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Biomedical subjects

G Hart

Publications and source records attributed to G Hart.

At least 37 records · Page 2Linked to original sources
PubMed2001

Early and intensive continuous hemofiltration for severe renal failure after cardiac surgery.

BACKGROUND: The aim of this study was to test whether early and intensive use of continuous venovenous hemofiltration (CVVH) achieved a better than predicted outcome in patients with severe acute renal failure undergoing cardiac operations, and whether a simple and yet accurate model could be developed to predict their outcome before starting CVVH. METHODS: Medical record analysis with collection of demographic, clinical, and outcome information was used. RESULTS: Sixty-five consecutive patients were treated with early and intensive CVVH (mean operation to CVVH time, 2.38 days; pump-controlled ultrafiltration rate, 2 L/h) after coronary artery bypass grafting (56.9%), single valve procedure (16.9%), or combined operations (26.2%). In 32.3% of patients, intraaortic balloon counterpulsation was required and 20% of patients were emergencies. Sustained hypotension despite inotropic and vasopressor support occurred in 40% of patients and prolonged mechanical ventilation in 58.5%. Using an outcome prediction score specific for acute renal failure, the predicted risk of death was 66%. Actual mortality was 40% (p = 0.003). Using multivariate logistic regression analysis and neural network analysis, patient outcome could be predicted with good levels of accuracy (receiver operating characteristic 0.89 and 0.9, respectively). CONCLUSIONS: Early and aggressive CVVH is associated with better than predicted survival in severe acute renal failure after cardiac operations. Using readily available clinical data, the outcome of such patients can be predicted before the implementation of CVVH.

Acute Kidney Injury↗
PubMed2001

An extracorporeal membrane oxygenation-based approach to cardiogenic shock in an older population.

BACKGROUND: We investigated the efficacy of an integrated system of advanced supportive care based on extracorporeal membrane oxygenation (ECMO) in older patients with an estimated mortality of more than 90% to establish whether its use is justifiable. METHODS: Treatment was provided by cardiac surgeons and critical care physicians and included the following key elements: (1) ECMO, (2) early application of continuous venovenous hemofiltration, (3) inhaled nitric oxide, (4) maintenance of perfusion pressure with norepinephrine, (5) maintenance of pulmonary blood flow by ventricular filling with intravenous colloids, (6) avoidance of early postoperative anticoagulation, (7) frequent use of transesophageal echocardiography, and (8) low tidal volume ventilation. Demographic features, intraoperative details, postoperative course, ECMO weaning rate, morbidity, survival to hospital discharge, and the quality of life of survivors were recorded. RESULTS: Seventeen consecutive patients (median age, 69 years) with refractory cardiogenic shock were studied. The median duration of ECMO was 86 hours (20 to 201 hours). Eleven patients (65%) were successfully weaned from ECMO. Seven patients (41%) survived to discharge. The major causes of morbidity were bleeding and leg ischemia. All patients who survived to discharge were alive and well at follow-up (median, 21 months) and reported a satisfactory quality of life. CONCLUSIONS: An ECMO-based approach can be used with acceptable results in the treatment of refractory cardiogenic shock, even in older patients.

Aged↗
PubMed2001

Telephone support group intervention for persons with hemophilia and HIV/AIDS and family caregivers.

The purpose of this pilot project was to test the feasibility of a telephone support group intervention for persons with hemophilia and HIV/AIDS and for their family caregivers. Their support needs were unique because they did not identify with predominant groups of persons with AIDS and were geographically dispersed from peers. The 12 week intervention involved separate telephone support groups for hemophiliacs and for family caregivers. The two groups, comprised of a predetermined maximum of six people, were co-led by a professional and a peer. The support group for family caregivers involved six people and the group for men with hemophilia included five people, including one peer facilitator and one professional facilitator in each group. The telephone support group discussions were taped, transcribed, and analyzed for prevalent themes. The peer and professional facilitators maintained weekly field notes. All participants reported that the telephone groups had a positive impact on meeting their support needs. They believed that they had benefitted from sharing information and that the support groups had decreased their feelings of isolation and loneliness. Participants, however, contended that the intervention should be longer than 12 weeks.

