High risk infusions--accuracy compromised by changes in patient venous pressure.

Intensive care often requires the simultaneous administration of high potency short half-life intravenous drugs. Numerous reported instances of unwanted transient flow characteristics such as bolus flow, slow start-up at set rate and fluid reflux-where fluid is found to flow away from the infusion site-have indicated a need for better understanding of the system dynamic. This article introduces a simple mathematical model of an infusion pump system, highlighting system mechanical compliance as a major contributory factor for flow error. The model is verified as correctly predicting flow variation caused by pump height change and is offered as an aid in the development of more accurate infusion devices. The accurate delivery of low flow rates requires small volume rigid components. This study also suggests that the current design of syringe infusion devices makes them susceptible to flow error caused by change in patient venous pressure.

Use of styrene radical cations as probes for the complexation dynamics of charged guests with alpha- and beta-cyclodextrins.

The complexation dynamics of radical cations with cyclodextrins (CD) was studied using photophysical techniques. Radical cations of 4-vinylanisole and trans-anethole were formed within alpha- and beta-CD cavities by two-photon photolysis of the respective styrene precursors. Exit of the radical cations from alpha-CD complexes with 1: 1 and 1:2 (guest: CD) stoichiometries and beta-CD complexes with 1:1 stoichiometries occurred with lifetimes shorter than 100 ns. Most of the radical cations formed escape from the CD cavities, but a small portion do react with alpha-CD when this host is present in high concentrations.

Issues associated with the design of a national probability sample for human exposure assessment.

Data obtained from national probability sample surveys provide important information on the prevalence of various health conditions and distributions of physical and biochemical characteristics of the U.S. population. The sample design of a survey specifies how sampling from a designated population over a stated period is to be accomplished. A survey's analytical objectives and interests--in particular subpopulations--affect the sample design strategy. Selected subdomains of the population often must be oversampled so that estimates can be made with acceptable precision. This article addresses sample design considerations for a national probability sample for human tissue monitoring and specimen banking. Among the sampling issues addressed are the oversampling of special populations e.g., minority groups and at-risk groups such as low income or elderly persons; geographic coverage; and sample size considerations. The sample design for a major health survey, the Third National Health and Nutrition Examination Survey (NHANES III), is used to illustrate a complex, multistage probability sample design and to highlight some of the sampling issues discussed in this article.

The seroepidemiology of human immunodeficiency virus in the United States household population: NHANES III, 1988-1991.

To provide an estimate of the seroprevalence of human immunodeficiency virus (HIV) in a representative sample of the U.S. household population, serum samples from participants in the third National Health and Nutrition Examination Survey (NHANES III) were tested for HIV antibody. The testing was performed anonymously on 5,430 individuals 18-59 years old from phase 1 of NHANES III conducted from 1988 to 1991. Twenty-nine individuals were HIV positive. The total weighted prevalence was 0.39%. The population estimate of infected individuals was 547,000, with a 95% confidence interval of 299,000-1,020,000 infected persons. Black participants were four times more likely to be HIV positive than white/other individuals and three times more likely than Mexican Americans. Men were three times more likely to be infected than women. Higher nonresponse to the survey and to phlebotomy was observed in young white men; therefore these data provide a conservative estimate of HIV infection in the general household population. This estimate does not include individuals who do not live in households and who may be at higher risk of infection, such as persons in penal institutions, the homeless, or certain hospitalized patients.

Use of exposure databases for status and trends analysis.

Exposure databases are useful for monitoring status and trends in environmental health. However, other supporting data are usually needed to infer human exposure or internal dose. Program planning and evaluation, environmental health surveillance, epidemiologic research, and contributions to international efforts are four major purposes for monitoring environmental exposure status and trends. Although databases play an important role in monitoring human exposure, certain methodological problems need to be overcome. The work group developed six criteria for meeting information needs for human exposure assessment. Areas that need attention are (1) specification of location, (2) specification of facility and chemical identifiers, (3) documentation of special populations at risk, (4) provision of early warning of new problems, (5) monitoring changes over time, and (6) enhancement of documentation. We tested these criteria by examining six available databases that might be used for monitoring exposure to contaminants in drinking water. Available data fell short of information needs. We drew four conclusions and offered several recommendations for each. First, available data systems lack adequate measures of human exposure. Second, data for monitoring exposures for many important population subgroups and environmental settings are inadequate. Third, an "early warning" system that monitors human exposures is needed. Fourth, designers of data-collection systems should consider the needs of users who monitor status and trends of human exposure.

Selected pesticide residues and metabolites in urine from a survey of the U.S. general population.

Residues of toxic chemicals in human tissues and fluids can be important indicators of exposure. Urine collected from a subsample of the second National Health and Nutrition Examination Survey was analyzed for organochlorine, organophosphorus, and chlorophenoxy pesticides or their metabolites. Urine concentration was also measured. The most frequently occurring residue in urine was pentachlorophenol (PCP), found in quantifiable concentrations in 71.6% of the general population with an estimated geometric mean level of 6.3 ng/ml. Percent quantifiable levels of PCP were found to be highest among males. Quantifiable concentrations of 3,5,6-trichloro-2-pyridinol (5.8%), 2,4,5-trichlorophenol (3.4%), para-nitrophenol (2.4%), dicamba (1.4%), malathion dicarboxylic acid (0.5%), malathion alpha-monocarboxylic acid (1.1%), and 2,4-D (0.3%) were found, but at much lower frequencies. No quantifiable levels of 2,4,5-T or silvex were found. Preliminary analyses showed an apparent relationship between residue concentration and two measures of urine concentration (osmolality and creatinine). A large segment of the general population of the United States experienced exposure to certain pesticides, including some considered biodegradable, during the years 1976-1980.

