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Biomedical subjects

K Lurie

Publications and source records attributed to K Lurie.

17 recordsLinked to original sources
PubMed2001

Arginine vasopressin during cardiopulmonary resuscitation and vasodilatory shock: current experience and future perspectives.

Epinephrine use during cardiopulmonary resuscitation (CPR) is controversial because of its receptor-mediated adverse effects such as increased myocardial oxygen consumption, ventricular arrhythmias, ventilation-perfusion defect, postresuscitation myocardial dysfunction, ventricular arrhythmias, and cardiac failure. In the CPR laboratory, vasopressin improved vital organ blood flow, cerebral oxygen delivery, resuscitability, and neurologic recovery more than did epinephrine. In patients with out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 hours than did patients treated with epinephrine. Currently, a large trial of out-of-hospital cardiac arrest patients being treated with vasopressin versus epinephrine is ongoing in Germany, Austria, and Switzerland. The new international CPR guidelines recommend 40 U vasopressin intravenously, and 1 mg epinephrine intravenously, as equally effective for the treatment of adult patients in ventricular fibrillation; however, no recommendation for vasopressin has been made to date for adult patients with asystole and pulseless electrical activity, or in children, because of lack of clinical data. When adrenergic vasopressors were unable to maintain arterial blood pressure in patients with vasodilatory shock, continuous infusions of vasopressin (0.04-0.10 U/min) stabilized cardiocirculatory parameters and even ensured weaning from catecholamines.

Arginine Vasopressin↗
PubMed2001

Mechanical advances in cardiopulmonary resuscitation.

Challenged by the continued high mortality rates for patients in cardiac arrest, the American Heart Association and the European Resuscitation Council developed a new set of guidelines in 2000 to help advance several new and promising cardiopulmonary resuscitation (CPR) techniques and devices. This is the first time these organizations have taken such a bold move, in part because of the poor results with standard closed-chest cardiac massage. The new techniques, interposed abdominal counterpulsation and active compression decompression CPR, each provide greater blood flow to the vital organs in animal models of CPR and lead to higher blood pressures in patients in cardiac arrest. In some clinical studies, both techniques have resulted in a significant increase in survival after cardiac arrest in comparison with standard CPR. Three of the four new CPR devices that were recommended in the new guidelines also provide superior vital organ blood flow and increased blood pressures in comparison with standard CPR. The three devices that improve the efficiency of CPR are the circumferential vest, an active compression decompression CPR device, and an inspiratory impedance valve used in combination with the active compression decompression CPR device. The fourth device type, one that compresses the thorax using an automated mechanical piston compression mechanism, was recommended to reduce the number of personnel required to perform CPR. However, no studies on the automated mechanical compression devices have showed an improvement in hemodynamic variables or survival in comparison with standard CPR. Taken together, these new technologies represent an important step forward in the evolution of CPR from a pair of hands to devices designed to enhance CPR efficiency. Each of these advances is described, and the recent literature about each of them is reviewed.

Cardiopulmonary Resuscitation↗
PubMed2000

Use of an inspiratory impedance threshold valve during cardiopulmonary resuscitation: a progress report.

Building upon studies on the mechanism of active compression-decompression (ACD) cardiopulmonary resuscitation, a new inspiratory impedance threshold valve has been developed to enhance the return of blood to the thorax during the decompression phase of CPR. Use of this device results in a greater negative intrathoracic pressure during chest wall decompression. This leads to improved vital organ perfusion during both standard and ACD CPR. Animal and human studies suggest that this simple device increases cardiopulmonary circulation by harnessing more efficiently the kinetic energy of the outward movement of the chest wall during standard CPR or active chest wall decompression. When used in conjunction with ACD CPR during clinical evaluation, addition of the impedance valve resulted in sustained systolic pressures of greater than 100 mmHg and diastolic pressures of greater than 55 mmHg. The new valve may be beneficial in patients in asystole or shock refractory ventricular fibrillation, when enhanced return of blood flow to the chest is needed to 'prime the pump'. The potential long-term benefits of this new valve remain under investigation.

