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Biomedical subjects

Elena Mancini

Publications and source records attributed to Elena Mancini.

12 recordsLinked to original sources
PubMed2005

Convective and adsorptive removal of beta2-microglobulin during predilutional and postdilutional hemofiltration.

BACKGROUND: Beta(2)-microglobulin (beta2-m) removal in patients with end-stage renal disease (ESRD) is maximal with convective techniques, such as hemofiltration (HF) or hemodiafiltration (HDF). Although the infusion mode of the replacement solution (predilution or postdilution) is expected to influence the efficiency of HF, experimental data in this respect are scanty. We therefore investigated the impact of the fluid reinfusion mode on the efficiency of HF in 11 ESRD patients who underwent both treatments. METHODS: The dialyzer (AK 200 ULTRA) was equipped with a 3-layer polyamide membrane (Poliflux 21 S, surface 2.1 m(2)) and blood flow was kept between 300 and 400 mL/min. beta2-m concentrations were measured in plasma water and ultrafiltrate at appropriate times during a 240-minute treatment. The following dialytic parameters were calculated: total amount of beta2-m removed (A(tot)), beta2-m removed by convection (A(con)) and by adsorption (A(ads)), percent reduction in beta2-m plasma water concentration (% Cpw(in)), total plasma water clearance (CLpw(tot)), convective plasma water clearance (CLpw(con)), adsorptive plasma water clearance (CLpw(ads)), and sieving coefficient (SC). RESULTS: CLpw(tot), CLpw(ads), and% Cpw(in) were similar in pre- and postdilutional conditions, whereas CLpw(con) and SC were higher and CLpw(ads) was lower in postdilution than in predilution HF. Since a significant inverse correlation was found between A(ads) and SC, predilution probably determines greater protein fouling than postdilution. CONCLUSION: The 2 techniques appear to be equivalent in terms of total beta2-m removal, although this final result is obtained by different contributions of convective and adsorptive elimination.

Aged↗
PubMed2004

Protein loss in on-line hemofiltration.

BACKGROUND: The albumin serum level is one of the most important nutritional indices and is directly correlated to the uremic patient's hemodialysis outcome. One of the factors that can interfere with protein metabolism is the possible loss of albumin through the dialysis membrane that can contribute to keeping levels chronically low, especially for high-flux convective treatments requiring high permeability membranes and the removal of high volumes of plasma water. METHODS: Twenty stable patients undergoing chronic renal replacement therapy for at least 3 months were included. Each patient performed four hemofiltration treatments, 2 in post-dilution and 2 in pre-dilution (post-D, pre-D) with a polyamide membrane (Poliflux, 2.1 m2). RESULTS: The amount of albumin found in the ultrafiltrate was 2.9 +/- 1.5 g in post-D and 1.7 +/- 0.8 g in pre-D (p < 0.01). Albumin loss during online HF was lower than 3 g per treatment, and significantly lower in pre-D than in post-D. Furthermore, we observed a correlation between the transmembrane pressure and the albumin loss in both techniques, but with different slopes (y = 0.351x - 10.014 in post-dilution and y = 0.0639x + 8.2403 in pre-dilution; p = 0.01): the same transmembrane pressure determines larger albumin losses in post-dilution than in pre-dilution. CONCLUSIONS: Convective treatments that utilize high exchange volume can be performed with no risk of a significant albumin loss, particularly in pre-D where the proteic component's contact with the dialysis membrane is lower. In post-dilution the transmembrane pressure is a relevant factor in determining the protein loss.

Adult↗
PubMed2003

Thermal balance in convective therapies.

