Pulmonary capillary wedge pressure and natriuretic peptide levels in patients with sinus rhythm and severe left atrial enlargement following mitral valve surgery: early and late changes

INTRODUCTION

Chronic mitral regurgitation is often accompanied by left atrial and ventricular remodeling and elevated natriuretic peptide levels. Our aim was to examine the relation between severe preoperative left atrial enlargement and changes in hemodynamics and natriuretic peptide levels after mitral valve surgery.

METHODS

A prospective study was conducted including 40 consecutive patients in sinus rhythm, with severe degenerative mitral regurgitation. N-terminal protype-B natriuretic peptide levels and hemodynamics were measured at predefined time points. An echocardiographic evaluation was performed the day before valve surgery and six months postoperatively.

RESULTS

Patients with left atrial volume index ≥60 mL/m(2), n=26, had higher baseline mean pulmonary capillary wedge pressure (17±9 mmHg vs 9±4 mmHg, p=0.010) and N-terminal protype-B natriuretic peptide (1326±2573 ng/L vs 233±221 ng/L, p=0.002) than patients with left atrial volume index <60 mL/m(2). The mean pulmonary capillary wedge pressure decreased to normal in patients with severe left atrial enlargement early after surgery, while it remained normal in patients without severe left atrial enlargement. The natriuretic peptide levels increased during the early postoperative period and decreased in both groups at 6-month follow-up.

CONCLUSIONS

A severe left atrial enlargement in patients with chronic degenerative mitral regurgitation and sinus rhythm indicates higher pulmonary capillary wedge pressure and natriuretic peptide levels than in those without. These findings may support early referral to surgery and may facilitate perioperative management. The potential reversibility of left atrial enlargement after surgery may be associated with postoperative reductions in pulmonary capillary wedge pressure and natriuretic peptide levels.

Investigation of prandial effects on hydrophilic matrix tablets

The prolonged release of drug from hydrophilic matrix tablets can be greatly affected by administration in connection with the intake of food. Changes of the tablet erosion are one of the main components of this effect. The aim of the present study was to identify the postprandial factors responsible for changes in tablet erosion and to develop predictive in vitro tests. Two formulations, one sensitive and the other robust to prandial effects in vivo, were investigated in vitro (a) in a complex physiological media simulating fasting and fed conditions; (b) according to a factorial experimental design that included agitation and pH concentrations of salt, surface-active agent, and nonionic solute as factors; and (c) at varying agitation intensities in three different sets of dissolution apparatus. Of the studied factors, only increased agitation enhanced the erosion of tablets in accordance with the in vivo effects of a meal. The other factors retarded erosion or had only minor effects. The hydrodynamic mechanical stress was thus considered to be the main factor responsible for postprandial effects on tablet erosion. The influence of changes in agitation and the opportunity to discriminate between sensitive and robust formulations differed among the three sets of dissolution apparatus. The modified USP II apparatus, operated at speeds of 50 and 100 rpm, is proposed as a discriminatory test.

In vitro and in vivo erosion of two different hydrophilic gel matrix tablets

The aim of the present work was to establish in vivo predictive in vitro tests for the tablet erosion of two different compositions (A and B) of hydrophilic matrix tablets based on hydroxypropyl methylcellulose. The tablet erosion was studied in a modified USP II apparatus at different agitation intensities and ionic strengths according to 2(2) factorial design. The in vivo tablet erosion was studied in 8 healthy human volunteers by gamma scintigraphy after administration of the tablets together with breakfast. In vitro agitation intensity increased the erosion rate for both tablets whereas increased ionic strength caused a slower rate for tablet A and a faster rate for tablet B. The choice of in vitro testing conditions proved to be critical for the attainment of in vivo predictive results. The best in vitro/in vivo correlation for the two formulations was obtained at a paddle stirring rate of 140 rpm and a ionic strength of 0.14 obtained by addition of sodium chloride.

