Drinking attitudes and behavior of high-school students in Kentucky.
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Achievement↗
Biomedical subjects
E Patterson
Publications and source records attributed to E Patterson.
The effectiveness of home care for general hospital patients.
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Adolescent↗
Long-term intracoronary ethanol administration electrophysiologic and morphologic effects.
The long-term intracoronary infusion of ethanol was used to evaluate the potential of ethanol to produce myocardial injury and cardiac rhythm disturbances. In 22 dogs, electrophysiologic testing was performed 48 hr after cessation of alcohol administration. Multiple premature ventricular beats occurred spontaneously in 3 dogs with spontaneous sustained monomorphic ventricular tachycardia observed in 1 dog. Provocative ventricular pacing produced ventricular tachycardia lasting 20 or more beats in 13 animals with sustained tachycardia observed in 3 animals. Provocative ventricular pacing in the presence of lidocaine or epinephrine produced sustained ventricular tachycardia in an additional 4 dogs. The electrophysiologic properties of Purkinje fibers from the zone receiving ethanol were altered when compared to the control zone. The resting membrane potential was decreased (-76 +/- 2 mV vs. -85 +/- mV, p less than 0.001) with a decrease in action potential amplitude (91 +/- 4 vs. 109 +/- 2 mV, p less than 0.001) and phase 0 upstroke (231 +/- 27 vs. 456 +/- 25 V/sec, p less than 0.02). Prolonged refractoriness was observed in the ethanol zone without a prolongation of action potential duration. Intramural lesions observed within the left circumflex distribution varied from focal acute myofibrillar degeneration and necrosis to severe local scarring. The data suggest that intracoronary ethanol administration at human abuse levels of blood alcohol concentrations produces histologic and electrophysiologic injury in the canine heart. The electrophysiologic ch changes provide a substrate sufficient for the induction and maintenance of ventricular arrhythmia.
Action Potentials↗
Disopyramide plasma and myocardial tissue concentrations as they relate to antiarrhythmic activity.
Antiarrhythmic concentrations of disopyramide in canine plasma and myocardium were determined by gas chromatography. Ventricular tachycardia was incuded in anesthetized dogs by the intravenous administration of ouabain. Disopyramide phosphate was then administered by a two-stage continuous infusion method. A rapid infusion of disopyramide (9.08 mg/kg/hr) was administered for 30 min, followed by a slow infusion (2.18 mg/kg/hr) to maintain steady-state plasma levels of 1.98-2.21, mean +/- SEM = 2.1 +/- 0.02 microgram/ml at the end of 2 hr. Myocardial tissue levels of disopyramide at steady-state plasma levels were four times those of plasma (atrial tissue, 8.91 +/- 0.10; right ventricular free wall, 8.93 +/- 0.13; left ventricular free wall, 9.11 +/- 0.16 microgram/gm wet tissue). The intravenous administration of 80 units crystalline zinc insulin produced both hypokalemia (3.78 +/- 0.22 reduced to 2.36 +/- 0.18 mEq potassium/liter plasma) and a reappearance of ventricular tachycardia despite no change in plasma and myocardial tissue concentrations of disopyramide from those which had been effective in establishing and maintaining sinus rhythm. The observations demonstrate a relationship between plasma and myocardial disopyramide concentrations such that the former can be used in assessing patient therapy. In addition, this study suggests the important of plasma potassium in determining the therapeutic effectiveness of disopyramide.
Animals↗
Clinical pharmacokinetics of intravenous and oral bretylium tosylate in survivors of ventricular tachycardia or fibrillation: clinical application of a new assay for bretylium.