Adaptation, Psychological↗
PubMed2001

Rate-dependent electrical, contractile and restitution properties of isolated left ventricular myocytes in guinea-pig hypertrophy.

Left ventricular hypertrophy predisposes to sudden cardiac death (SCD) and studies of human SCD suggest that the antecedent heart rate (HR) is usually < 100 beats min(-1). This is surprising in view of the known association between adrenergic receptor stimulation and SCD which by itself would suggest that it is more likely to occur from high rather than low HR. We therefore hypothesized that there may be electrical or mechanical abnormalities present in myocytes isolated from animals with left ventricular hypertrophy that predispose to SCD at low stimulation frequencies but which may not be present at high HR. Mild left ventricular hypertrophy was induced in guinea-pigs by infra-renal aortic banding. Electrical and mechanical properties of isolated myocytes were studied at different stimulation frequencies between 0.1 and 3 Hz. Action potential duration (APD) is prolonged in hypertrophy at stimulation frequencies < 1 Hz but not at faster rates. Contraction size, time-to-peak contraction (TTPC) and half-relaxation time are greatly enhanced in hypertrophy at all frequencies between 0.1 and 3 Hz. Electrical (50.3 +/- 5.2 ms in hypertrophy and 78.4 +/- 12.1 ms in control, P < 0.03) and mechanical (205 +/- 16 ms for hypertrophy and 266 +/- 24 ms for control cells, P < 0.03) restitution time constants are quicker in hypertrophy. The finding of APD prolongation at low but not at high frequencies is consistent with the finding that SCD arises from low and not high HR. This data supports the role of abnormal repolarization in SCD.

Action Potentials↗
PubMed2001

The use of a modified technique to reduce radioactive air contamination in aerosol lung ventilation imaging.

The aim of this study was to reduce airborne contamination resulting from the use of aerosols in lung ventilation scintigraphy. Lung ventilation imaging is frequently performed with 99mTc-diethylenetriaminepentaacetate aerosol (DTPA), derived from a commercial nebuliser. Airborne contamination is a significant problem with this procedure; it results in exposure of staff to radiation and can reduce gamma camera performance when the ventilation is performed in the camera room. We examined the level of airborne contamination resulting from the standard technique with one of the most popular nebuliser kits and tested a modification which significantly reduced airborne contamination. Air contamination was measured while ventilating 122 patients. The modified technique reduced air contamination by a mean value of 64% (p = 0.028) compared with the standard control technique. Additionally, differences in contamination were examined when a mask or mouthpiece was used as well as differences between operators. A simplified method of monitoring air contamination is presented using a commonly available surface contamination monitor. The index so derived was proportional to air contamination (r = 0.88). The problems and regulations associated with airborne contamination are discussed.

Aerosols↗
PubMed2001

"That sort of place...where filthy men go...": a qualitative study of women's perceptions of genitourinary medicine services.

BACKGROUND: A stigma is a pejorative social label. Stigmatisation is a process by which individuals are made to experience isolation and reduced opportunities in life. Some diseases are particularly associated with stigmatising attitudes; this applies particularly to sexually transmitted infections. Although several studies report the effects of stigma, no study to date has attempted to investigate its nature, which is a prerequisite to designing health interventions. METHODS: This qualitative, exploratory study investigated the experience of stigma among young women recently diagnosed with an STI and considered the implications of these experiences in terms of maximising access to GUM clinics. RESULTS: Three themes were identified from interviews undertaken with women recruited in family planning and genitourinary medicine (GUM) clinics: the perception of STIs as a condition of "others," the threatening nature of the GUM clinic, and the evolution of the experience of stigma within the GUM clinic. CONCLUSION: More open discussion and education about sexual health services and STIs should take place at a general population level; awareness of sexual health services should be raised in inclusive ways, which are seen as relevant to the needs of a wide range of individuals; medical, nursing, and counselling staff in GUM clinics should be supported in their efforts to reduce the experience of stigma. Finally, future interventions designed to improve access to sexual health services should formally assess their impact on stigma.

