Significance of radiation exposure from work-related chest X-rays for epidemiological studies of radiation workers.

BACKGROUND: Previous epidemiologic studies of workers at nuclear weapons facilities have not included X-ray exposures as part of the occupational radiation exposure. The research objective was to determine the contribution of work-related chest X-ray (WRX) exposure relative to the cumulative occupational radiation exposure. METHODS: Cases and controls were identified from a cohort of workers whose employment began as early as 1943. Medical records for 297 subjects were used to determine the bone marrow dose from their X-ray examinations. Individual dose data, however, were only available for 45 workers. Bone marrow dose estimates were calculated by converting the entrance-skin-exposure (from X-ray procedures) and occupational exposure (from monitoring data) to dose. RESULTS: Stereoscopic photofluorography delivered a bone marrow dose nearly 100 times that delivered by today's chest X-ray technique. Photofluorography was the predominant radiation source during the 1940s and 1950s. The cumulative WRX dose was, on average, 50 times their occupational doses. No correlation between occupational and WRX dose was found, but may be due to the small study size and incomplete dose data. CONCLUSIONS: These findings illustrate the importance of including WRX doses in retrospective epidemiological studies of radiation workers, especially if photofluorographic chest X-rays were performed and occupational exposure to ionizing radiation is low.

Clinical application of the Ottawa ankle rules for the use of radiography in acute ankle injuries: an independent site assessment.

OBJECTIVE: Previous studies show that the clinical criteria known as the Ottawa ankle rules (OAR), used for determining the need for radiographs of the ankle when a fracture is suspected, have a sensitivity of 100%, a specificity of 50%, and an overall reduction in radiographs of the ankle of 28%. The purpose of this study was to further assess the clinical usefulness of the OAR when implemented in an emergency department of a level 1 trauma center. SUBJECTS AND METHODS: Over a 1-year period, all patients who were between 18 and 55 years old and who presented to the emergency department with blunt ankle trauma were examined by emergency department clinicians who used the OAR to determine the need for ordering ankle radiographs. RESULTS: Of 926 patients with blunt ankle trauma, 759 met OAR criteria for ordering radiographs of the ankle. Of these patients, 152 were found to have a fracture. Another 167 of the patients were determined not to need ankle radiographs. Through either telephone contact or medical records review. 152 (91%) of these 167 patients were successfully followed up for the purpose of detecting any missed fractures. Two missed fractures were discovered, but only one required plaster immobilization. Based on these numbers, overall sensitivity using the OAR was 99% (confidence interval, 95-100%), and specificity was 22%. We found an overall 16% reduction in the number of ankle films ordered. CONCLUSION: When implemented at a level 1 trauma center, the OAR can adequately screen for ankle fractures.

Muscle fatigue in spinal muscular atrophy.

We previously reported that patients with spinal muscular atrophy do not lose muscle strength over time as measured quantitatively. However, we noted that many patients with spinal muscular atrophy suffer from what they call fatigue. We wondered if we could measure fatigue during a single maximal voluntary contraction, whether fatigue might increase with time, independent of muscle strength, and whether increasing fatigue might correlate with loss of function in some patients. We measured fatigue during a single maximal voluntary contraction in a cohort of patients having spinal muscular atrophy using quantitative strength testing. We included only patients with spinal muscular atrophy aged 5 years or older, so they could follow instructions regarding muscle contraction, and who were followed for at least 2 years. Seventy-six children with spinal muscular atrophy and 24 untrained individuals, aged 5 to 57 years (mean, 16.8 years), were studied. There was no discernible abnormal fatigue in patients with spinal muscular atrophy compared to untrained controls using our methodology. Thus, spinal muscular atrophy may not be associated with fatiguability. Moreover, spinal muscular atrophy does not appear to cause progressive muscle fatigue with age or loss of function. It is possible that fatigue was undetectable by our methods. An alternative explanation is that what patients describe as fatigue may be caused by factors outside the neuromuscular system. Such factors may include chronic respiratory insufficiency with hypoventilation and carbon dioxide retention as well as chronic malnutrition and negative nitrogen balance.

Intercorrelations and sources of variability in three mutagenicity assays: a population-based study.

The purpose of this study was to evaluate the intercorrelation between three genetic assays in 112 subjects. The group was pooled from two originally separate but homogeneous subgroups of 56 persons each. Procedures included assays for hprt mutant frequencies, micronuclei in human lymphocytes, and mutations at the glycophorin A (gpa) loci. We found no statistically significant or biologically important intercorrelations among the three biomarkers. We did, however, observe significant correlations between log(e) hprt mutant frequency and cloning efficiency (inverse correlation for these 2 variables), age and log(e) hprt mutant frequency, an inverse relationship between cloning efficiency and age, and an important differential sex effect favoring a greater micronuclei frequency in females than males. No significant correlations between the covariates of interest and glycophorin A variant frequencies NN or NO were observed. Using multivariable linear regression, age was found to account for the majority of the variability in hprt mutant frequency (greater than sex and/or smoking); for micronuclei data, only sex contributed a statistically significant and biologically important proportion to the total variation. We conclude that despite observing no significant intercorrelations between the three assays performed simultaneously from the same individuals in a large population database, a significant correlation between age and hprt mutant frequency and an inverse association between cloning efficiency and hprt do exist; furthermore, we verified the strong differential sex-specific effect on micronucleus frequencies.

Do persons living near a uranium processing site have evidence of increased somatic cell gene mutations? A first study.

