Intradialytic hypotension is severely underreported by intermittent blood pressure readings

Abstract

Background: Intradialytic hypotension (IDH) has been associated with both morbidity and mortality. Yet, as IDH often occurs asymptomatic, it might be easily missed with routine twice per hour brachial artery cuff-blood pressure (BAC-BP) readings. This study evaluated differences in IDH detection between intermittent BAC-BP and continuous BP monitoring with a finger cuff (FC-BP). Validation of the FC device was an additional objective.

Methods: In 40 chronic dialysis patients, intradialytic BP was measured during four sessions using (i) BAC-BP every 15 minutes and (ii) beat-to-beat FC-BP readings, which were averaged over 20-seconds intervals. IDH was defined as a systolic BP (SBP) <90 or <100 mmHg, depending on pre-dialysis SBP. Only FC measurements with an acceptable accuracy (i.e. mean SBP bias <= 10 mmHg) were used for the IDH analysis. For validation, sequential same-arm BP measurements were compared, using Bland-Altman analyses to assess agreement and four-quadrant plots to evaluate concordance.

Results: For IDH analysis, 144 BAC-BP readings and 18 163 FC-BP measurements were recorded in 106 hours. While BAC-BP identified 20 IDH episodes, 441 were detected by FC-BP. For validation, Bland-Altman analyses of 1221 paired BP readings showed a mean bias +/- limits of agreement of -13.3 +/- 44.5 mmHg for SBP and -13.3 +/- 25.5 mmHg for diastolic BP. Only 27.7% of the paired FC-BP readings met the acceptable accuracy criterion. Concordance rates were 34.3% and 36.3%, respectively. Conclusions: First, the occurrence of IDH is severely underestimated with intermittent BP monitoring. Second, FC-BP appears unsuitable for routine intradialytic BP monitoring due to its poor accuracy, precision, and concordance.