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People constantly process temporal, numerical, and length information in everyday activities and interactions with the environment. However, it is unclear whether quantity perception changes during ageing. Previous studies have provided heterogeneous results, sometimes showing an age-related effect on a particular quantity, and other times reporting no differences between young and elderly samples. However, three dimensions were never compared within the same study. Here, we conducted two experiments with the aim of investigating the processing of duration, numerosity and length in both healthy and pathological ageing. The experimental paradigm consisted of three bisection tasks in which participants were asked to judge whether the presented stimulus (i.e. a time interval, a group of dots, or a line) was more similar to the short/few or long/many standards. The first study recruited healthy young and elderly participants, while the second recruited healthy elderly participants and patients with Parkinson's disease, a clinical condition commonly associated with temporal impairments. The results of both experiments showed that discrimination precision differed between domains in all groups, with higher precision in the numerosity task and lower sensitivity in judging duration. Furthermore, while discrimination abilities were affected in healthy elderly and, even more so, in Parkinson's disease group, no domain-specific impairments emerged. According to our research, reduced discrimination precision might be explained by an alteration of a single system for all quantities or by an age-related general cognitive decline.
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In older adults' everyday life, time-based prospective memory (TBPM) is relevant as health-related intentions are often part of daily activities. Nonetheless, it is still unclear which task-related factors can potentially moderate the magnitude of age-related differences, such as duration of the PM target time (the time-window within which an individual must complete a given TBPM task), the frequency of the TBPM tasks, and the criterion chosen to compute PM accuracy. The present meta-analysis aimed to quantify age-related differences in laboratory TBPM tasks, and to investigate how specific task-related factors potentially moderate the magnitude of age effects. The results showed that age effects consistently emerged among the studies, with older adults showing lower TBPM performance and checking the clock less often than younger adults, especially for shorter intervals (e.g., ≤ 4â min). Furthermore, the results indicated that the duration of the PM target time interacted with the frequency of the PM task, suggesting that learning effects may attenuate the magnitude of age differences in TBPM performance. The results are discussed in terms of potential implications about the possible cognitive processes involved in TBPM and aging, as well as in terms of robustness of the TBPM laboratory paradigm in aging research.
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Memoria Episódica , Humanos , Anciano , Envejecimiento/psicología , Cognición , Tiempo , AprendizajeRESUMEN
It is becoming increasingly accepted that timing tasks, and underlying temporal processes, can be partitioned on the basis of whether they require an explicit or implicit temporal judgement. Most neuroimaging studies of timing associated explicit timing tasks with activation of the supplementary motor area (SMA). However, transcranial magnetic stimulation (TMS) studies perturbing SMA functioning across explicit timing tasks have generally reported null effects, thus failing to causally link SMA to explicit timing. The present study probed the involvement of SMA in both explicit and implicit timing tasks within a single experiment and using High-Definition transcranial Random Noise Stimulation (HD-tRNS), a previously less used technique in studies of the SMA. Participants performed two tasks that comprised the same stimulus presentation but differed in the received task instructions, which might or might not require explicit temporal judgments. Results showed a significant HD-tRNS-induced shift of perceived durations (i.e., overestimation) in the explicit timing task, whereas there was no modulation of implicit timing by HD-tRNS. Overall, these results provide initial non-invasive brain stimulation evidence on the contribution of the SMA to explicit and implicit timing tasks.
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Corteza Motora , Estimulación Transcraneal de Corriente Directa , Humanos , Estimulación Transcraneal de Corriente Directa/métodos , Corteza Motora/fisiología , Estimulación Magnética Transcraneal , Neuroimagen , JuicioRESUMEN
Many authors have analysed the effects of emotion recognition on time perception, showing that the more arousing the stimuli are the greater is the effect on duration perception. Visual stimuli, in particular faces, are the most recurrent stimuli employed in the literature. However, pictures in which emotional faces of older individuals have rarely been used, and when used, only young participants were tested. Hence, the present study is designed not only to analyse differences as regards duration perception in younger and older participants, but also to investigate the effects of neutral, happy, and angry facial expressions on younger and older participants when younger or older faces express those emotions. Results showed overestimation when emotional stimuli were presented. Interestingly, we observed temporal underestimation when the temporal intervals were marked by the image of younger participants and this was true in particular for older adults participants. Results are discussed in accordance with the internal clock model and in accordance with an inferential/reconstructive process occurring in memory and acting on temporal judgments.