Airway Resistance↗
PubMed2000

Improving the efficiency of cardiopulmonary resuscitation with an inspiratory impedance threshold valve.

In an effort to improve the efficiency of cardiopulmonary resuscitation (CPR), a new inspiratory impedance threshold valve has been developed to enhance the return of blood to the thorax during the chest decompression phase. This new device enhances negative intrathoracic pressure during chest wall recoil or the decompression phase, leading to improved vital organ perfusion during both standard CPR and active compression-decompression CPR. With active compression-decompression CPR, addition of the impedance threshold valve results in sustained diastolic pressures of >55 mm Hg in patients in cardiac arrest. The new valve shows promise for patients in asystole or shock refractory ventricular fibrillation, when enhanced return of blood flow to the chest is needed to "prime the pump." The potential long-term benefits of this new valve remain under study.

Airway Resistance↗
PubMed1995

Characterization of subcutaneous microvascular blood flow during tilt table-induced neurally mediated syncope.

OBJECTIVES: This study aimed to characterize subcutaneous blood flow changes during neurally mediated syncope and to determine whether microvasculature oscillation (vasomotion) is characteristically altered in conjunction with syncopal events. BACKGROUND: Marked pallor is commonly associated with neurally mediated syncope. However, little attention has been paid to the evaluation of subcutaneous blood flow and vasomotion in this setting. METHODS: This study utilized laser Doppler flowmetry to assess changes in subcutaneous microvascular blood flow during head-up tilt table testing in 13 patients with syncope and 6 control subjects. Blood flow and vasomotion frequency were measured continuously before, during and after completion of 80 degrees head-up tilt testing (< or = 25-min duration). RESULTS: Among the 13 patients with syncope, tilt testing reproduced syncopal symptoms in 9 (tilt-positive group) but not in 4 (tilt-negative group). None of the six control subjects developed symptoms during testing. Baseline mean subcutaneous blood flow did not differ significantly among the three groups. However, during upright tilt, blood flow gradually diminished in the tilt-positive group, reaching a nadir of 0.8 +/- 0.33 ml/min per 100 g of tissue (mean +/- SD), but remained relatively constant in the tilt-negative group and control subjects. The difference in mean blood flow response to tilt was statistically significant when the tilt-positive group was compared with either the tilt-negative group or control subjects (p < 0.001). Similarly, baseline blood flow oscillation frequency did not differ significantly in the three subgroups (tilt-positive group 0.2 +/- 0.11 Hz; tilt-negative group 0.2 +/- 0.02 Hz; control subjects 0.2 +/- 0.11 Hz). Subsequently, during tilt testing only the tilt-positive group exhibited increased oscillation frequency; oscillation frequency remained essentially constant throughout the tilt test in the tilt-negative group and control subjects (p < 0.001, tilt-positive group vs. either the tilt-negative group or control subjects). CONCLUSIONS: These findings document an expected diminution of subcutaneous blood flow in association with neurally mediated syncope and indicate that characteristic changes in microvasculature oscillation frequency occur in conjunction with syncopal symptoms. To the extent that microvasculature vasomotion is influenced by neural control, the changes in vasomotion frequency are consistent with relative diminution of peripheral sympathetic neural influence during neurally mediated syncopal episodes.

Adolescent↗
PubMed1994

Multiple-sensor systems for physiologic cardiac pacing.

PURPOSE: To review the status of artificial sensors in cardiac pacemakers and the rationale for developing pacing systems that use multiple sensors. DATA SOURCES: Journal articles published between 1982 and 1993 indexed in MEDLINE using the keywords pacemakers, sensors, and rate-adaptive, as well as abstracts and articles in the authors' personal files. STUDY SELECTION: Articles describing clinical experience with or clinical evaluation of cardiac pacing systems using multiple artificial sensors. DATA SYNTHESIS: Artificial sensors were created to adjust pacing rate reliably in response to changes in levels of physical exertion for patients with sinoatrial disease in whom exercise heart rate response is inadequate (for example, chronotropic incompetence in sinoatrial disease). To achieve this, various artificial sensors were developed and many reports confirm improved exertional tolerance. More recently, sensors have assumed a greater role in cardiac pacemakers. For example, sensors are used to permit automatic adjustment of certain programmable pacemaker settings, such as the atrioventricular interval. In the future, they may also be used to maximize pacemaker longevity by automatically optimizing energy output (voltage, pulse width). No single sensor is ideal for all potential applications, and investigators have advocated using two or more sensors. Several pacemakers that use multiple sensors with different but complementary operating characteristics are already commercially available outside the United States. Although preliminary findings are encouraging, additional clinical experience with these pacemakers is needed to determine their ultimate role in clinical practice. CONCLUSION: Simultaneous use of multiple complementary artificial sensors may permit development of cardiac pacemakers that operate more physiologically yet require less specialized medical follow-up.

