Brain penetration effects of microelectrodes and DBS leads in STN or GPi.

OBJECTIVE: To determine how intraoperative microelectrode recordings (MER) and intraoperative lead placement acutely influence tremor, rigidity, and bradykinesia. Secondarily, to evaluate whether the longevity of the MER and lead placement effects were influenced by target location (subthalamic nucleus (STN) or globus pallidus interna (GPi)). BACKGROUND: Currently most groups who perform deep brain stimulation (DBS) for Parkinson disease (PD) use MER, as well as macrostimulation (test stimulation), to refine DBS lead position. Following MER and/or test stimulation, however, there may be a resultant "collision/implantation" or "microlesion" effect, thought to result from disruption of cells and/or fibres within the penetrated region. These effects have not been carefully quantified. METHODS: 47 consecutive patients with PD undergoing unilateral DBS for PD (STN or GPi DBS) were evaluated. Motor function was measured at six time points with a modified motor Unified Parkinson Disease Rating Scale (UPDRS): (1) preoperatively, (2) immediately after MER, (3) immediately after lead implantation/collision, (4) 4 months following surgery-off medications, on DBS (12 h medication washout), (5) 6 months postoperatively-off medication and off DBS (12 h washout) and (6) 6 months-on medication and off DBS (12 h washout). RESULTS: Significant improvements in motor scores (p<0.05) (tremor, rigidity, bradykinesia) were observed as a result of MER and lead placement. The improvements were similar in magnitude to what was observed at 4 and 6 months post-DBS following programming and medication optimisation. When washed out (medications and DBS) for 12 h, UPDRS motor scores were still improved compared with preoperative testing. There was a larger improvement in STN compared with GPi following MER (p<0.05) and a trend for significance following lead placement (p<0.08) but long term outcome was similar. CONCLUSION: This study demonstrated significant acute intraoperative penetration effects resulting from MER and lead placement/collision in PD. Clinicians rating patients in the operating suite should be aware of these effects, and should consider pre- and post-lead placement rating scales prior to activating DBS. The collision/implantation effects were greater intraoperatively with STN compared with GPi, and with greater disease duration there was a larger effect.

Price competition and hospital cost growth in the United States (1989-1994).

In recent years, most health care markets in the United States (US) have experienced rapid penetration by health maintenance organizations (HMOs) and preferred provider organizations (PPOs). During this same period, the US has also experienced slowing health care costs. Using a national database, we demonstrate that HMOs and PPOs have significantly restrained cost growth among hospitals located in competitive hospital markets, but not so in the case of hospitals located in relatively concentrated markets. In relative terms, we estimate that HMOs have contained cost growth more effectively than PPOs.

Histological patterns of atherosclerotic plaques in unstable angina patients vary according to clinical presentation.

BACKGROUND: Unstable angina is a heterogeneous clinical syndrome. The diverse clinical presentations of unstable angina may reflect different pathogenic mechanisms within the plaque. OBJECTIVE: To investigate the cellular constituents of culprit coronary atheromatous plaques in patients with stable angina pectoris and patients with diverse clinical presentations of unstable angina. METHODS: 48 patients who underwent coronary atherectomy for management of ischaemic heart disease: 23 had stable angina and 25 had unstable angina. Of the latter, 11 patients were classified as Braunwald's IIB and 14 as Braunwald's IIIB unstable angina. The presence of thrombus, cholesterol clefts, and smooth muscle cell proliferation was assessed in atherectomy samples using standard histological techniques. Monoclonal antibodies were used to identify smooth muscle cells and macrophages within atherosclerotic plaque fragments. RESULTS: Fresh thrombus was more frequently found in patients with Braunwald's IIIB unstable angina (64%) than in patients with stable angina (22%) or IIB unstable angina (27%) (p < 0.0006). A pattern of smooth muscle cell proliferation ("accelerated progression pattern") was observed which was also associated with coronary thrombus. This pattern was present in 30% of patients with stable angina, 64% of patients with IIIB unstable angina, and in all patients (100%) with IIB unstable angina. Atherosclerotic plaques with thrombus, cholesterol clefts, and macrophages were more common in patients with unstable angina than in stable angina patients. CONCLUSION: The presence of a specific smooth muscle cell proliferation (accelerated progression) pattern in patients with unstable angina, particularly in those with Braunwald's IIB unstable angina, suggests that episodic plaque disruption and subsequent healing may be an important mechanism underlying angina symptoms in these patients.

Paralysis in AIDS vaccine development violates ethical principles and human rights.

AIDS: Although a preventive vaccine is essential for controlling the HIV/AIDS epidemic and AIDS vaccine candidates exist, field trials of AIDS vaccine candidates are still not underway. Reasons for field trials of HIV vaccines not being underway include: ethical issues regarding how such trials would be conducted, fear that trial failure would make successive trials impossible to conduct, and controversy among the scientific community that the current crop of vaccines will effectively protect against HIV infection. Explanations for why none of these arguments are realistic reasons for delays in testing are provided. The ethical and human rights issues underlying the failure to proceed with field trials are also explored.^ieng

A profile of uncompensated hospital care, 1983-1995.

This DataWatch examines national trends in the provision of uncompensated hospital care. It shows that rapid growth from 1983-1986 was followed by modest growth through 1990, a time during which managed care was becoming established in some regions. There was then another spurt in uncompensated care from 1991-1993, a period that corresponds to sizable increases in disproportionate-share payments. Uncompensated care growth again slowed through 1995. The increase in uncompensated care levels after 1988 appears not to have kept pace with growth in hospital expenses or the number of uninsured. However, the trend data do not suggest a large-scale reduction of effort.

Medicine and public health, ethics and human rights.