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Emociones , Percepción del Tiempo , Anciano , Ira , Expresión Facial , Felicidad , HumanosRESUMEN
The present review includes transcranial magnetic and transcranial electric stimulation studies on time perception and shows that the neural processing of time requires the activity of wide range-distributed brain networks. Moreover, a critical discussion regarding non-invasive brain stimulation in the study of time processing is included to give the reader insights into the study of temporal processing in neuroscience. The cerebellum and auditory cortex seem most crucial when participants are required to estimate the passage of sub-seconds intervals and this conclusion holds independently of the modality used to mark the temporal intervals. Conversely, the primary visual area and MT/V5 seem to process primarily visual stimuli. The areas included in the prefrontal cortex are mostly implicated in the processing of supra-second time intervals and when time is processed in conjunction with other cognitive functions. Although previous fMRI studies showed activation in the supplementary motor area during sub-second timing tasks, TMS studies failed to confirm these observations. We conclude that the contribution of these strongly interconnected structures in the processing of temporal information is not fixed; their contribution depends not only on the duration of the time interval to be assessed by the brain but also on the cognitive set involved in the chosen task and on the stimulus modality used for marking time. Critical observations regarding the specificity of each method of stimulation as well as limitations and criticisms of the studies that used brain stimulation techniques will be also discussed.
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Cerebelo/fisiología , Corteza Cerebral/fisiología , Red Nerviosa/fisiología , Percepción del Tiempo/fisiología , Estimulación Transcraneal de Corriente Directa , Estimulación Magnética Transcraneal , Humanos , Estimulación Transcraneal de Corriente Directa/normas , Estimulación Magnética Transcraneal/normasRESUMEN
The understanding of the mechanisms underlying the representation of temporal intervals in the range of milliseconds/seconds remains a complex issue. Different brain areas have been identified as critical in temporal processing. The activation of specific areas is depending on temporal range involved in the tasks and on the modalities used for marking time. Here, for the first time, transcranial random noise stimulation (tRNS) was applied over the right posterior parietal (P4) and right frontal (F4) cortex to investigate their role in intra- and intermodal temporal processing involving brief temporal intervals (<1 sec). Eighty University students performed a time bisection task involving standard durations lasting 300 ms (short) and 900 ms (long). Each empty interval to be judged was marked by two successive brief visual (V) or auditory (A) signals defining four conditions: VV, VA, AV or AA. Participants were assigned to one of these four conditions. Half of the participants received tRNS over P4 and half over F4. No effect of stimulation was observed on temporal variability (Weber ratio). However, participants that were stimulated over P4 overestimated temporal intervals in the random condition compared to the sham condition. In addition to showing an effect of tRNS on perceived duration rather than on temporal variability, the results of the present study confirm that the right posterior parietal cortex is involved in the processing of time intervals and extend this finding to several sensory modality conditions.
