Abstract
BackgroundThe mechanisms of intradialytic increases in blood pressure are not well defined. The present study was undertaken to assess the role of autonomic nervous system activation during intradialytic hypertensive episodes.Methodology/Principal FindingsContinuous interbeat intervals (IBI) and systolic blood pressure (SBP) were monitored during hemodialysis in 108 chronic patients. Intradialytic hypertensive episodes defined as a period of at least 10 mmHg increase in SBP between the beginning and the end of a dialysis session or hypertension resistant to ultrafiltration occurring during or immediately after the dialysis procedure, were detected in 62 out of 113 hemodialysis sessions. SBP variability, IBI variability and baroreceptor sensitivity (BRS) in the low (LF) and high (HF) frequency ranges were assessed using the complex demodulation technique (CDM). Intradialytic hypertensive episodes were associated with an increased (n = 45) or decreased (n = 17) heart rate. The maximal blood pressure was similar in both groups. In patients with increased heart rate the increase in blood pressure was associated with marked increases in SBP and IBI variability, with suppressed BRS indices and enhanced sympatho-vagal balance. In contrast, in those with decreased heart rate, there were no significant changes in the above parameters. End-of- dialysis blood pressure in all sessions associated with hypertensive episode was significantly higher than in those without such episodes. In logistic regression analysis, predialysis BRS in the low frequency range was found to be the main predictor of intradialytic hypertension.Conclusion/SignificanceOur data point to sympathetic overactivity with feed-forward blood pressure enhancement as an important mechanism of intradialytic hypertension in a significant proportion of patients. The triggers of increased sympathetic activity during hemodialysis remain to be determined. Intradialytic hypertensive episodes are associated with higher end-of- dialysis blood pressure, suggesting that intradialytic hypertension may play a role in generation of interdialytic hypertension.
Highlights
IntroductionBlood pressure usually decreases with ultrafiltration and weight loss
During hemodialysis treatment, blood pressure usually decreases with ultrafiltration and weight loss
There is no standard definition for intradialytic hypertension; some of the most common accepted criteria reviewed by Chazot and Jean [2] include a 15 mmHg increase of mean arterial pressure between the start and the end of a dialysis session [3], hypertension resistant to ultrafiltration occurring during or immediately after the dialysis procedure [4], or at least a 10 mmHg increase in the systolic blood pressure from pre-to post-dialysis [5]
Summary
Blood pressure usually decreases with ultrafiltration and weight loss. Other popular hypotheses link intradialytic hypertension to variations in potassium or ionized calcium concentrations [8,9], antihypertensive drug removal during hemodialysis [10], hemoconcentration [11], recombinant erythropoietin administration, stimulation of the renin-angiotensin system during ultrafiltration [12], and to hemodynamic changes including increased cardiac output and vasoconstriction [13]. The latter is believed to be caused by endothelial dysfunction [14] and/or with increased endothelin secretion and altered nitric oxide/endothelin balance [13,15]. The present study was undertaken to assess the role of autonomic nervous system activation during intradialytic hypertensive episodes
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