Adolescent↗
PubMed2001

Mechanisms underlying delayed afterdepolarizations in hypertrophied left ventricular myocytes of rats.

Cardiac hypertrophy was induced in rats by daily injection of isoproterenol (5 mg/kg ip) for 7 days. Membrane voltage and currents were recorded using the whole cell patch-clamp technique in left ventricular myocytes from control and hypertrophied hearts. Ryanodine-sensitive delayed afterdepolarizations (DADs) and transient inward current (I(ti)) appeared in hypertrophied cells more often and were of larger amplitude than in control cells. DADs and I(ti) are carried principally by Na/Ca exchange with smaller contributions from a nonselective cation channel and from a Cl- channel. The latter is expressed only in hypertrophied myocytes. In hypertrophy, the density of caffeine-induced Na/Ca exchange current (I(Na/Ca)) was increased by 26%, sarcoplasmic reticulum (SR) Ca2+ content as assessed from the integral of I(Na/Ca) was increased by 30%, the density of Na-pump current (I(pump)) was reduced by 40%, and the intracellular Na+ content, measured by Na+-selective microelectrodes was increased by 55%. The results indicate that DADs and I(ti) are generated by spontaneous Ca2+ release from an overloaded SR caused by a downregulated Na pump and an upregulated Na/Ca exchange. These findings may explain the propensity for arrhythmias seen in this model of hypertrophy.

Action Potentials↗
PubMed2000

Attitudes, beliefs and behaviour regarding the use of sunbeds amongst healthcare workers in Bradford.

Although cosmetic tanning and unprotected solar exposure are common, little is known about general attitudes, beliefs and behaviour regarding the use of sunbeds. We sought to determine the frequency of sunbeds use in a select sample and to assess the knowledge and beliefs regarding this behaviour. A self-administered anonymous questionnaire was distributed to a sample of 648 employees work for Bradford Hospitals NHS Trust. The questionnaire explored demographic information (including hair and skin type, family history with skin cancer), frequency of sunbeds use, knowledge about the risks of UV exposure and motivations for practising this behaviour. Four hundred and eighteen women and 52 men completed the questionnaire, making a response rate of 73%. Nearly half of respondents (207; 44%) reported using sunbeds to some extent; of those 12% reported frequent use. Appearance ('to look better') was the most popular reason given by respondents for using sunbeds, followed by 'feel healthy'. Frequency of using sunbeds was found to be negatively correlated with the age of respondents and the existence of family experience with skin cancer, and strongly associated with the opinion that it is safer to use a sunbed than subathing outdoors, the female sex and smoking. It is clear from this study that the psychological factors that influence sunbeds use are complex and that so far public education campaigns have had little impact on it. This study highlights some of these psychological factors.

Adult↗
PubMed2000

Men's sexual health matters: promoting reproductive health in an international context.

Recent concern regarding the control of sexually transmitted infections (STIs) has resulted in an increased interest in the sexual health of men. This interest has primarily focused on strategies to 'encourage and enable men to take responsibility for their sexual and reproductive behaviour and their social and family roles' (United Nations 1994). Whilst men are deemed to have 'responsibilities', women are said to have 'rights' with regard to making choices about reproductive health and accessing appropriate and effective services. Here it is argued that, whilst provision of services and interventions against STIs in men should never be at the expense of those for women, it is often clinically easier and more effective to diagnose and treat men with STIs compared to women in resource-poor settings. Indeed, this may prove to be an effective strategy in controlling the spread of STIs, and hence reducing the disproportionate burden of their complications suffered by women. The paper reviews key issues in relation to improved service delivery for sexual and reproductive health in men, notably: the heterogeneity of male populations; current knowledge regarding men's sexual behaviour; the role of sexuality; methods of studying sexual behaviour in resource poor countries; men's own concerns in relation to sexual and reproductive health; and where and how they access treatment. It is argued that the time has now come to determine and address men's sexual health needs if we are to expect them to participate fully as responsible partners in improving and protecting their own and others' sexual and reproductive health.

