S. Sanz de Castro

Assessment of glomerular filtration rate in transplant recipients with severe renal insufficiency by Nankivell, Modification of Diet in Renal Disease (MDRD), and Cockroft-Gault equations

Measurement of glomerular filtration rate (GFR) is time consuming and cumbersome. Several formulas have been developed to predict creatinine clearance (CrCl) or GFR using serum creatinine (Cr) concentrations and demographic characteristics. However, few studies have been performed to discern the best formula to estimate GFR in kidney transplantation. In this study, Cockroft-Gault (CG), Nankivell, and Levey (MDRD) formulas were tested to predict GFR in 125 cadaveric renal transplant patients with severe renal insufficiency (GFR less than 30 mL/min per 1.73 m2). The GFR was estimated as the average Cr and urea clearances. The mean GFR estimated by averaged Cr and urea clearances (22.18+/-5.23 mL/min per 1.73 m2) was significantly different from the mean values yielded by the MDRD formula (20.42+/-6.65 mL/min per 1.73 m2, P=.000), the Nankivell formula (30.14+/-11.98 mL/min per 1.73 m2, P=.000), and the CG formula (29.42+/-8.64 mL/min per 1.73 m2, P=.000). The MDRD formula showed a better correlation (R=0.741, P=.000) than the CG (R=0.698, P=.000) and the Nankivell formulas (R=0.685, P=.000). Analysis of differences using the Bland-Altmann method demonstrated that MDRD gave the lowest bias (MDRD: -1.65+/-4.4 mL/min per 1.73 m2; CG: 7.33+/-6.24 mL/min per 1.73 m2; Nankivell: 8.05+/-9.23 mL/min per 1.73 m2) and narrower limits of agreement (Nankivell: -10.41-26.51 mL/min per 1.73 m2; CG: -5.15-19.81 mL/min per 1.73 m2; MDRD: -10.61-7.31 mL/min per 1.73 m2). In transplant patients with severe renal insufficiency, the MDRD equation seems better than the other formulas to estimate GFR.

Dialysis Membranes and PTH Changes during Hemodialysis in Patients with Secondary Hyperparathyroidism

Changes in parathyroid hormone (PTH) during hemodialysis have been explained by the influence of ionized calcium changes on PTH secretion. In this study we have investigated the influence of dialysis membranes of different permeability on PTH changes during hemodialysis. Five chronic renal failure patients underwent three consecutive hemodialysis sessions with cuprophane (CUP) polysulfone (PS) and polyacrylonitrile (PAN). Two hours of isolated ultrafiltration were followed by 3 h dialysis. A significant decrease in carboxy terminal PTH (COOH PTH) was observed with PAN (p < 0.05) but not with CUP or PS. Intact PTH decreased (p < 0.001) with all three membranes, following a significant increase in ionized calcium (p < 0.001). Sieving coefficients for COOH PTH were significantly lower with CUP than with PS (p < 0.05) or PAN (p < 0.001). Intact PTH sieving coefficients were near zero for all three membranes. COOH PTH and intact PTH clearance rates were significantly higher with PAN (p < 0.001) than with PS or CUP, either in isolated ultrafiltration or with dialysis fluid. Thus PTH changes during hemodialysis do not only depend on the increase in calcium but also on the nature of the dialysis membrane. Adsorption of PTH to the PAN membrane surface explain the high PTH clearance rates achieved with this filter.

Pulse pressure is an independent risk factor of cardiovascular disease in renal transplant patients

Elevated pulse pressure in the general population has been shown to be associated with cardiovascular disease, which is the main cause of death in renal transplant patients. We investigated the effects that a wide pulse pressure has on cardiovascular disease after renal transplantation in a cohort of 532 transplant patients with functioning grafts for more than one year. Patients were classified into two groups depending on whether the one-year pulse pressure was less than or greater than 65 mm Hg. We analyzed patient survival, posttransplant cardiovascular disease and principle causes of death. Five- and ten-year patient survival were lower among the group with higher pulse pressures. The main cause of death was vascular disease in both groups. The presence of posttransplant cardiovascular disease was higher among the group with higher pulse pressures (RR=1.73). In addition, the incidence of an elevated pulse pressure was directly associated with recipient age and posttransplant diabetes mellitus. In conclusion, pulse pressure represents an independent risk factor for increased cardiovascular morbidity and mortality in renal transplant patients.

