Prevalence and relatedness of Escherichia coli O157:H7 strains in the feces and on the hides and carcasses of U.S. meat goats at slaughter.

We determined the prevalences of Escherichia coli O157:H7 in feces, hide, and carcasses of meat goats at a U.S. processing plant. Prevalences were 11.1%, 2.7%, and 2.7%, respectively. Sixteen pulsed-field gel electrophoresis (PFGE) subtypes were identified among 49 E. coli O157:H7 isolates, some of which were present on multiple sample types or collection days.

Film dosimetry for fluoroscopic procedures: potential errors.

Kodak EDR 2 film was calibrated across the range of beam qualities and exposure rates typically used in our cardiac catheterisation laboratory. Its dose-response curve was successfully modelled up to its saturation point of 1 Gy. The consistency of the film's response with film batch, time between exposure and processing processor and day-to-day variations in performance, was investigated. The effects of field size, exposure rate, beam quality and use of the dynamic wedge filter were quantified. The overall uncertainty in dose was estimated to be between -20% and +40%, at 160 mGy. This uncertainty increases as the film approaches its saturation point. In addition, some unusual artefacts were observed.

Pharmacological properties of kryptopyrrole and its oxidation products on isolated sciatic nerve of rat and on guinea-pig ileum.

1 Kryptopyrrole (2, 4-dimethyl, 3-ethylpyrrole) inhibited conduction in rat sciatic nerve by a local anaesthetic action. 2 Tone and both spontaneous and electrically-induced contractions of guinea-pig ileum were also inhibited by kryptopyrrole. The concentration of kryptopyrrole required for 50% inhibition of a maximum twitch tension (ID50) was 0.085 mM. 3 Oxidation products of kryptopyrrole with chromatographic properties similar to those of urinary constituents reported in schizophrenia and hepatic porphyrias had little or no effect at similar concentrations. 4 Dose-response curves to exogenous acetylcholine in guinea-pig ileum were shifted to the right by kryptopyrrole, with loss of parallelism and reduction in the maximum contraction. 5 Acetylcholine overflow from ileal segments at rest and during electrical stimulation was reduced by kryptopyrrole. 6 These results on ileal segments are consistent with kryptopyrrole having both a post-junctional site of action, presumably directly on the muscle, and a pre-junctional site reducing the output of acetylcholine from the myenteric plexus. 7 The significance of these findings is discussed in relation to a possible clinical pathological role for these compounds.

Models for investigating the aetiology of cerebral arterial spasm: comparative responses of the human basilar artery with rat colon, anococcygeus, stomach fundus, and aorta and guinea-pig ileum and colon.

1 The pharmacological similarity between human basilar artery and a number of isolated tissues (rat colon, anococcygeus, stomach fundus and aorta and guinea-pig ileum and colon) has been assessed during investigations of the aetiology of cerebral arterial spasm. 2 The responses of each of the six tissues to human normal and abnormal cerebrospinal fluid (CSF) and to human serum were compared with those of the human isolated basilar artery. 3 These studies revealed the presence of a vasodilator factor in CSF from subarachnoid haemorrhage patients and several tissues may be of use for further work in identifying the vasoactive substances in CSF. 4 No tissue displayed exactly the same spectrum of biological reactivity as the human basilar artery. The rat stomach fundus showed the closest similarity and was further studied for similarities in drug-induced responses. 5 The rat stomach fundus, like the human basilar artery, was contracted by 5-hydroxytryptamine, prostaglandin F2alpha and histamine and relaxed by dopamine. However, noradrenaline relaxed the fundus but contracted the basilar artery.

Regional cerebrovascular reactivity to carbon dioxide during cardiopulmonary bypass in patients with cerebrovascular disease.

