Blood pressure response to uncomplicated hemodialysis: The importance of changes in stroke volume

Background: The cause of blood pressure ( BP) changes during uncomplicated hemodialysis (HD) has not been fully investigated. Controversy exists whether changes in BP result from changes in stroke volume (SV) or total peripheral resistance (TPR). Methods: We investigated 19 patients using continuous BP monitoring (Portapres(R)) and subsequent Modelflow(R) analysis, yielding continuous SV, cardiac output ( CO) and TPR values. Blood volume (BV) monitoring was also performed. For each patient, the sensitivity index ( SI) was calculated. The SI is the slope of the curve depicting the relationship between the systolic BP (SBP) response and the BV response. The patients were divided into two groups: group A had an SI > which means a decrease in SBP in response to BV change, and group B had an SI < 1. In these patients, SBP remained stable despite a BV change. Results: Baseline characteristics and baseline values of all parameters were similar between the groups. In group A, SBP decreased by 25 +/- 19 mm Hg and in group B the SBP increased by 5.0 +/- 29 mm Hg ( p < 0.05), while BV change was similar (10.6 +/- 4.9 and 11.2 +/- 4.2%, respectively). The difference in SBP response was caused by a different SV response (group A - 44 +/- 16% and group B - 26 +/- 18%, p = 0.04), while the TPR response was similar ( 71 +/- 27% in group A vs. 59 +/- 58% in group B). Conclusion: Patients responding with a BP decrease to BV reduction during uncomplicated HD differ in their SV response from patients with a stable BP. Copyright (C) 2004 S. Karger AG, Basel.