Preserved Cerebral Oxygenation with Worsening Global Myocardial Strain during Pediatric Chronic Hemodialysis
Authors: Idrovo Alexandra , Pignatelli Ricardo , Loar Robert , Nieuwsma Asela , Geer Jessica , Solomon Catharina , Swartz Sarah , Ghanayem Nancy , Akcan-Arikan Ayse , Srivaths Poyyapakkam 
Published: September 2021

Significance Statement
Even though pediatric patients receiving chronic hemodialysis have fewer cardiovascular risk factors compared with adult patients, cardiovascular morbidity and mortality remain prominent. Adults experience myocardial strain and cerebral hypoperfusion during hemodialysis. Measured central venous oxygen saturation (mCVO2) as a potential marker for hemodialysis-related tissue hypoxia has been studied in adults. Simultaneous cardiovascular function, regional cerebral oxygenation, and mCVO2 during hemodialysis have not previously been studied in pediatric patients. The authors show that cardiac global longitudinal strain significantly worsened and mCVO2 decreased during pediatric hemodialysis; both factors were associated with intradialytic blood volume change. Regional cerebral oxygenation was unchanged, suggesting that cerebral oxygenation remains intact in pediatric patients receiving hemodialysis. This study provides insight into the effects of hemodialysis on myocardial and cerebral oxygenation in pediatric patients.

Background
Cerebral and myocardial hypoperfusion occur during hemodialysis in adults. Pediatric patients receiving chronic hemodialysis have fewer cardiovascular risk factors, yet cardiovascular morbidity remains prominent.

Methods
We conducted a prospective observational study of pediatric patients receiving chronic hemodialysis to investigate whether intermittent hemodialysis is associated with adverse end organ effects in the heart or with cerebral oxygenation (regional tissue oxyhemoglobin saturation [rSO2]). We assessed intradialytic cardiovascular function and rSO2 using noninvasive echocardiography to determine myocardial strain and continuous noninvasive near-infrared spectroscopy for rSO2. We measured changes in blood volume and measured central venous oxygen saturation (mCVO2) pre-, mid-, and post-hemodialysis.

Results
The study included 15 patients (median age, 12 years; median hemodialysis vintage, 13.2 [9–24] months). Patients were asymptomatic. The rSO2 did not change during hemodialysis, whereas mCVO2 decreased significantly, from 73% to 64.8%. Global longitudinal strain of the myocardium worsened significantly by mid-hemodialysis and persisted post-hemodialysis. The ejection fraction remained normal. Lower systolic BP and faster blood volume change were associated with worsening myocardial strain; only blood volume change was significant in multivariate analysis (β-coefficient, −0.3; 95% confidence interval [CI], −0.38 to −0.21; P<0.001). Blood volume change was also associated with a significant decrease in mCVO2 (β-coefficient, 0.42; 95% CI, 0.07 to 0.76; P=0.001). Access, age, hemodialysis vintage, and ultrafiltration volume were not associated with worsening strain.

Conclusions
Unchanged rSO2 suggested that cerebral oxygenation was maintained during hemodialysis. However, despite maintained ejection fraction, intradialytic myocardial strain worsened in pediatric hemodialysis and was associated with blood volume change. The effect of hemodialysis on individual organ perfusion in pediatric versus adult patients receiving hemodialysis might differ.