Among the factors causing intradialytic haemodynamic instability, dialysate temperature has been shown to play a relevant role. An improved cardiovascular response during isolated ultrafiltration or with cooled dialysate has been described in the past. Cold dialysate may increase the external heat loss compensating for the increase in core temperature, thus avoiding vasodilatation, but it also increases myocardial contractility. However, a better haemodynamic response to dialysis treatment has long been known in convective therapies as well, and the hypothesis of a leading role for thermal balance is under discussion. In conventional haemofiltration (HF), venous blood cooling is expected, on the basis of the infusate temperature and the filtration fraction. In on-line HF, the infusate temperature and its volume may have a different impact on thermal balance depending on the site of infusion (pre- or post-dialyser). In an in vitro study comparing haemodialysis (HD) (conventional HD, dialysate 37 degrees C; and cold HD, dialysate 35.5 degrees C) with HF (pre- and post-dilution, 37 degrees C), we observed a more negative thermal balance with cold HD (-130 kJ/h) and with post-dilution HF (-75 kJ/h). The beneficial pressor effects of HF have been confirmed even in on-line HF, which actually has very few differences in the thermal balance compared with conventional HD (dialysate 37 degrees C). In on-line HF, the amount of warm infusion, often exceeding the blood flow, makes the achievement of a negative thermal balance highly unlikely. Thus, there is not sufficient evidence that vascular stability in on-line HF is solely related to different thermal energy balances. Other factors playing a relevant role in the cardiocirculatory response to convective dialysis should thus be considered.

Body Temperature Regulation↗
PubMed2003

Electrocardiographic changes during hemodiafiltration with different potassium removal rates.

BACKGROUND/AIMS: Sudden K removal is thought to be implicated in ECG alterations observed during hemodialysis (HD). The effects of the K removal rate on ECG-derived parameters have been investigated. METHODS: Two different hemodiafiltration (HDF) schedules were used for 10 HD patients: the dialysate K concentration was kept constant in HDFst, while in HDFK it was decreased during the session in order to maintain a uniform plasma-dialysate K gradient. A 12-lead Holter monitor was used to acquire the ECG in the course of the treatments. Classical ECG parameters and overall indices for quantifying ventricular repolarization abnormalities were evaluated. RESULTS: Several ECG parameters were affected by both HD therapies (ST depression, QRS amplitude and QT dispersion), but only indices of the homogeneity of repolarization (PCA-T, E1-T) were significantly affected by the K removal rate. CONCLUSION: The present study confirms the large impact of HD therapy on ECG. The analysis of the spatial T wave complexity points out the intrinsic arrhythmogenic implications of the K removal rate.

Aged↗
PubMed2002

Blood volume controlled hemodialysis in hypotension-prone patients: a randomized, multicenter controlled trial.

BACKGROUND: Recently we have devised and tested a biofeedback system for controlling blood volume (BV) changes during hemodialysis (HD) along an ideal trajectory (blood volume tracking, BVT), continuously modifying the weight loss rate and dialysate conductivity. This multicenter, prospective, randomized, crossover study aimed to clarify whether BVT (treatment B) can improve hypotension-prone patients' treatment tolerance, compared with conventional hemodialysis (treatment A). METHODS: Thirty-six hypotension-prone patients enrolled from 10 hemodialysis (HD) centers were randomly assigned to either of the study sequences ABAB or BABA, each lasting four months. RESULTS: A 30% reduction in intradialytic hypotension (IDH) events was observed in treatment B as compared with A (23.5% vs. 33.5%, P = 0.004). The reduction was related to the number of IDH in treatment A (y = 0.54x + 5; r = 0.4; P < 0.001): the more IDH episodes in treatment A, the better the response in treatment B. The best responders to treatment B showed pre-dialysis systolic blood pressure values higher than the poor responders (P = 0.04). A 10% overall reduction in inter-dialysis symptoms was obtained also in treatment B compared to A (P < 0.001). Body weight gain, pre-dialysis blood pressure, intradialytic weight loss as well as Kt/V did not differ between the two treatments. CONCLUSIONS: An overall improvement in the treatment tolerance was observed with BVT, particularly intradialytic cardiovascular stability. Patients with the highest incidence of IDH during conventional HD and free from chronic pre-dialysis hypotension seem to respond better. Inter-dialysis symptoms also seem to improve with control of BV.

Aged↗
PubMed2002

Effect of electrolyte and pH changes on the sinus node pacemaking in humans.

