Halothane, catecholamines, and cardiac conduction: anything new?
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Adrenergic alpha-Agonists↗
Biomedical subjects
L A Turner
Publications and source records attributed to L A Turner.
Actions of halothane, isoflurane, and enflurane on the regional action potential characteristics of canine Purkinje fibers.
The effects of halothane, isoflurane, and enflurane on proximal (false tendon) and distal (apical) canine Purkinje fibers were measured in vitro to assess their comparative effects on fibers exhibiting characteristically long (proximal) and short (distal) action potential duration. High- and low-dose anesthetic effects were evaluated in three groups of six left ventricular preparations and were compared with the changes occurring at identical times in six control preparations using analysis of variance with repeated measures. Under control conditions in all groups, the action potential duration, measured at 90% repolarization (APD90, mean +/- SEM), of proximal fibers was longer than that of distal fibers (320 +/- 16 vs 252 +/- 11 ms, P less than or equal to 0.01). Halothane (0.3 and 0.7 mM), isoflurane (0.4 and 0.8 mM), and enflurane (0.6 and 1.0 mM) produced a dose-dependent decrease (P less than or equal to 0.01) of proximal fiber APD90 with less (P less than or equal to 0.01) change of distal fiber APD90 and reduced (P less than or equal to 0.05) regional differences of APD90 at the higher dose. The decreases of proximal fiber APD90 were greater (P less than or equal to 0.01) for 1.0 mM (1.7 MAC) enflurane (-66 +/- 7 ms) and 0.8 mM (3.0 MAC) isoflurane (-69 +/- 9 ms) than for 0.7 mM (2.9 MAC) halothane (-33 +/- 8 ms). We conclude that the regional actions of anesthetics on Purkinje fiber repolarization may influence conduction during the relative refractory period and the occurrence of arrhythmias associated with disparity of regional refractory characteristics in the ventricular conduction system.
Action Potentials↗
Treating erectile dysfunction with external vacuum devices: impact upon sexual, psychological and marital functioning.
We evaluated prospectively the medical, sexual and psychosocial outcome of external vacuum devices in the treatment of erectile dysfunction. A total of 29 men regularly used such a device for 6 months and reported statistically significant improvements in erectile quality, frequency of intercourse attempts, frequency of orgasm and sexual satisfaction, as well as decreased psychiatric symptomatology, increased self-esteem and a trend toward improved marital satisfaction. Of the partners 18 reported improved sexual functioning, including increased frequency of orgasm, decreased masturbation and greater sexual satisfaction, with no changes in psychosocial parameters. The vacuum device was effective in producing erections in 89% of the men. Dropout, only 19% within 6 months, was primarily due to insufficient or pivoting erections and bruising. The most frequent adverse effects were blocked ejaculation and physical discomfort. Vacuum devices appear to provide a safe, effective, inexpensive, noninvasive treatment for erectile failure that enjoys high patient and partner acceptance.
Adult↗
Differential protective effects of halothane and isoflurane against hypoxic and reoxygenation injury in the isolated guinea pig heart.
The authors investigated the effects of halothane (HAL) and isoflurane (ISO) on cardiac depression produced by global hypoxia and the recovery of function following reoxygenation is isolated guinea pig hearts perfused with Krebs' solution at constant pressure. Isovolumetric left ventricular systolic (LVSP) and end-diastolic pressures (LVEDP) were measured by placing a saline filled, latex balloon into the left ventricle. Bipolar electrodes were placed in the right atrium and right ventricle for measurements of heart rate (HR), atrioventricular conduction time (AVCT), and determination of the incidence and severity of dysrhythmias occurring during hypoxia and reoxygenation. Hearts were divided into three groups: control (n = 20), halothane (n = 12), and isoflurane (n = 13). All hearts were exposed in sequence to oxygenated perfusate (PO2, 530 mmHg), moderately hypoxic perfusate (PO2, 91 mmHg) for 30 min, and then to oxygenated perfusate for 40 min. Halothane (1%, 0.4 mM) or isoflurane (1.5%, 0.5 mM) were administered 10 min before hypoxia, during hypoxia, and during the first 10 min of reoxygenation. Exposure to halothane and isoflurane before hypoxia produced a 14 and 11% decrease in heart rate, a 32 and 23% increase in AVCT, and a 47 and 28% decrease in LVSP (all P less than or equal to 0.001) for halothane and isoflurane, respectively, and no significant change in LVEDP. During hypoxia, HR decreased and AVCT increased similarly in both groups. Left ventricular systolic pressure (LVSP) decreased sharply with a narrowing of the prehypoxic differences among the groups. In the control and isoflurane groups, LVEDP increased during hypoxia but remained unchanged in the halothane group.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
A comparison of the effects of halothane and tetrodotoxin on the regional repolarization characteristics of canine Purkinje fibers.
