Biomedical subjects

C B Johnson

Publications and source records attributed to C B Johnson.

60 records · Page 4Linked to original sources

PubMedDate not supplied

Effects of alfentanil on the equine electroencephalogram during anaesthesia with halothane in oxygen.

Opioids have variable effects on the minimum alveolar concentration of inhaled anaesthetics in the horse. During halothane anaesthesia at an end-tidal halothane concentration between 0.75 and 0.85 percent, the electroencephalogram (EEG) frequency power spectrum and the auditory evoked potential were recorded continuously in eight ponies during an infusion of approximately 40 micrograms kg-1 alfentanil over five minutes, and for a further 55 minutes. The spectral edge and median frequency of the EEG and the mid-latency of the auditory evoked potential at the time of maximum change of these variables were compared with those recorded before the start of the infusion. The mean (SD) spectral edge and median frequencies were reduced by 26 (5) percent and 36 (6) percent respectively. The mid-latency of the auditory evoked potential did not change. These cortical effects of alfentanil in the horse are qualitatively the same as in other species, suggesting that the alfentanil-induced excitement observed in horses in not of cortical origin.

Alfentanil↗

PubMedDate not supplied

Barriers to accessing hospice services before a late terminal stage.

Although hospice care has been available in the United States for over 25 years, the trend of late terminal access persists. Quality assessments and interventions that will continue through a year of bereavement are based on early interactions and the formation of caring and trusting bonds. A qualitative research study was conducted to identify and describe barriers to timely access as perceived by those involved in hospice care: caregivers, hospice staff and volunteers, and referring physicians. Major findings include persistent knowledge deficits including misconceptions and lack of awareness of components and skill associated with hospice care: reluctance to disclose, discuss, or acknowledge patient terminality, and access of hospice care being perceived as giving up on the patient.

Health Services Accessibility↗

PubMedDate not supplied

Effects of ketamine on the equine electroencephalogram during anesthesia with halothane in oxygen.

OBJECTIVE: To investigate the effects of ketamine on the electroencephalogram (EEG) of the horse. STUDY DESIGN: Prospective experimental study. ANIMALS: Eight Welsh mountain pony geldings weighing between 280 and 330 kg, 5 to 9 years old. METHODS: During halothane anesthesia at an end-tidal halothane concentration between 0.75 and 0.85%, the EEG frequency power spectrum and the auditory evoked potential were recorded while an infusion of ketamine was given. Ketamine 200 mg was infused over 5 minutes in 8 ponies. The effects of ketamine on the EEG were recorded continuously during the infusion and for a further 55 minutes. RESULTS: The ketamine infusion produced a plasma ketamine concentration that was significantly greater than the baseline until 7 minutes after the start of the infusion. The highest recorded ketamine concentration was 4.2+/-1.1 microg/ml recorded at 5 minutes after the start of the infusion. The spectral edge and median frequency of the EEG and the midlatency of the auditory evoked potential were compared with those recorded before the start of the infusion. The spectral edge, median frequencies and mid-latency of the auditory evoked potential were reduced by 21+/-13%, 31+/-20% and 19+/-36% respectively (mean +/- SD). Only the reduction in spectral edge frequency reached statistical significance. CONCLUSIONS: These results compared with those from other anesthetic and sedative agents suggest that the spectral edge frequency is an indicator of general central nervous system depression whereas the median frequency may be an indicator of antinociception.

Anesthesia↗

PubMedDate not supplied

Spatial extrapolation of soil characteristics using whole-soil particle size distributions.

Soils support ecosystem functions such as plant growth and water quality because of certain physical, chemical, and biological properties. These properties have been studied at different spatial scales, including point scales to satisfy basic research needs, and regional scales to satisfy monitoring needs. Recently, soil property data for the entire USA have become available in the State Soil Geographic Data Base (STATSGO), which is appropriate for regional-scale research. We analyzed and created models of STATSGO data in this study to serve as a research tool, for example, for linking the soil to regional water quality monitoring data in our companion paper. Map units in STATSGO define geographic land areas by soil characteristics (SCs) of similar soil series. We selected 27 SCs that influenced water properties (in varying degrees), aggregated the layer and component SCs to map unit SCs, and used SCs to calculate relationships among map units. The relationships were defined by equations of conditional mean for the qth SC (SCq), while using the remaining 26 SCs as predictors. The relative standard errors for 22 of the 27 SCs were less than 10%, and less than 22% for the remaining five. We conclude that spatial extrapolation of SCs is feasible and the procedures are a first step toward extrapolating information across a region using SC-water property relationships. Although our procedure is for regional scale monitoring, it is also applicable to finer spatial scales commensurate with available soil data.

Ecosystem↗

PubMedDate not supplied

Predicting physical and chemical water properties from relationships with watershed soil characteristics.

The Surface Waters component of the Environmental Monitoring and Assessment Program (EMAPSW) was developed by the USEPA to evaluate the extent and condition of lakes and streams over national and regional scales. Realistically, chemical or physical water properties (WPs) such as acidity or turbidity can be field-sampled for only a small portion of all lakes and streams. However, soil characteristics (SCs) affect WPs and broad-scale soil survey data have become available in the State Soil Geographic Data Base (STATSGO). We developed models relating observed WPs to SCs to extrapolate the sampled WPs to a region, potentially reducing extensive monitoring needs. Our study region consisted of 13 northeastern and Mid-Atlantic states and contained 882 STATSGO soil map units. We used map units as the spatial component of WP analysis. The WPs were sampled in 721 randomly selected EMAPSW study sites. The watersheds of these sites represent 7.1% of the region's total area and spatially intersect 400 of its soil map units. Each intersected map unit was assigned the weighted average WPs from the corresponding watersheds. Conditional expectation models were used to extrapolate sampled WPs to 882 map units. The relative standard errors ranged from low for pH (0.8%), intermediate for total P (12.1%), and very high for chloride (54.8%). The high extrapolation errors indicate outlier conditions from natural, non-soil, or anthropogenic sources.

Ecosystem↗

PubMedDate not supplied

Reese Osteotomy Guide System.

This paper has been developed to provide surgeons with a new technique called the Reese Osteotomy Guide System. This technique allows surgeons to perform and determine osteotomies with more precision, resulting in better bone healing, greater stability, and more predictable results.

Biomechanical Phenomena↗