In patients with cerebrovascular disease, hypercarbia may cause redistribution of regional cerebral blood flow from marginally perfused to well-perfused regions (intracerebral steal), as evidenced by regional cerebral blood flow studies during carotid endarterectomy. During hypothermic cardiopulmonary bypass, the pH-stat method of acid-base management produces relative hypercarbia. To determine whether pH-stat management produces relative hypercarbia. To determine whether pH-stat management induces intracerebral steals, we investigated nine patients with cerebrovascular disease undergoing coronary artery bypass grafting. During hypothermic cardiopulmonary bypass, arterial carbon dioxide tension was varied in random order between 40 mm Hg and 60 mm Hg (uncorrected for body temperature). Regional cerebral blood flow was measured by clearance of 133 xenon injected into the arterial inflow cannula. Nasopharyngeal temperature (26.8 degrees-28.0 degrees +/- 2.2 degrees-3.0 degrees C), perfusion flow rate (2.14-2.18 +/- 0.70-0.73 L/min/m2), mean arterial pressure (67-68 +/- 6-9 mm Hg), arterial carbon dioxide tension (302-308 +/- 109-113 mm Hg), and hematocrit (23% +/- 4%) were maintained within narrow limits in each patient during arterial carbon dioxide tension manipulation. Global mean cerebral blood flow values were similar to previously reported values in patients free of cerebrovascular disease; patients in this study averaged 15.2 +/- 2.5 ml/100 gm/min at an arterial carbon dioxide tension of 46.1 +/- 8.4 mm Hg and 25.3 +/- 6.1 ml/100 gm/min at an arterial carbon dioxide tension of 71.1 +/- 11.8 mm Hg. Carbon dioxide reactivity, defined as mean global cerebral blood flow (in ml/100 gm/min) divided by arterial carbon dioxide tension (in mm Hg), was similar in the region having the lowest regional cerebral blood flow and in the brain as a whole. No patient developed evidence of an intracerebral steal at the higher arterial carbon dioxide tension. During hypothermic cardiopulmonary bypass, higher levels of arterial carbon dioxide tension, such as those associated with the pH-stat management technique, are apparently not associated with potentially harmful redistribution of cerebral blood flow in patients with cerebrovascular disease.

Cerebrovascular and cerebral metabolic effects of alterations in perfusion flow rate during hypothermic cardiopulmonary bypass in man.

Recent experimental and clinical investigations provide conflicting evidence regarding the effects of changes in the systemic flow rate from the pump oxygenator on cerebral blood flow and the cerebral metabolic rate of oxygen consumption. However, the results of existing clinical studies are difficult to interpret because of the confounding effects of differences in management of arterial carbon dioxide tension and use of anesthetic and vasoactive agents during cardiopulmonary bypass. To clarify the relationship among perfusion flow rate, cerebral blood flow, and cerebral metabolic rate of oxygen consumption in man during hypothermic cardiopulmonary bypass, we varied perfusion flow rate in random order to either 1.75 or 2.25 L.min-1.m-2 and studied cerebral blood flow (measured by clearance of xenon 133) and cerebral metabolic rate of oxygen consumption (estimated as the product of cerebral blood flow and the cerebral arteriovenous oxygen content difference) in patients managed with both the alpha-stat (group 1) and the pH-stat (group 2) methods of pH and arterial carbon dioxide tension adjustment. We measured the cerebral arteriovenous oxygen content difference using radial arterial and jugular venous bulb blood samples. In each patient other variables known to exert effects on cerebral blood flow and cerebral metabolic rate of oxygen consumption, including temperature, arterial carbon dioxide tension, arterial oxygen tension, mean arterial pressure, and hematocrit, were maintained constant between measurements. In both groups, mean arterial pressure at both pump flow rates was similar because of spontaneous reciprocal alterations in systemic vascular resistance, that is, as perfusion flow rate declined, systemic vascular resistance increased; as perfusion flow rate increased, systemic vascular resistance declined. Under these tightly controlled conditions, pump flow variation per se exerted no effect on cerebral blood flow or cerebral metabolic rate of oxygen consumption in either group.

Heparin dosing and monitoring for cardiopulmonary bypass. A comparison of techniques with measurement of subclinical plasma coagulation.