Androgen hormone binding to adipose tissue in rats

Nuclear binding of androgen was examined, using R 1881, a synthetic androgen. The amount of androgen-receptor complexes bound to isolated nuclei was determined in isolated adipocytes from the epididymal (Epi), retroperitoneal (Ret), inguinal (Ing) and mesenteric (Mes) adipose tissues from intact and castrated rats. The binding was specific and saturable with a Kd in the nanomolar range. Binding was examined after 2 days and after 1 and 2 weeks after castration, showing a higher binding in the Mes tissue in comparison with Ing at all time-points (P < 0.05). Mes adipocytes showed a trend (0.05 < P < 0.1) to up-regulate their binding capacity 2 days after castration, and a significant (P < 0.05) downregulation 2 weeks after castration. Two days after castration, R 1881 binding, expressed per mg triacylglycerol (TG), was generally higher in the Mes region (P < 0.05). This was not fully significant in comparison with Epi tissue in intact rats. When expressed per cell the differences were somewhat diminished, due to differences in cell sizes. Androgen binding showed a negative correlation with TG-uptake in vivo (r = 0.85, P < 0.01), suggesting that a higher density of androgen receptors leads to a more inhibited lipid uptake. In conclusion, a specific androgen receptor was demonstrated in adipose tissue in rat, showing regional differences and a negative correlation with the lipid accumulation of the tissue.

Glucocorticoid hormone binding to rat adipocytes

Previous quantification of glucocorticoid receptor (GR) binding in adipose tissue has been performed in cytosol preparations, which did not allow the determination of the total number of GR in the cell. Therefore, GR binding was determined in intact adipocytes. Dexamethasone (dex) was used as a ligand in adipocytes isolated from epididymal (Epi), retroperitoneal (Ret), inguinal (Ing) and mesenteric (Mes) adipose tissue regions in male rats. The binding was saturable and specific with a Kd in the nanomolar range, not different from previously reported affinity of binding in cytosol preparations from adipocytes. Binding capacity rose after removal of endogenous glucocorticoids either by adrenalectomy (ADX) or culture in a glucocorticoid-free medium. Binding capacity of adipocytes was in general higher in Mes adipose cells than in adipocytes from Epi, Ing and Ret tissues from intact and ADX animals when expressed per unit of triglyceride weight of adipose tissues. This seemed to be largely explainable by a higher cellular density in Mes than in other adipose tissues. When comparisons were performed with binding per adipocyte, intraabdominal (Epi, Ret and Mes) cells bound more dex than adipocytes from subcutaneous (Ing) adipose tissue. It is suggested that in comparison with other adipose tissues Mes tissue has a higher density of the GR in situ, due mainly to a higher cellular density. Intraabdominal adipocytes in general seem to have a higher GR density than subcutaneous cells. This might explain the high activity of glucocorticoid-regulated metabolic pathways in intraabdominal particularly Mes adipose tissue.

Surface replacement of the humeral head in the rheumatoid shoulder

The clinical results obtained an average of 4.2 years after resurfacing of the humeral head in 72 rheumatoid shoulders showed 94% of the patients being pleased regarding pain relief and 82% reporting improved shoulder mobility. Shoulder function was significantly improved. The radiographs were analyzed regarding the position of the humeral head resurfacing cup, proximal migration of the humerus, and glenoid attrition during the follow-up period. Change of the distance between the superior margin of the cup and the greater tuberosity and/or change of inclination of the prosthesis were regarded as signs of prosthetic loosening. With that definition, 25% of the cups were found to be loose at follow-up. Prosthetic loosening, however, had no bearing on the clinical result. Also, no relationship was found between the position of the cup and the clinical outcome. Neither progressive proximal migration of the humerus in 38% of the shoulders nor central attrition of the glenoid in 22% of the shoulders showed any relationship to gain of mobility, pain relief, or functional ability.

