Defibrillation Energy Requirements Differ Between Anesthetic Agents

We examined the effect of anesthesia on the energy requirements for internal defibrillation (DF) in dogs anesthetized with pentobarbital (30 mg/kg IV followed by 2–3 mg/kg/hr constant infusion) (n = 20), fentanyl (25 μg/kg/hour) (n = 25), and enflurane (0.5%–1.5%) (n = 8). Multiple shocks of varying energies were applied through left and right ventricular epicardial patch electrodes to relate delivered energy to percent success in DF. The energies required for 50% success (E₅₀) and 80% success (E₈₀) in DF were estimated using logistic regression. E₅₀ in fentanyl anesthetized animals (3.8 ± 2.3 J) was significantly lower than in those given pentobarbital (6.9 ± 3.0 J) (P < 0.01), and lawer than those given enflurane (5.7 ± 2.8 J) (NS). E₈₀ with fentanyl (6.5 ± 4.0 J) was also lower than that of pentobarbital (10.4 ± 4.9 J) (P < 0.01) and enflurane (7.6 ± 4.3 J) (NS) animals. lawer defibrillation energy requirements (DER) with fentanyl anesthesia, when compared with pentobarbital, were associated with significantly longer ventricular effective refractory periods (VERP) (171 ± 20 versus 142 ± 15 msec: P < 0.01), lower mean arterial pressures (114 ± 20 vs 136 ± 25 mmHg: P < 0.01), and Iower heart rates (90 ± 37 versus 164 ± 19 b/m; P < 0.01).
Anesthetic agents may modify DER; their effects need to be taken into account in the assessment of DER in patients receiving implanted defibrillators and in the evaluation of the results of defibrillation research in anesthetized animals.     

The white blood cell count: its relationship to plasma insulin and other cardiovascular risk factors in healthy male individuals

Targher G, Seidell JC, Tonoli M, Muggeo M, De Sandre G, Cigolini M (Division of Endocrinology and Metabolic Diseases, Institute of Clinical Medicine, University of Verona, Italy; and Department of Chronic Diseases and Environmental Epidemiology-RIVM, Bilthoven, The Netherlands). The white blood cell count: relationship to plasma insulin and other cardiovascular risk factors in healthy males. J Intern Med 1996; 239: 435–41. Objectives. To evaluate the relationships of total and differential white blood cell (WBC) count to the components of the so-called insulin resistance syndrome. Subjects and design. The study population consisted of a random sample of 90 38-year-old healthy men with normal glucose tolerance. Interventions. A 75 g oral glucose tolerance test was performed in all participants. Main outcome measures. Total and differential WBC count, lipids, blood pressure, plasma glucose, C-peptide and insulin (at fasting and 2 h after glucose load). Results. Total WBC count correlated consistently with plasma 2-h glucose (r=0.38; P<0.001), fasting and 2-h postload insulin (r=0.26 and r=0.33; P<0.01–0.001, respectively) and C-peptide (r=0.28 and r=0.32; P<0.01–0.001) concentrations. Smokers had significantly higher total leukocytes (P<0.01), neutrophils and lymphocytes than nonsmokers. Furthermore, total WBC count correlated positively with body mass index, blood pressure, plasma triglycerides, fibrinogen, and negatively with HDL cholesterol concentration. As differential WBC count, most variables correlated essentially to neutrophils and/or lymphocytes, whereas plasma insulin and C-peptide concentrations correlated essentially to lymphocytes and monocytes, but not to neutrophils. In a multiple linear regression analysis, only 2-h plasma glucose (P<0.01) and fibrinogen (P<0.05) were positive predictors of total WBC count after adjusting for all potentially confounding variables. Conclusions. The results indicate that increased, albeit normal, WBC count associates with the cluster of metabolic and haemodynamic disorders typical of the insulin resistance syndrome, and suggest that increased WBC count may be yet another component of this syndrome.     

Activated Pyrolytic Carbon Tip Pacing Leads: An Alternative to Steroid-Eluting Pacing Leads?

