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Biomedical subjects

John Harris

Publications and source records attributed to John Harris.

At least 19 recordsLinked to original sources
PubMed2003

Endogenous opioids support the spinal inhibitory action of an alpha 2-adrenoceptor agonist in the decerebrated, spinalised rabbit.

The present study examined the possible contribution of endogenous opioids to inhibition of spinal reflexes by an alpha(2)-adrenoceptor agonist. In rabbits decerebrated and spinalised under halothane/nitrous oxide anaesthesia, the selective alpha(2)-adrenoceptor agonist dexmedetomidine (3-30 microg intrathecal) induced significant decreases in short- and long-latency reflex responses evoked in medial gastrocnemius (MG) motoneurones by stimulation of the sural nerve. After recovery from dexmedetomidine, the mu-opioid receptor antagonist beta-funaltrexamine (beta-FNA; 100 microg intrathecal) significantly enhanced short-latency but not long-latency MG reflex responses. After beta-FNA, inhibition of all reflexes by dexmedetomidine was significantly weaker than in the control state, whereas the cardiovascular actions of dexmedetomidine were unaffected. These data confirm that activation of spinal alpha(2)-adrenoceptors depresses MG reflexes evoked by all groups of sural nerve afferent fibres, and shows that endogenous opioid tone supports the inhibitory action of alpha(2) agonists, possibly by a synergistic interaction in the spinal cord.

Adrenergic alpha-2 Receptor Agonists↗
PubMed2003

Organisation of sensitisation of hind limb withdrawal reflexes from acute noxious stimuli in the rabbit.

Spatial aspects of central sensitisation were investigated by studying the effects on three hind limb withdrawal reflexes of an acute noxious stimulus (20 % mustard oil) applied to a number of locations around the body in decerebrate and in anaesthetised rabbits. Reflex responses to electrical stimulation of the toes were recorded from the ankle flexor tibialis anterior (TA) and the knee flexor semitendinosus (ST), whereas responses to stimulation of the heel were recorded from the ankle extensor medial gastrocnemius (MG). In non-spinalised, decerebrated, pentobarbitone-sedated preparations, flexor reflexes were facilitated significantly from sites on the plantar surface of the ipsilateral foot but were either inhibited or unaffected by stimulation of sites away from this location. The heel-MG reflex was facilitated from the ipsilateral heel and was inhibited from a number of ipsilateral, contralateral and off-limb sites. In decerebrated, spinalised, pentobarbitone-sedated animals, mustard oil applied to any site on the ipsilateral hind limb enhanced both flexor reflexes, whereas the MG reflex was enhanced only after stimulation at the ipsilateral heel and was inhibited after stimulation of the toe tips or TA muscle. Mustard oil on the contralateral limb had no effect on any reflex. In rabbits anaesthetised with pentobarbitone and prepared with minimal surgical interference, the sensitisation fields for the heel-MG and toes-TA reflexes were very similar to those in non-spinal decerebrates whereas that for toes-ST was more like the pattern observed in spinalised animals. In no preparation was sensitisation or inhibition of reflexes related to the degree of motoneurone activity generated in direct response to the sensitising stimulus. This study provides for the first time a complete description of the sensitisation fields for reflexes to individual muscles. Descending controls had a marked effect on the area from which sensitisation of flexor reflexes could be obtained, as the sensitisation fields for the flexor reflexes evoked from the toes were larger in spinalised compared to decerebrated, non-spinalised animals. The intermediate sizes of sensitisation fields in anaesthetised animals suggests that the area of these fields can be dynamically controlled from the brain. On the other hand, the sensitisation field for the heel-MG reflex varied little between preparations and appears to be a function of spinal neurones.

Animals↗
PubMed2003

Vascular disease risk factor management 4 years after carotid endarterectomy: are opportunities missed?

