Biomedical subjects
Publications and source records attributed to M Barton.
Many OH departments within the public and private sectors of industry are considering the need to install computer systems to record and manage their employee medical records. Michael Barton stresses that consideration has to be given to the reasons for computerisation, clarification of the its benefits and also the importance of dispelling any myths about computer systems before embarking on such a course of action.
Four strategies for selecting cows for intramammary therapy with benzathine cloxacillin at drying off were compared in 12 Victorian dairy herds. The bacteriological status of all quarters of all (1044) cows was determined just before drying off, within 2 d of calving, and again 3 to 5 months after calving. All cases of clinical mastitis (from calving to mid-lactation) were recorded. Cows not infected at drying off were allocated randomly to 2 subgroups of approximately 350 cows each: not infected, not treated (NI-NT), or not infected, all quarters treated (NI-AT). New infection rates in the dry period (3.8% for NI-NT vs 2.1% for NI-AT) and in early lactation (4.1% for NI-NT vs 3.9% for NI-AT) were low and these differences were not significant. Incidence of clinical mastitis in early lactation was almost 50% higher for the treated group of uninfected cows compared with the untreated group (0.05 less than p less than 0.1). Cows infected in one or more quarters at drying off were split randomly into 2 subgroups of approximately 170 cows each: infected, all quarters treated (I-AT), or infected quarters treated only (I-QT). The new infection rate during the dry period was nearly 4 times higher for I-QT (15.3%) due to significantly more new infections by Staphylococcus aureus and Streptococcus uberis.(ABSTRACT TRUNCATED AT 250 WORDS)
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A gunshot wound to the right chest in a 21-year-old female resulted in an acute aortocaval fistula at the level of the diaphragm. An operative approach planned for maximal exposure, vascular control with intraluminal balloon catheters, and conservation of blood with an intraoperative autotransfusion system resulted in successful repair and long-term survival.
UNLABELLED: Positive end-expiratory pressure (PEEP) is commonly used in the treatment of critically ill patients whose sympathetic nervous system is stressed; however, PEEP's actions on sympathetic nervous system activity are unknown. We therefore measured the plasma noradrenaline response (an index of sympathetic nervous system activity) to graded doses of PEEP in nine mongrel dogs. After 30 minutes at each level of PEEP, plasma noradrenaline concentrations increased from baseline mean values of 300 (SD 108) pg/ml to 388 (SD 225) pg/ml (P less than 0.05) at 5 cm, 433 (SD 255) pg/ml (P less than 0.01) at 10 cm and 1194 (SD 882) pg/ml (P less than 0.01) at 20 cm water pressure of PEEP. The increases in plasma noradrenaline concentrations correlated inversely (r = -0.43, P less than 0.01) with PEEP-induced changes in cardiac output. Plasma adrenaline levels did not change significantly in response to 5 or 10 cm of PEEP; however, plasma adrenaline increased, while heart rate and mean arterial blood pressure fell, at 20 cm water pressure of PEEP (P less than 0.05). Within 15 minutes after discontinuation of PEEP, the plasma catecholamine concentrations returned to baseline levels. CONCLUSIONS: 1. PEEP significantly increases sympathetic nervous system activity in a rapid, dose-dependent, reversible manner; 2. the PEEP-induced increases in sympathetic activity may explain the reductions in organ blood flow which others have observed following the initiation of PEEP; 3. PEEP-related changes in sympathetic nervous system activity are a consequence of PEEP-induced reductions in cardiac output.
The hospital-based orthodontist is involved with the management of cleft palate patients. Removable orthodontic appliance therapy as an adjunct to speech problems is described and discussed. The literature is reviewed and the investigation and management of speech problems related to palate-pharyngeal incompetence and hypernasal speech is outlined.
The endogenous catecholamine response to hemorrhagic hypotension is poorly defined since most data have been derived from experiments in lower animal species. To clarify this situation we studied the plasma norepinephrine (NE) and epinephrine (Epi) responses to hemorrhagic hypotension in ten healthy male baboons (Papio anubis). After an overnight fast, animals were tranquilized with 100 mg of ketamine hydrochloride after which femoral artery and vein catheters were inserted. The animals then underwent phlebotomy of 20 ml/kg over 60 minutes with retransfusion of the autologous blood over the next 30 minutes. Plasma specimens for catecholamines were collected at 5, 15, 30, and 60 minutes during phlebotomy and again at 15 and 30 minutes during retransfusion. Plasma NE and Epi concentrations were measured by a radioenzymatic technique. Mean arterial blood pressure (MAP) decreased (p less than 0.01) and heart rate (HR) increased (p less than 0.01) within 15 minutes of phlebotomy, and these variables returned to baseline with retransfusion. Plasma NE and Epi levels increased (p less than 0.025) within 5 minutes of the onset of 'hemorrhage' and within 15 minutes plasma NE concentrations were 56% above baseline, whereas plasma Epi levels were six times greater than baseline. With retransfusion, plasma NE and Epi levels returned to baseline concentrations. We conclude: 1) in a primate species, the sympathetic nervous system responds rapidly to hemorrhage; 2) contrary to prior studies in rats, plasma NE increases as rapidly as Epi but not to the same degree; 3) plasma NE and Epi concentrations rapidly return to baseline levels with fluid resuscitation; and 4) there is little justification for the use of exogenous synthetic catecholamines in hemorrhagic hypotension where fluid resuscitation remains the treatment of choice.
