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Biomedical subjects

Søren Holm

Publications and source records attributed to Søren Holm.

At least 19 recordsLinked to original sources

Teaching old dogs new tricks: the role of analogies in bioethical analysis and argumentation concerning new technologies.

New medical technologies provide us with new possibilities in health care and health care research. Depending on their degree of novelty, they may as well present us with a whole range of unforeseen normative challenges. Partly, this is due to a lack of appropriate norms to perceive and handle new technologies. This article investigates our ways of establishing such norms. We argue that in this respect analogies have at least two normative functions: they inform both our understanding and our conduct. Furthermore, as these functions are intertwined and can blur moral debates, a functional investigation of analogies can be a fruitful part of ethical analysis. We argue that although analogies can be conservative; because they bring old concepts to bear upon new ones, there are at least three ways in which they can be creative. First, understandings of new technologies are quite different from the analogies that established them, and come to be analogies themselves. That is, the concepts may turn out to be quite different from the analogies that established them. Second, analogies transpose similarities from one area into another, where they previously had no bearing. Third, analogies tend to have a figurative function, bringing in something new and different from the content of the analogies. We use research-biobanking as a practical example in our investigations.

Bioethical Issues↗

Global bioethics -- myth or reality?

BACKGROUND: There has been debate on whether a global or unified field of bioethics exists. If bioethics is a unified global field, or at the very least a closely shared way of thinking, then we should expect bioethicists to behave the same way in their academic activities anywhere in the world. This paper investigates whether there is a 'global bioethics' in the sense of a unified academic community. METHODS: To address this question, we study the web-linking patterns of bioethics institutions, the citation patterns of bioethics papers and the buying patterns of bioethics books. RESULTS: All three analyses indicate that there are geographical and institutional differences in the academic behavior of bioethicists and bioethics institutions. CONCLUSION: These exploratory studies support the position that there is no unified global field of bioethics. This is a problem if the only reason is parochialism. But these regional differences are probably of less concern if one notices that bioethics comes in many not always mutually understandable dialects.

Advisory Committees↗

What should other healthcare professions learn from nursing ethics.

This paper analyses the question what other healthcare professions should learn from nursing ethics, e.g. what should medical ethics learn from nursing ethics. I first analyse and reject all strong versions of the claim that nursing ethics is unique, because nursing is a unique practice. I then move to the question of whether the link between nursing ethics and nursing theory can be a model for other areas of healthcare ethics. I provide an analysis of the possibility of creating a theory of medicine and find that there cannot be a theory of medicine, and I argue briefly that this finding is also applicable to nursing. If there cannot be a theory of nursing, this entails that nursing ethics cannot be justifiably based on such a theory. In the final section, I then analyse the success of nursing ethics in resisting certain of the vices of Anglo-American analytic ethics, in particular the reductionism and individualism that characterizes much of healthcare ethics. I conclude that other healthcare ethics could usefully learn from this aspect of nursing ethics.

Ethical Analysis↗

Positron emission tomographic evaluation of regulation of myocardial perfusion in physiological (elite athletes) and pathological (systemic hypertension) left ventricular hypertrophy.

Myocardial perfusion (MP) may differ in physiologic and pathologic left ventricular hypertrophy (LVH). We compared MP in LVH in elite athletes and patients with hypertension with healthy, age-matched subjects. We included 12 rowers with LVH, 19 patients with hypertension with LVH, and 2 age-matched groups of healthy subjects (n = 11 and n = 12). The left ventricular mass index was determined echocardiographically. MP was measured by N-13 ammonia positron emission tomography. The maximal perfusion and perfusion reserve were studied using dipyridamole, and endothelial function was assessed by a cold pressor test. The degree of LVH was similar in athletes and those with hypertension. Compared with controls, athletes had 20% lower baseline MP (p <0.05), a similar response to the cold pressor test, and a higher perfusion reserve (31%, p <0.05). The patients with hypertension had a 25% higher baseline MP (p <0.05), a reduced increase during the cold pressor test (12% vs 25% in controls, p <0.05), and a reduced perfusion reserve (27% lower, p <0.001). The peak global perfusion (MP x left ventricular mass index) was 62% higher in athletes (p <0.05) than in controls, but the peak global perfusion in patients with hypertension did not differ from that of controls. In conclusion, physiologic LVH in athletes is suited for a high peak workload at the cost of only a small increase in basal myocardial oxygen consumption. In contrast, LVH in the presence of hypertension is a good adaptation to the increased baseline workload with maintained maximal cardiac performance. Endothelial dysfunction may contribute to the reduced perfusion reserve seen in hypertensive LVH.

