Biomedical subjects
Publications and source records attributed to C McKenna.
Blunt force trauma to the chest can result in rupture of the heart. We report the youngest survivor of this injury, followed by a literature review, description of the epidemiology, and mechanism and guidelines for diagnosis and aggressive management.
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Stress-induced hemodynamic and hemostatic responses may acutely trigger atherosclerotic plaque disruption and thrombosis leading to myocardial infarction. This study was designed to evaluate the responses to three stressors and to determine if once-daily sustained release verapamil (Verelan) modified these responses. We studied 13 patients with mild to moderate hypertension in a randomized, double-blind, placebo-controlled crossover trial. After 4 weeks of therapy, patients were evaluated following assumption of the upright posture, mental stress, and cold pressor test. During placebo, the stressors produced an increase in systolic pressure (144 +/- 2 to 167 +/- 3 mmHg, p < 0.001), heart rate (70 +/- 2 to 77 +/- 2 beats/ min, p < 0.001), and platelet aggregability to adenosine diphosphate (threshold concentration fell from 2.8 +/- 0.4 to 1.9 +/- 0.1 microM, p = 0.05) and epinephrine (3.4 +/- 0.9 to 1.6 +/- 0.6 microM, p < 0.001). Verapamil lowered systolic pressure at baseline (144 +/- 2 to 134 +/- 2 mmHg, p < 0.001), and after stress (167 +/- 3 to 154 +/- 3 mmHg, p < 0.001), but did not alter the absolute increase with stress. During verapamil, platelet reactivity did not increase with stress, and the post-stress response to epinephrine was reduced (higher threshold concentration) compared with placebo (3.9 +/- 1.3 vs. 1.5 +/- 0.3 microM, p = 0.05). Verapamil also reduced the response to collagen (increased lag time) at baseline and after stress (111 +/- 9 vs. 91 +/- 3 s, p < 0.01). We conclude that verapamil blunted potentially harmful stress-induced hemodynamic and hemostatic changes. Further studies are required to determine whether these effects translate into a lower incidence of acute cardiovascular events.
Monosomy 7 is a non-random cytogenetic abnormality that is frequently associated with myelodysplastic syndromes (MDS). Twenty-four bone marrow samples from five pediatric patients with MDS were analysed using both traditional and interphase cytogenetic analysis. The majority of the metaphases were monosomic for chromosome 7 while interphase cytogenetic analysis consistently detected a disomic cell population in nondividing cell populations. This suggests that the monosomy 7 cells have a distinct proliferative advantage compared to the disomic cell population. The results demonstrate that interphase cytogenetic analysis provides important cytogenetic information about non-dividing cell subpopulations, enhancing our understanding of the cell dynamics of normal and monosomy 7 cells in MDS.
Although controlled clinical trials have had a major impact in many areas of cardiovascular disease management, they have had little influence on preoperative cardiac risk reduction. Over the past 2 years, we have conducted the Reduction of Cardiac Operative Risk (RCOR) Trial, a pilot study designed to determine enrollment and event rates for a definitive trial evaluating a strategy to reduce cardiac risk associated with noncardiac surgery. This experience indicates that a successful, definitive trial will require recognition of the multiple questions to be answered, accurate identification of the study population, a large sample size, cooperation between internists, surgeons, and anesthesiologists, and strategies to minimize cost. The high costs and difficulties of such a trial are likely to be outweighed by the enormous benefit of identifying the proper strategy for the use of the expensive testing methods that are currently employed.
Two phenotypically abnormal liveborns in whom trisomy 16 mosaicism was diagnosed prenatally by amniocentesis are described. Analysis of a percutaneous umbilical blood sample in one case revealed a normal chromosomal complement. Ultrasound examinations performed at the time of amniocentesis were normal. Serial sonography during the late second and third trimesters demonstrated progressive intrauterine growth retardation (IUGR) in both fetuses and a cardiac defect in one. At birth, both infants had dysmorphic features and multiple congenital anomalies. Trisomy 16 mosaicism was confirmed postnatally in both infants in skin fibroblasts; however, peripheral blood samples contained only chromosomally normal cells. The two mosaic trisomy 16 cases described in this report, together with the five confirmed cases reported previously, demonstrate the need for caution in the counselling of patients when trisomy 16 mosaicism is diagnosed prenatally in amniotic fluid samples. Such cases potentially can result in the birth of dysmorphic infants with significant birth defects, growth retardation, and possible developmental disabilities.
