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Biomedical subjects

J Hare

Publications and source records attributed to J Hare.

At least 19 recordsLinked to original sources
PubMed2003

Recent trends in tracheal intubation: a retrospective analysis of 97904 cases.

We conducted a review of routine anaesthetic audit data collected between April 1995 and December 2001 at Northampton General Hospital. A total of 97 904 anaesthetics were given. The average monthly rate of tracheal intubation fell during the study period from approximately 450 per month to approximately 280 per month. This was largely at the expense of tracheal tubes used during normal working hours, which fell by 40% (from approximately 390 per month to approximately 230 per month). Use outside normal working hours did not change. Of those cases managed in normal working hours with a tracheal tube, the decline in use over time was most obvious in patients of ASA physical status 1-2, and whose surgery was classified as elective or scheduled. The proportion of cases classified as ASA 3-5 or whose surgery was urgent or emergency increased (from 15.5% to 22.3%, and from 7.5% to 15.5%, respectively.) There was considerable variation across surgical specialities, with the greatest decline in tracheal intubation in head and neck surgery. These changes in practice have implications for the teaching of airway management skills.

Anesthesia, General↗
PubMed2000

Acute hemodynamic and clinical effects of levosimendan in patients with severe heart failure. Study Investigators.

BACKGROUND: We determined the short-term hemodynamic and clinical effects of levosimendan, a novel calcium-sensitizing agent, in patients with decompensated heart failure. METHODS AND RESULTS: One hundred forty-six patients with New York Heart Association functional class III or IV heart failure (mean left ventricular ejection fraction 21+/-1%) who had a pulmonary capillary wedge pressure >/=15 mm Hg and a cardiac index </=2.5 L x min(-1) x m(-2) were enrolled in a multicenter, double-blind, placebo-controlled study and randomized 2:1 to intravenous infusion of levosimendan or placebo. Drug infusions were uptitrated over 4 hours from an initial infusion rate of 0.1 microg x kg(-1) x min(-1) to a maximum rate of 0.4 microg x kg(-1) x min(-1) and maintained at the maximal tolerated infusion rate for an additional 2 hours. Levosimendan caused dose-dependent increases in stroke volume and cardiac index beginning with the lowest infusion rate and achieving maximal increases in stroke volume and cardiac index of 28% and 39%, respectively. Heart rate increased modestly (8%) at the maximal infusion rate and was not increased at the 2 lowest infusion rates. Levosimendan caused dose-dependent decreases in pulmonary capillary wedge, right atrial, pulmonary arterial, and mean arterial pressures. Levosimendan appeared to improve dyspnea and fatigue, as assessed by the patient and physician, and was not associated with a significant increase in adverse events. CONCLUSIONS: Levosimendan caused rapid dose-dependent improvement in hemodynamic function in patients with decompensated heart failure. These hemodynamic effects appeared to be accompanied by symptom improvement and were not associated with a significant increase in the number of adverse events. Levosimendan may be of value in the short-term management of patients with decompensated heart failure.

Cardiotonic Agents↗
PubMed2000

Licania michauxii Prance root extract induces hsp 70 mRNA and necrotic cell death in cultured human hepatoma and colon carcinoma cell lines.

An extract of Licania michauxii Prance root was found to be cytotoxic to cultured human hepatoma (HepG2) and colon carcinoma (Caco-2) cells. Morphological and nuclear characteristics of treated cells were consistent with necrotic death. Increases in the chaperone protein hsp 70 and hsp 70 mRNA were dose dependent reaching peak mRNA levels (40-fold above control) at 6 h. Increases in nuclear localization of hsp 70 was also observed with treatment. Heat treatment of cells for 45 min to induce hsp 70 prior to treatment with the extract provided transient protection from the necrotic response.

Cell Death↗
PubMed2000

Effects of electrical stimulation postcardiomyoplasty in a model of chronic heart failure: hemodynamic results after daily 12-hour cessation versus a nonstop regimen.