The importance of plasma electrolytes and pH levels in determining heart rate is not yet well grounded. Hemodynamic and biochemical data were collected during 8 purely diffusive hemodialysis, which allowed changes in extracellular fluid to be achieved without eliciting notable changes in the autonomic control of heart rate. A significant heart rate increase was obtained after potassium decrease and calcium and pH increase, with no significant variations in indices of autonomic activity. Model-based computer simulations were then used to separate the effects of each ionic species and pH on sinus node cell pacemaker activity. This analysis revealed that changes in physiological range of potassium, calcium, and pH could cause large heart rate variations from 60 to 90 bpm. Nonlinear heart rate dependence on potassium was also recognized. It was concluded that electrolyte and pH changes in physiological range have an important, complex, impact on the pacemaking rhythm independently of autonomic outflow.

Action Potentials↗
PubMed2002

Cardiac effects of chronic inflammation in dialysis patients.

Cardiovascular pathology is the major cause of death in uraemia. There is evidence that a chronic inflammation with activation of C-reactive protein, interleukin-6, tumour necrosis factor-alpha and other cytokines is associated with vascular pathology, both in the general population and in dialysis patients. The cardiovascular system, and particularly the vascular wall, is the main target of the inflammatory process. Inflammation of the coronary arteries could be involved in the development of atherosclerosis and its related clinical syndromes. In the uraemic state, an increased production of pro-inflammatory cytokines may trigger the onset and progression of atherosclerosis and favour the subsequent complications, such as plaque fissuration and rupture. However, inflammatory cytokines also have a depressant action on the myocardium, thus inducing myocardial dysfunction. Together, these conditions may ultimately enhance the risk of myocardial infarction and death. From this standpoint, cardiovascular disease should also be investigated with the traditional biochemical inflammation markers and the evaluation of the circulating cytokine level, although new reliable markers could provide further diagnostic help. New therapeutic approaches should also be considered.

Acute-Phase Proteins↗
PubMedDate not supplied

Biofeedback in dialysis.

The traditional control of the dialysis session comes about by means of an open-loop system. At the beginning of the session some parameters are set, such as the kind of dialyzer, the blood flow, the ultrafiltration rate, the dialysate conductivity and the dialysate temperature. Generally speaking, these parameters are not modified unless there occur complications in the patient that call for adjustments to be made. The biofeedback concept, which is synonymous with a closed-loop control of biological variables, presupposes, on the other hand: the continuous measurement of a variable thanks to a specific sensor its evaluation by a sort of expert system--the so-called controller and a series of means--the actuators--that allow the behavior of the variable to be directly or indirectly influenced. In clinical practice, different biofeedback systems are emerging, addressed to the control of blood volume, body temperature, and blood pressure. Each one of these systems has been successfully deployed, especially in the management of "difficult" patients unstable from the hemodynamic point of view. However, the future will be an integrated system that sees a complex adaptive, multi-input, multi-output controller which, with a great simplicity of use and low costs, will allow renal replacement therapy to be increasingly physiological and more efficient.

Blood Pressure↗
PubMedDate not supplied

Vascular access for hemodialysis.

A well-functioning vascular access for hemodialysis plays a key role in the quality of life and clinical outcome of dialysis patients. A vascular access for dialysis is considered to be adequate when it provides a blood flow of at least 250 ml/min in the standard dialysis and up to 350-400 ml/min in the high-efficiency dialysis. So far, Cimino-Brescia arterio-venous fistula still remains the gold standard among the available vascular accesses. It should be the first-choice vascular access. Unfortunately, due to the growing age of patients requiring dialysis, to the late-referral phenomenon, to the poor forearm vascular district, and to the increase in acute forms of renal disease, the use of vascular prostheses and central venous catheter becomes more and more frequent. The most important complications of vascular access are stenoses, thromboses, infections. Infections, more frequent in synthetic vascular access than in native fistulas, are responsible for the increase in patients' morbidity and, consequently, in public health costs. An integrated multi-professional approach of vascular access, involving nephrologists, vascular surgeons, interventional radiologists, and trained dialysis nurses should be implemented in order to early detect vascular access complications and failure.

Arteriovenous Shunt, Surgical↗