Faculty Bibliography

It has been observed that while most hypertensive hemodialysis patients normalize their blood pressure with volume removal, there is a population of hemodialysis patients whose hypertension is refractory to volume removal. Our hypothesis is that such patients are still volume overloaded posthemodialysis and are not at a "true" dry weight. This study used atrial natriuretic peptide (ANP) assays (as a marker of hydration status) to study this hypothesis. Three groups of patients were studied: normotensive hemodialysis patients (n = 12; group 1), hypertensive hemodialysis patients who consistently normalize their blood pressure with fluid removal (n = 12; group 2), and hypertensive hemodialysis patients whose hypertension is refractory to fluid removal (n = 9; group 3). Plasma ANP levels were measured before and after hemodialysis by radioimmunoassay after extraction on Sep-Pac (Penninsula Laboratories, Belmont). On the day of study the predialysis mean arterial pressures in the three groups were 94.9 +/- 1.9 mm Hg in the normotensive group, 119.5 +/- 2.7 mm Hg in the dialysis-sensitive hypertension group, and 134.4 +/- 3.8 mm Hg in the dialysis-refractory hypertension group (P < 0.05 for comparisons between all groups). Mean arterial pressure did not change predialysis and postdialysis in the normotensive group (94.9 +/- 1.9 mm Hg to 93.1 +/- 1.8 mm Hg, respectively; P = 0.24), decreased in the dialysis-sensitive hypertension group (119.5 +/- 2.7 mm Hg to 100.8 +/- 3.7 mm Hg, respectively; P < 0.0001), and did not change in the dialysis-refractory hypertension group (134.4 +/- 3.8 mm Hg to 133.8 +/- 2.9 mm Hg, respectively; P = 0.77). Predialysis and postdialysis serum ANP levels were, respectively, 235.8 +/- 27.7 pg/mL and 237.8 +/- 36.2 pg/mL (P = 0.92) in the normotensive group, 809.2 +/- 295.5 pg/mL and 161.1 +/- 48.6 pg/mL (P = 0.03) in the dialysis-sensitive hypertension group, and 1,728.3 +/- 309.9 pg/mL and 1,936.1 +/- 359.1 pg/mL (P = 0.22) in the dialysis-refractory hypertension group. Mean predialysis ANP levels were higher in the dialysis-refractory hypertension group than in the dialysis-sensitive hypertension group (1,728.3 +/- 309.9 pg/mL v 809 +/- 359.1 pg/mL; P = 0.048). Mean prehemodialysis ANP in all hypertensive patients (n = 21) was higher (1,203.1 +/- 232.9) than in the normotensive patients (235.8 +/- 27.7) (P = 0.004). In conclusion, our findings are consistent with a hypothesis that inadequate removal of excess volume during hemodialysis plays a major role in dialysis-refractory hypertension.

The ankle-arm blood pressure index (AAI, ratio of ankle to arm systolic blood pressure), a simple, noninvasive, and inexpensive screening test, has recently been found to be highly predictive of subsequent mortality in several populations. The purpose of this study was to evaluate the relationship of the AAI to cardiovascular and all-cause mortality in hemodialysis patients. A cohort of 132 patients was followed for 1 year. The primary outcome measures were cardiovascular and all-cause mortality. An AAI of <0.9 was associated with a relative risk (RR) of cardiovascular mortality of 7.5, (95% CI, 2.3 to 24.8). Other predictive variables included diabetes mellitus RR 3.0, (95% CI, 1.2 to 7.3), and a history of any vascular disease RR 2.6 (95% CI, 1.0 to 7.0). An AAI of <0.9 was also predictive of all-cause mortality, RR 2.4 (95% CI, 1.2 to 4.7). Other predictive variables for all-cause mortality included older age, RR 1.4 per 10 years (95% CI, 1.0 to 2.1), decreased serum albumin RR 0.9 per 0.1 mg/dL (95% CI, 0.8 to 1.0), and diabetes mellitus RR 2.0 (95% CI, 1.0 to 3.7). Multivariate analysis showed an AAI of <0.9 and diabetes mellitus to be the only independent predictors of cardiovascular mortality, and an AAI of <0.9, older age, and a decreased serum albumin were independent predictors of all-cause mortality. In conclusion, we have found an AAI of <0.9 to be a powerful, independent predictor of mortality in hemodialysis patients.

It is unknown whether predialysis serum biochemical parameters may differ among chronic hemodialysis patients depending on the shift during which they are dialyzed. We studied 115 patients on chronic hemodialysis in our institution for 3 consecutive months and compared clinical and biochemical parameters based on the shift during which they were dialyzed. Predialysis serum potassium was found to be progressively higher for patients dialyzed on later as compared with earlier dialysis shifts, and phosphate was significantly higher for patients dialyzed during the evening shift as well. Regression analysis suggested that higher of potassium and phosphate levels were related to the time of day these sessions and not to patient age, amount of dialysis given or diet. By contrast, serum albumin, creatinine, sodium, and chloride levels were found to differ depending on dialysis shift, though these differences appeared to be accounted for by patient age. We concluded that the time of day of the beginning of the dialysis shift appears to mildly influence the levels of serum predialysis biochemical parameters which are important in monitoring patients on chronic hemodialysis, in particular potassium and phosphate. Further insight into the mechanism of this observed effect might improve our ability to interpret and treat derangements of these serum biochemical parameters in patients on chronic hemodialysis.