The hemodynamic effects of cardiomyoplasty (CMP) have been investigated in many centers, but the question of whether it is necessary to stimulate the latissimus dorsi muscle (LDM) 24 hours a day has not been answered. The main goal of our investigation was to determine whether hemodynamic results after CMP were impaired when continuous electrical stimulation (ES) was off for 12 hours a day. A model of chronic heart failure was created in 12 sheep by performing an arteriovenous anastamosis and administering doxorubicin. Two weeks after the anastomosis, CMP was performed in eight sheep (experimental series); ES training was begun at 2 weeks after CMP. After completion of the initial ES conditioning (8 weeks after CMP), one group of sheep continued to receive ES 24 hours daily. Another group of sheep had only 12 hours of ES daily. Hemodynamic parameters were investigated 2 weeks later with the stimulator turned on and then off. With doxorubicin administration, arteriovenous anastamosis created a stable model of biventricular heart failure (right atrial pressure 20 +/- 3 mmHg vs 6 +/- 2 mmHg at baseline; pulmonary capillary wedge pressure 18 +/- 3 mmHg vs 9 +/- 2 mmHg; left ventricular end-diastolic area 15.2 +/- 1.2 cm2 vs 6.4 +/- 0.7 cm2; left ventricular ejection fraction 0.38 +/- 0.6 vs 0.65 +/- 0.7). Cardiomyoplasty improved hemodynamic status in all eight experimental sheep. However, when the investigation was performed with the stimulator off, this improvement was statistically insignificant. With stimulation on, there was decreased right atrial pressure, pulmonary capillary wedge pressure, left ventricular end-diastolic volume, and increased left ventricular ejection fraction. With the stimulator turned off for 12 hours daily, hemodynamic measurements did not differ from data with continuous ES for 24 hours daily. Because hemodynamic results do not seem to be impaired, we recommend daily, periodic cessation of stimulation to prevent damage to the LDM after CMP.

Animals↗
PubMed2000

Why older age predicts lower acceptance of physician-assisted suicide.

BACKGROUND: Prior research has shown that older Americans have less accepting attitudes toward the legalization of physician-assisted suicide (PAS). OBJECTIVE: The current study tests nine explanations for why older Americans are less accepting of PAS. DESIGN: Survey questionnaires in two settings: a small rural community and an internal medicine clinic in western Wisconsin (n = 1,311). RESULTS: Overall, 57% of this sample supported legalization of PAS while 31% opposed and 12% were in the middle. Two of the nine factors significantly (and negatively) predicted attitudes toward PAS: religious beliefs and belief that life's transitions have value. One factor is shown to mediate the relationship between age and PAS. Older subjects' greater focus on religious beliefs was able to significantly explain their lower levels of acceptance of PAS, as compared to younger subjects. CONCLUSION: Findings from this study support other PAS studies, which indicate that most Americans support the legalization of PAS. More importantly, it clarifies the role of age--that is, age is not important in and of itself. Rather, it is important as a predictor of religious beliefs which in turn predict negative attitudes and unique influences on the thinking of American adults concerning the legalization of PAS.

Adolescent↗
PubMed1999

The struck-off mystery.

Observations on ward rounds suggested that psychiatric patients might be at special risk of removal from their general practitioner's list. Little has been published on why patients are struck off and our first attempt at investigation was by direct appeals for patients. This drew a small and unsatisfactory sample. We then asked two family health services authorities to distribute questionnaires to struck-off patients. One agreed, but later withdrew cooperation. There is a danger that struck-off patients will become an underclass excluded from primary care. We propose anonymous collection of information by health authorities, so that policy can be reviewed if necessary.

Community Psychiatry↗
PubMed1998

Optimization of shocking lead configuration for transvenous atrial defibrillation.