The treatment of allergies is based more on sound scientific principles today than it was 20 years ago; however, allergy control still suffers from controversial diagnostic and treatment methods. Controlled studies have failed to support the skin titration (Rinkel method) used to establish an optimal dose for the relief of hay fever symptoms. Determining the clinical usefulness of cytotoxic testing is fraught with lack of clinical correlations and a high percentage of false positives. The results of double-blind studies demonstrated that cytotoxic testing is not a reliable diagnostic technique. Similarly, controlled studies do not corroborate the clinical usefulness proponents advocate for sublingual and provocative subcutaneous testing for diagnosing and treating allergy. The use of autogenous-urine immunization has no proven efficacy and can predispose the patient to potential harmful effects. These diagnostic modalities have not proved to be helpful and should not be employed in the assessment of the allergic patient.
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Platelet-activating factor (PAF-acether), a known platelet stimulant and bronchoconstrictor (in vivo), is a potential mediator of inflammation and thrombosis. However, all smooth muscle effects of PAF-acether described to date are indirect, relying upon intravascular platelet activation. Novel actions of PAF-acether and serotonin (5-HT) are presented here; these actions may lead to the development of a practical bioassay for PAF-acether and contribute to the understanding of the mechanism of action for both substances. PAF-acether, when added to a spiral cut guinea-pig trachea suspended in a tissue bath containing Krebs-Henseleit buffer, produced a dose-dependent loss of active tissue tension. The ED50 for this effect of PAF-acether was 75 ng/ml. PAF-acether produced a maximal relaxation which was 68% of that produced by PGE1 and the effect could not be modified by aspirin or propranolol pretreatment. 5-HT, alone, contracted the guinea-pig trachea strip in a dose-dependent manner, but caused relaxation instead when methysergide was present. Aspirin, phenoxybenzamine and propranolol did not alter this loss of active tissue tension. A similar observation was made in vivo using the guinea-pig bronchoconstriction model, in which PAF-acether as well as 5-HT given to methysergide-treated animals caused a decrease in intratracheal pressure. This action of PAF-acether may yield a suitable bioassay method which could facilitate routine measurements of the substance. Furthermore, the similarity in action of PAF-acether and of 5-HT on methysergide-treated animals leads one to speculate about the relationship between the two substances and their mechanism of action in smooth muscle.
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Hypocalcemia is an important metabolic problem in critical care medicine. To determine the frequency of this problem and the patient subsets at risk, a retrospective study of a large series of ICU patients was performed. During the study period, 259 patients were admitted to the ICU, of whom 210 (81%) had a serum calcium (Ca++) measured. Of these 210 patients, 135 (64%) were hypocalcemic (serum Ca++ less than 8.5 mg/dl) and 75 (36%) were normocalcemic. Serum albumin concentration was less than 3.5 g/dl in 70% of the hypocalcemic patients who hd albumin measured, suggesting that the ionized Ca++ concentration may have been normal in many of these patients. On the other hand, 32% of the hypocalcemic patients were alkalotic (pH greater than or equal to 7.45) which indicates that ionized Ca++ levels may have been low because Ca++ binding to protein increases with alkalosis. Gastrointestinal bleeders and postabdominal surgery patients were more likely to have low total serum Ca++ whereas cardiac and neurosurgical patients were more likely to have a normal total serum Ca++ (p less than 0.05). Ionized Ca++ was calculated in 36 of the normocalcemic and 80 of the hypocalcemic patients. The hypocalcemic group had significantly lower ionized Ca++ levels when compared to those of the normocalcemic group (p less than 0.001). Patients with low serum Ca++ values spent a longer time in the ICU (p less than 0.01), had an increased incidence of renal failure and sepsis (p less than 0.01), had an increased mortality rate (p less than 0.001), and received a greater number of blood transfusions (p less than 0.001) than patients in the normocalcemic group. It is concluded that: (1) hypocalcemia is a frequent finding in critically ill patients; (2) determining ionized Ca++ levels is useful because many ICU patients have alterations in both arterial pH and serum albumin levels; (3) hypoalbuminemia, sepsis, red cell transfusions, and renal failure are predisposing factors for hypocalcemia; and (4) hypocalcemic patients do less well clinically than normocalcepatientsmic patients.
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1. After intravenous administration to 19 subjects, aged 18-95 years, plasma diazepam concentrations were measured over 160 h. Plasma protein binding of diazepam was also measured in each subject. 2. The terminal plasma half-life of diazepam ranged from 15.0 to 125 h and was positively correlated with age (r = 0.797). Total plasma diazepam clearance was not correlated with age (r = -0.017). 3. The free fraction of diazepam ranged from 0.0137 to 0.0386 and was significantly correlated with age (r = +0.863). Free diazepam clearance, which ranged from 432 to 1870 ml/min, was also correlated with age (r = -0.717). 4. It is concluded that the increased sensitivity of the elderly to diazepam is, at least in part, due to pharmacokinetic factors.