Biomedical subjects

S E Johnston

Publications and source records attributed to S E Johnston.

7 recordsLinked to original sources

PubMed1995

Using a computerized scheduling system to predict procedure lengths.

To determine the effectiveness of our computerized OR scheduling system and database, we compared scheduled surgical procedure lengths to actual procedure lengths for a large, multispecialty sample (1,103 procedures in 14 surgical subspecialties). We were able to accurately predict procedure lengths, within 15 minutes, 65% of the time. The estimated procedure lengths were more accurate in some surgical subspecialties than others, and four specific factors accounted for a large percentage (ie, 84%) of all delayed start times.

Alabama↗

PubMed1993

Bayesian inference for model-based segmentation of computed radiographs of the hand.

We present a method for medical image understanding by computer that uses model-based, hierarchical Bayesian inference to accurately segment imaged anatomy. A first application is a prototype system that automatically segments and measures symptoms of arthridities in hand radiographs. This is potentially useful in radiological diagnosis and tracking of arthridities. Key steps of the model-based, Bayesian inference approach are: (1) prediction of imagery features from 3D models of anatomy, parameterized by population statistics, (2) local image feature extraction in predicted sub-regions, and (3) the use of a probabilistic calculus to accrue results of image processing and image feature matching procedures in support or denial of hypotheses about the imaged anatomy. The prototype system for hand radiograph analysis accurately segments normal and somewhat degenerated hand anatomy. Results are shown of the ability of the automated system to 'fail soft', recognizing when segmentation is inadequate for accurate measurement. This self evaluation capability improves reliability of measurements for potential clinical use.

Arthritis↗

PubMed1990

Serious unintentional injuries associated with architectural glass.

Injuries associated with architectural glass have become a matter of considerable concern in recent years. Despite this concern there has been no attempt to document either the extent of the problem in New Zealand or the circumstances under which these events occur. In this study, national injury mortality data for the period 1977-86 were examined and cases selected if the cause of death was attributable to an event involving architectural glass. A total of nine deaths were identified. All discharges from New Zealand public hospitals during 1986 were examined to identify victims who had been treated for injuries associated with architectural glass. Descriptive information contained on each patient record was coded to provide more specific information on the circumstances of injury. A total of 501 first admissions to hospital were identified, giving an incidence rate of 15 per 100,000 persons per year. The highest rate of 60 per 100,000 per year, was found for males in the age group 15-24 years. Seventy-eight percent of the events involved males, 62% occurred at home, 64% involved windows, and 32% involved doors. Ninety-three percent of the injuries were open wounds. Seventy-nine percent of the injuries were to the upper limbs, 13% were to lower limbs and 5% were to the head. The mean length of stay in hospital was 3.3 days. Opportunities for injury prevention are discussed including visual and physical barriers, mandatory glazing standards and public education. Specific areas requiring further research are identified.

Accident Prevention↗

PubMed1990

Purposely self-inflicted injury resulting in death and hospitalisation in New Zealand.

Purposely self-inflicted injury is the second most common cause of injury death in New Zealand and is also a major cause of hospitalisation. Despite the significance of the problem there has been relatively little research undertaken in New Zealand. Injury mortality and morbidity data files for 1984 were examined and upgraded to provide as comprehensive an overview of this injury problem as the data would permit. The results show that the fatality rate was highest amongst the elderly, and males had higher death rates than females for all ages. In contrast to this, hospitalisation rates peaked among the 15-20 year olds and females had higher rates than males for all ages. Whereas Maori had a significantly lower fatality rate than non-Maori the converse was the case for hospitalisation. A more consistent effect occurred for marital status, the married group had significantly lower fatality and hospitalisation rates than the non-married group. The major occupational group "production, transport and labourers" had the highest mortality rate, whereas service workers, in particular house staff, had the highest rate of morbidity. Whereas hanging was the most common method (33%) used in fatal injury events, poisoning was the most common method (91%) used for those events which resulted in hospitalisation. In the latter case, psychotropic agents, in particular tranquillisers, accounted for 50 per cent of all poisoning. These data show that mortality experience is not a reliable guide to injury morbidity experience. Prevention is discussed in the context of limiting the availability and lethality of agents.