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Percepción del Tiempo , Estimulación Transcraneal de Corriente Directa/métodos , Estimulación Acústica , Adulto , Femenino , Lóbulo Frontal/fisiología , Humanos , Masculino , Lóbulo Parietal/fisiología , Estimulación Luminosa , Adulto JovenRESUMEN
AIM: Many studies showed that visual stimuli are frequently experienced as shorter than equivalent auditory stimuli. These findings suggest that timing is distributed across many brain areas and that "different clocks" might be involved in temporal processing. The aim of this study is to investigate, with the application of tDCS over V1 and A1, the specific role of primary sensory cortices (either visual or auditory) in temporal processing. METHOD: Forty-eight University students were included in the study. Twenty-four participants were stimulated over A1 and 24 participants were stimulated over V1. Participants performed time bisection tasks, in the visual and the auditory modalities, involving standard durations lasting 300ms (short) and 900ms (long). RESULTS: When tDCS was delivered over A1, no effect of stimulation was observed on perceived duration but we observed higher temporal variability under anodic stimulation compared to sham and higher variability in the visual compared to the auditory modality. When tDCS was delivered over V1, an under-estimation of perceived duration and higher variability was observed in the visual compared to the auditory modality. CONCLUSION: Our results showed more variability of visual temporal processing under tDCS stimulation. These results suggest a modality independent role of A1 in temporal processing and a modality specific role of V1 in the processing of temporal intervals in the visual modality.
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Corteza Auditiva/fisiología , Percepción del Tiempo/fisiología , Corteza Visual/fisiología , Estimulación Acústica , Adulto , Humanos , Estimulación Luminosa , Estimulación Transcraneal de Corriente Directa , Adulto JovenRESUMEN
The present study investigated the effect of Parkinson's disease (PD) on prospective memory (PM) tasks by varying the emotional content of the PM actions. Twenty-one older adults with PD and 25 healthy older adults took part in the present study. Participants performed three virtual days in the Virtual Week task. On each virtual day, participants performed actions with positive, negative or neutral content. Immediately following each virtual day, participants completed a recognition task to assess their retrospective memory for the various PM tasks. PD patients were less accurate than the control group at both PM accuracy and recognition task accuracy. The effect of emotional valence was also evident, indicating that all participants were more accurate on positive PM tasks than both negative and neutral. This study confirmed PM impairment in PD patients and extended previous research showing how positive emotional stimuli can influence PM performance.
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Several studies about schizophrenia have shown a cognitive bias named "Jumping to Conclusions" (JTC), defined as a decision made quickly on the basis of little evidence that occurs in these patients when performing probabilistic reasoning paradigms. The main objective of this study is to compare JTC bias and BADE (Bias Against Disconfirmatory Evidence) in patients with schizophrenia vs. participants with high/low schizotypy to understand the underlying mechanism of these cognitive biases. Probabilistic reasoning was assessed using a modified version of Drawing to Decision task. In addition to the traditional parameters of this task (Plausibility Rating (PR), Draws to Decision (DTD), BADE) we also calculated new parameters, overall accuracy and one named Feedback Sensitivity (FS) which lower scores shows greater use of feedback. The results of the study suggest a context effect: in the cued condition, there were not main differences between groups. In the uncued condition, we found higher JTC bias at stage 1 for patients. At the same time, PR at first stages related positively with Feedback Sensitivity and negatively with accuracy for patients and high schizotypy participants (high confidence is associated with worse performance and lower feedback use). BADE seems unrelated to JTC bias and FS. The results are discussed in terms of JTC like as a clinical bias and whether patients with schizophrenia are less able to use feedback.
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Toma de Decisiones/fisiología , Retroalimentación Psicológica/fisiología , Esquizofrenia/fisiopatología , Trastorno de la Personalidad Esquizotípica/fisiopatología , Pensamiento/fisiología , Adulto , Femenino , Humanos , MasculinoRESUMEN
In this study, we investigated time perception in patients with traumatic brain injury (TBI). Fifteen TBI patients and 15 matched healthy controls participated in the study. Participants were tested with durations above and below 1s on three different temporal tasks that involved time reproduction, production, and discrimination tasks. Data variables analyzed included amount of errors, relative errors, and coefficient of variation. Both groups completed a neuropsychological battery that included measures of attention, working memory, and executive functions. Results revealed significant differences between groups on the time reproduction and discrimination tasks, whereas groups showed similar performance on the time production task. Correlation analyses showed involvement of attention, working memory and executive functions on the time reproduction and time discrimination tasks, but there was no involvement on the time production task. These findings suggest that TBI does not impact specific temporal function. Rather, impairments in attention, working memory and executive function abilities may explain lower temporal performance in people with TBI.