We studied 12 patients receiving either chronic oral (p.o.) maintenance bretylium and/or acute intravenous (i.v.) bretylium to evaluate drug efficacy and pharmacokinetics. All patients were survivors of ventricular tachycardia or fibrillation. A new assay for bretylium was applied, and it proved sensitive and reliable. After single intravenous dosing, bretylium was eliminated from serum with a mean rate constant of lambda iv1 = 0.0515 hr-1 and a corresponding elimination half-life of tiv1/2 = 13.5 hr (7 studies), similar to previous results in normals. Total body clearance averaged 428 ml/min, of which virtually all was accounted for by renal clearance. Seven patients responding to intravenous bretylium were transferred to oral drug. During chronic therapy (mean dose, 41 mg/kg/day bretylium tosylate), mean minimum steady-state concentration of bretylium was 186 ng/ml (range, 72-461) and was accurately predicted, within experimental error, by using the elimination rate constant determined for oral, but not intravenous, drug in normal subjects (lambda po1 = 0.115 hr-1). Determination of average steady-state concentration (Css) yielded similar conclusions. Mean 24 hr urinary excretion of bretylium during oral therapy was 18.3% (range, 9-13%). These results lend validity to earlier observations in normals and suggest route and concentration dependence of disposition. Transfer to oral bretylium allowed continued control of sustained ventricular tachycardia in all 7 patients and of unsustained ventricular tachycardia in 5. Orthostatic hypotension in 4 responded to protriptyline. Six were discharged on bretylium, with a mean follow-up of 12.2 months (range, 1-25.5). Four maintained a favorable response, and 2 died suddenly at 1 and 3 months. We conclude that further evaluation or oral bretylium is justified; attempts should be made to increase steady-state concentrations during oral therapy.
Administration, Oral↗
Chronic ventricular tachyarrhythmias in the conscious dog: prevention by UM-272 (dimethylpropranolol).
The ability of chronic UM-272 (dimethylpropranolol) treatment to prevent the induction of reentrant ventricular tachyarrhythmias was assessed in the conscious dog subjected to serial programmed electrical stimulation on days 3--5 after myocardial infarction. In 20 untreated control animals, programmed electrical stimulation produced nonsustained ventricular tachycardia in 6 animals (30%), sustained ventricular tachycardia in 8 animals (40%), and ventricular fibrillation in 6 animals (30%) on the third day after occlusion and reperfusion of the left anterior descending coronary artery. On day 4, programmed electrical stimulation produced nonsustained ventricular tachycardia in 5 animals (36%), sustained ventricular tachycardia in 7 animals (50%), and ventricular fibrillation in 2 animals (14%). UM-272, 5 or 10 mg/kg, i.v., was administered every 12 hr to a separate group of 8 dogs after the induction of ischemic myocardial injury. Programmed electrical stimulation on day 3 after myocardial infarction failed to elicit ventricular arrhythmias in 4 animals (50%, p = 0.014), with acute administration of the next UM-272 dose preventing the induction of ventricular tachyarrhythmias in 7 animals (88%, p less than 0.0001). On day 4, programmed electrical stimulation failed to elicit ventricular arrhythmias in 5 aminals (63%, p = 0.0021). Thirty-six hours after the withdrawal of UM-272, programmed electrical stimulation produced ventricular fibrillation in 5 animals (63%) and sustained ventricular tachycardia which degenerated to ventricular fibrillation in 3 animals (37%). UM-272 significantly (p less than 0.05) depressed conduction in both normal and ischemically injured myocardium while also increasing (p less than 0.05) ventricular effective refractory periods. The results of these investigations suggest that UM-272 may be effective in preventing reentrant ventricular rhythms in hearts subjected to chronic myocardial ischemic damage and, therefore, may be of potential value in preventing reentrant ventricular arrhythmias in man.
Animals↗
Serial electrophysiologic effects of bretylium in man and their correlation with plasma concentrations.
