Faster rate of blood volume change in pediatric hemodialysis patients impairs cardiac index

Intradialytic hypotension and myocardial stunning are proposed as contributing to the pathogenesis of increased cardiovascular disease burden and death in patients receiving maintenance hemodialysis (HD). Noninvasive cardiac output measurements provide a dynamic, real-time assessment of hemodynamic parameters. We investigated intradialytic changes in hemodynamic parameters in pediatric outpatients receiving chronic HD and determined patient and treatment risk factors associated with such intradialytic changes.

Hemodialysis was performed using linear fluid removal over 4 h with polysulfone dialyzers. Continuous wave Doppler ultrasound was used to measure hemodynamic parameters prior, 2 h into, and after the mid-week HD treatment session. Pulse wave tonometry was performed at the same time. The percentage change in blood volume was measured by noninvasive hematocrit monitoring during HD.

Twenty-two patients fit the inclusion criteria, of whom 16 (73 %) were male. The mean age of the patients was 17 ± 3.8 years, and the dialysis vintage was 47.8 ± 33.7 months. The cardiac index decreased significantly midway through the HD treatment session and remained low until the end of treatment. A significant decline in cardiac index without hypotension occurred in 12 (54 %) patients. Expected increase in systemic vascular resistance index to preserve the cardiac index was not observed. Weight, percentage fluid overload, dialysis vintage, and adequacy did not correlate with the observed decline in the cardiac index. The decrease in blood volume at the 2 h (R = 0.43, p = 0.045) and 4 h (R = 0.56, p = 0.007) time points was the only factor associated with cardiac index decline.

The cardiac index and stroke volume decreased significantly during the HD session. Patients with larger blood volume changes during the first 2 h of HD and at 4 h showed a significant decrease in cardiac index that did not recover at the completion of the HD treatment. Rate of fluid removal was the only significant risk factor for compromised cardiac index during HD. Conventional methods currently used for assisting fluid removal in HD are inadequate to assess hemodynamic changes.