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Lesiones Encefálicas/fisiopatología , Trastornos de la Percepción/fisiopatología , Índice de Severidad de la Enfermedad , Percepción del Tiempo/fisiología , Adulto , Atención/fisiología , Lesiones Encefálicas/complicaciones , Femenino , Humanos , Masculino , Memoria a Corto Plazo/fisiología , Persona de Mediana Edad , Pruebas Neuropsicológicas , Trastornos de la Percepción/etiología , Adulto JovenRESUMEN
The relationship between dietary intake and acid-base metabolism has been investigated in the past by means of the inorganic cation-anion difference (C(+)(nm)-A(-)(nm)) method based on dietary ash-acidity titration after the oxidative combustion of food samples. Besides the inorganic components of TA (A(-)(nm)-C(+)(nm)), which are under renal control, there are also metabolizable components (A(-)(nm)-C(+)(nm)) of TA, which are under the control of the intermediate metabolism. The whole body base balance, NBb(W), is obtained only by the application of C(+)(nm)-A(-)(nm) to food, feces and urine, while the metabolizable component (A(-)(nm)-C(+)(nm)) is disregarded. A novel method has been subsequently suggested to calculate the net balance of fixed acid, made up by the difference between the input of net endogenous acid production: NEAP = SO(4)(2-)+A(-)(m)-(C(+)(nm)-A(-)(nm)), and the output of net acid excretion: NAE = TA + NH(4)(+) - HCO(3)(-). This approach has been criticized because 1) it includes metabolizable acids, whose production cannot be measured independently; 2) the specific control of metabolizable acid and base has been incorrectly attributed to the kidney; 3) the inclusion of A-m in the balance input generates an acid overload; 4) the object of measurement in making up a balance has to be the same, a condition not fulfilled as NEAP is different from NAE. Lastly, by rearranging the net balance of the acid equation, the balance of nonmetabolizable acid equation is obtained. Therefore, any discrepancy between these two equations is due to the inaccuracy in the urine measurement of metabolizable cations and/or anions.
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Equilibrio Ácido-Base/fisiología , Fenómenos Fisiológicos de la Nutrición/fisiología , Aniones/metabolismo , Cationes/metabolismo , HumanosRESUMEN
Left ventricular hypertrophy is an independent cardiovascular risk factor in the general population and in patients with chronic renal failure. Relatively little is known about the effects of renal transplantation on left ventricular hypertrophy. The aim of this study was to determine the changes in left ventricular mass after successful renal transplantation and to evaluate the importance of some clinical, laboratory, and echocardiographic variables on the trend to left ventricular hypertrophy. Twenty-three patients with end-stage renal disease were studied by ambulatory blood pressure monitoring and echocardiography before and 2 years following renal transplantation. After 24 months of follow-up, all transplant recipients had adequate renal function (serum creatinine <2 mg/dL). At the end of the study, we observed a significant decrease in left ventricular mass and left ventricular mass index compared to the pretransplantation period. In renal transplant recipients, the prevalence of left ventricular hypertrophy significantly decreased (78% versus 44%, P < .03) after 2 years of follow-up. Systolic 24-hour blood pressure was the only predictor of left ventricular mass and of left ventricular mass index at 2 years after transplantation. In conclusion, successful renal transplantation produces a regression of left ventricular hypertrophy. This beneficial effect depends on a decrease in systolic pressure levels.