Subclinical plasma coagulation during cardiopulmonary bypass has been associated with marked platelet and clotting factor consumption in monkeys. To better define subclinical coagulation in man, we measured plasma fibrinopeptide A concentrations before, during, and after cardiopulmonary bypass. Patients were assigned to one of three groups of heparin management: group 1 (n = 10)--initial heparin dose 300 IU/kg, with supplemental heparin if the activated coagulation time fell below 400 seconds; group 2 (n = 6)--initial heparin dose 250 IU/kg, with supplemental heparin if activated coagulation time was less than 400 seconds; and group 3 (n = 5)--initial heparin dose 350 to 400 IU/kg, with supplemental heparin if whole blood heparin concentration was less than or equal to 4.1 IU/ml. Activated coagulation time and heparin concentration were measured every 30 minutes during cardiopulmonary bypass, and fibrinopeptide A was measured at hypothermia, normothermia, and whenever activated coagulation time was less than 400 seconds. Quantitative and qualitative blood clotting competence was assessed after cardiopulmonary bypass, including mediastinal drainage for the first 24 hours. Fibrinopeptide A values were markedly elevated during cardiopulmonary bypass but were well below the levels present before and after cardiopulmonary bypass. Fibrinopeptide A correlated inversely with heparin concentration during cardiopulmonary bypass (r = -0.46, p = 0.03), but higher fibrinopeptide A levels during cardiopulmonary bypass did not correlate with post-cardiopulmonary bypass coagulopathy. Group 3 patients received the highest heparin doses (p less than 0.05) and had the greatest postoperative blood loss (p less than 0.05). Protamine dose and heparin concentration during cardiopulmonary bypass correlated best with postoperative mediastinal drainage. Our findings support the following conclusions: (1) compensated subclinical plasma coagulation activity occurs during cardiopulmonary bypass despite activated coagulation time greater than 400 seconds or heparin concentration greater than or equal to 4.1 IU/ml; (2) post-cardiopulmonary bypass mediastinal drainage correlates strongly with increased heparin concentration during cardiopulmonary bypass (p less than 0.05) and protamine dose (p less than 0.05); and (3) during cardiopulmonary bypass at both normothermia and hypothermia, activated coagulation times greater than 350 seconds result in acceptable fibrinopeptide A levels and post-cardiopulmonary bypass blood clotting.

Development of a neuronal pressure sensor.

Neuronal sensory systems are capable of performing very complex signal processing functions. Reconstruction of such sensory systems in vitro should enable whole-cell biological sensors to be generated that possess inherent signal processing capabilities. In this paper, the results of preliminary investigations to produce a mechanosensory neuronal network are presented. An in vitro network of rat dorsal root ganglion neurons has been produced on a microelectrode plate revealing an interesting rhythmical pattern of spontaneous discharges. This periodic activity has been shown to be disrupted following the application of a static pressure to the cell culture. These results indicate that neuronal networks represent a practical system that may be used for the development of intelligent, whole-cell, biological sensors.

Intraoperative use of dual-chamber demand pacemakers for open heart operations.

The availability of external atrioventricular sequential pacemakers has improved the management of patients with sinus bradycardia, junctional rhythm, and atrioventricular block. However, these pacemakers are of less value in patients with postoperative heart block and accelerated atrial rhythms. The temporary use of a modified explanted dual-chamber demand pacemaker may counteract that problem by providing atrially triggered, P-wave-synchronous ventricular pacing. We report 2 patients in whom the temporary use of the dual-chamber demand pacemaker greatly facilitated weaning from cardiopulmonary bypass after coronary artery bypass grafting.

Risk factors and solutions for the development of neurobehavioral changes after coronary artery bypass grafting.

BACKGROUND: As operative mortality for coronary artery bypass grafting has decreased, greater attention has focused on neurobehavioral complications of coronary artery bypass grafting and cardiopulmonary bypass. METHODS: To assess risk factors and to evaluate changes in surgical technique, between 1991 and 1994 we evaluated 395 patients undergoing coronary artery bypass grafting with an 11-part neurobehavioral battery administered preoperatively and at 1 and 6 weeks postoperatively. Patients were instrumented with 5-MHz focused continuous-wave carotid Doppler transducers intraoperatively to estimate cerebral microembolism as an instantaneous perturbation of the velocity signal. Microembolism data were quantitated and compared with surgical technical maneuvers during operation and with neurobehavioral deficit (> or = 20% decline from preoperative performance on two or more neurobehavioral tests) postoperatively. These data and patient demographics were statistically analyzed (chi2, t test) and the results at 2 years (1991 and 1992; group A) were used to influence surgical technique in 1993 and 1994 (group B). RESULTS: Significantly associated with new neurobehavioral deficits were increasing patient age (p < 0.05), more than 100 emboli per case (p < 0.04), and palpable aortic plaque (p < 0.02). Group B patients had a significant decline in the neurobehavioral event rate (group A, 69%, 140/203; versus group B, 60%, 115/192; p < 0.05) of postoperative neurobehavioral deficits at 1 week and at 1 month (group A, 29%, 52/180; versus group B, 18%, 35/198; p < 0.01). The stroke rate was less than 2% in both groups (p = not significant). Modifications of surgical technique used in group B patients included increased use of single cross-clamp technique, increased venting of the left ventricle, and application of transesophageal and epiaortic ultrasound scanning to locate and avoid trauma to aortic atherosclerotic plaques. CONCLUSIONS: Neurobehavioral changes after coronary artery bypass grafting are common and associated with cerebral microembolization. Surgical technical maneuvers designed to reduce emboli production may improve neurobehavioral outcome.

alpha-Bungarotoxin binding sites in rat hippocampal and cortical cultures: initial characterisation, colocalisation with alpha 7 subunits and up-regulation by chronic nicotine treatment.