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Patients with substance dependence and psychiatric symptoms often present a diagnostic conundrum because each of these problems may mutually and reciprocally complicate the other. This may challenge the ability to identify dual-diagnosis patients who have both a substance abuse disorder and a definitive symptom-based psychiatric disorder. The main purpose of this explorative study was to identify variables suggestive of dual diagnosis in the population of substance-dependent patients with psychiatric symptoms. A secondary purpose was to examine the subgroups in this population for their distinctiveness from one another. Based upon clinical experience and the literature, seven independent variables were hypothesized as suggestive of dual diagnosis. Seventy-nine patients with substance dependence and psychiatric symptoms of depression, anxiety, and/or psychosis were assessed for symptom and disorder status generating three subgroups: I) 20 patients with psychiatric symptoms not meeting thresholds for clinical significance; II) 36 patients exhibiting a psychiatric disorder (dual diagnosis); and III) 23 patients with psychiatric symptoms meeting thresholds for clinical significance but not for a disorder. Odds ratios were calculated to examine the risk for dual diagnosis using the seven independent variables. A persistent increased risk for dual diagnosis was observed in patients who were positive for the seven variables. The seven variables were combined into an overall measure of patients' risk for dual diagnosis. Mean scores were significantly different for the three groups F(2, 76) = 8.4, p < .001. This study indicates variables that may be suggestive of dual diagnosis and finds subgroup distinctiveness in this sample. Both of these findings have treatment implications.
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OBJECTIVE: To determine the hours, volume, and type of work undertaken by preregistration house officers. DESIGN: Continuous observation of 472 hours of work performed by 12 preregistration house officers based in medical wards, using standard procedures for studying work patterns. SETTING: A teaching hospital with 340 beds assigned to general medicine and coronary care. SUBJECTS: 12 Of the 16 preregistration house officers in medicine at the hospital. MAIN OUTCOME MEASURES: The hours, volume, and type of work undertaken by preregistration house officers in February 1989, as recorded by trained observers on a one to one basis. RESULTS: The hours of duty ranged from 83 to 101 hours each week, the longest period of continuous duty being 58 hours. Each shift, house officers spent up to 25 minutes travelling between wards and an average of 85 minutes treating patients in wards that were cross covered. Between 50% and 71% of house officers' time was spent on patient oriented duties during the day; this fell to between 21% and 53% at night. Each doctor spent an average of 40 minutes filing when off duty after 6 pm. CONCLUSIONS: Established procedures for studying workload were effective in monitoring doctors' hours, providing accurate information on the volume and type of work, which is essential to resolve the problems of medical staffing. The study showed that more house officers were needed and that the cross cover system should be stopped. As a result three extra preregistration house officers were appointed.
A standard method for the assessment of cell viability has been developed for marine phytoplankton using an inexpensive stain, fluorescein diacetate (FDA), at .75 microM for 10 min. A flow cytometer was used as the fluorescence detector, providing an assessment of viability for each individual particle. Cell size and chlorophyll fluorescence per cell were assessed simultaneously, permitting an assignment of viability to specific subpopulations, thus increasing the power of the technique. A reasonable correspondence between FDA mean fluorescence intensity per cell and an independent metabolic indicator, photosynthetic capacity measured by 14C, was found. Both FDA mean fluorescence intensity and photosynthetic capacity vary as a function of cell volume. Recovery after extended periods of darkness indicate that cells that are FDA negative may not be dead, but merely quiescent or inactive.
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Percutaneous Transvenous Mitral Commissurotomy (PTMC) is an alternative to surgical mitral valvuloplasty for treatment of selected patients with rheumatic mitral stenosis. We report our initial experience with the technique in 10 patients. The procedure was successful in all patients. There were no major complications. Mitral valve area increased from a mean (+/- SD) of 0.95 +/- 0.2 to 2.18 +/- 0.8 cm2. Transmitral pressure gradient fell from 12 +/- 8 to 4 +/- 5 mmHg while New York Heart Association functional class improved by 1 grade or more in all patients. PTMC is a safe and cost effective alternative to surgical mitral valvotomy in appropriately selected cases.