The serial electrophysiologic effects of bretylium were studied in 10 patients undergoing cardiac catheterization before giving the drug, at the end of bretylium tosylate-loading infusion (5 mg/kg/15 min), and after 1 h of intravenous drug maintenance (1.5 mg/min). Mean blood pressure increased during drug loading from 93.6 +/- 10.9 mm Hg to 121.1 +/- 16.2 mm Hg (p less than 0.01, t = 15 min) but returned toward control (100.9 +/- 18.7 mm Hg, p = NS) during drug maintenance (t = 75 min). Small changes in PR, QRS, QTc, AH, and HV intervals during spontaneous and paced rhythms were not significant. Comparison of the control electrophysiologic study with early and late postdrug studies showed no significant changes in corrected sinus node recovery times and in Wenckebach cycle lengths, but small decreases in refractory periods occurred. After drug loading, decreases in mean effective refractory periods of atrium, AV node, and right ventricle of 12, 2, and 16 ms, respectively, occurred (p = NS); during drug maintenance (t = 75 min), these refractory periods had decreased with respect to control by 21, 36, and 13 ms, respectively (p less than 0.05, 0.05, and 0.01). Functional refractory period of the AV node decreased at 75 min by 31 ms (p less than 0.01). The observed shortening of refractory periods contrasts with the direct effects of bretylium in isolated ventricular muscle and Purkinje fibers, which consist of prolongation of effective refractory periods and action potential duration. Thus, indirect (adrenergic) effects may be more important to overall clinical electrophysiologic actions not only acutely during loading but also during at least the first 60-90 min of maintenance therapy, which spans the expected time of initial clinical antifibrillatory response.
Adult↗
Electrophysiologic actions of lidocaine in a canine model of chronic myocardial ischemic damage--arrhythmogenic actions of lidocaine.
Lidocaine facilitated the induction of ventricular arrhythmias by programmed electrical stimulation in 16 dogs, 5 to 14 days after a temporary (90-min) occlusion of the left anterior descending coronary artery. In these 16 animals, programmed stimulation failed to produce ventricular tachyarrhythmias in any animal before lidocaine administration (3 mg/kg), while after lidocaine administration, programmed stimulation produced nonsustained ventricular tachycardia in four animals (25%), sustained ventricular tachycardia in nine animals (56%), and ventricular fibrillation in one animal (6%). Delayed electrical activity in ischemically injured ventricular myocardium produced by premature ventricular stimuli (mean +/- SD = 179 +/- 34 ms) was delayed further by the administration of lidocaine (237 +/- 42 ms, p less than 0.01), resulting in continuous local electrical activity between the final premature ventricular stimulus and the initial beat of the resultant ventricular tachycardia. Lidocaine administration did not alter myocardial refractoriness in normal ventricular tissue, but it prolonged refractoriness in ischemically injured ventricular myocardium. These results show that lidocaine can have arrhythmogenic actions when administered in the presence of existing ischemic injury, possibly the result of increased delay in activation of ischemically injured ventricular myocardium with localized reentry of myocardial electrical activity.
Animals↗
Antifibrillatory actions of d,l-nadolol in a conscious canine model of sudden coronary death.
The role of beta-adrenergic receptor blockade in preventing ventricular fibrillation in a conscious canine model of sudden coronary death was examined using d,l-nadolol and the non-beta-adrenergic receptor blocking isomer, d-nadolol. On day 4, after a temporary 90-min occlusion of the left anterior descending coronary artery, an anodal current of 150 microA was applied to the intimal surface of the left circumflex coronary artery. Occlusive or nonocclusive thrombosis of the artery was accompanied by ST-segment changes. In saline-treated animals (n = 15), ST-segment changes were followed by sinus tachycardia and QT-segment prolongation, with development of ventricular premature beats. Ventricular fibrillation developed in 14 animals (93%). Pretreatment with 1 (n = 9) or 8 mg/kg d,l-nadolol (n = 13) did not alter the development of left circumflex coronary artery thrombosis and ischemic ST-segment changes, but decreased the incidence of ventricular fibrillation and increased survival at 24 h (56% and 63%, respectively) (p less than 0.01 versus saline). d,l-Nadolol also attenuated the sinus tachycardia and QT-interval prolongation accompanying acute ischemia. d-Nadolol (1 mg/kg), the non-beta-adrenergic receptor blocking isomer, failed to prevent development of ST-segment changes. Sinus tachycardia and QT-interval prolongation were not prevented, and ventricular fibrillation developed in all eight animals (100%). In animals without previously induced anterior myocardial ischemic injury (n = 10), left circumflex coronary artery thrombosis failed to produce sinus tachycardia and QT-interval prolongation and was associated with a lower incidence of ventricular fibrillation (20%, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenergic beta-Antagonists↗
Development of ventricular tachyarrhythmias in the conscious canine during the recovery phase of experimental ischemic injury: effect of bethanidine administration.