INTRODUCTION: High atrial defibrillation energy requirements (ADER) in patients with chronic atrial fibrillation (AF) may limit the acceptance of transvenous atrial defibrillation. We evaluated an optimized defibrillation electrode configuration that could help to reduce the ADER in patients with AF. METHODS AND RESULTS: We tested ten different configurations in nine dogs with AF (3.33+/-2.92 days) induced by rapid atrial pacing. The configurations were: right atrial (RA) appendage as anode and coronary sinus (CS) as cathode; RA and innominate vein (I) as anode to CS (cathode); RA-CS (anode) to I (cathode); I-CS (anode) to RA (cathode); RA and left lateral subcutaneous patch (P) as anode to CS (cathode); RA-CS (anode) to P (cathode); P-CS (anode) to RA (cathode); superior vena cava (SVC) and CS (anode) to RA (cathode); RA-CS (anode) to SVC (cathode); and RA-SVC (anode) to CS (cathode). ADER was defined as the voltage needed to defibrillate the atria in 10% to 90% of 20 consecutive shocks. Three lead systems had ADER lower than the RA (anode) to CS (cathode) configuration, which required a mean of 143+/-58 volts. These three were: RA-SVC (anode) to CS (cathode) 103+/-29 V; I-CS (anode) to RA (cathode) 129+/-39 V; and P-CS (anode) to RA (cathode) 130+/-38 V. The remaining configurations had ADER higher than the RA (anode) to CS (cathode) configuration. CONCLUSION: Adding an additional shocking electrode may reduce ADER when compared with the RA (anode) to CS (cathode) configuration. This concept could be incorporated into future implantable atrial defibrillators or used for refractory patients undergoing temporary transvenous cardioversion.

Animals↗
PubMed1997

Safety of atrial defibrillation shocks synchronized to narrow and wide QRS complexes during atrial pacing protocols simulating atrial fibrillation in dogs.

BACKGROUND: The potential ventricular proarrhythmic effect of atrial defibrillation shocks (ADS) remains a concern with automatic internal atrial defibrillation. Optimal R-wave synchronization alone may not be sufficient to prevent the induction of ventricular fibrillation (VF). METHODS AND RESULTS: The proarrhythmic effect of ADS synchronized to normally conducted QRS complexes (NQRS) and to supraventricular complexes with left or right bundle-branch block (L/RBBB) was investigated in a canine atrial pacing study. Short-long-short, single premature, and burst pacing protocols from the high right atrium were performed at baseline, during isoproterenol infusion, and after intravenous procainamide. The ADS were delivered between decapolar catheters in the coronary sinus and lateral right atrium. They were initially delivered 20 milliseconds (ms) after the end of the last conducted QRS complex and then scanned decrementally through that complex until VF was induced. For NQRS complexes, VF occurred only when the ADS were delivered at or before the onset of the QRS complex and never during the complex itself. In the presence of LBBB or RBBB, VF was induced by ADS delivered at the onset of or within the first 45 ms of the QRS complex in 16 animals. The longest RR (VV) intervals preceding ADS-induced VF were 345 ms at baseline and 380 ms after procainamide. CONCLUSIONS: In this study, ADS synchronized to NQRS complexes appeared to be safe regardless of the preceding RR interval. In the presence of LBBB or RBBB, RR intervals preceding the ADS of >345 ms at baseline and >380 ms in the presence of procainamide would have been required to avoid VF. Alternatively, ADS delivered 50 ms after the onset of the RV electrogram appeared to be safe in all circumstances regardless of the preceding RR interval.

Animals↗
PubMed1997

The effects of electrode-tissue contact on radiofrequency lesion generation.

During the generation of radiofrequency (RF) lesions in the ventricular myocardium, the maintenance of adequate electrode-tissue contact is critically important. In this study, lesion dimensions and temperature and impedance changes were evaluated while controlling electrode-tissue contact levels (-5, 0, +1, and +3 mm) and power levels (10, 20, and 30 W). This data was used to assess the ability of impedance and temperature monitoring to provide useful information about the quality of electrode-tissue contact. The results show that as the electrode-tissue contact increases, so does the amount of temperature rise. With the electrode floating in blood (-5 contact), the average maximum temperature increase with 20 and 30 W was only 7 +/- 1 and 11 +/- 2 degrees C, respectively. At 20 and 30 W the temperature plateaued shortly after the initiation of power application. With good electrode-tissue contact (+1 mm or +3 mm), the temperature increase within the first 10 seconds was significantly greater than the temperature increase from baseline with poor contact (0 mm or -5 mm) and reached a maximum of 60 +/- 1 degrees C after 60 seconds of power application. As the electrode-tissue contact increased, so did the rate and level of impedance decrease. However, the rate of impedance decrease was slower compared to the rate of temperature rise. With the electrode floating in blood, the maximum impedance decreases with 20 and 30 W were 6 +/- 6 omega and 9 +/- 5 omega, respectively. The impedances plateaued after a few seconds of power application. With the electrode in good contact, the maximum impedance decreases with 20 and 30 W were 25 +/- 2 omega and 20 +/- 6 omega, respectively. In these cases the rate of the impedance decrease plateaued after 40 seconds of power application. The increase in lesion diameter and depth correlate well with decreasing impedance and increasing temperature. However, lesion depth appears to correlate better with impedance than temperature. We conclude that, since the electrode-tissue contact is not known prior to the application of power to the endocardium, in the absence of a temperature control system, the power should initially be set at a low level. The power should be increased slowly over 20-30 seconds, and then maintained at its final level for at least 90 seconds to allow for maximal lesion depth maturation. The power level should be lowered if the impedance drop exceeds 15 omega.

