High Dialysate Calcium Concentration is Associated with Worsening Left Ventricular Function.

Dialysate calcium concentration (d[Ca]) might have a cardiovascular impact in patients on haemodialysis (HD) since a higher d[Ca] determines better hemodynamic tolerability. We have assessed the influence of d[Ca] on global longitudinal strain (GLS) by two-dimensional echocardiography using speckle-tracking imaging before and in the last hour of HD. This is an observational crossover study using d[Ca] 1.75 mmol/L and 1.25 mmol/L. Ultrafiltration was the same between interventions; patients aged 44 ± 13 years (N = 19). The 1.75 mmol/L d[Ca] was associated with lighter drop of blood pressure. Post HD serum total calcium was higher with d[Ca] 1.75 than with 1.25 mmol/L (11.5 ± 0.8 vs. 9.1 ± 0.5 mg/dL, respectively, p < 0.01). In almost all segments strain values were significantly worse in the peak HD with 1.75 mmol/L d[Ca] than with 1.25 mmol/L d[Ca]. GLS decreased from -19.8 ± 3.7% at baseline to -17.3 ± 2.9% and -16.1 ± 2.6% with 1.25 d[Ca] and 1.75 d[Ca] mmol/L, respectively (p < 0.05 for both d[Ca] vs. baseline and 1.25 d[Ca] vs. 1.75 d[Ca] mmol/L). Factors associated with a worse GLS included transferrin, C-reactive protein, weight lost, and post dialysis serum total calcium. We concluded that d[Ca] of 1.75 mmol/L was associated with higher post dialysis serum calcium, which contributed to a worse ventricular performance. Whether this finding would lead to myocardial stunning needs further investigation.

Reference values for Doppler ultrasound parameters of the thyroid in a healthy iodine-non-deficient population.

The aim of this study was to describe normal Doppler parameter values in the thyroid arteries in an iodine-replete region. 165 individuals were randomly selected in a community located in the south-east of Brazil. We obtained a clinical history on each subject and determined serum thyrotropin, antiperoxidase antibodies, thyrotropin receptor antibody (TRAb) and thyroid volumes through ultrasound. Subjects with thyroid disease and those under 20 years of age were excluded. 84 representative subjects (30 men and 54 women) remained. The systolic peak velocity (SPV), resistive index (RI) and pulsatility index (PI) in the superior and inferior thyroid arteries were measured using a 5-12 MHz linear probe. Except for the RI, the distribution of all Doppler parameters was non-gaussian. The median and mean references for the SPV, RI and PI were 24.80 cm s(-1) and 25.85 cm s(-1), 0.60 and 0.62, and 0.98 and 1.04, respectively, for superior thyroid arteries; these reference values for the inferior thyroid artery were 20.92 cm s(-1) and 21.50 cm s(-1), 0.57 and 0.57, and 0.84 and 0.88, respectively (p<0.001). Women had greater SPV values (p<0.01). We have determined reference thyroid Doppler parameter values in our iodine-non-deficient population and prepared tables by sex and age.

Differentiation between the two types of amiodarone-associated thyrotoxicosis using duplex and amplitude Doppler sonography.

PURPOSE: To evaluate the usefulness of Doppler parameters in the differentiation between the two types of amiodarone-associated thyrotoxicosis (AAT). MATERIAL AND METHODS: One hundred thirty-seven individuals were selected at our institution. They were divided into four groups: 84 normal subjects (N), 30 euthyroids taking amiodarone (A), 14 AAT type 1 patients (AAT1), and nine AAT type 2 patients (AAT2). Each AAT type was classified according to (131)I uptake and clinical outcome. Blindly, the resistance and pulsatility indexes (RI, PI), systolic peak velocity, and color pixel density (CPD) were calculated. RESULTS: AAT1 had greater CPD than AAT2 (P = 0.02). The latter group had similar vascularization to the N and A groups (P = 0.45). The area under the receiver operating characteristic (ROC) curve showed that systolic peak velocity in the inferior thyroid arteries and CPD were the best parameters in the differentiation between AAT type 1 and AAT type 2 (Az = 0.83 and 0.84, respectively). Impedance indexes were useless. CONCLUSION: Our results demonstrate that objective tests such as systolic peak velocities in the thyroid arteries and CPD are reliable parameters for differentiating between the two types of AAT.

Types of arrhythmia among cases of American trypanosomiasis, compared with those in other cardiology patients.