The effects of halothane, tetrodotoxin (TTX), veratridine (VTD), and alterations of extracellular calcium ion concentration [Ca++]0) on regional differences of canine Purkinje fiber action potential duration (APD50 and APD90) were investigated in vitro at a paced rate of 75 beats per min. Under control conditions (n = 15 hearts) APD90 of proximal (false tendon) fibers (289 +/- 6 ms) always exceeded (P less than or equal to 0.01) that of distal (apical) fibers (213 +/- 4 ms). Halothane (0.35-1.07 mM) reduced regional differences of APD90 by producing dose-dependent decreases of proximal APD90 without decreases of distal APD90. The regional actions of halothane were similar to those of low (0.33-1.0 microM) concentrations of the Na+ channel antagonist TTX, which also decreased proximal APD90 more than distal APD90. The actions of halothane in combination with TTX further decreased proximal APD90, whereas the Na+ channel agonist VTD, which increased proximal APD90 more than distal APD90, reversed the regional actions of halothane. Decreasing Ca++ influx by reducing [Ca++]0 from 1.8 to 0.6 mM increased proximal APD90 more than distal APD90 in a manner opposite to the regional actions of halothane. Although there was no difference between the values of APD90 obtained for each region in the presence of halothane at 0.6, 1.8, and 3.6 mM [Ca++]0, the action of halothane decreasing APD90 of proximal fibers was more prominent at 0.6 mM [Ca++]0 because of the increased APD90 of fibers under this condition. The findings are consistent with, but do not definitively prove, the hypothesis that halothane may decrease APD90 of proximal Purkinje fibers by a mechanism similar to that of TTX involving inhibition of plateau-phase inward Na+ current.
Action Potentials↗
Side effects of self-administration of intracavernous papaverine and phentolamine for the treatment of impotence.
Beginning October 1985, 111 men agreed to enter a prospective study of the side effects of low dose papaverine/phentolamine therapy. A total of 46 men dropped out, 30 during the initial phase. The percentage of men with painless nodules almost consistently doubled from one followup examination to the next: 8 per cent at 1 month, 17 per cent at 3 months, 32 per cent at 6 months and 57 per cent at 12 months. The average injection frequency of those with nodules was 2 1/2 times higher than those without nodules. Of the men 41 per cent required an increased dose of medications during followup, and 40 per cent of 50 men had at least 1 abnormality of liver function, most of these involving mild to moderate elevations of alkaline phosphatase and lactic dehydrogenase. Priapism was not encountered during self-injection but it did occur twice in 329 physician-administered injections. Careful regular monitoring of patients should continue as some patients enter the second year of treatment.
Adult↗
Why do so many people drop out from auto-injection therapy for impotence?
Although intracavernous injection of vasoactive substances has been shown to be a reasonable and reliable method of reversing impotence, studies assessing patient acceptance of this new technology are lacking. By prospectively following patients and willing partners over a 2-year period, this study sought to document patient utilization rates and the reasons why patients decline or discontinue injection therapy. The cumulative dropout rate was 46%, with patients being most at risk for leaving the program after evaluation or during the trial dose phase. Patients decline treatment because they are unable to accept the idea of injecting themselves or because of potential side effects. Patients discontinue treatment because of perceived lack of efficacy. Patient and programatic obstacles to utilization of self-injection therapy are analyzed.
Erectile Dysfunction↗
Self-injection of papaverine and phentolamine in the treatment of psychogenic impotence.
This study prospectively assessed the use, effectiveness, and sexual and psychosocial impact of self-injection treatment in 15 men with psychogenic impotence. Sixty percent dropped out of self-injection treatment by 6 months. Those who remained used self-injections about four times monthly with a 94% success rate. Frequency of intercourse and sexual satisfaction increased. Anxiety decreased, and trends toward improvement in depression and self-esteem were evident. Qualitative data indicated that performance anxiety was not alleviated, dependence upon injections for intercourse remained, symptom substitution did not occur, and capacity for intimacy was not improved.
Erectile Dysfunction↗
Increased intraoperative cardiovascular morbidity in diabetics with autonomic neuropathy.