There is more to modern health than new scientific discoveries, the development of new technologies, or emerging or re-emerging diseases. World events and experiences, such as the AIDS epidemic and the humanitarian emergencies in Bosnia and Rwanda, have made this evident by creating new relationships among medicine, public health, ethics, and human rights. Each domain has seeped into the other, making allies of public health and human rights, pressing the need for an ethics of public health, and revealing the rights-related responsibilities of physicians and other health care workers.

Weight bearing and velocity in trans-tibial and trans-femoral amputees.

The purpose of this study was to review the clinical utility of static weight bearing (SWB) and maximal self-selected ambulatory velocity as objective quantifiable measures in an outpatient lower limb prosthetic clinic. Seventy-three (n = 73) consecutive trans-tibial (TTA) and trans-femoral amputees (TFA) attending an outpatient prosthetic clinic were studied. Prosthetic weight bearing was measured on a bathroom scale (mass in kg), normalised to body mass then expressed as a percentage and labelled static weight bearing (SWB). Maximum safe self-selected ambulatory velocity over a 10 metre level walkway (m/s) was measured with a stopwatch. The SWB mean for the TTA group was 94.93% range 77-100%) and 88.36% for the TFA group (range 43-100%). The mean ambulatory velocity was 1.70 m/s (range 0.07-5.75) for the TTA group and 0.78 m/s (range 0.10-1.54) for the TFA group. A statistically significant relationship (p < 0.05) was found between SWB and ambulatory velocity in trans-tibial and trans-femoral amputees in this study. A ceiling effect was noted in the trans-tibial group with 42% achieving 100% SWB through their prosthetic limb so it was concluded that ambulatory velocity was the more sensitive measure in established trans-tibial prosthetic limb users. SWB may be the more appropriate quantifiable measure for use in established trans-femoral prosthesis users. Prosthetic training programmes would benefit from the objective measurement of SWB. Once optimal SWB was achieved, ambulatory velocity would be the more sensitive measure of prosthetic use.

Propofol and alfentanil for sedation during placement of retrobulbar block for cataract surgery.

STUDY OBJECTIVE: To determine if the addition of alfentanil to propofol is more effective than propofol alone to provide adequate conditions for placement of a retrobulbar block prior to cataract surgery. DESIGN: Randomized, double-blinded study. SETTING: Outpatients at a university hospital. PATIENTS: 40 adult ASA physical status I, II, and III outpatients scheduled for elective cataract surgery. INTERVENTIONS: Patients were randomly assigned to receive one of four drug combinations prior to the placement of a retrobulbar block: Group 1, propofol alone; Group 2, alfentanil 5 micrograms/kg plus propofol; Group 3, alfentanil 10 micrograms/kg plus propofol; Group 4, alfentanil 15 micrograms/kg plus propofol. All patients were preoxygenated by face mask for two minutes prior to drug administration. The quality of conditions for block placement were determined by: (1) assessing the amount of movement by the patients while the block needle was in place, (2) cooperativeness of the patients during the operation, (3) hemodynamic side effects, (4) incidence and severity of respiratory depression, (5) incidence of nausea and vomiting, (6) recall of placement of the block, and (7) time to discharge from the hospital. MEASUREMENTS AND MAIN RESULTS: The addition of alfentanil to propofol for sedation prior to placement of the retrobulbar block resulted in a dose-dependent reduction in movement by the patients. However, the highest dose of alfentanil (15 micrograms/kg) resulted in the greatest frequency (40% of the patients in this group) of respiratory depression (SpO2 < 90%). All patients were cooperative during the operation and responsive to verbal command within 5 minutes of placement of the block. In addition, all of the patients denied being nauseated, having vomited, or recalling block placement in the recovery room or the next day. CONCLUSIONS: The combination of alfentanil and propofol may be used to sedate patients in order to limit movement and provide a cooperative, alert patient with stable hemodynamics and limited respiratory depression during placement of retrobulbar block prior to ophthalmic surgery. However, excessive dosage of these drugs may result in hazardous respiratory depression in this patient population.

Global expansion of HIV infection and AIDS.

The decline of new HIV infections among subgroups in industrialized countries has created a false sense of security; globally, about 13,000 new infections occur each day. In developing countries, limited health care spending bars all but a privileged few from access to new treatment. In the absence of an effective vaccine and intensified prevention, spread of the virus will continue unabated.

Vulnerable plaque. Relation of characteristics to degree of stenosis in human coronary arteries.

BACKGROUND: The microanatomic features of the atherosclerotic plaque at risk of disruption include a large lipid core, a high macrophage content, and a thin cap. The relation between lipid core size, plaque size, and cap thickness either with each other or with the degree of stenosis has yet to be evaluated in human coronary arteries. METHODS AND RESULTS: Atherosclerotic coronary plaques (n = 160) were obtained from 31 subjects who died suddenly of ischemic heart disease. In coronary arteries perfused with formol saline at a pressure of 100 mm Hg, stenosis was measured by comparison of the minimal lumen size at the site of a plaque with that of the lumen in an adjacent normal segment of artery. Plaque size, the size of the lipid core, and the thickness of the cap were measured in histological sections. Lipid core size ranged from 0% to 82% of overall plaque size. Seventeen percent of plaques had a core size of > 50%. Linear regression showed no relation of core size to stenosis (r = .21). Absolute plaque size bore no relation to core size (r = .14). Minimal cap thickness was not related to core size (r = .06). Ten percent of plaques predicted to be angiographically invisible had cores of > 50%. CONCLUSIONS: Two major determinants of plaque vulnerability, core size and cap thickness, are not statistically related. Neither of these two factors that confer vulnerability are related to absolute plaque size or to the degree of stenosis.