Clinical Trials as Topic↗
PubMed1993

Head-up tilt testing with and without isoproterenol infusion in healthy subjects of different ages.

Passive head-up tilt testing with or without infusion of isoproterenol is used in the investigation and management of patients with syncope. Twenty-five healthy asymptomatic volunteers prospectively grouped according to age (young [28 +/- 1.7 years]: n = 9; middle [51 +/- 3.3 years]: n = 11; elderly [81 +/- 2.4 years]: n = 5; mean +/- SE) were studied during: (1) supine carotid sinus massage; (2) 60 degrees head-up tilt alone; and (3) infusion of isoproterenol to raise the heart rate 20% above supine baseline, prior to 10-minute repeat tilt. Symptoms occurred in three subjects (12%) and only occurred with passive tilting alone. Two young subjects had syncope with sinus pauses greater than 10 seconds. One elderly subject developed atrial flutter. No subject had symptoms or hypotension during tilt plus isoproterenol or a pause greater than 3 seconds with carotid sinus massage. With passive tilt, mean heart rate increased by 16 +/- 6 beats/min and 18 +/- 7.8 beats/min in the young and middle aged subjects (P < 0.05), but only by 6 +/- 5 beats/min in the elderly (P = NS, supine vs 60 degrees in each group). With head-up tilt plus isoproterenol infusion, the mean heart rate elevation in response to tilt was 17 +/- 9 beats/min, 8 +/- 3 beats/min, and 12 +/- 4 beats/min for the young, middle, and elderly subjects, respectively (P < 0.05, supine vs 60 degrees in each group).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Tilt-table testing and syncope.

Syncope is a common clinical problem with multiple potential causes. Recent studies have delineated the natural history and most frequent causes of recurrent syncopal episodes. The medical history and detailed physical examination are particularly important. Clinical electrophysiologic testing has also played a critical role in assessing causes of syncope, but recent reports suggest that its value lies primarily in treating patients with evident underlying structural heart disease. Among patients without structural heart disease, the neurally mediated forms of syncope, particularly the emotional or vasovagal faint, are by far the most common basis for symptoms. In these patients, head-up tilt-table testing has proved particularly valuable in defining the origin of the problem and in assessing therapeutic alternatives. Protocols for upright tilt-table testing remain in evolution. Nonetheless, current practice suggests that 25-minute tilt-test duration is reasonable if pharmacologic provocation is to be used for further evaluation of patients with negative initial findings. However, for those laboratories that do not favor pharmacologic intervention, a 45-minute tilt-test duration is probably essential. Overall, tilt-table testing has proved relatively sensitive and appropriately specific for the identification of patients susceptible to neurally mediated syncopal syndromes.

Electrophysiology↗
PubMed1988

Improved treatment of intra-abdominal abscess. A result of improved localization, drainage, and patient care, not technique.

Outcome in patients with abdominal abscesses treated at the University of Pennsylvania, Philadelphia, between 1973 and 1978 (group 1) was compared with that in patients treated between 1981 and 1986 (group 2). Mortality was less in group 2 patients (21% vs 39% in group 1). The decrease in mortality in group 2 was accompanied by a greater percentage of successful predrainage localization (74% vs 55% in group 1), successful initial drainage (76% vs 55% in group 1), and decreased predrainage organ failure (23% vs 52% in group 1). Because failure of initial drainage and predrainage organ failure were associated with increased mortality, improvement in both of these criteria contributed substantially to the lower mortality in group 2 patients. There were no differences in mortality, in initial success in drainage, or in length of hospital stay when 29 group 2 patients who underwent percutaneous drainage were compared with 37 patients who underwent surgical drainage. Mortality (22% vs 21%) and initial success (78% vs 72%) were similar for patients who underwent surgical and percutaneous drainage, respectively. We conclude that initial success in localization and drainage of the abscess is more important than whether drainage is surgical or percutaneous.

