Effects of skewness and kurtosis on model selection criteria

We consider the behavior of model selection criteria in AR models where the error terms are not normal by varying skewness and kurtosis. The probability of estimating the true lag order for varying degrees of freedom (k) is the interest. For both small and large samples skewness does not effect the performance of criteria under consideration. On the other hand, kurtosis does effect some of the criteria considerably. In large samples and for large values of k the usual asymptotic theory results for normal models are confirmed. Moreover, we showed that for small sample sizes performance of some newly introduced criteria which were not considered in Monte Carlo studies before are better

Can subtypes of white blood cells predict mortality in hemodialysis patients? [Beyaz kan hücre alt tipleri hemodiyaliz hastalari{dotless}nda mortaliteyi öngörebilir mi?]

Objective: To investigate whether increased white blood cell count (WBC) is an independent risk factor for mortality in hemodialysis (HD) patients. There are limited number of studies that evaluate the WBC subtypes and mortality in HD patients. Material and Methods: In this 36 months long prospective study, predictive value of WBC subtypes for mortality was investigated in 910 HD patients (male 55%, diabetes 29.3%, age 59 ± 14; HD duration 44 ± 39 months). Results: There was significant correlation between high sensitive C-reactive protein and neutrophils (r= 0.43, p< 0.001) and monocytes (r= 0.24, p< 0.001). During the study 202 (22%) patients died mainly of cardiovascular disease (%57). Survivals at 1,2 and 3 years were calculated with Kaplan Meier analysis and were found as 90%, 80% and %73, respectively. Kaplan Meier analysis showed that increased basal neutrophil count (>5.040/mm3), increased monocytes (>740/mm3) and decreased lymphocytes (<1.620/mm3) were correlated with poor survival. In Cox regression analysis, monocyte count over 1.267/mm3 and lymphocyte count less than 461/mm3 were found as independent factors for overall survival after correction for classical risk factors. However, neutrophil count was not correlated with mortality. Conclusion: Increased blood monocyte count and decreased lymphocyte count are independent risk factors for long-term mortality. © 2011 by Türkiye Klinikleri

Comparison of the effects of enalapril and theophylline on polycythemia after renal transplantation

PubMed ID: 7778179Posttransplant erythrocytosis (PTE) is a potentially serious complication for which (apart from phlebotomy) two alternative treatments have been proposed: Theophylline (Theo) and angiotensin-converting enzyme inhibitors. We investigated 28 patients with PTE, who were assigned to 3 matched groups. Group 1 (10 patients) received 10 mg of Enalapril (Ena)/day. After 2 months, mean hematocrit (Ht) had dropped from 0.57 (range 0.52-0.62) to 0.45 (0.34-0.49). Ena was stopped and, after a period of 3.8±0.3 months, Ht had risen again to baseline values (0.56, range 0.52-0.61) in 8 of them. These 8 patients were then given 5 mg/day Ena. Ht decreased more slowly, and after 3 months reached a mean of 0.49 (0.44-0.54). Group 2 (9 patients) received 600 mg/day Theo in 2 doses. After 2 months, Ht had decreased from 0.56 (0.52-0.61) to 0.52 (0.46-0.63), but in 5 patients, Ht remained above 0.51. After 1 month discontinuation of treatment, PTE persisted in 7 patients. These patients were given 10 mg/day Ena, whereupon Ht decreased from 0.55 (0.52-0.64) to 0.46 (0.40-0.53) after 2 months and to 0.41 (0.33-0.47) after 3 months. Group 3 did not receive medical treatment. After 3 months, PTE persisted in 8 out of the 9 patients and remained unchanged during the following 3 months. Mean values for Ht were: Baseline, 0.55 (0.52-0.58); after 3 months, 0.56 (0.53-0.59); and after 6 months, 0.55 (0.52-0.60). We conclude that Ena is superior to Theo in the treatment of PTE. There were no resistant patients, but individual sensitivity differs. Its effect is dose dependent, reversible, and reproducible. Excessive Ht decrease may occur; thus, doses should be titrated individually. © 1995 by Williams & Wilkins

Requirement of emergency hemodialysis in a peritoneal dialysis patient; Laxative induced hypermagnesemia: A case report [Periton Diyalizi Hastasinda Acil Hemodiyaliz Gereksinimi; Laksatif Kullanimina Bagli Hipermagnezemi: Olgu Sunumu]