Adult↗

Effects of high thoracic epidural analgesia on myocardial blood flow in patients with ischemic heart disease.

BACKGROUND: In patients with ischemic heart disease, high thoracic epidural analgesia (TEA) has been proposed to improve abnormalities of coronary function by inhibiting cardiac sympathetic tone. We evaluated the effect of TEA on myocardial blood flow in patients with ischemic heart disease. METHODS AND RESULTS: Twenty male patients with multivessel ischemic heart disease were studied. An epidural catheter was inserted between the second and third thoracic vertebral interspace (Th2 to Th3). Analgesia was induced by epidural injection of bupivacaine 0.5%, and a sensory block from the sixth cervical (C6 to C7) to Th10 (Th8 to Th11) vertebral interspace was achieved. Myocardial blood flow was measured with dynamic 13N-ammonia PET with and without TEA at rest, during pharmacological vasodilation with dipyridamole, and during sympathetic stimulation with the cold pressor test. Myocardial blood flow during dipyridamole increased similarly, regardless of TEA, in all regions except in myocardium subtended by collateral arteries in which blood flow increased more with than without TEA (P<0.05). Without TEA, myocardial blood flow during the cold pressor test remained unchanged compared with myocardial blood flow at rest. In contrast, with TEA, myocardial blood flow increased in all vascular territories. Coronary vascular resistance increased during the cold pressor test without TEA, whereas with TEA, coronary resistance decreased in myocardium subtended by nonstenotic and stenotic coronary vessels and remained unchanged in myocardium subtended by occluded vessels. CONCLUSIONS: In patients with multivessel ischemic heart disease, TEA partly normalizes the myocardial blood flow response to sympathetic stimulation.

Aged↗

Patients with obsessive-compulsive disorder have increased 5-HT2A receptor binding in the caudate nuclei.

The pharmacological efficacy of serotonergic-acting drugs suggest that patients with obsessive-compulsive disorder (OCD) may have alterations in their cerebral serotonergic (5-HT) receptor system, and previous neuroimaging studies of OCD patients have shown abnormalities in several fronto-subcortical regions. In this study we investigated cerebral 5-HT(2A) receptor binding in 15 untreated OCD patients and in 15 age- and gender-matched healthy volunteers by magnetic resonance imaging and [(18)F]altanserin positron emission tomography (PET). Eleven of the patients were rescanned with PET after receiving treatment with a selective serotonin reuptake inhibitor (SSRI). The distribution volumes of specific tracer binding (DV(3)') were calculated for 12 brain regions, and comparisons were made between: (1) healthy volunteers vs. untreated OCD patients, (2) healthy volunteers vs. treated OCD patients, and (3) OCD patients before and during treatment. When comparing the distribution volume for specific fronto-subcortical brain regions, significantly higher values were recorded in the caudate nuclei in OCD patients (DV(3)': 0.24+/-0.14) compared to the healthy control group (DV(3)': 0.15+/-0.13) (p<0.05, Wilcoxon matched-pairs test). This difference between groups was not present after treatment with SSRIs. There was no correlation between the severity of OCD symptoms and 5-HT(2A )receptor binding. An increase in 5-HT(2A) receptor binding is found in the caudate nuclei of untreated patients with OCD. The up-regulation in 5-HT(2A) receptors might be compensatory for a lack of serotonin in the feedback loop between the thalamus and orbito-frontal cortex, the caudate nuclei, and the globus pallidus.

Adolescent↗

The relationship between cerebral blood flow and volume in humans.

The purpose of this study was to establish the relationship between regional CBF and CBV at normal, resting cerebral metabolic rates. Eleven healthy volunteers were investigated with PET during baseline conditions, and during hyper- and hypocapnia. Values for rCBF and rCBV were obtained using 15O-labelled water and carbon monoxide, respectively. The mean value of rCBF using PET was 62 +/- 18 ml 100 g(-1) min(-1) during baseline conditions, with an average increase of 46% during hypercapnia, and a decrease of 29% during hypocapnia; baseline rCBV was 7.7 ml/100 g, with 27% increase during hypercapnia and no significant decrease during hypocapnia. A regionally uniform exponential relationship was confirmed between PaCO2 and rCBF as well as rCBV. It is shown that the theoretical implication of this is that the rCBV vs. rCBF relationship should be modelled by a power function; however, due to pronounced intersubject variability, the goodness of fit for linear and nonlinear models were not significantly different. The results of the study are applied to a numerical estimation of regional brain deoxy-haemoglobin content. Independently of the choice of model for the rCBV vs. rCBF relationship, a nonlinear deoxy-haemoglobin vs. rCBF relationship was predicted, and the implications for the BOLD response are discussed.