Thirty-eight consenting subjects scheduled for elective ophthalmologic surgery were classified as nondiabetics (n = 21) or diabetics (n = 17) and were tested preoperatively for autonomic dysfunction. The autonomic tests consisted of respiratory sinus arrhythmia and heart rate responses to the Valsalva maneuver to test cardiac vagal function and diastolic blood pressure responses to head-up tilt and cold pressor test to assess sympathetic efferent integrity. At a separate time, anesthesia was established with fentanyl (2 micrograms/kg), sodium thiopental (3-5 mg/kg), and vecuronium (0.1 mg/kg), and maintained with isoflurane, oxygen, and nitrous oxide. An anesthesiologist, blinded to the autonomic test results, recorded perioperative blood pressure and heart rate. The autonomic test results revealed significant autonomic dysfunction among the diabetics. Heart rate and blood pressure declined to a greater degree (P less than 0.05) during induction of anesthesia in diabetics compared with controls and there was less of an increase in these same parameters following tracheal intubation in diabetic patients. Thirty-five percent of diabetics required intraoperative vasopressors compared with only 5% of control patients (P less than 0.05). A major finding was that the diabetics who required intraoperative blood pressure support had significantly greater impairment of autonomic test results compared with those diabetics who did not need vasopressors. Diabetics are at increased risk for cardiovascular lability during anesthesia and preoperative screening of diabetics with simple noninvasive autonomic tests may be useful in identifying those at high risk for perioperative cardiovascular instability.
Anesthesia, Inhalation↗
Hemin and cyclic AMP stimulate message-dependent translation in lysates from Friend erythroleukemia cells.
A message-dependent, cell-free translation system was prepared from both uninduced and N,N'-hexamethylene-bis-acetamide-induced Friend erythroleukemia cells following modification of standard protocols. Active extracts were prepared by lysing Friend erythroleukemia cells in hypotonic buffer containing 50 microM hemin and 10 mM cyclic adenosine monophosphate (cAMP), and assaying translation in vitro in the absence of exogenous nucleoside triphosphates. Both hemin and cAMP were required for full activity and appeared to act by prolonging initiation in vitro. Following treatment of cell extracts with micrococcal nuclease, brome mosaic virus, globin, equine herpesvirus type 1, and frog virus 3 mRNA were efficiently translated to yield full-sized products. Using brome mosaic virus as a test message, levels of translation equivalent to 30%-50% of that seen in mock-treated lysates were obtained. These results attest to the translational efficiency of extracts prepared and assayed in the manner described above, and suggest that such extracts may be useful both for routine translational studies, and as a tool to dissect translational changes accompanying erythroid differentiation in vitro.
Acetamides↗
Recent advances in antiherpetic drugs.
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Antiviral Agents↗
Determination of conformational properties of glycolipid head groups by 2H NMR of oriented multibilayers.
The conformations and orientations of the glucose and glycerol moieties of a monoglucosyl lipid in hydrated bilayers have been determined in detail by deuterium nuclear magnetic resonance (2H NMR). Multibilayer membranes of 1,2-di-O-tetradecyl-3-O-(beta-D-glucopyranosyl)glycerol (DTGL), of dimyristoylphosphatidylcholine (DMPC), and of a mixture of DTGL and DMPC were oriented between glass plates. The glucolipid was selectively labeled with deuterium on the pyranose ring and at C3 of glycerol, whereas DMPC was labeled at the C4 position of the sn-2 chain. Quadrupolar splittings were measured as a function of the angle between the bilayer normal and the magnetic field direction. The results establish that the director of motional averaging, the direction about which motion and order are axially symmetric, is the bilayer normal for all the head group, the glycerol backbone, and the hydrophobic core. Segmental order parameters were determined to be 0.45, 0.65, and 0.40, respectively, for the various regions of DTGL in the membranes. The latter results indicate that there is some motion on the time scale of 10(5) s-1 about the C1'(glucose)-O-C3(glycerol) glycosidic bond but that its amplitude is very restricted. Comparison of 1H-decoupled and 1H-coupled 2H NMR spectra of the C3-labeled glycolipid gave estimates of the 2H-2H dipolar coupling between the deuterons at this position. The orientation of the glycerol C3 hydroxymethylene subunit was calculated relative to the bilayer normal, and the C2-C3 bond was found to be tilted away from the bilayer normal by 3 +/- 1 degree.(ABSTRACT TRUNCATED AT 250 WORDS)
1,2-Dipalmitoylphosphatidylcholine↗
Intracavernosal injection in the treatment of impotence: a prospective study of sexual, psychological, and marital functioning.