Hypermagnesemia is rarely seen in peritoneal dialysis (PD) patients because PD can lower the plasma magnesium (Mg) concentration effectively. In this report, a continuous ambulatory peritoneal dialysis (CAPD) patient with life-threatening hypermagnesemia treated by hemodialysis (HD) is presented. A 52-year-old male patient on PD treatment was admitted to our clinic with complaints of fatigue and muscle weakness. Decrease in deep tendon reflexes (DTR), decrease in muscle strength at bilateral upper and lower extremities, and increased level of magnesium (7.7 mg/dl) were detected. Bradycardia, prolongation of the P-R interval, and an increase in Q-T interval were found on the electrocardiography. HD was performed two times. After HD, all the signs and symptoms of the patient improved. HD is a dialysis modality that should be preferred in the treatment of symptomatic patients with hypermagnesemia, because of providing more rapid clearance of Mg

Regression of left ventricular hypertrophy in haemodialysis patient by ultrafiltration and reduced salt intake without antihypertensive drugs

PubMed ID: 9641180Background. Left ventricular hypertrophy (LVH) is very frequent in haemodialysis patients. Only few investigations have reported its regression, and only by the use of antihypertensive drugs. Because volume load is at least as important as pressure load, we investigated whether persistent strict volume control by ultrafiltration alone may be effective in improving LVH. Methods. Using blood pressure (BP) and cardiac dimensions as a guide, we treated all hypertensive patients in our dialysis unit during the 3 times weekly dialysis sessions for 4 h per session with as much ultrafiltration as they could stand. If they gained too much weight an extra isolated ultrafiltration (UF) session was applied. Special attention was given to dietary salt restriction. The study group of all 15 patients in whom echocardiographic assessment had been made at least 1.5 years previously was selected retrospectively, and we acknowledge that important confounding factors might not have been controlled for. Cardiothoracic index (CTI) was estimated on the chest X-ray. Diameters of left atrium (LA), left ventricle systolic (LVS) and diastolic (LVD), interventricular septum (IVS), posterior wall (PW), and left ventricular mass index (LVMI) were estimated by standard echocardiographic methods. Results. Mean arterial pressure of the study group had been lowered by UF before the first echocardiogram from predialysis 136 ± 11 to 101 ± 14 and from postdialysis 119 ± 8 to 92 ± 12 mmHg. During a mean follow-up period of 37 ± 11 months LVMI decreased from 175 ± 60 to 105 ± 11 g/m2 CTI decreased further from 48 ± 3 to 43 ± 4%, while significant decreases of LA (22.5 ± 3 to 19.9 ± 4 mm/m2), LVS (18.7 ± 4 to 15.9 ± 3 mm/m2) and LVD (28.3 ± 4 to 24.0 ± 3 mm/m2) were seen in all patients. There also was a further decrease in both pre- and postdialysis BP to 116 ± 12/73 ± 7 and 105 ± 7/65 ± 3 mmHg respectively. Conclusion. The results of this uncontrolled retrospective study suggest that good long-term BP control and a decrease of LVM can be achieved by continuous efforts to control hypervolaemia. The decrease in volume may be even more important than pressure reduction to achieve this goal

‘Paradoxical’ rise in blood pressure during ultrafiltration in dialysis patients

PubMed ID: 8538935In some hypertensive haemodialysis (HD) patients, blood pressure rises further during ultrafiltration (UF). We investigated seven such patients, who were not responsive to hypotensive drugs, including converting enzyme inhibitors. All had marked cardiac dilatation, but most were non-oedematous. They were treated with repeated intense UF while monitoring cardiac function by echocardiography. After a variable time period they all became (near) normotensive without medication. Mean systolic and diastolic blood pressure decreased by 46 ± 18 and 22 ±9 mmHg respectively while bodyweight decreased by a mean of 6.7 ± 3.0 kg. Plasma volume decreased by 22%, and mean albumin increased from 3.9 ± 0.3 to 4.2 ± 0.3 g/dl. Cardiothoracic index decreased from a 0.56 ± 0.02 to 0.45 ± 0.03. Mitral and tricuspid insufficiency was present in four patients and improved or disappeared in all of them. Diameters of the inferior vena cava, left atrium, and end systolic and diastolic left ventricle markedly decreased in all patients. Ejection fraction increased, but remained subnormal in some patients, while cardiac output increased in five and decreased in two patients. We conclude that paradoxical blood pressure rise with UF usually occurs in the presence overhydration and cardiac dilatation and should be treated by intensified UF. The explanation of this phenomenon remains speculative. © 1995 European Dialysis and Transplant Association-European Renal Association