Impaired glucose tolerance in women using oral contraceptives: United States, 1976-1980.

Based on 75-g oral glucose tolerance test results from the second National Health and Nutrition Examination Survey (1976-1980), women 20-44 years reporting the use of oral contraceptives (OCs) had decreased glucose tolerance compared with women not using OCs in this age group. Estimates of decreased glucose tolerance after adjustment for age and body mass index were 15.4% (95% CI, 7.6-23.2%) in OC users vs 6.3% (95% CI, 4.5-8.1%) in nonusers. Oral contraceptive use was associated with elevations in 1 and 2 hour plasma glucose concentrations. The mean adjusted difference between OC users and nonusers at 1 and at 2 hours postchallenge was 14 and 13 mg/100 ml, respectively. Characteristics of study nonrespondents vs respondents were analyzed to estimate potential bias due to nonresponse. No appreciable biases were found, but this does not rule out the possibility that some bias may exist.

Cardiovascular risk status and oral contraceptive use: United States, 1976-1980.

Data from the second National Health and Nutrition Examination Survey, conducted in 1976-1980, were analyzed for the prevalence of cardiovascular risk factors (cigarette smoking, serum cholesterol, and blood pressure) among 2,342 premenopausal women ages 20-44 years, stratified by oral contraceptive use. For oral contraceptive users and non-users, adjusted means were serum cholesterol, 205 vs 188 mg/dl (P less than 0.05); systolic blood pressure, 116 vs 113 mm Hg (P less than 0.01); and diastolic blood pressure, 74 vs 73 mm Hg (NS). The prevalence of cigarette smoking was significantly higher among oral contraceptive users (44% compared with 36% among nonusers; P less than 0.05). Using the 1984 NIH Consensus Development Conference Statement on Lowering Blood Cholesterol to define risk levels for serum cholesterol, 23% of the oral contraceptive users were at high risk compared with 12% of the nonusers, and 16% of the oral contraceptive users vs 11% of the nonusers were at moderate risk. For users and nonusers, the respective prevalence of a blood pressure at or above 140/90 mm Hg was 5.3% vs 8.8% (unadjusted) and 8.6% vs 8.0% (age adjusted). The percentage of women with multiple risk factors was also higher among oral contraceptive user; 14% of the users had two or more risk factors vs 7% of the nonusers (P less than 0.05). These cross-sectional national data support data from clinical studies regarding the effect of oral contraceptives on cholesterol and blood pressure levels. In addition, since the use of oral contraceptives is widespread in the population and users tend to see physicians more regularly than other women, the data suggest that users of the pill are a good target group among which to screen and monitor cardiovascular risk factors.

Selected pesticide residues or metabolites in blood and urine specimens from a general population survey.

The National Center for Health Statistics collaborated with the National Human Monitoring Program of the U.S. Environmental Protection Agency (EPA) in a four-year study to assess the exposure of the general population to selected pesticides through analysis of blood serum and urine specimens. Specimens were collected on a national probability half sample of persons 12-74 years of age from 64 locations across the United States comprising the sample areas in the Second Health and Nutrition Examination Survey (NHANES II) and analyzed for selected organochlorine, carbamate, chlorophenoxy and organophosphorus pesticides. Medical, nutritional and pesticide usage data are also available for each sample person. Preliminary results of the blood serum and urine analyses indicate that the general population is being exposed to some of these types of pesticides. Since 1970, EPA has conducted a national probability sampling of human adipose tissue. Specimens obtained on a survey design representative of the general population were analyzed for selected organochlorine pesticides and toxic chemicals. Findings from the 1978 survey also indicate exposure of the general population to some of these chemicals. Medical data collected from both surveys have yielded no overt correlations between health effects and residue levels. More intensive statistical analyses are underway to investigate the possible existence of more subtle relationships.

National estimates of blood lead levels: United States, 1976-1980: association with selected demographic and socioeconomic factors.

Data from the second National Health Nutrition Examination Survey showed that 22 per cent of persons six months through 75 years old had blood lead levels under 10 micrograms per deciliter; 1.9 per cent had elevated levels (greater than or equal to 30 micrograms per deciliter [greater than or equal to 1.45 mumol per liter]). Among children six months through five years old the prevalence of elevated levels was significantly higher (4 per cent) than previously predicted on the basis of fewer data. The prevalence of elevated lead levels was 12.2 per cent in black children and 2.0 per cent in white children. Mean levels of blood lead were higher in blacks than white among children and adults, among young children living in urban and rural areas, and among members of low-income, moderate-income, and higher-income families. These racial contrasts may reflect different lead exposure or absorption (or both). Young children from families (both white and black) whose incomes were under $6,000 had a significantly higher prevalence of elevated lead levels than those from households with incomes of $6,000 or more.