Cause of Death↗

PubMed1984

Tizanidine (DS103-282), a centrally acting muscle relaxant, selectively depresses excitation of feline dorsal horn neurones to noxious peripheral stimuli by an action at alpha 2-adrenoceptors.

The effects of microiontophoretic ejection of tizanidine were compared with those of adrenoceptor agonists on responses of single laminae IV and V neurones to noxious and innocuous cutaneous stimuli. Tizanidine, noradrenaline and clonidine depressed neuronal responses to noxious but not innocuous stimuli. Spontaneous activity was also depressed by these three substances. By contrast, beta- and alpha 1-adrenoceptor agonists had no consistent effect on neuronal responses to cutaneous stimuli. The selective actions of tizanidine, noradrenaline and clonidine were reversibly antagonized by the alpha 2-adrenoceptor antagonist RX781094 but not by WB4101 (alpha 1 antagonist). The binding of an alpha 2-adrenoceptor ligand to rat brain membranes was preferentially displaced by tizanidine. These results indicate an interaction of tizanidine with central alpha 2-adrenoceptors.

Animals↗

PubMed1984

Selective antinociceptive effects of tizanidine (DS 103-282), a centrally acting muscle relaxant, on dorsal horn neurones in the feline spinal cord.

The effects of the centrally acting muscle relaxant tizanidine (DS 103-282) have been examined on the responses of laminae IV and V dorsal horn neurones to peripheral noxious and non-noxious stimuli in cats spinalized at L1. Iontophoretic ejection of tizanidine near the cell bodies of the recorded neurones or more dorsally into laminae II-III resulted in a marked and prolonged depression of excitation of laminae IV and V neurones evoked by noxious stimuli. Spontaneous firing was also depressed in many neurons but responses to innocuous stimuli were unaffected. Intravenous administration of tizanidine also produced a long lasting and selective reduction in responses of laminae IV and V neurones to noxious stimuli and depressed the long latency excitation of these neurones evoked by electrical stimulation of small diameter unmyelinated primary afferents. In contrast to the selective antinociceptive effect of tizanidine, ejection of gamma-aminobutyric acid (GABA) near laminae IV and V neurones or isoguvacine into laminae II-III produced parallel reductions in responses to noxious and non-noxious stimuli. Furthermore, ejections of the excitant amino acid kainate into laminae II-III produced parallel enhancement of responses induced by both types of stimuli. The site and mechanism of the antinociceptive action of tizanidine is not known but does not appear to involve an interaction with opiate receptors as it was not antagonized by naloxone. The possibility is discussed that tizanidine acts at synapses formed between excitatory interneurones in lamina II or III and laminae IV and V neurones, either interfering with transmitter release or its postsynaptic action. The effects of iontophoretically administered tizanidine are quite distinct from those of baclofen, which produced non-selective depression of responses to both noxious and innocuous stimuli, but were similar to those of noradrenaline. This raises the possibility that noradrenaline and tizanidine may act at a common site in the spinal cord.

Amino Acids↗

PubMed1981

Descending inhibitions from the nucleus raphe magnus and adjacent reticular formation to the dorsal horn of the rat are not antagonized by bicuculline or strychnine.

The effects of iontophoretically applied bicuculline and strychnine on brainstem-and segmental-evoked inhibitions of dorsal horn cells have been examined in the rat. Both antagonists failed to reduce the descending inhibitory influences at concentrations which selectively blocked responses to GABA or glycine and segmentally-derived inhibitions of the same neurones. These results suggest that neither GABA nor glycine is involved in brainstem inhibition of rat dorsal horn cells.

Animals↗