Adult↗

"Central command" and insular activation during attempted foot lifting in paraplegic humans.

The relationship between cardiovascular regulation and brain activation was investigated during attempted foot lifting in paraplegic subjects and during rhythmic handgrip exercise at one-third of maximum voluntary contraction force. Brain areas of interest were the primary sensory-motor area and the insula, a hypothesized center for a central nervous feed-forward mechanism involved in cardiovascular control ("central command"). This mechanism is complementary to the usual known feedback pathways such as skeletal muscle afferent signals. Regional cerebral blood flow (rCBF) was measured in eight normal and three paraplegic subjects using positron emission tomography (PET) and oxygen-15-labeled water. Statistical parametric maps were calculated from the images comparing rest and handgrip. Paraplegics were also scanned during attempted foot lifting, a condition without sensory feedback. During activation tasks, heart rate and mean arterial pressure increased. PET activation responses (P < 0.05, corrected for multiple comparisons) were found in the contralateral primary sensory-motor area, the supplementary motor area, ipsilateral cerebellum, and bilaterally in the insula. A conjunction analysis showing responses common to handgrip and attempted foot lifting revealed activation in the right central insula (P < 0.05, corrected) in concordance with the concept of a central command feed-forward hypothesis.

Adult↗

Accountability for reasonableness: opening the black box of process.

Norman Daniels' and James Sabin's theory of "accountability for reasonableness" (A4R) is a much discussed account of due process for decision-making on health care priority setting. Central to the theory is the acceptance that people may justifiably disagree on what reasons it is relevant to consider when priorities are made, but that there is a core set of reasons, that all centre on fairness, on which there will be no disagreement. A4R is designed as an institutional decision process which will ensure that only those reasons which everybody will agree are relevant and appropriate form part of decision-making. The argument which we will put forward in this paper questions whether it is a simple matter to delineate the core set of reasons and claims that it is a potential problem in A4R that it does not provide an indication of the exact content of this process. The paper first briefly outlines the content of A4R. It is argued that disagreement on what services should be high priorities cannot be resolved solely with a reference to "due process." In order to retain consistency over time, decision-makers are required to agree and articulate what reasons qualify as relevant and how conflicting reasons are to be balanced in the course of the process. The second and main part of the paper then considers how the reason of "solidarity" can be handled within the A4R framework, and it is shown that deciding whether solidarity should be admitted to the core set of allowable reasons is not a simple matter.

Bioethics↗

Justifying patient self-management--evidence based medicine or the primacy of the first person perspective.

Patient self-management programs have become increasingly popular and are now also receiving official endorsements. This paper analyses two possible types of positive justifications for promoting patient self-management: evidence-based and patient-centred justifications. It is argued that evidence-based justifications, although important politically are deficient and that the primary justification for patient self-management must be a patient-centred justification focusing on the patient's privileged access to his or her own lived body.

Adaptation, Psychological↗

Embryonic stem cell research and the moral status of human embryos.

The paper analyses whether the old problem concerning the moral status or value of human embryos is implicated in the moral evaluation of embryonic stem cell research. It briefly outlines the moral status debate and then proceeds to show that all current attempts to bypass the problem fail.

Embryo Research↗

MR-based automatic delineation of volumes of interest in human brain PET images using probability maps.

The purpose of this study was to develop and validate an observer-independent approach for automatic generation of volume-of-interest (VOI) brain templates to be used in emission tomography studies of the brain. The method utilizes a VOI probability map created on the basis of a database of several subjects' MR-images, where VOI sets have been defined manually. High-resolution structural MR-images and 5-HT(2A) receptor binding PET-images (in terms of (18)F-altanserin binding) from 10 healthy volunteers and 10 patients with mild cognitive impairment were included for the analysis. A template including 35 VOIs was manually delineated on the subjects' MR images. Through a warping algorithm template VOI sets defined from each individual were transferred to the other subjects MR-images and the voxel overlap was compared to the VOI set specifically drawn for that particular individual. Comparisons were also made for the VOI templates 5-HT(2A) receptor binding values. It was shown that when the generated VOI set is based on more than one template VOI set, delineation of VOIs is better reproduced and shows less variation as compared both to transfer of a single set of template VOIs as well as manual delineation of the VOI set. The approach was also shown to work equally well in individuals with pronounced cerebral atrophy. Probability-map-based automatic delineation of VOIs is a fast, objective, reproducible, and safe way to assess regional brain values from PET or SPECT scans. In addition, the method applies well in elderly subjects, even in the presence of pronounced cerebral atrophy.

Aged↗