The levels of salivary urea, uric acid, creatinine and stress axes during the dialysis process

Aim: Patients with ESRD accumulate toxic metabolites like urea, uric acid, and creatinine, necessitating hemodialysis. The relationship between dialysis, stress, and the effects of these metabolites on the ANS and HPA axis remains unclear, as does their trajectory in saliva. This thesis aims to explore temporal changes in serum and salivary levels of urea, uric acid, creatinine, cortisol, and HRV during hemodialysis and their interrelationships. Material and method: The study included 30 patients undergoing hemodialysis treatment. Blood and saliva samples were collected immediately before, midway through, and immediately after the treatment, and an ECG was performed to measure HRV. Urea (BUN), uric acid, and creatinine were analyzed from blood samples, while urea, uric acid, creatinine, and cortisol levels were measured from saliva samples. Results: Serum and salivary levels of urea, uric acid, and creatinine demonstrated significant differences across all three time points (p<0.001), with a moderately strong correlation between the two fluids (r>0.37). Cortisol levels also exhibited significant variations (p<0.001), whereas no significant differences were identified among time- or frequency-dependent HRV parameters (p>0.05). Both serum and salivary levels were associated with cortisol; however, no parameter showed any relationship with HRV. Conclusion: During hemodialysis, levels of urea, uric acid, and creatinine in serum and saliva exhibit a correlation, and the concurrent reduction in cortisol levels alongside these metabolites suggests a potential association with the HPA axis. However, the absence of significant differences in HRV parameters indicates no connection with the ANS. Furthermore, the findings reveal that dialysis may have distinct relationships with the HPA axis and the ANS.