Browsing by Author "Molina, Christopher"
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Item Acute Effect of High vs Low Dialysate Sodium on Endothelial Cell Function During Hemodialysis(2013-01-22) D'Silva, Kristin; Molina, Christopher; van Buren, Peter; Kim, Catherine; Inrig, JulaBACKGROUND: Intradialytic hypertension (HTN), a rise in blood pressure that occurs during hemodialysis (HD) treatments in up to 15% of patients, is associated with higher morbidity and mortality. The cause of intradialytic HTN is unknown but may be due to endothelial cell (EC) dysfunction. In vitro exposure of ECs to high sodium (Na+) concentration promotes EC stiffness and imbalances in vasoconstrictors (endothelin-1 [ET-1]) and vasodilators (nitric oxide [NO]). We hypothesized that, among patients with intradialytic HTN, exposure to high dialysate Na+ would lead to a decrease in NO and increase in ET-1 during HD. METHODS: We performed a 3-week, 2-arm, randomized crossover study among 16 HD patients with intradialytic HTN and compared the effects of high dialysate-to-serum Na+ gradients (5 mEq/L above participants' baseline Na+) vs low dialysate-to-serum Na+ gradients (5 mEq/L below baseline Na+ with lower limit of 134 mEq/L) on intradialytic changes in nitrite and ET-1. Differences between treatments were compared with repeated measures mixed linear regression and included randomization arm (high - low Na+ vs low - high Na+), treatment effect (high vs low Na+), subject, time and session. RESULTS: Study participants (N=16) had an average age of 58.8 years, 38% were black, 56% were Hispanic, and 94% were male. Intradialytic changes in NO and ET-1 with high and low dialysate-to-plasma Na+ gradients are shown in Figure 1. In the primary comparison of high vs low dialysate-to-serum Na+ gradient, there were no significant differences in intradialytic levels of NO or ET-1 (Table 1). However, when compared by randomization arm, participants who received the low dialysate-to-serum Na+ gradient followed by high compared to those who received the high dialysate-to-serum Na+ gradient followed by low had a significant decrease in ET-1 (parameter estimate -0.49 pg/mL, p=0.04) and significant increase in nitrite during hemodialysis (parameter estimate +0.16 nM, p=0.02) (Table 1). CONCLUSIONS: Patients who received the low dialysate-to-serum Na+ gradient before the high dialysate-to-serum Na+ gradient had higher levels of nitrite and lower levels of ET-1 throughout the three week study period compared to patients who received the high dialysate-to-serum Na+ gradient before the low dialysate-to-serum Na+ gradient. This suggests that the dialysate Na+ concentration may have longer-term effects on endothelial cell function.Item The Effect of Extracellular Volume Status on Intradialytic Hypertension(2014-02-04) Molina, Christopher; Van Buren, Peter; Toto, RobertBACKGROUND: lntradialytic hypertension (HTN), defined as an increase in systolic blood pressure (BP) >10 mmHg from pre to post-hemodialysis (HD),occurs regularly in approximately 15o/o of HD patients. Previous studieshave shown patients with intradialytic HTN display higher overall ambulatory BP and have higher mortality rates when compared to HD controls. As extracellular volume overload contributes to HTN in HD patients, it has been proposed that intradialytic HTN patients have increased extracellular volume. Still, atypical ambulatory BP patterns seen in intradialytic HTN patients suggest extracellular volume may not be a primary determinant of BP in this population. Thus, we hypothesize extracellular fluid volume will be similar in patients with intradialytic HTN and HD controls when adjusting for total body water. METHODS: ln a case control study we recruited hypertensive HD patients with pre HD systolic BP >140 mmHg or post HD systolic BP >130 mmHg. Case subjects with intradialytic HTN were defined as having systolic BP increases >10 mmHg from pre to post-HD. Control subjects were defined as having systolic BP decreases >10 mmHg from pre to post- HD. We obtained measurements of total body water, extracellular water, and intracellular water before and after HD in all subjects using multifrequency bioimpedance spectroscopy. We compared the ratio of extracellular water to total body water between groups using t-tests for pre and post dialysis measurements. RESULTS: Case subjects (n=4) had an average ambulatory systolic BP of 140 mmHg (20) and controls (n=4) had an average of 1a0 (9.8). Before dialysis, case subjects had a ratio of 0.49 (.03) vs. 0.a6 (.02) in controls (p=0.2). After dialysis, the ratio was 0.45 (0.03) in cases and .44 (0.01) in controls (p=0.4). DISCUSSION: The ratio of extracellular water to total body water was similar in subjects with intradialytic HTN both before and after HD compared to HD controls. While a larger sample size will be required to establish whether extracellular volume status is different in this patient population, the results of this study suggest increased extracellular volume is not a distinguishing feature of intradialytic HTN. Further etiologies for increased BP including excessive vascular resistance should be explored to explain the phenomenon of intradialytic hypertension.