Abdomen↗
PubMed1987

Enhancement of survival and proliferation of clonogenic cells by monocyte-derived growth factors.

Human peripheral blood monocytes release a factor that enhances the clonal growth of human epithelial tumor cells in soft agar. The monocyte-derived growth factor was needed for both cellular proliferation and survival. Survival of SW-13 colony-forming cells decreased linearly in the absence of monocyte-conditioned media (MO-CM). Cells failed to respond to MO-CM after four days in culture. Although MO-CM enhanced growth when cells were plated at low density, growth was also enhanced when cell density was not a limiting factor. MO-CM increased DNA synthesis of SW-13 cells growing in monolayer culture as measured by tritiated-thymidine incorporation. These findings support evidence indicating inflammatory products may play a role in maintenance of the transformed phenotype.

Adrenal Cortex Neoplasms↗
PubMed1987

Intra-abdominal abscess in the 1980s.

Prompt recognition, early localization, and adequate drainage have contributed to the decreased morbidity and mortality rates associated with intra-abdominal abscess in the last decade. The physical examination, ultrasonography, computed tomography, and radionuclide scans provide information that leads to early detection and localization of abscess in almost all patients. Percutaneous drainage should be the initial procedure unless specific indications for surgery exist.

Abdomen↗
PubMed1986

Monocyte-derived growth factors for human tumor clonogenic cells.

Human peripheral blood monocytes secrete a soluble factor that enhances the ability of human epithelial tumor cell lines to clone in soft agar. Monocytes increased colony growth in a concentration-dependent manner, although inhibition of cell growth was observed in the presence of high concentrations of monocytes. Addition of indomethacin to monocytes did not abrogate this inhibition. Exposure of monocytes to endotoxin increased their ability to secrete stimulatory factors. Nonadherent lymphocytes were unable to support colony growth. Conditioned media from unstimulated monocytes also increased colony growth. Growth-promoting activity was detected in the media within the first 24 hr of culture, reaching a peak at 72 hr. Activity was not observed in monocyte lysates. Monocytes released this activity when cultured in the presence of both serum-free and serum-containing media. The activity was nondialyzable, relatively heat stable, and failed to adhere to CM-Sephadex. The demonstration of a monocyte-derived factor that enhances growth of epithelial tumor colonies supports findings indicating that inflammatory products may enhance tumor cell growth in vitro.

Adenocarcinoma↗
PubMed1982

Decreased catecholamine sensitivity and beta-adrenergic-receptor density in failing human hearts.

To identify the role of the myocardial beta-adrenergic pathway in congestive heart failure, we examined beta-adrenergic-receptor density, adenylate cyclase and creatine kinase activities, muscle contraction in vitro, and myocardial contractile protein levels in the left ventricles of failing and normally functioning hearts from cardiac-transplant recipients or prospective donors. Eleven failing left ventricles had a 50 to 56 per cent reduction in beta-receptor density, a 45 per cent reduction in maximal isoproterenol-mediated adenylate cyclase stimulation, and a 54 to 73 per cent reduction in maximal isoproterenol-stimulated muscle contraction, as compared with six normally functioning ventricles (P less than 0.05 for each comparison). In contrast, cytoplasmic creatine kinase activity, adenylate cyclase activities stimulated by fluoride ion and by histamine, histamine-stimulated muscle contraction, and levels of contractile protein were not different in the two groups (P less than 0.05). We conclude that in failing human hearts a decrease in beta-receptor density leads to subsensitivity of the beta-adrenergic pathway and decreased beta-agonist-stimulated muscle contraction. Regulation of beta-adrenergic receptors may be an important variable in cardiac failure.

Adenylyl Cyclases↗