Blood pressure measurement in hemodialysis: The importance of the measurement technique

Systemic arterial hypertension contributes to the high cardiovascular morbidity in hemodialysis (HD) patients, but the accuracy of blood pressure (BP) measurement in this population has not been well studied. To evaluate the agreement between BP measurement using the routine measurement technique (usual method) and the technique recommended by the VII Joint (standard method). This cross-sectional study enrolled 124 patients in a single center who had undergone dialysis for more than three months and were 18 years of age or older. The BP was verified at the start of dialysis by the nursing team (usual method) and by the researchers (standard method). The agreement between the systolic and diastolic BP (SBP and DBP) measurements was tested by the Bland-Altman analysis. A difference in BP measurement higher than ±5 mm Hg was considered clinically significant. The studied group had a mean age of 53.2 years. The average difference between routine and standard BP measurement was -6 mm Hg for SBP (limits of agreement: -40.1-28 mm Hg; P <0.001) and -5.6 mm Hg for DBP (limits of agreement: -33.1-21.8 mm Hg; P <0.001). A clinically significant difference in BP measured by both methods was observed in 69.4% of the patients for SBP and in 61.3% for DBP. The disagreement between the results of different BP measurement methods in HD patients was significant and the BP was underestimated using the usual BP method. BP measurement standardization should be encouraged to avoid errors in diagnosis and therapy.

The renal PTH/PTHrP receptor is down-regulated in rats with chronic renal failure

Hypocalcemia, hyperphosphatemia, and resistance to the action of PTH are well characterized features in the setting of advanced chronic renal failure (CRF). Although the underlying mechanisms are ill-understood, clinical and experimental evidence points to both PTH receptor down-regulation and post-receptor abnormalities in their pathogenesis. In the present study we have examined the effect of advanced CRF in rats on the renal expression of PTH/PTHrP receptor (PTH-R). CRF was created by a standard two-step operation (5/6 nephrectomy). Four weeks thereafter, 19 uremic rats were compared with 23 sham-operated rats. Uremic rats had higher mean (+/- SD) plasma creatinine levels than control rats, 164 +/- 107 microM versus 43 +/- 5 microM, respectively. They also had higher plasma phosphorus and iPTH levels, 4.70 +/- 1.71 mM versus 2.59 +/- 0.37 mM and 561 +/- 336 versus 27 +/- 18 pg/ml, respectively. Mean plasma total calcium and blood ionized calcium were significantly lower in uremic than in control rats, 2.13 +/- 0.06 mM versus 2.61 +/- 0.10 mM and 1.07 +/- 0.11 versus 1.31 +/- 0.06 mM, respectively. Mean plasma calcitriol concentration was also significantly lower in uremic than in control rats, 39.8 +/- 14.6 and 80.4 +/- 15.2 pg/ml, respectively. Nine out of the 19 rats were examined for renal PTH-R gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of 22-oxa-calcitriol on calcium metabolism in rats with severe secondary hyperparathyroidism

The purpose of the present study was to examine the effect of a two day and a five day administration of 22-oxa-calcitriol (OCT) on calcium metabolism in rats with advanced chronic renal failure and severe secondary hyperparathyroidism. A first series of 27 uremic rats received either placebo, OCT or calcitriol (0.3 microgram i.p./rat) 48 and 24 hours before sacrifice. A second series of 18 uremic rats received either placebo, OCT (0.3 microgram i.p./rat) or calcitriol (0.05 microgram i.p./rat) for five days. We found that after 48 hours (series 1) both calcitriol and OCT increased blood ionized calcium (Ca2+) as compared to vehicle (1.23 +/- 0.04 and 1.10 +/- 0.02 mM, P < 0.01 and P < 0.05, respectively vs. control, 1.02 +/- 0.03 mM). Duodenal Ca transport (S/M) using the everted gut sac technique was not stimulated by OCT, even though it increased from 2.8 +/- 0.4 to 7.0 +/- 0.6 (P < 0.01) with calcitriol. In contrast, duodenal calbindin-D9k mRNA expression and protein content increased to a similar extent with OCT and calcitriol. Calcitriol was more potent in reducing plasma iPTH1-34 levels than OCT: 344 +/- 75 pg/ml (calcitriol) versus 632 +/- 46 pg/ml (OCT) compared with 897 +/- 74 pg/ml (control), P < 0.01. In the second series of rats, the injection of OCT (0.3 microgram i.p./rat) over five days was less effective than the lower dose of calcitriol (0.05 microgram i.p./rat) in reducing circulating iPTH: 110 +/- 26 (calcitriol) and 281 +/- 64 (OCT) versus 624 +/- 135 pg/ml (control), P < 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of glucagon on glomerular filtration rate and urea and water excretion

Clearance experiments were performed in anesthetized male Wistar rats to reevaluate the renal effects of glucagon (Gluc) on glomerular filtration rate (GFR) and solute and water excretion. After an 80-min control period, these effects were evaluated in the last 80 min of a 2-h intravenous Gluc infusion. Gluc induced significant increases in GFR (+20%), urine flow rate (+150%), free water reabsorption (+50%), urea synthesis and urea excretion (+66%), and nonurea solute excretion (+67%). In addition, fractional urea excretion (FEurea) increased by 43% (P less than 0.01). Additional experiments showed that increases in either urea excretion or urine flow rate (induced by appropriate infusion of urea or half-dilute saline), similar to those seen after Gluc, could not account for the increased FEurea. All significant effects of Gluc were also observed during infusion of antidiuretic hormone or during water diuresis. The tubular effects of Gluc could be explained by a reduction in proximal reabsorption. The dose of Gluc required to induce all the effects described above was 12 ng.min-1.100 g body wt-1, a dose producing an approximately 10-fold supraphysiological peripheral plasma concentration but a "physiological" level for the liver. Infusion of 1.2 ng induced almost no change in renal function, and infusion of 120 ng induced no greater effects than 12 ng. These results suggest 1) that Gluc, a hormone liberated after protein ingestion, exerts coordinated effects on liver and kidney to increase simultaneously urea synthesis and excretion and to promote water conservation and 2) that these effects could, at least in part, be indirect and depend on the Gluc-induced stimulation of hepatocyte metabolism.