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Hipertrofia Ventricular Izquierda/complicaciones , Fallo Renal Crónico/complicaciones , Fallo Renal Crónico/cirugía , Trasplante de Riñón/fisiología , Adulto , Presión Sanguínea , Femenino , Estudios de Seguimiento , Humanos , Hipertrofia Ventricular Izquierda/fisiopatología , Trasplante de Riñón/métodos , Masculino , Persona de Mediana Edad , Análisis de Regresión , Estudios Retrospectivos , Factores de RiesgoRESUMEN
The aim of this work was to study the effect of early administration of angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II type-I receptors blockers (ARB) on renal function and proteinuria in renal transplant recipients with good, stable renal function and mild proteinuria. Twenty four patients started ACEI/ARB therapy within 14 months after surgery (RAS-). Before (T0) and every month for 2 years after the initiation of ACEI/ARB we evaluated creatinine clearance (CrCl), proteinuria/day (UP), UP/CrCl (FUP), arterial blood pressure, and serum lipid levels. Twenty-eight patients who never received ACEI/ARB (RAS+) were studied in the same fashion. In the RAS+ CrCl was reduced after 2 years compared with T0 (64.5 +/- 2.6 vs 75.0 +/- 3.2 mL/min, P < .003); UP and FUP were both significantly increased (666 +/- 65 vs 132 +/- 20 mg/day 8.8 +/- 1.2 vs 2.6 +/- 0.6 mg/mL x 10(3); P < .001 and .002) compared with T0. Moreover, UP (P < .04), FUP (P < .03), and the percentage reduction of CrCl (11.4% +/- 5% vs 4.6% +/- 1.8%; P < .05) were greater in RAS+ than RAS- subjects at 2 years of the study. The values of other parameters did not show significant differences between the two groups. In conclusion, this study suggested that ACEI/ARB have renoprotective effects, when used in patients with good stable renal function and mild proteinuria. These drugs may play a role to prevent chronic allograft nephropathy.
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Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Trasplante de Riñón/fisiología , Sistema Renina-Angiotensina/efectos de los fármacos , Antihipertensivos/uso terapéutico , Presión Sanguínea/efectos de los fármacos , Creatinina/metabolismo , Enalapril/uso terapéutico , Estudios de Seguimiento , Humanos , Hipertensión/tratamiento farmacológico , Pruebas de Función Renal , Losartán/uso terapéutico , Proteinuria , Ramipril/uso terapéutico , Arteria Renal/ultraestructura , Tetrazoles/uso terapéutico , Factores de Tiempo , Valina/análogos & derivados , Valina/uso terapéutico , ValsartánRESUMEN
Twenty renal transplant recipients (RTx) with a normal ultrasound pattern of renal artery who began angiotensin-converting enzyme inhibitor (ACEI) therapy within 14 months after surgery (ACEI(+)) were studied retrospectively to evaluate endogenous creatinine clearance/1.73 m(2) body surface area (CrCl), proteinuria (UP), UP/CrCl (FUP), mean arterial pressure (MBP), total cholesterol, LDL, HDL, and triglycerides. Before (T(0)) and every month for 2 years after initiation of ACEI. Twenty-four RTx who never received ACEI (ACEI(-)) were studied in the same fashion. No differences in the parameters were noted at T(0); all RTx had CrCl >60 mL/min, Up less than 0.5 g/d, and stable renal function for 3 months before the study. In the ACEI cohort CrCl was reduced after 2 years compared with T(0) (65.6 +/- 2.8 vs 76 +/- 3.2 mL/min, P <.004), UP and FUP were both increased (660 +/- 60 vs 130 +/- 20 mg/d, 8.9 +/- 1.3 vs 2.8 +/- 0.6 mg/mL x 10(3); P <.001 and.002, respectively). UP >0.5 g/d was present in three cases. After 2 years the ACEI(+) group showed a decrease in CrCl (68.2 +/- 3.1 vs 73 +/- 2.2 mL/min) and the increase in UP (181 +/- 21 vs 139 +/- 18 mg/d) and in FUP (3.1 +/- 0.7 vs 2.6 +/- 0.9 mg/mL x 10(3)), which were not significantly different from the values at T(0). No cases showed UP >0.5 g/d. Moreover UP (P <.04), FUP (P <.03) and the percent reduction of CrCl (11.2 +/- 2.5% vs 4.6 +/- 1.8%, P <.05) were greater among ACEI(-) than ACEI(+) patients at 2 years. ACEI(-) patients showed correlation between the percent reduction of CrCl and UP (r =.51, P <.04). The values of MBP and lipids did not reveal any significant difference between the two groups. In conclusion, this study suggests that ACEI have a renoprotective effect, when used early, and may also prevent chronic allograft nephropathy.