The antiarrhythmic and antifibrillatory actions of bethanidine were evaluated in two conscious canine models which are capable of developing ventricular tachyarrhythmias during the recovery phase of myocardial infarction. In the first model, nonsustained (n = 3) or sustained (n = 12) ventricular tachycardia (cycle length, 165 +/- 6 ms; mean +/- SD) was initiated by programmed electrical stimulation, 4-9 days after experimental myocardial infarction. Bethanidine was administered in cumulative doses of 2, 4, 8, and 16 mg/kg and programmed stimulation repeated. Bethanidine, in doses of 4, 8, and 16 mg/kg, slowed the cycle length of the tachycardia and allowed slower rates of ventricular pacing to produce equivalent delays at epicardial sites in the ischemic zone. Despite these changes, induction of sustained ventricular tachycardia was prevented in only two of 13 animals. Bethanidine (8 mg/kg i.v. every 8 h, n = 4; 16 mg/kg i.v. every 8 h, n = 5) failed to prevent the development of premature ventricular beats, ventricular tachycardia, and ventricular fibrillation which developed in response to a transient ischemic episode superimposed on the heart that had a previous acute myocardial infarction. No differences in survival at 24 h were observed between saline- (10%, n = 10) and bethanidine-treated (0%, n = 9) groups. These results suggest that bethanidine acts to increase the refractory period and depresses conduction velocity in ischemically injured tissue, slowing the rate of ventricular tachycardia. However, the drug fails to suppress the development of ventricular arrhythmias and ventricular fibrillation in both canine models.
Animals↗
The antiarrhythmic actions of intravenous and oral UM424 in postinfarction canine myocardium.
The electrophysiologic and antiarrhythmic effects of oral and intravenous UM424 were studied in canine models of acute and chronic myocardial injury. In the first phase of this study, reentrant ventricular tachyarrhythmias and/or ventricular fibrillation were initiated by programmed electrical stimulation techniques in seven dogs 48-120 h after myocardial infarction. The cycle length of these reentrant ventricular beats was 176 +/- 16 ms, and they were accompanied by fractionated asynchronous epicardial electrical activity in the injured region that bridged the diastolic interval, i.e., 143 +/- 37 ms. When this prolonged, diastolic electrical activity ceased, the ventricular tachyarrhythmias ceased. UM424 5 mg/kg i.v. increased the effective refractory period of the normal myocardium by 21 ms (p less than 0.05), depressed cardiac conduction in the injured, infarcted myocardium and suppressed these reentrant tachyarrhythmias. Ventricular fibrillation could not be initiated after UM424. In the second phase of this study, a canine model of coronary artery thrombosis was used to produce spontaneous ventricular arrhythmias. UM424 60 mg/kg p.o. converted these ventricular arrhythmias to normal sinus rhythm. This pharmacologic action was not associated with deleterious hemodynamic side effects and lasted for 3 h, the duration of each experiment. These results demonstrate that after oral or intravenous administration, UM424 possess antiarrhythmic and antifibrillatory actions in canine models of acute and chronic myocardial injury.
Administration, Oral↗
Longitudinal dissociation within the posterior AV nodal input of the rabbit: a substrate for AV nodal reentry.