Pyrolytic carbon technology is known for its excellent mechanical properties and electrical conductivity; it is particularly biocompatible and does not require high production costs. The Sorin S100/4 lead is a ventricular passive fixation lead with a hemispherical electrode surface area of 4 mm²; the stimulating tip is made of a graphite core coated by a thin activated pyrolytic carbon layer. We evaluated the acute and medium-term performance of the unipolar version of this lead in 65 patients. At implantation, pacing threshold (at 0.5 ms) was 0.26 ± 0.08 V; pacing impedance (at 5 V and 0.5 ms) was 537 ± 94 Ω and Ft wave amplitude was 15.0 ± 5.5 mV. No lead related complications (dislodgment, perforation, exit block, etc.) occurred in any patient; one patient presented with a wire fracture after 26 months, due to subclavian crush syndrome. Follow-up procedures were performed at 1 week, and 2-, 10-, 18-, and 30-months postimplant. Since the leads were connected to pacemakers from different manufacturers, either voltage or duration thresholds were measured, In approximately two thirds of the patients, with an output of 2.5 V, a mean duration threshold of 0.16 ± 0.13 ms at 1 week, 0.12 ± 0.08 ms at 2 months, 0.11 ± 0.06 ms at 10 months, 0.09 ± 0.06 ms at 18 months, and 0.07 ± 0.03 ms at 30 months, was measured. In the remaining one-third of the patients, a comparable voltage threshold trend was measured. The mean pacing impedance showed a transient drop at 1 week, and then increased to a plateau of about 600 fl reached after 10 months. No sensing defect occurred in any patient. Our data show good acute and intermediate-term results of the S100/4 lead; the early rise in threshold was remarkably blunted. Activated pyrolytic carbon tip leads might therefore be considered as a possible, inexpensive alternative to steroideluting leads.     

Discovery of a pituitary adenoma following a gonadotropin-releasing hormone agonist in a patient with prostate cancer

Gonadotropin-releasing hormone (GnRH) agonists have become the treatment of choice for locally advanced and metastatic prostate cancer. We report a case of prostate cancer in which this treatment led to severe symptoms of intracranial hypertension due to the concomitant presence of an asymptomatic functional pituitary adenoma. A 70-year-old white man was initially evaluated for a multifocal adenocarcinoma, Gleason score 6 (3+3) with perineural invasion suggesting an extracapsular extension. A conformational external beam radiation (74 Gy) with a concomitant GnRH agonist (leuprolide) was initiated. Almost 10 days after the administration of leuprolide the patient complained of visual disturbance, diplopia and other symptoms of intracranial hypertension. Magnetic resonance imaging (MRI) of the brain demonstrated a large sella mass lesion. To relieve the patient's symptoms, a transsphenoidal subtotal tumorectomy was necessary. The histopathological examination revealed an invasive gonadotroph pituitary adenoma. Two years later, there is no sign of progression either on his prostatic disease (prostate-specific antigen of 0.21 ng/mL) or on his pituitary disease (FSH, 4.7 UI/L, LH, 3.1 UI/L and total testosterone, 627 ng/dL) with values of the hypothalamic-pituitary axis in the normal range. We advocate that a high index of suspicion of pituitary tumor must be considered in any case of intracranial hypertension following the administration of GnRH agonist. Abarelix could have a place in such cases.     

Randomized Clinical Trials of Neurally Mediated Syncope

Evidence for therapy of neurally mediated syncope is generally weak. Many drugs have been used for the treatment of vasovagal syncope (beta-blockers, disopyramide, scopolamine, clonidine, theophylline, fludrocortisone, ephedrine, dihydroergotamine, etilefrine, midodrine, clonidine, serotonin reuptake inhibitors, enalapril). In general, although the results have been satisfactory in uncontrolled trials or short-term controlled trials, the majority of long-term placebo-controlled prospective trials have not been able to show a benefit of the active drug over placebo. Only two well-designed double-blind placebo-controlled randomized trials have been performed—one for etilefrine and the other for atenolol—and both were unable to show a superiority of the active drug versus placebo. Four randomized clinical trials of pacing therapy—three positive and one negative—have been performed in patients affected by vasovagal syncope. The relationship between carotid sinus hypersensitivity and spontaneous, otherwise unexplained, syncope has been demonstrated. Cardiac pacing appears to be beneficial in carotid sinus syndrome; its efficacy has been demonstrated by two randomized controlled trials and confirmed by several pre-post comparative studies, one controlled trial, and one prospective observational study. There is evidence and general agreement that cardiac pacing is useful in patients with cardioinhibitory or mixed carotid sinus syndrome. Usefulness of the treatment is less well established and divergence of opinion exists with regard to cardiac pacing in patients with cardioinhibitory vasovagal syncope. The evidence fails to support the efficacy of beta-blocking drugs. As yet there are insufficient data to support the use of any other pharmacologic therapy for vasovagal syncope. (J Cardiovasc Electrophysiol, Vol. 14, pp. S64-S69, September 2003, Suppl.)     