The frequencies of each type of arrythmia were investigated, by age and sex, among 3056 Brazilian patients with cardiac arrhythmia. Each patient investigated had been tested serologically for American trypanosomiasis and 1013 had been found seropositive for the disease. In general, the seropositive 'chagasic' patients were each likely to be suffering from more types of arrhythmia than the seronegative 'non-chagasic', with means of 1.81 and 1.03 types/patient, respectively. Right-branch bundle blocks (RBBB), ventricular extrasystoles (VE) and left anterior hemiblocks (LAHB) were the commonest cardiac arrhythmias among the chagasic patients, and each of these types of arrhythmia (alone or with other types of arrythmia) was more frequent in the chagasic patients than the non-chagasic. The incidence of RBBB among the arrhythmic varied significantly with age in the non-chagasic patients (increasing with age among both the males and females) but not among the chagasic subjects. When the frequencies of each type of arrythmia and each combination of types were compared, the co-occurrence of RBBB and another type of arrhythmia was almost indicative of American trypanosomiasis (occurring in 30.6% of the chagasic subjects but only 2.6% of the non-chagasic). Similarly, only 0.4% of the non-chagasic patients but 7.4% of the chagasic had RBBB, VE and LAHB concurrently. However, the frequencies of RBBB in isolation (i.e. with no other, concurrent, electrocardiographic abnormality), VE in isolation, or LAHB in isolation were not significantly different in the chagasic and non-chagasic patients.

Lamotrigine analysis in blood and brain by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatography assay was developed and validated to determine plasma and brain lamotrigine concentrations allowing pharmacokinetic-pharmacodynamic studies of this new antiepileptic drug in patients and laboratory animals. Lamotrigine and its internal standard were extracted, under alkaline conditions, from plasma and brain homogenate, into ethyl acetate; brain proteins were previously precipitated with trichloroacetic acid. The method was linear between 0.1 and 15.0 mg/l for plasma, with a detection limit of 0.008 mg/l, and between 0.1 and 5.0 mg/l for brain homogenate, with a detection limit of 0.023 mg/l. The method proved to be simple, useful and appropriate, not only for clinical and experimental research, but also for routine monitoring of lamotrigine concentrations in patients.

Regulation of intracellular [Ca2+] and GABA release by presynaptic GABAB receptors in rat cerebrocortical synaptosomes.

In this study we determined the changes in the intracellular free Ca2+ concentration, associated with the inhibitory modulation of the exocytotic release of GABA by GABAB receptor activation in rat cerebrocortical synaptosomes. We observed that SK&F 97541 and (-)baclofen both act as agonists of the presynaptic GABAB receptors in modulating GABA release and Ca2+ influx due to KCl (10 mM) depolarization, but SK&F 97541 is more potent than (-)baclofen in modulating both Ca2+ influx and GABA release. Thus, activation of GABAB receptors by either SK&F97541 (10 microM) or by (-)baclofen (100 microM) caused about 18% inhibition of the increase in [Ca2+]i, due to KCl depolarization, and inhibited the [3H]GABA release by about 30%. The pharmacological similarities of the GABAB receptor activation in producing inhibition of both calcium channel mediated influx of Ca2+ and transmitter release suggest that presynaptic inhibition of GABA release by GABAB receptor activation may result, at least in part, from inhibition of Ca2+ influx through P-type (or possibly Q-type) Ca2+ channels, sensitive to omega-Agatoxin IVA (200 nM). Furthermore, modulation of GABA release of GABAB receptors was abolished by preincubation with pertussis toxin, suggesting that a pertussis toxin sensitive G protein may be the coupling factor between GABAB receptors and the voltage-dependent Ca2+ channels associated with the exocytotic release of GABA in rat cerebrocortical nerve terminals.

Pharmacological characterization of the postsynaptic alpha-adrenoceptors in human uterine artery.

Prazosin and yohimbine were used to differentiate postjunctional alpha-adrenoceptors in the human uterine artery in-vitro. Two postjunctional alpha-adrenoceptor subtypes were distinguished by the affinities of the receptor for yohimbine and prazosin. The pA2 for prazosin was 8.91 against phenylephrine with a slope not significantly different from unity (0.91), and the pA2 for yohimbine was 7.25 against naphazoline and 8.70 against clonidine, with slopes not significantly different from unity (1.11 and 1.18, respectively). Yohimbine was not very active against phenylephrine, while prazosin was very active against the mixed and selective alpha 2-adrenoceptor agonist noradrenaline and clonidine; the intercepts of the Schild plot were 8.80 and 8.82 but with slopes significantly less than unity (0.77 and 0.67, respectively). Prazosin competitively antagonized phenylephrine at the alpha 1-adrenoceptor, whereas yohimbine competitively antagonized naphazoline and clonidine at the alpha 2-adrenoceptor. It is concluded that both alpha 1- and alpha 2-adrenoceptors are present in the human uterine artery.