Vasopressin release is enhanced by the Hemocontrol biofeedback system and could contribute to better haemodynamic stability during haemodialysis

Background. Haemodialysis with the Hemocontrol biofeedback system (HHD) is associated with improved haemodynamic stability compared with standard haemodialysis (HD) (SHD). Although the bene ﬁ cial effect of HHD on haemodynamic stability is generally explained by its effect on blood volume, we questioned whether additional factors could play a role. Since HHD is associated with higher initial dialysate sodium concentrations and ultra ﬁ ltration (UF) rate, we studied whether the bene ﬁ cial effect of HHD on haemodynamic stability may be explained by an increased release of the vasoconstrictor arginine vasopressin (AVP). Methods. Fifteen chronic dialysis patients underwent SHD and HHD in random order. All other treatment factors were identical and patients served as their own control. Plasma levels of AVP were measured pre-dialysis, at 30 and 60 min intra-dialysis and, next, hourly until completion of the dialysis session. Results. Plasma AVP levels did not change signi ﬁ cantly during SHD, whereas AVP levels rose signi ﬁ cantly within 30 min after the start of HHD (P < 0.01). AVP levels were signi ﬁ cantly higher at 30 and 60 min of HHD in comparison with SHD (P < 0.05). Dialysis hypotension occurred signi ﬁ cantly less frequent during HHD than during SHD (P < 0.05). Conclusions. HHD is associated with higher initial AVP levels compared with SHD. The enhanced release of the vasoconstrictor AVP with HHD could contribute to the lower frequency of dialysis hypotension by facilitating ﬂ uid removal during the ﬁ rst part of the dialysis session, permitting lower UF rates during the second half of the dialysis session. AbstractBackground. Optimal treatment for secondary hyperparathyroidism (SHPT) has not been de ﬁ ned. The IMPACT SHPT identi study assessed whether dose-titrated paricalcitol plus sup-plemental cinacalcet only for hypercalcaemia is superior to cinacalcet plus low-dose vitamin D in controlling intact parathyroid hormone (iPTH) levels in patients with SHPT on haemodialysis. Methods. multicentre, open-label Phase 4 participants randomly selected paricalcitol or cinacalcet low-dose D. Randomization ﬁ ed by mode of paricalcitol administration (IV) oral]. The primary ef ﬁ cacy end point was the proportion of subjects who achieved a mean iPTH value of 150 300 pg/mL during 21 of the oral more 21 included in the primary analysis. In the IV stratum, 57.7% of subjects in the paricalcitol versus 32.7% in the cinacalcet group (P = 0.016) achieved the primary end point. In the oral stratum, the corresponding proportions of subjects were 54.4% for paricalcitol and 43.4% for cinacalcet (P = 0.260). Cochran – Mantel – Haenszel analysis, controlling for stratum, revealed overall superiority of paricalcitol (56.0%) over cinacalcet (38.2%; P = 0.010) in achieving iPTH 150 – 300 pg/mL during Weeks 21 – 28. Hypercalcaemia occurred in 4 (7.7%) and 0 (0%) of paricalci-tol-treated subjects in the IV and oral strata, respectively. Hypocalcaemia occurred in 46.9% and 54.7% of cinacal-cet-treated subjects in the IVand oral strata, respectively. Conclusion. Paricalcitol versus cinacalcet plus low-dose vitamin D provided superior control of iPTH, with low in-cidence of hypercalcaemia.