Delivery of Health Care↗
PubMed2000

Social and behavioural factors associated with HIV seroconversion in homosexual men attending a central London STD clinic: a feasibility study.

An unmatched retrospective case control study was conducted to test the feasibility of investigating social and behavioural factors which may have contributed to recent HIV seroconversion in a group of homosexual men. Participants, recruited from a London sexually transmitted disease (STD) clinic, were sexually active and had had a negative HIV test with a subsequent test (positive (cases) or negative (controls)) within three to 15 months. Twenty cases and 22 controls were recruited between February and October 1995. There was no difference between cases and controls in: the number of regular or casual sexual partners, the proportion who were unaware of their regular partners' serostatus (cases 60%, controls 59%), or the proportion who had known HIV-positive regular partners (cases 20%, controls 23%). A significant difference in sexual behaviour was found only when the HIV status of partners, if known, was taken into account: cases were more likely than controls to have had unprotected receptive anal intercourse with a partner not known to be HIV-negative (OR = 5.5, CI = 1.15-29.50). Fifty per cent of the cases and 27% of the controls acquired acute STDs between the two HIV tests. All participants achieved high self-efficacy scores, but the controls believed their peers placed a greater value on safer sex. Cases cited emotional issues and the use of drugs and alcohol as contributing to their seroconversion, whereas controls cited a commitment to safer sex and the avoidance of high-risk situations as contributing to their remaining HIV-negative. The results illustrate the importance of acknowledging the concept of 'negotiated safety' in studies of sexual behaviour; seroconversion was only associated with unprotected sex with a partner not known to be HIV-negative. Despite high self-efficacy scores, indicating the skills to negotiate safer sex, high levels of unsafe anal intercourse were reported. Differences between cases and controls included the importance of safer sex, periods of emotional vulnerability, influence of peers and the appropriate use of condoms. There is a need for these results to be confirmed in a larger and more powerful study.

Adult↗
PubMed2000

Can clinical assessment of chest pain be made more therapeutic?

We describe the referral and management of consecutive patients attending a cardiac service with the presenting complaint of chest pain. Of 610 consecutive new referrals to five Oxford cardiac clinics over 12 weeks, 202 had chest pain as the presenting complaint: 91 (45%) angina, 101 (50%) non-cardiac chest pain, 8 (4%) both and 2 (1%) uncertain diagnosis. Information in clinic letters was sometimes ambiguous and contradictory and suggested a lack of precise information to patients. Patients with non-cardiac chest pain often had long histories, including considerable previous use of services and specialist investigations. There were delays in referral and assessment of patients. There are opportunities for simple changes in assessment procedures which might have substantial advantages for outcome and resource: (i) more detailed referral information from general practitioners, with an explicit statement of the reasons for referral; (ii) minor modifications to augment the assessment by provision of unambiguous information to patients and primary care at discharge.

Angina Pectoris↗
PubMed2000

The effects of [K+]o on regional differences in electrical characteristics of ventricular myocytes in guinea-pig.

Altering [K+]o might have different effects on action potential duration (APD) in myocytes from different regions. Therefore, the effects of [K+]o on regional differences in action potential characteristics were investigated in sub-endocardial, mid-myocardial and sub-epicardial myocytes isolated from the base of guinea-pig left ventricular free wall using three different [K+]o (2.7, 5.4 and 8.1 mM KCl). Action potentials were recorded using the switch-clamp technique at 0.5 Hz. Increasing [K+]o from 2.7 to 8.1 mM shortened the action potential duration to 90 % repolarization (APD90; mean APD90 values in sub-endocardial, mid-myocardial and sub-epicardial myocytes were, respectively, 295 +/- 9, 286 +/- 9 and 266 +/- 8 ms in 2.7 mM [K+]o, 270 +/- 7, 255 +/- 7 and 215 +/- 7 ms in 5.4 mM [K+]o, 234 + 7, 212 +/- 10 and 155 +/- 8 ms in 8.1 mM [K+]o), depolarized the resting potential, and reduced the amplitude of the action potential. The effect of increasing [K+]o on action potential characteristics was more pronounced in sub-epicardial myocytes than in sub-endocardial and mid-myocardial myocytes. The regional differences in APD90 in 5.4 mM [K+]o were increased in 8.1 mM [K+]o and abolished in 2.7 mM [K+]o. In conclusion, changing [K+]o produces more pronounced effects on action potentials in sub-epicardial myocytes than in sub-endocardial myocytes, modifying the normal heterogeneity of action potentials. The differences in the response of sub-epicardium and sub-endocardium to [K+]o may contribute to the flattening or inversion of the T wave commonly seen in patients presenting with hypokalaemia and the upright and tall T waves observed in electrocardiograms recorded during hyperkalaemia, although the underlying ionic currents remain to be determined.