This study assessed the sexual, psychosocial, and medical impact of intracavernosal injection of papaverine hydrochloride and phentolamine mesylate in the treatment of impotence. Ninety-six percent of patients initially achieved satisfactory erections with injections. Common side effects of self-injections included bruising (26%), nodule development (21%), abnormal liver function tests (7%), and pain (5%). No nodules resulted in penile bending or pain, and no patient discontinued treatment due to nodule development. Dropout rate to date was 35%. Self-injection treatment was associated with increases in erection quality, intercourse frequency, and sexual satisfaction, and decreases in masturbation frequency for patients. Partners also reported increases in intercourse frequency, coital arousal, and satisfaction. Decreases in general psychiatric symptomatology and increases in relationship satisfaction and self-esteem were apparent for patients, but not for partners.
Erectile Dysfunction↗
Actions of halothane on the electrical activity of Purkinje fibers derived from normal and infarcted canine hearts.
The effects of 0.39 mM halothane (approx. 1.1 vol%) on the action potentials of proximal (false tendon) and distal (apical) left ventricular Purkinje fibers were compared in analogous in vitro preparations derived from normal dogs and animals surviving 1 day following acute myocardial infarction. In ten noninfarcted hearts, halothane reduced regional differences in repolarization by decreasing action potential duration (APD90, mean +/- SE) in proximal fibers from 300 +/- 7 to 277 +/- 6 msec (P less than or equal to 0.01) without decreasing APD90 in distal fibers (control 240 +/- 4 msec, halothane 249 +/- 5 msec). In ten infarcted hearts, halothane accentuated pathologic differences in repolarization by decreasing APD90 in the non-ischemic proximal fibers from 311 +/- 8 to 287 +/- 7 msec (P less than or equal to 0.01), while increasing APD90 in the ischemic distal fibers from 375 +/- 15 to 406 +/- 18 msec (P less than or equal to 0.01). Halothane also decreased the overshoot from 32.9 +/- 1.0 to 28.4 +/- 0.8 m V (P less than or equal to 0.01) and Vmax from 356 +/- 28 to 300 +/- 22 V/s (P less than or equal to 0.05) in ischemic fibers. In seven infarcts evaluated by extrastimulus techniques, halothane slowed the conduction of premature impulses and prolonged refractoriness, while, in five of the seven hearts, it reversibly increased the range of coupling intervals which induced probable reentrant responses. In a separate study of seven infarcts, halothane decreased the rate of spontaneous activity originating in the ischemic region. It is concluded that halothane facilitates the occurrence of re-entry while inhibiting the initiation of abnormal impulses in the in vitro canine infarction model.
Action Potentials↗
Sharing and subdividing private market housing.
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Aged↗
Attributional retraining and the teaching of strategies.
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Adolescent↗
Autonomic modulation of refractoriness in canine specialized His-Purkinje system.
The effects of autonomic efferent stimulation on refractoriness of the specialized His-Purkinje system were examined in open-chest dogs anesthetized with 1.0% halothane. In eight animals submaximal bilateral stimulation of the ventral ansae subclavia decreased (P less than or equal to 0.01) the average functional refractory period for the propagation of His bundle extrastimuli to five ventricular recording sites (HP-FRP) by 10.9 +/- 0.6 ms. Submaximal stimulation of the decentralized vagal nerves that produced first degree atrioventricular block did not affect ventricular refractoriness. Combined vagosympathetic stimulation produced a smaller (P less than or equal to 0.01) decrease of the average HP-FRP (7.2 +/- 1.1 ms) than that produced by sympathetic stimulation alone. Administration of atropine abolished (P less than or equal to 0.05) vagal antagonism of the shortening effect of isoproterenol on the average HP-FRP. Treatment with propranolol reversed (P less than or equal to 0.01) the sympathetic effect on the average HP-FRP and nonuniformly increased refractoriness in the His-Purkinje system. The latter changes were abolished (P less than or equal to 0.05) by infusion of phentolamine. The autonomic nervous system modulates His-Purkinje refractoriness by actions mediated by cholinergic and both alpha- and beta-adrenergic receptors.
Animals↗
Spontaneous rehearsal by mildly mentally retarded children and adolescents.
The use of a rehearsal strategy by 10-, 12-, and 14-year-old mildly mentally retarded children and adolescents was investigated using a self-paced recall readiness task. This task, in contrast to those typically used to study rehearsal by retarded individuals, allowed subjects to study items in any order as many times as desired. Each age group used rehearsal, as indicated by increasing study time patterns and the number of repetitions per item. We suggest that previous studies have failed to detect rehearsal by retarded persons because the tasks used have constrained the range of possible types of study behavior. The implication of this finding for rehearsal deficit theories was discussed.
Adolescent↗