BACKGROUND: Because a large percentage of patients surviving carotid endarterectomy (CEA) subsequently die from a vascular cause, the aim of the present paper was to determine risk factor management for a cohort of patients 4 years after their CEA. METHODS: Surviving patients who had a CEA within the region administered by the Central Sydney Area Health Service in 1995 were asked to complete a self-administered questionnaire to determine vascular risk factors. RESULTS: Of the 181 patients eligible to participate, 162 returned questionnaires (response rate: 90%). While 106 (65.4%) patients recalled that they had been diagnosed with high blood pressure either before or after their CEA, only 79.2% recalled that their latest blood pressure reading was 'about right for my age'. Nearly one in five (16.7%) who had had their cholesterol level checked in the last 12 months (n = 120) indicated that the reading was 'too high'. Only 76.5% reported taking medications to 'thin the blood'. Almost one-fifth of patients (17.3%) were current smokers. Only 35.2% of patients participated in a level of physical activity sufficient to confer a health benefit. Further, 30.2% of patients were overweight and 14.8% were obese. The majority of patients (98.1%) reported having a regular general practitioner (GP). Of these, 98.7% had visited their GP at least once within the previous 6 months. CONCLUSIONS: Vascular risk factor management following CEA is suboptimal, inviting the implementation and evaluation of strategies to improve outcomes.

Aged↗
PubMed2003

Consent and end of life decisions.

This paper discusses the role of consent in decision making generally and its role in end of life decisions in particular. It outlines a conception of autonomy which explains and justifies the role of consent in decision making and criticises some misapplications of the idea of consent, particular the role of fictitious or "proxy" consents. Where the inevitable outcome of a decision must be that a human individual will die and where that individual is a person who can consent, then that decision is ethical if and only if the individual consents. In very rare and extreme cases such a decision will be ethical in the absence of consent where it would be massively cruel not to end life in order to prevent suffering which is in no other way preventable. Where, however, the human individual is not a person, as is the case with abortion, the death of infants like Mary (one of the conjoined twins in a case discussed in the paper), or in the very rare and extreme cases of those who have ceased to be persons like Tony Bland, such decisions are governed by the ethics of ending the lives of non-persons.

Child↗
PubMed2002

Australian audit for the endoluminal repair of abdominal aortic aneurysm: the first 12 months.

BACKGROUND: The Australian Safety and Efficacy Register for New Interventional Procedures - Surgical (ASERNIP-S) was contracted by the Commonwealth Department of Health and Aged Care to audit the procedure of endoluminal repair of abdominal aortic aneurysm. The purpose of the audit was to examine the safety and efficacy of the endoluminal graft (ELG) and, where possible, compare it to the open procedure. The first 12 months of data collection has now been completed. An overview of these results and some of the problems associated with the establishment of this audit are given. METHODS: The administrative infrastructure to support the audit is based at the ASERNIP-S office in Adelaide. To achieve high compliance rates, regular contact was maintained with surgeons. A reference group of senior vascular surgeons was established to provide expert support to the audit. RESULTS: By December 2000, ASERNIP-S had collected data on approximately 85% of privately performed ELG procedures during the first year of the audit. The early mortality rate was 1.3% in the endoluminal group compared to 2.6% in the open group. The rate of procedural complications was 15% in both groups, but the percentage of systemic complications was higher following the open repair. Aneurysm size and the number of pre-existing conditions had a statistically significant relationship to the variation in the number of complications for ELG patients. CONCLUSIONS: Good compliance has been obtained from vascular surgeons for submission of the operative data sets. ASERNIP-S aims to follow this group of patients closely to assess the medium to long-term durability of this procedure.

Aged↗
PubMed2002

Audit of long-term mortality and morbidity outcomes for carotid endarterectomy.