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Inhibidores de la Enzima Convertidora de Angiotensina/uso terapéutico , Supervivencia de Injerto/fisiología , Pruebas de Función Renal , Trasplante de Riñón/fisiología , Presión Sanguínea , Colesterol/sangre , Creatinina/metabolismo , Supervivencia de Injerto/efectos de los fármacos , Humanos , Proteinuria , Estudios Retrospectivos , Trasplante Homólogo , Triglicéridos/sangreRESUMEN
Chronic renal failure needs substitutive treatment such as haemodialysis and peritoneal dialysis for the patient to survive. Kidney transplantation (KTx) improves survival of the patient with chronic renal failure. Since the first KTx, performed by Merrill in Boston in 1959, advances in medical therapy, immunosuppressive therapy and refinements in surgical technique have improved the quality of life of the transplant patient. We present a review of the incidence, diagnosis and therapy of surgical complications after KTx reported in the literature and a retrospective analysis of 297 consecutive cadaveric donor kidney transplants done in our institution from September 1993 to September 2002. Vascular complications represent 5-10% of postoperative complications. Our experience showed an incidence of 1.7% renal artery thrombosis, 1.4% renal vein thrombosis, 1.7% renal artery stenosis, 1.4% arterial rupture due to fungal arteritis, 0.7% spontaneous graft ruptures and 12% lymphoceles. Urological complications account for 10-15% of postoperative complications. In our series we found an incidence of 7.4% urinary leakage, 2.7% urinary obstruction and 3% urinary reflux. Gastrointestinal complications represent 16% of postoperative complications. Our series showed 1% pancreatitis with an overall mortality of 33% and an incidence of 1.7% intestinal perforations. Surgical complications still represent a challenge that increments morbidity and mortality among kidney transplant recipients. Data shown may offer some guidance on how to deal with early and late post-transplant surgical complications.
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Trasplante de Riñón/efectos adversos , Arteritis/diagnóstico , Arteritis/epidemiología , Arteritis/etiología , Cadáver , Humanos , Incidencia , Italia/epidemiología , Linfocele/diagnóstico , Linfocele/epidemiología , Linfocele/etiología , Micosis/complicaciones , Complicaciones Posoperatorias/diagnóstico , Complicaciones Posoperatorias/epidemiología , Complicaciones Posoperatorias/etiología , Arteria Renal , Obstrucción de la Arteria Renal/diagnóstico , Obstrucción de la Arteria Renal/epidemiología , Obstrucción de la Arteria Renal/etiología , Venas Renales , Estudios Retrospectivos , Rotura Espontánea , Trombosis/diagnóstico , Trombosis/epidemiología , Trombosis/etiología , Enfermedades Urológicas/diagnóstico , Enfermedades Urológicas/epidemiología , Enfermedades Urológicas/etiologíaRESUMEN
Cardiovascular disease is the leading cause of morbidity and mortality following renal transplantation. Because many renal transplant recipients die with functioning grafts, deaths resulting from cardiovascular disease have became an increasingly important cause of graft loss, particularly after the first post-transplantation year. Moreover, a contribution of some cardiovascular risk factors to renal allograft dysfunction has been demonstrated. A number of observational studies suggest that cardiovascular disease is more common in renal transplant patients than in the general population. The excessive risk for cardiovascular disease is related to a high prevalence and accumulation of atherogenic risk factors before and after transplantation. Hypertension, post-transplantation diabetes and hyperlipidemia are well-recognized risk factors for the development of cardiovascular events after renal transplantation and are strongly associated with immunosuppressive therapy. Progressive renal dysfunction may also influence the risk of cardiovascular complications after renal transplantation. The elevated risk may also be caused by non- traditional risk factors such as anaemia, adhesion molecules, hyperhomocysteinemia, microinflammatory state, abnormal coagulation and oxidative stress. To prevent post-transplantation cardiovascular disease it is crucial to define the etiological risk factors. Some risk factors can be modified, and for some of these, there is strong evidence from studies in the general population that intervention improves survival. Given the significant morbidity and mortality of cardiovascular disease in renal transplant recipients, aggressive treatment intervention for potentially modifiable factors are strongly advocated after transplantation. In addition to treatment intervention, risk management should also involve tailoring the immunosuppressive regimen to minimize both direct and indirect cardiovascular risks. In this article we attempted to review and quantify the post-transplant risk factors for cardiovascular disease as well as offer suggestions on optimizing the therapy or treatment strategies to minimize the risk of cardiovascular complications in renal transplant patients. Reduction of cardiovascular morbidity and mortality can improve not only the life expectancy and quality of life of the transplant recipients but also their graft function and survival.
