. We begin by evaluating the respective roles of plain radiographs, cineradiography, computer tomography, and magnetic resonance imaging in examining the cervical spine. Then we consider Moiré photography, inclinometers, and some opto-electronic scanners, as well as the mathematical techniques needed to correlate skin and spine motion with these devices. We find that there does not appear to be an effective non-invasive tool for comprehensive clinical cervical motion analysis; in particular, coupled joint motion is inadequately quantified. Improperly diagnosed cervical spine injuries, such as hyperextension and hyperflexion, may result in chronic long-term effects. Therefore, instrumentation that would permit objective, routine clinical evaluation of patients could help to avoid such situations.

Biomechanical Phenomena↗
PubMed1993

Examining motion in the cervical spine. II: Characterization of coupled joint motion using an opto-electronic device to track skin markers.

Analysis of coupled motion in the cervical spine may be useful in helping to identify injuries. In order to investigate this possibility, the nature of coupled motion in the spine and previous investigations on this subject are reviewed here. An enhanced set of displays are developed for an existing opto-electronic device employed for the non-invasive measurement of movement in the upper spine. This instrument consists of a high resolution motion analysis system which tracks small infrared emitting diodes (IREDs). Kinematic data for the motion of the markers is processed and absolute coordinates for the location of each IRED at any time are tabulated; coupled motion with respect to a fixed calibration frame, as well as for vertebrae relative to each other, is deduced from these. Overall analysis provided by the original device includes assessment of cervical lordosis, thoracic kyphosis, and inter-segmental mobility. Characterization of coupled motion, in particular, involves a series of plots showing principal versus secondary motion. Principal movements include flexion-extension, lateral bending, and axial rotation, corresponding to motion in the sagittal, transverse, and horizontal planes, respectively. Mobility is represented in terms of the direction angles made by virtual vectors orthogonal to the planes made by markers on the head, neck, and shoulders. Development of the enhanced displays and the required refinements are described. Precision of the deduced angles is found to be approximately 1 degree. This representation of coupled motion is expected to be valuable in improving the accuracy of attempts to identify normal versus pathological motion in the cervical spine.

Algorithms↗