Design of a new multiple-unit controlled-release formulation of metoprolol--metoprolol CR

A new controlled-release (CR) formulation of the beta 1-selective adrenoceptor antagonist metoprolol has been developed, aiming at an even 24-h pharmacological effect. In order to achieve this, using a once-daily dose, factors such as absorption characteristics, physicochemical properties, and technological aspects had to be considered. The new formulation, called metoprolol CR, is a disintegrating tablet consisting of several hundred coated pellets of metoprolol succinate, each pellet being its own CR delivery unit. In vitro testing and in vivo studies in healthy volunteers show that the new CR formulation gives continuous delivery of metoprolol throughout the day, resulting in smooth plasma concentration profiles, without peaks and troughs. The release of the drug is independent of pH and other physiological variables, such as food intake, which do not seem to alter the biopharmaceutical properties of the formulation.

Force-displacement measurements in tableting

The influence of particle interaction, i.e. friction and bonding, on the net work (NETW) during compaction and on Heckel plots was tested by varying the particle size, the lubrication or the moisture content. The NETW was found to be significantly affected by particle interaction. The yield pressure, calculated from Heckel plots, was far less dependent on particle interaction and appears to be more useful for the evaluation of the deformation properties of materials. The NETW may be useful as a test of inter-lot variations in compaction behaviour of materials, due to its high sensitivity to both inter- and intraparticle properties, good reproducibility and low dependence upon die wall conditions. However, it appears to be a poor measure of the plastic properties of the substance.

Work of friction and net work during compaction

Series of tablets were compressed in a reciprocating tablet machine with a gradually increasing die wall friction. The force needed on the upper punch to maintain the tablet dimensions constant increased with the die wall friction while the lower punch force decreased. The change in punch forces due to differences in die wall friction had no effect on the tablet strength. The net work of compaction should be constant under these circumstances. The net work calculated by subtracting the work of friction and the expansion work from the gross work input was constant when the frictional work was calculated according to one of the two equations proposed in the literature (Järvinen & Juslin 1974) while the other appears to give an overestimation of the work of friction.

The influence of food on side effects and absorption of lithium

In a cross-over study, 24 mmol of lithium sulphate was given as a single dose in slow release tablets to 30 healthy volunteers fasting and after a standardised meal. Comparisons were also made with lithium citrate in slow release tablets and placebo. Postprandial administration of lithium gave practically no side effects, while lithium on an empty stomach gave diarrhoea in about 20% of the subjects. The absorption was measured by determination of the amount of lithium excreted in the urine in a group of ten subjects. Lithium was completely absorbed when given after food, but when given on an empty stomach the absorption was lower in some subjects, apparently due to rapid gastrointestinal passage in connection with diarrhoea. Lithium should therefore preferably be administered after meals.

Pharmacokinetics of procainamide intravenously and orally as conventional and slow-release tablets

Pharmacokinetics of procainamide were studied in healthy volunteers after single doses intravenously and orally as conventional and slow-release tablets and after repeated oral doses to steady state. The initial distribution after intravenous administration was rapid and the overall elimination in the beta-phase corresponded to t1/2 of 2.7 hr. The mean volume of the central compartment was small and only 4 percent of V-d (beta), which was 2.3 l/kg body weight. About 65 percent was excreted unchanged after intravenous administration and about 55 percent after a single oral dose of 500 mg. The recovery of the metabolite N-acetylprocainamide was 12 percent after both routes of administration. Procainamide was completely absorbed from the gastrointestinal tract and the first-pass elimination was very limited. The rates of absorption from the tablet compositions were well correlated to the in vitro dissolution properties. Administration of slow-release tablets every 8 hr gave about the same mean plasma level at steady state as ordinary tablets given every 4 hr, and the availability was the same from both preparations. The occasional high plasma concentration peaks after ordinary tablets were not observed after the slow-release tablets. Renal clearance was about 500 ml/min, indicating an active secretion in the tubules.