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Enfermedades Cardiovasculares/etiología , Enfermedades Cardiovasculares/prevención & control , Trasplante de Riñón/efectos adversos , Anemia/complicaciones , Trastornos de la Coagulación Sanguínea/complicaciones , Complicaciones de la Diabetes , Rechazo de Injerto/complicaciones , Humanos , Hiperhomocisteinemia/complicaciones , Hiperlipidemias/complicaciones , Hipertensión/complicaciones , Obesidad/complicaciones , Policitemia/complicaciones , Proteinuria/complicaciones , Factores de Riesgo , Fumar/efectos adversosAsunto(s)
Antihipertensivos/uso terapéutico , Hipertensión/tratamiento farmacológico , Trasplante de Riñón/fisiología , Nefrectomía/métodos , Presión Sanguínea/efectos de los fármacos , Diástole , Estudios de Seguimiento , Humanos , Hipertensión/fisiopatología , Estudios Retrospectivos , Sístole , Factores de Tiempo , Resultado del TratamientoAsunto(s)
Azatioprina/uso terapéutico , Eritropoyetina/biosíntesis , Trasplante de Riñón/fisiología , Ácido Micofenólico/análogos & derivados , Ácido Micofenólico/uso terapéutico , Quimioterapia Combinada , Eritropoyetina/sangre , Femenino , Ferritinas/sangre , Estudios de Seguimiento , Hemoglobinas/metabolismo , Humanos , Hierro/sangre , Trasplante de Riñón/inmunología , Masculino , Persona de Mediana Edad , Hormona Paratiroidea/sangre , Esteroides/uso terapéutico , Factores de TiempoRESUMEN
Acid generation and elimination processes were compared with total base (bicarbonate plus metabolizable anions) turnover in 18 anuric patients undergoing post-dilutional haemofiltration. The study was conducted during the second haemodialysis session of the week by means of a whole-body base balance technique. The results showed that the mean rates of base loss and base gain during dialysis did not differ (i.e. the dialysis base balance approximated to zero). The concurrent mean rate of intestinal base absorption was 66+/-26 mmol/2 days, as calculated from the whole-body balance of the various inorganic cation and anion differences in a metabolic steady state. This level of intestinal base absorption would be capable of neutralizing the 59+/-21 mmol of H(+) ions/2 days that is contributed by sulphuric acid, which is the most important endogenous acid produced in anuric patients. In spite of the fact that intestinal base supply was adequate to neutralize endogenous acid production completely, our patients presented with pre-dialysis non-carbonic acidosis. The depression of plasma bicarbonate levels could not, however, be explained by increased concentrations of the anion gap and organic acids, which were within normal limits both before and after dialysis. We suggest as an alternative hypothesis that this pre-dialysis acidosis may represent an isotonic dilution acidosis that is induced by the ingestion of base-free tap water in order for plasma tonicity to be protected from the accumulation of impermeant dietary solutes, which takes place during the interdialysis period in anuric patients.