Angiographic Correlates of Different Mechanical Effects During the Dipyridamole Echocardiography Test Shortly After Acute Myocardial Infarction

The aim of this study was to analyze the different mechanical patterns during the dipyridamole echocardiography test (DET) performed in 167 patients 8–10 days after a first myocardial infarction. The results were correlated with coronary angiography. In a first series of 98 patients retrospectively analyzed (group I), four different types of dipyridamole-induced wall-motion abnormalities were observed: (1) worsening of wall motion in the same region showing asynergy at rest (type I); (2) new wall-motion abnormality in a territory adjacent to the resting asynergies and fed by the same vessel (type II); (3) new wall-motion abnormality in a territory adjacent to the resting asynergies, but supplied by a vessel different from the infarct related artery (type III); and (4) new wall-motion abnormality not directly adjacent to the infarct zone (type IV). Type IV asynergies were found in one of 44 patients with single vessel disease and in 14 of 54 patients with multivessel disease (sensitivity 70.4%, specificity 92.3%). Type III asynergies developed in two patients with single vessel disease and in 24 of those with multivessel disease. The frequency and distribution of the four asynergy types were subsequently analyzed in a second prospective series of 69 patients (group II). Type III and IV asynergies were found almost exclusively in patients with multivessel disease (17/34 patients with multivessel disease and 2/35 with single vessel disease) (sensitivity 50%, specificity 94.3%). Combining type III and IV asynergies, an overall sensitivity of 62% and a specificity of 94% for predicting multivessel disease were obtained. The ability of DET to predict specific vessel obstruction was also investigated. A positive correlation was found only for the laterobasal segment (specificity 82% in predicting critical stenosis of the left circumflex artery [LCX]), and for the apical and distal septal segments (specificity 95% and 93% for lesions of the left anterior descending artery [LAD], respectively). A substantial overlap was noted when an attempt was made to distinguish LCX from right coronary artery (RCA) lesions. Nevertheless, new simultaneous wall-motion abnormalities of the posterobasal septal and laterobasal segments were observed in all but one patient with combined lesions of LCX and RCA (specificity 99%). In conclusion, the mechanical patterns of dipyridamole-induced new wall-motion abnormalities correlate with coronary angiography: new remote asynergies are highly specific in predicting multivessel disease, but are not frequent. New asynergies adjacent to the infarct zone can also predict multivessel disease, provided they are located in a different vascular region. The ability of DET to predict specific vessel obstructions was excellent for LAD lesions, but it was less helpful in differentiating LCX from RCA lesions. Nevertheless, new simultaneous wall-motion abnormalities of the posterobasal septal and laterobasal wall predict critical lesions of the LCX and RCA.     

Can improvements in water supply reduce childhood diarrhoea?

The effects of improving the water supply on the incidence ofdiarrhoea in 1096 children from three neighbouring villagesof the Kirotshe rural health district. Northern Kivu, Zairewere investigated. Two of these villages had piped water, whilethe third village had no such facility. Children aged underfour years on registration were visited fortnightly for oneyear. Median diarrhoea incidence per two weeks proved to besignificantly lower in the two intervention villages than inthe control village. In the two intervention villages, mediandiarrhoea incidence per two weeks was halved in children wholived in households located less than a five-minute walk fromthe public standpipe, or in households using more than 50 litresof water a day. The association between diarrhoea incidenceand facility use did not differ after stratification by socioeconomicvariables. These findings underscore the fact that children in householdsthat use standpipes are exposed to a lower risk of diarrhoea.Therefore, it is important to stress that those in charge ofthe planning and implementation of water supply interventionsinvestigate the access to, and use of, water amongst the targetpopulation.