High density neuronal cultures from rat E18 hippocampus and cortex have been characterised with respect to cholinergic binding sites. No specific binding of [3H]nicotine or [3H]cytisine to live cells in situ was detected although the limit for detection was estimated to be 30 fmol/mg protein. Muscarinic binding sites labelled with [3H]QNB were present at a density of 0.75 pmol/mg protein. [125I]alpha-Bungarotoxin (alpha Bgt) bound to hippocampal cultures with a Bmax of 128 fmol/mg protein and a Kd of 0.6 nM; cortical cultures expressed five times fewer [125I]alpha-Bgt binding sites. Fluorescence cytochemistry with rhodamine-alpha-Bgt indicated that 95% of hippocampal neurons were labelled, compared with only 36% of cortical neurons. Average densities of 4 x 10(4) and 2 x 10(4) binding sites/cell were calculated for hippocampal and cortical cultures, respectively. Double labelling experiments with mAb307 (which recognises the rat alpha 7 nicotinic receptor subunit) and rhodamine-alpha-Bgt gave coincident labelling patterns, supporting the correlation between the alpha 7 subunit and Bgt-sensitive neuronal nicotinic receptor. Treatment of hippocampal cultures with 10 microM nicotine for 14 days elicited a 40% increase in the numbers of [125I]alpha-Bgt binding sites, mimicking the up-regulation observed in in vivo studies. Primary cultures offer a useful in vitro system for investigating the expression and regulation of brain alpha-Bgt-sensitive receptors.

Neurotrophic activities of normal and motor neurone disease patient skeletal muscle extract on cultured rat spinal neurones.

Cultured foetal rat spinal neurones, grown in serum-free medium from day 3, respond to neuronotrophic factors present in adult human skeletal muscle extracts. Levels of total protein, neurofilament protein and choline acetyltransferase (ChAT) activity are all increased approx. 2 to 3-fold at 200 micrograms extract/ml medium. Culture survival is also extended from an average of 21 days to more than 30 days. Extracts prepared from skeletal muscle biopsies of motor neurone disease (MND) patients do not differ significantly from non-MND patient muscle extracts in their ability to boost the parameter levels or survival of the cultures. The results show no evidence that neuronotrophic factors are lacking in the skeletal muscle of MND patients.

Physiology and pharmacology of cerebral blood flow and metabolism.

In many critically ill patients, long-term neurologic outcome may depend on the adequacy of regional or global CBF. Despite this possibility, clinical protocols for the management of the cerebral circulation in acute neurologic disease have developed slowly. Perhaps progress in central nervous system monitoring, coupled with recent advances in cerebrovascular pharmacology, will alter the management and prognosis of patients with critical neurologic illness.

Cerebral physiologic monitoring.

Cerebral physiologic monitoring techniques can be categorized into those measuring perfusion, metabolism, and function. The physiologic basis for each of these is outlined, with a description of the clinical methods currently available. The clinical application of each monitoring modality is discussed with special reference to its impact on outcome of the brain-injured patient.

A comparison of computed tomography practice in 1989 and 1991.

In December 1991, the National Radiological Protection Board (NRPB) published the results of national surveys of the frequency, quality assurance and dosimetric aspects of computed tomography (CT) examinations carried out in hospitals in the UK in 1989. A study of the patient records at two of the original participating hospitals was undertaken to establish whether there had been any change in CT practice between the years 1989 and 1991. Aspects of examination frequency, age distribution and dose were analysed. The results showed significant variations in the patient age distributions between the sub-population studied and the larger sample used by the NRPB, and between the patient age distribution for CT examinations in the years 1989 and 1991 at the two hospitals in this study. The results also showed that in one hospital, where magnetic resonance imaging (MRI) was available and where dose reduction measures had been implemented, there was a net decrease in the collective effective dose from 1989 to 1991, whilst at the other hospital, where MRI was not available and where the introduction of dose saving strategies had been delayed, there was a substantial increase in the collective effective dose from 1989 to 1991. The possibility of continuing increases in the annual collective effective dose attributable to CT underlines the importance of local CT audit to ensure that CT doses are as low as reasonably achievable.

Dose-area product measurements in a range of common orthopaedic procedures and their possible use in establishing local diagnostic reference levels.