Animals↗
PubMed1996

Distribution of atrial electrogram types during atrial fibrillation: effect of rapid atrial pacing and intercaval junction ablation.

OBJECTIVES: This study examined the anatomic distribution types and possible determinant of atrial electrogram types during atrial fibrillation. BACKGROUND: Different types of atrial electrograms during atrial fibrillation have been observed and classified, but their anatomic distribution patterns, determinants and potential usefulness in guiding future catheter ablation are unknown. METHODS: Two animal models of atrial fibrillation were used: the sterile pericarditis model (n = 10) and the rapid atrial pacing model (400 beats/min for 6 weeks, n = 6). The atrial electrogram of atrial fibrillation and the atrial effective refractory period were obtained from multiple sites of the right and left atrium. In addition, decremental rapid atrial stimulation was applied to the site of shortest and longest atrial effective refractory periods until atrial fibrillation induction in a subgroup of nine dogs. Ablation of the intercaval junction was performed using the radiofrequency catheter technique in dogs with atrial fibrillation duration > 1 min. RESULTS: In both models, organized atrial electrograms (type I) were predominantly observed at the left atrial sites and the right atrial appendage, whereas disorganized atrial electrograms (type III) were mainly observed at the right posterolateral atrium. The distribution of the atrial electrogram types closely followed that of the atrial effective refractory period, with the shortest atrial effective refractory period corresponding to organized atrial electrograms (type I) and the longest atrial effective refractory period corresponding to disorganized atrial electrograms (type III). The correlation of atrial electrogram type with the atrial effective refractory period was further demonstrated by the effect of rapid atrial stimulation. When rapid atrial stimulation was applied to the site with the shortest atrial effective refractory period, disorganized atrial electrograms were observed at sites with the longest atrial effective refractory period, whereas 1:1 atrial capture was still present at the stimulation site. Ablation of the intercaval junction made atrial fibrillation noninducible or tended to shorten the atrial fibrillation duration (from 26.4 +/- 24.2 to 8.8 +/- 22.6 min in the pericarditis group, p = 0.02, and from 33.7 +/- 29.2 to 12.1 +/- 23.8 min in the rapid pacing group, p = 0.09) but did not change the atrial electrogram types during atrial fibrillation. CONCLUSIONS: Various types of atrial electrograms are present at different locations during atrial fibrillation. The atrial electrogram characteristics of atrial fibrillation at a specific location are related to the atrial effective refractory period, with short effective refractory periods associated with organized atrial electrograms and long effective refractory periods associated with disorganized electrograms.

Animals↗
PubMed1996

Microwave applicator design for cardiac tissue ablations.

A variety of microwave applicators were designed, fabricated and tested for catheter applications: I-radiators, U-radiators, O-radiators, forward helical coil radiator, reverse helical coil, double coil radiator, loaded monopole radiator, leaky coaxial radiator and tee radiators. The comparative and relative radiation characteristics of these applicators were tested in a saline bath and tissues. Most radiators designed produced larger lesions than have been described previously.

Animals↗
PubMed1994

The anatomical determinants for the design of intracardiac mapping and ablation catheters.

