Supplementary Material for: A Pilot and Feasibility Study of Continuous Cardiac Output and Blood Pressure Monitoring during Intermittent Hemodialysis

Introduction: Hypotension is common during intermittent hemodialysis (IHD) and may be due to a decreased cardiac index (CI). However, no study has simultaneously and continuously measured CI and mean arterial pressure (MAP) to understand the prevalence, severity, and duration of CI decreases or relate them to MAP, blood volume (BV) and net ultrafiltration (NUF) rate.
Methods: In a prospective, pilot and feasibility investigation, we studied 10 chronic IHD patients. We used the ClearSight System™ to continuously monitor CI and MAP; the CRIT-LINE®IV monitor to detect BV changes and collected data on NUF rate.
Results: Device tolerance and compliance was 100%. All patients experienced at least ≥ 1 episode of severe CI decrease (> 25% from baseline), with a median duration of 24 minutes [IQR 6-87] and of 68 minutes [14-106] for moderate decreases (>15% but  25% from baseline). Eight patients experienced a low CI state (<2.2 L/min/m2). The lowest CI was 0.9 L/min/m2 with a concomitant MAP of 94 mmHg. When the fall in CI was severe, MAP increased in 58% of cases and remained stable in 28%. Overall, CI decreased by -0.55 L/min/m2 when BV decrease was moderate vs mild (p<0.001) and by -0.8 L/min/m2 when NUF rate was high vs low (p<0.001).
Conclusion: Continuous CI monitoring is feasible in IHD and shows frequent moderate-severe CI decreases, sometimes to low CI state levels. Such decreases are typically associated with markers of decreased intravascular volume status but not with a decrease in MAP, implying marked vasoconstriction.