Action Potentials↗
PubMed2000

Prolongation of the QT interval in heart failure occurs at low but not at high heart rates.

Abnormal left ventricular structure and function as in, for example, left ventricular hypertrophy or chronic heart failure, is associated with sudden cardiac death and, when the ejection fraction is depressed, with prolongation of the QT interval. The dependence on heart rate of QT interval prolongation in these conditions, and the relationship of any abnormalities either to deranged autonomic nervous system function or to an adverse prognosis, has not been well studied. We therefore investigated (1) the dependence on heart rate of the QT interval, and (2) the relationship between both QT interval and the QT/heart rate slope and markers of adverse prognosis in these two conditions. The QT interval was measured at rest and during exercise in 34 subjects with heart failure, 16 subjects with left ventricular hypertrophy and 16 age-matched controls with normal left ventricular structure and function. QTc (corrected QT) intervals at rest were significantly longer in heart failure patients (471+/-10 ms) than in controls (421+/-6 ms) or in subjects with hypertrophy (420+/-6 ms) (P<0.05). At peak exercise, despite the attainment of similar heart rates, the QT intervals no longer differed from each other, being 281+/-7 ms for controls, 296+/-11 ms in hypertrophy and 303+/-10 ms in heart failure (no significant difference). The QT/heart rate slope was significantly increased in heart failure [2.3+/-0.1 ms.(beats/min)(-1)] compared with controls [1.55+/-0.06 ms.(beats/min)(-1)] and hypertrophy [1. 66+/-0.1 ms.(beats/min)(-1)] (P<0.001). In left ventricular hypertrophy, despite animal data suggesting that QT interval prolongation should occur, no abnormalities were found in QT intervals at rest or during exercise. The QT/heart rate slope did not relate to any markers for an adverse prognosis, except that of prolongation of QT interval. Long QT intervals were associated principally with impairment of left ventricular systolic function. Our data emphasize the dynamic nature of the QT interval abnormalities found in heart failure.

Analysis of Variance↗
PubMed1999

Investigating the relaxation rate, following diazo-2 photolysis, of a skinned trabecular preparation from guinea-pig hypertrophied left ventricle.

Cardiac hypertrophy in the guinea-pig is not accompanied by a large shift in the expression of the predominant isoform of myosin in the left ventricle; however, in this species, thin filament proteins do change. We examined the relaxation, following laser flash photolysis of the photolabile caged Ca2+ chelator diazo-2, of a skinned trabecular preparation from the left ventricle of guinea-pigs that had undergone abdominal aortic banding. Sham-operated animals were used as controls; no guinea-pigs showed any signs of heart failure. We report that mild cardiac hypertrophy does not affect the relaxation rate of Triton-skinned trabeculae from the guinea-pig. However, there was a 35% reduction in the maximum force generated by trabeculae from the left ventricle of the abdominal aortic-banded animals. Additionally, alterations in key troponin subunits occur in the left ventricle of guinea-pigs with mild hypertrophy. We conclude that the thin filament protein changes do not influence trabecular relaxation rates, even though they probably affect maximal force generation. The cellular membrane systems of the intact guinea-pig heart, which were not a factor in this present study, appear to have an important role in the altered cardiac relaxation rates seen in hypertrophy.

Animals↗