There is a national drive towards establishing reference doses for radiological procedures with the aim of optimizing patient doses. Furthermore, the establishment of diagnostic reference level doses became a legal requirement for all hospitals on 13 May 2000. However, to date there are little published data on patient radiation doses from fluoroscopic procedures during orthopaedic surgery. Data relating to patient dose for 492 patients undergoing fluoroscopic examinations during a range of surgical orthopaedic procedures in 1997-1998 have been analysed. Median dose-area product (DAP) readings and interquartile ranges for a variety of common fluoroscopic orthopaedic procedures are presented. In general, the median DAP for procedures on limbs and extremities was quite low (0.04-1.62 Gy cm2), with screening times in the range 0.2-2.0 min, whilst for procedures involving the hips and spine the median DAP was considerably higher (0.4-10.2 Gy cm2), although overall screening times were similar, in the range 0.2-1.4 min. Approximate effective doses have been estimated. For procedures involving the limbs and extremities, the effective dose was generally less than 10 microSv, and for procedures involving the hips and spine it was found that the effective dose could rise to about 1 mSv. Collective doses for each procedure have been calculated to inform prioritization of procedures for local dose reduction strategies.

A generic approach to risk assessment for the Ionising Radiations Regulations 1999.

The Ionising Radiations Regulations 1999 (IRR99) require that an explicit risk assessment be carried out to control properly the risks associated with the use of ionising radiation. Prior to IRR99, risk was controlled implicitly via mechanisms such as Local Rules and staff monitoring, which were initiated by the Radiation Protection Adviser using professional judgement. To enable a consistent approach across our Trust's radiation users, a generic model of risk assessment was employed. This had been developed previously by the Trust in response to a national initiative within the NHS to manage risk. The methodology involves the generation, by a multidisciplinary staff brain-storming session, of a complete list of all possible risks. This is followed by a risk stratification process based upon severity of consequence and frequency of risk. Auditable controls are then applied and quantifiable outcome measures are monitored for continued compliance. Template risk assessments are presented to aid others in this process. It is estimated that even in a large teaching hospital with a full complement of medical radiation applications, the time resource necessary for this approach is of the order of a few days.

Barium enema: use of increased copper filtration to optimize dose and image quality.

The purpose of this study was to determine and validate the optimum copper filtration for adult double contrast barium enema examinations. Entrance surface dose rates to polymethyl methacrylate slabs and corresponding image intensifier input kermas, were measured for various added copper filters. Image contrast was assessed using a Leeds TO.10 test object. Copper filter thickness of 0.3 mm was chosen, as this reduced entrance surface dose rate by 56%, without substantially degrading image contrast due to kV and mA saturation. 20 sets of clinical films taken with each of 0.3 mm copper, 0.1 mm copper and no copper were reviewed following randomization, by a specialist gastrointestinal radiologist. Each set of digital spot and conventional films was allocated a score for each of three regions of the bowel, on a scale of 0-3 for perceived barium coating. The Kruskal-Wallis test showed no significant difference in perceived coating between the three groups (Digital spot: sigmoid colon p=0.207, splenic flexure p=0.103, hepatic flexure p=0.894. Screen-film: left colon p=0.803, right colon p=0.487, transverse colon p=0.905). All examinations but one were classified as diagnostic. The remaining one was classified indeterminate, due to poor distension of the colon. On adding 0.3 mm copper filtration, the mean dose-area product per examination was reduced by 57%, from 17.7 Gy cm(2) to 7.6 Gy cm(2). The estimated reduction in effective dose was 11%, from 3.0 mSv to 2.7 mSv. X-ray tube loading increased by 30%, but this caused no overheating with our local examination protocol and schedule. Additional filtration of 0.3 mm copper for adult double contrast barium enemas has now been implemented in routine clinical use at our hospital.

External radiation protection audit in National Health Service hospitals. Radiation protecgtion advisors (RPA) of the Nottingham City Hospital NHS Trust and the Oxford Radcliffe Hospital NHS Trust.

Radiation protection advisers are accustomed to carrying out internal audit in organizations for which they provide services but, traditionally, external audit has not been a part of the radiation protection adviser function. To provide an external audit function, two teams of radiation protection advisers undertook external radiation protection audits of their respective organizations, including the radiation protection adviser function itself. These audits were more representative of audits or inspections carried out by government agencies, for example the Health and Safety Executive and the former Inspectorate of Pollution, now the Environment Agency. Subsequently, reports, including recommendations for remedial action, were prepared for each management by the external auditors. The process of setting up and carrying out the external audits is described. Guidelines are suggested for those seeking to carry out an external audit.