BACKGROUND: Longitudinal dissociation of an anatomic pathway into 2 electrophysiologically distinct pathways has been hypothesized as a basis for localized AV nodal reentry and supraventricular arrhythmias. METHODS AND RESULTS: Extracellular bipolar and intracellular microelectrodes were used to record activation in the superfused rabbit AV junction. A subset of rabbit hearts (n=19 of 72) demonstrated dissociation of the posterior AV nodal input into >/=2 functional pathways. Antegrade AH conduction was maintained by a pathway just inferior to the tendon of Todaro. Rate-dependent conduction block was observed in a second pathway just superior to the tricuspid annulus, allowing retrograde activation of the distal portion of the inferior posterior AV nodal input and leading to the formation of apparent "dead-end" pathways. The superior (antegrade) and inferior (retrograde) pathways were separated by a band of well-polarized but poorly excitable transitional cells. Additional decreases in the atrial cycle length progressively increased the AH interval, further delaying retrograde activation of the inferior pathway, and progressively moved the site of conduction block in the inferior pathway proximally, thus extending the length of the retrograde conduction pathway and allowing circus movement within the transitional cells of the posterior AV nodal connection. CONCLUSIONS: Longitudinal dissociation within the posterior AV nodal input can give rise to localized reentry and AV nodal reentrant tachycardia.
Action Potentials↗
A descriptive study of nurses employed by general practitioners in south-east Queensland.
The aim of this study was to describe the demographic and occupational characteristics of a sample of nurses employed by general medical practitioners and the factors perceived to be influential in their role development. Telephone and mail surveys were undertaken within one general practice division in South-East Queensland. Thirty-seven of the 67 (55%) practice nurses responded to the mailed questionnaire. Of these respondents, ten were collectively interviewed to elaborate on the survey results. Findings indicated that the primary work of these nurses is one of assistant to the doctor. Autonomous nursing initiatives are largely opportunistic. Perceived barriers to role expansion included Medicare restrictions, inadequate basic and ongoing education programs, financial and space limitations of the practice, reluctance of general practitioners, and a lack of professional support.
Adult↗
Antiarrhythmic and antifibrillatory actions of the levo- and dextrorotatory isomers of sotalol.
The electrocardiographic responses to programmed ventricular stimulation and acute posterolateral myocardial ischemia were studied in conscious dogs treated with the resolved optical isomers of sotalol. Studies were conducted 3-7 days after anterior myocardial infarction to determine the relative contributions of beta-adrenergic receptor blockade and direct Class III electrophysiologic actions in the antiarrhythmic and antifibrillatory actions of the isomers. With cumulative i.v. administration of up to 8 mg/kg, both the beta-blocking levorotatory isomer and the dextrorotatory isomer suppressed the induction of ventricular tachyarrhythmias by programmed stimulation in at least 50% of dogs tested. Both isomers produced equivalent 15-20% increases in normal zone ventricular refractoriness, thereby preventing propagation of programmed ventricular extrastimuli of sufficient prematurity to elicit tachyarrhythmias. The levorotatory isomer of sotalol prolonged the PR interval; the administration of the dextrorotatory isomer increased QTc and, in several dogs, was associated with the development of ventricular ectopy. The prior administration of 8 mg/kg of either optical isomer of sotalol prevented the immediate spontaneous development of ventricular fibrillation in response to ischemia at a distance from the previous site of infarction. These results suggest that alterations in ventricular refractoriness may underlie the antiarrhythmic and antifibrillatory actions of the optical isomers of sotalol and of racemic sotalol.
Action Potentials↗
Evaluation of California's statewide implementation of enhanced perinatal services as Medicaid benefits.
The authors evaluated enhanced perinatal services developed by public health specialists that were implemented statewide through specially certified Medicaid providers to find out whether they were as effective as those services originally tested in the public health agency's pilot project, and more effective than services from regular Medicaid providers. Multivariate logistic regression analyses yielded adjusted odds ratios of use of care and health outcome measures for the statewide services compared with both the pilot project and routine Medicaid care. Although women receiving the enhanced services implemented statewide did not return for prenatal visits as well as those in the pilot project, they did better than women with routine Medicaid providers. Women who kept at least the eight prenatal visits recommended by the Public Health Service in 1989 had risks of low weight births no different from those in the pilot project and significantly better than those for women with at least eight visits with routine Medicaid providers (adjusted odds ratio 0.70 with a 95 percent confidence interval from 0.54 to 0.91). Thus, there is evidence for the efficacy of the services, but additional improvement could be realized through improving the use of care.
California↗