There have been no Australian studies of long-term mortality status and cause of death after carotid endarterectomy (CEA) or, for survivors, quality-of-life. We first determined rate and cause of death for a cohort of patients four years after CEA. Surviving patients were surveyed to ascertain health status, using MOS SF-36. Of 238 patients who underwent CEA in our health service in 1995, 44 (18.5%) had died within four years. The majority of deaths (61.4%) were attributable to vascular causes. Of the surviving 162 patients (survey response fraction 90%), 10 (6.2%) subsequently had suffered a non-fatal stroke in the four years following their CEA. With respect to health status, Physical Functioning scores differed significantly by age (t = 2.65, df = 149, P = 0.01) as did Role Physical scores (t = 2.10, df = 142, P = 0.04). We conclude that patients undergoing CEA are at high risk of dying from vascular causes, inviting concerted efforts in discharge planning to co-ordinate optimal vascular risk factor management.

Aged↗
PubMed2002

Extending human lifespan and the precautionary paradox.

This paper argues that a precautionary approach to scientific progress of the sort advocated by Walter Glannon with respect to life-extending therapies involves both incoherence and irresolvable paradox. This paper demonstrates the incoherence of the precautionary approach in many circumstances and argues that with respect to life-extending therapies we have at present no persuasive reasons for a moratorium on such research.

Aging↗
PubMed2002

Commentary on Skene and Parker: the role of a church (or other ideologically based interest group) in developing the law--a plea for ethereal intervention.

This paper discusses the provocative views of Skene and Parker as to the role of religious or other ideologically based interest groups in law and policy making. We draw distinctions between doctrine and prejudice and between argument and ideology which we trust take the debate further. Finally we recommend an ethereal, democratic, and populist partial solution.

Abortion, Legal↗
PubMed1999

Restoring natural function: access to infertility treatment using donated gametes.

Fertility services are the only area of medicine in which health professionals are required by law to make social judgements about a person's suitability for treatment. The Human Fertilisation and Embryology Act of 1990 imposes restrictions on access to licensed fertility treatment based on social judgements about the probable welfare of any resulting child. In this paper, it is argued that just as social judgements are inappropriate in other contexts, so they are in the context of fertility treatment. Furthermore, the ambiguous requirement for concern for the welfare of the resulting child simply does not provide a just and ethically defensible solution to the problem of access to licensed fertility treatment. born as a result of the treatment (including the need of that child for a father) and of any other child who may be affected by the birth treatment.

Journal Article↗
PubMed1999

Justice and equal opportunities in health care.

The principle that each individual is entitled to an equal opportunity to benefit from any public health care system, and that this entitlement is proportionate neither to the size of their chance of benefitting, nor to the quality of the benefit, nor to the length of lifetime remaining in which that benefit may be enjoyed, runs counter to most current thinking about the allocation of resources for health care. It is my contention that any system of prioritisation of the resources available for healthcare or of rationing such resources must be governed by this principle. This can have apparently paradoxical conclusions in that it can seem wasteful to give someone with a very slim chance of a lifesaving treatment the same priority as someone with a much better chance. In an important and thoughtful recent paper, Julian Savulescu has concentrated on this apparent weakness and has argued for a particular conception of the good or benefit to be achieved by a healthcare system which purports to demonstrate the inadequacies of an equal opportunities approach to prioritisation and to replace it with an altogether better account. This paper will show that a rational 'reasons based consequentialism' is more in line with the equal opportunities approach, which I defended some time ago in these pages, than with that of Savulescu. I shall then examine more closely the conception of equal opportunities in health care and show that if we give weight to an individual's reasons, and what is expected to be good for them, we will opt for exactly the equality based account of distributive justice that I have recommended.

Delivery of Health Care↗
PubMed1999

The concept of the person and the value of life.

The concept of the person has come to be intimately connected with questions about the value of life. It is applied to those sorts of beings who have some special value or moral importance and where we need to prioritize the needs or claims of different sorts of individuals. "Person" is a concept designating individuals like us in some important respects, but possibly including individuals who are very unlike us in other respects. What are these respects and why are they important? This paper sets out to answer these questions and to develop a coherent and useful concept of the person.

Animal Rights↗