The objective of this study was to examine if individuals living near a uranium processing site have greater mutagenic damage, as measured by three mutagenicity assays, compared with subjects unexposed to any nuclear facilities. The design was a cross-sectional exploratory analysis of 112 subjects; 56 volunteer residents were from within a 5-mile radius of the Fernald Uranium Processing site and 56 'control' subjects were from a geographically separate area unexposed to any known uranium emissions. The groups were constrained to be similar in age and sex composition. The main outcome measures were three human somatic gene mutation assays consisting of the HPRT T-lymphocyte cloning assay to measure 6-thioguanine resistant lymphocytes; the glycophorin A assay to detect the loss of expression of the M or N allele; and the micronucleus assay as a marker of chromosomal damage. The results showed no statistically significant or quantitatively important differences between groups for all three mutagenicity assays; only the unselected cloning efficiency was statistically significantly different between groups (0.42 +/- 0.16 for the Fernald versus 0.35 +/- 0.12 for the comparison groups). In both groups, age was significantly related to HPRT mutant frequency, with a 1.25% rate of increase in mutant frequencies for each 1-year gain of age in the Fernald group and a 1.12% rate of increase in mutant frequencies for each 1-year gain of age in the comparison group. For the micronucleus data, females had a greater mean micronucleus frequency than males. In addition, smokers had an increased mean ln (natural logarithm) HPRT mutant frequency (3.06 +/- 0.14 for current smokers compared with a mean of 2.72 +/- 0.05 for non-current (i.e. never plus former) smokers). Our results are consistent with the previously reported association between sex type and micronucleus frequency, the known relationship between age and T-lymphocyte cloning efficiency and age and HPRT mutant frequency, and verify the wide inter-subject variability for the latter. Finally, we conclude that at a population level, the relationships between current cigarette use and HPRT mutant frequency, and sex type and micronucleus frequency, are stronger than is the association between geographic proximity to a uranium processing site and mutagenic abnormalities.

Duration of antagonistic effects of nalmefene and naloxone in opiate-induced sedation for emergency department procedures.

Naloxone is an effective opiate antagonist, but its short half-life limits its usefulness. For outpatient procedures, a longer acting opiate antagonist could eliminate two to four hours of nursing observation in patients postoperatively. A controlled, randomized, double-blind trial comparing the effects of nalmefene, naloxone, and placebo in reversing opiate-induced sedation was carried out to determine efficacy, duration of action, and adverse effects in patients undergoing outpatient procedures. Each patient received 1.5 to 3.0 mg/kg meperidine intravenously before the procedure. After the procedure, each patient received either nalmefene, 1.0 mg; naloxone, 1.0 mg; or saline, 1.0 mL intravenously. Vital signs and assessments for alertness were performed for four hours. Naloxone significantly reversed sedation for only 15 minutes, whereas nalmefene was significantly effective (P less than .05) for up to 210 minutes. Nalmefene was significantly more effective than naloxone in reversing sedation at 60, 90, and 120 minutes. Nalmefene is an effective agent for the reversal of opiate-induced sedation after outpatient procedures.

The effects of protective equipment on styrene exposure in workers in the reinforced plastics industry.

This study was designed to determine whether styrene absorption through the skin results in measurable changes in biologic indicators of styrene exposure using a group of workers engaged in hand lay-up operations during which extensive styrene skin contact occurs. Serial measurements of expired breath and blood styrene and urinary excretion of mandelic and phenylglyoxylic acid were made in eight female workers during 4 consecutive days using different experimental conditions including either (1) gloves/protective clothing alone, (2) respirator alone, (3) both gloves/protective clothing and respirator, or (4) neither respirator nor gloves/protective clothing. A two-by-two factorial design imbedded in a Latin square design allowed estimation of the effects of the two types of protection (i.e., gloves/clothing and respiratory) and any interaction. Levels of styrene in venous blood and expired breath and urine mandelic and phenylglyoxylic acid excretion were no different when gloves/clothes were used as protection compared to no protection at all. Significant reduction in all biologic indices occurred when respiratory protection was used. The results of the study suggest that percutaneous absorption of styrene is not a significant exposure source and does not significantly contribute to the body burden of styrene of workers in the reinforced plastic industry engaged in hand lay-up operations. Respiratory protective devices were the most effective means for reducing styrene absorption. Even though skin absorption of styrene is limited, skin protection is necessary because of the risk of dermatitis.

New vacuum stethoscope for immediate monitoring and recording of resuscitation of the newborn.

A new, low-cost, noninvasive system is described, which accurately monitors and records both the initial respirations and heart rate of the neonate during resuscitation and the first critical seconds of life. The apparatus consists of a vacuum stethoscope attached to an ordinary cassette tape recorder and a 12-inch loudspeaker. The system was found to be a more accurate tool for assessing neonatal heart rate than the empirical estimation as part of the Apgar scoring system. In 6 of 37 births monitored, recordings indicated discrepancy between the actual heart rate and that estimated in the Apgar scoring system.

On-line computerized data handling system for treating patients with renal disease.

Some patients with renal disease accrue 6,000 to 8,000 individual data items relating to symptoms, signs, laboratory information, and treatment in one year. To deal with the problem of handling so many data items, the following steps were taken: (1) a dictionary of terms peculiar to nephrology was created; (2) manual time-oriented records for nephrology were constructed; and (3) an on-line data processing system, using a PDP-11/70 computer and remote teleprocessing terminal, was developed. On the terminal screen, up to 11 consecutive patient visits can be displayed horizontally, with 18 data items displayed vertically. Up to 30 of the most recent patient visits are easily accessible. For patient treatment, a special feature allows a rearrangement and instantaneous display of any combination of data, thus permitting review of essential feedback relationships between clinical events and treatment.