Clinical and Epidemiological Characteristics of Refractory Hypertension in Renal Transplant Patients

Hypertension is common following renal transplantation, affecting up to 80% of recipients. It is generally accepted that hypertension is associated with poor graft survival and reduced life expectancy, contributing to increased cardiovascular risk factors and mortality rates. The prevalence of refractory hypertension among renal transplant patients is unknown; it may be associated with a worse prognosis. The aim of our study was to determine the prevalence of refractory hypertension among 529 stable renal transplant recipients and to describe its clinical and epidemiological features. We divided this population into 4 groups to make comparisons: normotensive (n = 82), controlled hypertension (n = 228), uncontrolled hypertension but not refractory (n = 183), and refractory hypertension (n = 36) as defined by a systolic blood pressure >or= 140 mm Hg and/or a diastolic blood pressure >or= 90 mm Hg among patients treated with 3 or more drugs (1 of them being a diuretic). The proportion of patients with refractory hypertension in our transplant unit was 6.8%. The main characteristics of patients with refractory hypertension versus normotensive patients were: mainly systolic hypertension (152.5 +/- 10.32 vs 121.6 +/- 9.26 mm Hg; P < .012), elderly age (59.47 vs 48.33 years; P < .000), diabetes (36.2% vs 1.2%; P < .000), poorer renal function as measured by glomerular filtration rate (36.15 +/- 20.41 vs 56.12 +/- 15.75 mL/min/1.73 m(2); P < .004), higher 24-hour urinary protein excretion (2.55 +/- 2.61 vs 0.5 +/- 0.8 g; P < .003), and steroid treatment (47.2% vs 23.2%; P < .000). The results of this study may help identify the clinical and epidemiological factors which correlated with refractory hypertension for future interventional applications to reduce the morbidity/mortality among the renal transplant population.

Risk of Cardiovascular Disease Associated With Refractory Hypertension in Renal Transplant Recipients

BACKGROUND Hypertension is common after renal transplantation, affecting as many as 80% of recipients. It is generally accepted that hypertension is associated with poor graft survival and reduced life expectancy because of increased cardiovascular risk factors. The prevalence of refractory hypertension in renal transplant recipients is unknown, and could be associated with a poor prognosis. OBJECTIVE To investigate the effects of refractory hypertension on cardiovascular disease (CVD) after renal transplantation in 486 patients with grafts functioning for longer than 1 year. PATIENTS AND METHODS Patients were classified into 2 groups: (1) 57 with refractory hypertension, that is, systolic blood pressure 130 mm Hg or greater or diastolic blood pressure 80 mm Hg or greater, and receiving treatment with at least 3 drugs, one of which was a diuretic; and (2) the remaining 429 patients. Patient and graft survival, and posttransplantation CVD were analyzed. RESULTS Refractory hypertension was associated with male sex (82.5% vs 66.5% [P<.01]), poor renal function (mean [SD] serum creatinine concentration 2.2 [1.2] mg/dL vs 1.6 [0.6] mg/dL; Modification of Diet in Renal Disease score 39.2 [20.0] mL/min/1.73 m2 vs 49.2 [18.0] mL/min/1.73 m2 [P=.000]; and steroid therapy (94.7% vs 79.0% [P=.001]). In the group with refractory hypertension, 5-year patient and graft survival rates were lower, and the incidence of posttransplantation CVD was greater (relative risk, 1.7; 95% confidence interval, 1.05-2.18; P=.03). CONCLUSION Refractory hypertension is an independent risk factor for increased cardiovascular morbidity and mortality in renal transplant recipients.