An important factor in the efficient and successful completion of the ablation procedure is the design characteristics of the mapping/ablation catheters. These procedures are often hampered by the inability to maneuver the catheter to the desired location, in part because the catheters only have a single plane deflection capability and are not designed for the specific cardiac anatomical structures that contain the arrhythmogenic substrate. Single and Biplane Deflectable Catheters: Using measurements taken from six normal human cadaver hearts, ablation catheter design characteristics are presented for posterior, posterior septal, lateral, and posterior lateral pathways for retrograde and transseptal approaches. Three catheter designs based on anatomical characteristics were also evaluated. Pigtail Catheter: This catheter adapts to the atrial side of the mitral ring and improves positioning and stability for mapping and ablation of left-sided accessory pathways. Loop Catheter: This catheter is positioned at the perivalvular tricuspid ring and provides simultaneous mapping and ablation capabilities without the need to move the catheter or the need for additional catheters. Rotating Tip Catheter: The tip of this catheter is made up of three elongated teeth, which were curved 120 degrees apart into the rotating tip electrode. This electrode was designed to negotiate the surfaces of the atrial and intraventricular chambers. It is capable of discrete movements and has a large electrode-tissue contact area for the ablation of atrial and ventricular arrhythmias. Catheter designs presented in this article are based on the ability of the catheter to adapt to the anatomical location of the arrhythmogenic tissue as well as the maneuverability of the catheter's mapping and ablation electrodes. An anatomical approach to the design of ablation catheter technology is likely to reduce the x-ray radiation exposure for patient and operator, and may further increase the success rate of the procedure.

Animals↗
PubMed1993

Repeated use of ablation catheters: a prospective study.

OBJECTIVES: The objective of this study was to provide insight into the time course of electrical, physical and mechanical changes in ablation catheters after each use that may affect the safety and efficacy of the ablation procedure. BACKGROUND: An increasing number of institutions are reusing deflectable ablation catheters. At present, there are no data concerning the safety of reusing ablation catheters. METHODS: Over a period of 1 year, 69 Webster/Mansfield deflectable catheters used in 336 ablation procedures were prospectively studied. An additional 18 new catheters were tested after multiple sterilizations only. The catheters were evaluated for electrical and physical integrity and mechanical capabilities. These include deflection at room temperature and 37 degrees C, shaft compression and buckling during deflection, tip craters, torquing ability, glue separation and tip attachment using a stereoscope at x30 magnification and electrical resistance for each electrode. After each use, the catheters were gas-sterilized with ethylene oxide. RESULTS: The most common reasons for catheter rejection were tip electrode glue separation after 4.3 +/- 4.3 uses and loss of deflection after 5.0 +/- 3.3 uses. Electrical discontinuity between the catheter handle and electrodes was observed after 10.0 +/- 3.7 uses. There was no significant decrease in catheter torquing ability with repeated use. In this study the total estimated savings was $128,133, which includes the cost of catheter reprocessing. The reuse of Webster/Mansfield ablation catheters has not resulted in any major catheter failure or any major adverse clinical complications. CONCLUSIONS: On the basis of these observations, we believe that the Webster/Mansfield catheter can be reused an average of five times. It is strongly recommended that after each use catheters be carefully examined under appropriate magnification (x30) and that special attention be given to the ablation tip electrode. The catheters should also be tested for deflection and electrical integrity.

Catheter Ablation↗
PubMed1993

Physics and engineering of transcatheter cardiac tissue ablation.

Ablation of arrhythmogenic cardiac tissues has emerged as one of the most important advances in cardiac electrophysiology. With the introduction of transcatheter ablation, the treatment of ventricular tachycardia, Wolff-Parkinson-White syndrome and other cardiac arrhythmias has progressed from an expensive and painful surgical therapy accompanied by a long recovery period to the less expensive, less traumatic transcatheter approach. The feasibility of cardiac ablation, along with the increasing number of physicians using the technique, requires understanding of the anatomic and electrophysiologic bases of transcatheter ablation as well as the different technologies, their limitations and complications. This report provides an overview of the physical, scientific and technical aspects of cardiac ablation performed with the methods currently available and a summary of the limitations of each method and expected future technologic developments in this growing field. Emphasis is placed on radiofrequency and direct current energies, the primary methods now used. Methods such as cryoablation and laser, and microwave and chemical ablation are discussed with less detail because the method of delivering energy for these ablative procedures has not been fully developed.

Animals↗